2024 |
Sengupta C, Nguyen DT, Moodie T, Mason D, Luo J, Causer T, et al., 'The first clinical implementation of real-time 6 degree-of-freedom image-guided radiotherapy for liver SABR patients', Radiotherapy and Oncology, 190 (2024) [C1]
Purpose: Multiple survey results have identified a demand for improved motion management for liver cancer IGRT. Until now, real-time IGRT for liver has been the domain of dedicate... [more]
Purpose: Multiple survey results have identified a demand for improved motion management for liver cancer IGRT. Until now, real-time IGRT for liver has been the domain of dedicated and expensive cancer radiotherapy systems. The purpose of this study was to clinically implement and characterise the performance of a novel real-time 6 degree-of-freedom (DoF) IGRT system, Kilovoltage Intrafraction Monitoring (KIM) for liver SABR patients. Methods/Materials: The KIM technology segmented gold fiducial markers in intra-fraction x-ray images as a surrogate for the liver tumour and converted the 2D segmented marker positions into a real-time 6DoF tumour position. Fifteen liver SABR patients were recruited and treated with KIM combined with external surrogate guidance at three radiotherapy centres in the TROG 17.03 LARK multi-institutional prospective clinical trial. Patients were either treated in breath-hold or in free breathing using the gating method. The KIM localisation accuracy and dosimetric accuracy achieved with KIM + external surrogate were measured and the results were compared to those with the estimated external surrogate alone. Results: The KIM localisation accuracy was 0.2±0.9 mm (left¿right), 0.3±0.6 mm (superior-inferior) and 1.2±0.8 mm (anterior-posterior) for translations and -0.1¿±0.8¿ (left¿right), 0.6¿±1.2¿ (superior-inferior) and 0.1¿±0.9¿ (anterior-posterior) for rotations. The cumulative dose to the GTV with KIM + external surrogate was always within 5% of the plan. In 2 out of 15 patients, >5% dose error would have occurred to the GTV and an organ-at-risk with external surrogate alone. Conclusions: This work demonstrates that real-time 6DoF IGRT for liver can be implemented on standard radiotherapy systems to improve treatment accuracy and safety. The observations made during the treatments highlight the potential false assurance of using traditional external surrogates to assess tumour motion in patients and the need for ongoing improvement of IGRT technologies.
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2023 |
Kaur G, Lehmann J, Greer PB, Martin J, Simpson J, 'Clinical validation of the Varian Truebeam intra-fraction motion review (IMR) system for prostate treatment guidance.', Phys Eng Sci Med, 46 131-140 (2023) [C1]
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2023 |
Sengupta C, Skouboe S, Ravkilde T, Poulsen PR, Nguyen DT, Greer PB, et al., 'The dosimetric error due to uncorrected tumor rotation during real-time adaptive prostate stereotactic body radiation therapy.', Med Phys, 50 20-29 (2023) [C1]
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2023 |
Greer PB, Standen T, David R, Miri N, Bobrowski K, Lehmann J, et al., 'Remote EPID-based dosimetric auditing using DVH patient dose analysis', PHYSICS IN MEDICINE AND BIOLOGY, 68 (2023) [C1]
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2023 |
Richardson M, Sidhom M, Keall P, Leigh L, Ball H, Bucci J, et al., 'Genitourinary Quality-of-Life Comparison Between Urethral Sparing Prostate Stereotactic Body Radiation Therapy Monotherapy and Virtual High-Dose-Rate Brachytherapy Boost.', Int J Radiat Oncol Biol Phys, 116 1069-1078 (2023) [C1]
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2023 |
Phonlakrai M, Ramadan S, Simpson J, Gholizadeh N, Arm J, Skehan K, et al., 'Determination of hepatic extraction fraction with gadoxetate low-temporal resolution DCE-MRI-based deconvolution analysis: validation with ALBI score and Child-Pugh class.', Journal of medical radiation sciences, 70 Suppl 2 48-58 (2023) [C1]
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2023 |
Chourak H, Barateau A, Greer P, Lafond C, Nunes JC, de Crevoisier R, et al., 'Determination of acceptable Hounsfield units uncertainties via a sensitivity analysis for an accurate dose calculation in the context of prostate MRI-only radiotherapy', Physical and Engineering Sciences in Medicine, 46 1703-1711 (2023) [C1]
Radiation therapy is moving from CT based to MRI guided planning, particularly for soft tissue anatomy. An important requirement of this new workflow is the generation of syntheti... [more]
Radiation therapy is moving from CT based to MRI guided planning, particularly for soft tissue anatomy. An important requirement of this new workflow is the generation of synthetic-CT (sCT) from MRI to enable treatment dose calculations. Automatic methods to determine the acceptable range of CT Hounsfield Unit (HU) uncertainties to avoid dose distribution errors is thus a key step toward safe MRI-only radiotherapy. This work has analysed the effects of controlled errors introduced in CT scans on the delivered radiation dose for prostate cancer patients. Spearman correlation coefficient has been computed, and a global sensitivity analysis performed following the Morris screening method. This allows the classification of different error factors according to their impact on the dose at the isocentre. sCT HU estimation errors in the bladder appeared to be the least influential factor, and sCT quality assessment should not only focus on organs surrounding the radiation target, as errors in other soft tissue may significantly impact the dose in the target volume. This methodology links dose and intensity-based metrics, and is the first step to define a threshold of acceptability of HU uncertainties for accurate dose planning.
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2023 |
Altowairqi S, Luo S, Greer P, 'A Review of the Recent Progress on Crowd Anomaly Detection', International Journal of Advanced Computer Science and Applications, 14 659-669 (2023) [C1]
Surveillance videos are crucial in imparting public security, reducing or avoiding the accidents that occur from anomalies. Crowd anomaly detection is a rapidly growing research f... [more]
Surveillance videos are crucial in imparting public security, reducing or avoiding the accidents that occur from anomalies. Crowd anomaly detection is a rapidly growing research field that aims to identify abnormal or suspicious behavior in crowds. This paper provides a comprehensive review of the state-of-the-art in crowd anomaly detection and, different taxonomies, publicly available datasets, challenges, and future research directions. The paper first provides an overview of the field and the importance of crowd anomaly detection in various applications such as public safety, transportation, and surveillance. Secondly, it presents the components of crowd anomaly detection and its different taxonomies based on the availability of labels, and the type of anomalies. Thirdly, it presents the review of the recent progress of crowd anomaly detection. The review also covers publicly available datasets commonly used for evaluating crowd anomaly detection methods. The challenges faced by the field, such as handling variability in crowd behavior, dealing with large and complex data sets, and addressing the imbalance of data, are discussed. Finally, the paper concludes with a discussion of future research directions in crowd anomaly detection, including integrating multiple modalities, addressing privacy concerns, and addressing crowd monitoring systems¿ ethical and legal implications.
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2023 |
O'Connor LM, Quinn A, Denley S, Leigh L, Martin J, Dowling JA, et al., 'Cone beam computed tomography image guidance within a magnetic resonance imaging-only planning workflow', Physics and Imaging in Radiation Oncology, 27 100472-100472 (2023) [C1]
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2023 |
Yang G, Luo S, Greer P, 'A Novel Vision Transformer Model for Skin Cancer Classification', Neural Processing Letters, 55 9335-9351 (2023) [C1]
Skin cancer can be fatal if it is found to be malignant. Modern diagnosis of skin cancer heavily relies on visual inspection through clinical screening, dermoscopy, or histopathol... [more]
Skin cancer can be fatal if it is found to be malignant. Modern diagnosis of skin cancer heavily relies on visual inspection through clinical screening, dermoscopy, or histopathological examinations. However, due to similarity among cancer types, it is usually challenging to identify the type of skin cancer, especially at its early stages. Deep learning techniques have been developed over the last few years and have achieved success in helping to improve the accuracy of diagnosis and classification. However, the latest deep learning algorithms still do not provide ideal classification accuracy. To further improve the performance of classification accuracy, this paper presents a novel method of classifying skin cancer in clinical skin images. The method consists of four blocks. First, class rebalancing is applied to the images of seven skin cancer types for better classification performance. Second, an image is preprocessed by being split into patches of the same size and then flattened into a series of tokens. Third, a transformer encoder is used to process the flattened patches. The transformer encoder consists of N identical layers with each layer containing two sublayers. Sublayer one is a multihead self-attention unit, and sublayer two is a fully connected feed-forward network unit. For each of the two sublayers, a normalization operation is applied to its input, and a residual connection of its input and its output is calculated. Finally, a classification block is implemented after the transformer encoder. The block consists of a flattened layer and a dense layer with batch normalization. Transfer learning is implemented to build the whole network, where the ImageNet dataset is used to pretrain the network and the HAM10000 dataset is used to fine-tune the network. Experiments have shown that the method has achieved a classification accuracy of 94.1%, outperforming the current state-of-the-art model IRv2 with soft attention on the same training and testing datasets. On the Edinburgh DERMOFIT dataset also, the method has better performance compared with baseline models.
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2023 |
Phonlakrai M, Ramadan S, Simpson J, Skehan K, Goodwin J, Trada Y, et al., 'Non-contrast based approach for liver function quantification using Bayesian-based intravoxel incoherent motion diffusion weighted imaging: A pilot study.', J Appl Clin Med Phys, 24 e14178 (2023) [C1]
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2023 |
Dogan N, Mijnheer BJ, Padgett K, Nalichowski A, Wu C, Nyflot MJ, et al., 'AAPM Task Group Report 307: Use of EPIDs for Patient-Specific IMRT and VMAT QA.', Med Phys, 50 e865-e903 (2023) [C1]
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2023 |
Young T, Dowling J, Rai R, Liney G, Greer P, Thwaites D, Holloway L, 'Clinical validation of MR imaging time reduction for substitute/synthetic CT generation for prostate MRI-only treatment planning', Physical and Engineering Sciences in Medicine, 46 1015-1021 (2023) [C1]
Radiotherapy treatment planning based only on magnetic resonance imaging (MRI) has become clinically achievable. Though computed tomography (CT) is the gold standard for radiother... [more]
Radiotherapy treatment planning based only on magnetic resonance imaging (MRI) has become clinically achievable. Though computed tomography (CT) is the gold standard for radiotherapy imaging, directly providing the electron density values needed for planning calculations, MRI has superior soft tissue visualisation to guide treatment planning decisions and optimisation. MRI-only planning removes the need for the CT scan, but requires generation of a substitute/synthetic/pseudo CT (sCT) for electron density information. Shortening the MRI imaging time would improve patient comfort and reduce the likelihood of motion artefacts. A volunteer study was previously carried out to investigate and optimise faster MRI sequences for a hybrid atlas-voxel conversion to sCT for prostate treatment planning. The aim of this follow-on study was to clinically validate the performance of the new optimised sequence for sCT generation in a treated MRI-only prostate patient cohort. 10 patients undergoing MRI-only treatment were scanned on a Siemens Skyra 3T MRI as part of the MRI-only sub-study of the NINJA clinical trial (ACTRN12618001806257). Two sequences were used, the standard 3D T2-weighted SPACE sequence used for sCT conversion which has been previously validated against CT, and a modified fast SPACE sequence, selected based on the volunteer study. Both were used to generate sCT scans. These were then compared to evaluate the fast sequence conversion for anatomical and dosimetric accuracy against the clinically approved treatment plans. The average Mean Absolute Error (MAE) for the body was 14.98 ± 2.35 HU, and for bone was 40.77 ± 5.51 HU. The external volume contour comparison produced a Dice Similarity Coefficient (DSC) of at least 0.976, and an average of 0.985 ± 0.004, and the bony anatomy contour comparison a DSC of at least 0.907, and an average of 0.950 ± 0.018. The fast SPACE sCT agreed with the gold standard sCT within an isocentre dose of -0.28% ± 0.16% and an average gamma pass rate of 99.66% ± 0.41% for a 1%/1 mm gamma tolerance. In this clinical validation study, the fast sequence, which reduced the required imaging time by approximately a factor of 4, produced an sCT with similar clinical dosimetric results compared to the standard sCT, demonstrating its potential for clinical use for treatment planning.
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2023 |
Min H, Dowling J, Jameson MG, Cloak K, Faustino J, Sidhom M, et al., 'Clinical target volume delineation quality assurance for MRI-guided prostate radiotherapy using deep learning with uncertainty estimation.', Radiother Oncol, 186 109794 (2023) [C1]
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2022 |
O'Connor LM, Choi JH, Dowling JA, Warren-Forward H, Martin J, Greer PB, 'Comparison of Synthetic Computed Tomography Generation Methods, Incorporating Male and Female Anatomical Differences, for Magnetic Resonance Imaging-Only Definitive Pelvic Radiotherapy', FRONTIERS IN ONCOLOGY, 12 (2022) [C1]
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2022 |
Dai W, Woo B, Liu S, Marques M, Engstrom C, Greer PB, et al., 'CAN3D: Fast 3D medical image segmentation via compact context aggregation', Medical Image Analysis, 82 (2022) [C1]
Direct automatic segmentation of objects in 3D medical imaging, such as magnetic resonance (MR) imaging, is challenging as it often involves accurately identifying multiple indivi... [more]
Direct automatic segmentation of objects in 3D medical imaging, such as magnetic resonance (MR) imaging, is challenging as it often involves accurately identifying multiple individual structures with complex geometries within a large volume under investigation. Most deep learning approaches address these challenges by enhancing their learning capability through a substantial increase in trainable parameters within their models. An increased model complexity will incur high computational costs and large memory requirements unsuitable for real-time implementation on standard clinical workstations, as clinical imaging systems typically have low-end computer hardware with limited memory and CPU resources only. This paper presents a compact convolutional neural network (CAN3D) designed specifically for clinical workstations and allows the segmentation of large 3D Magnetic Resonance (MR) images in real-time. The proposed CAN3D has a shallow memory footprint to reduce the number of model parameters and computer memory required for state-of-the-art performance and maintain data integrity by directly processing large full-size 3D image input volumes with no patches required. The proposed architecture significantly reduces computational costs, especially for inference using the CPU. We also develop a novel loss function with extra shape constraints to improve segmentation accuracy for imbalanced classes in 3D MR images. Compared to state-of-the-art approaches (U-Net3D, improved U-Net3D and V-Net), CAN3D reduced the number of parameters up to two orders of magnitude and achieved much faster inference, up to 5 times when predicting with a standard commercial CPU (instead of GPU). For the open-access OAI-ZIB knee MR dataset, in comparison with manual segmentation, CAN3D achieved Dice coefficient values of (mean = 0.87 ± 0.02 and 0.85 ± 0.04) with mean surface distance errors (mean = 0.36 ± 0.32 mm and 0.29 ± 0.10 mm) for imbalanced classes such as (femoral and tibial) cartilage volumes respectively when training volume-wise under only 12G video memory. Similarly, CAN3D demonstrated high accuracy and efficiency on a pelvis 3D MR imaging dataset for prostate cancer consisting of 211 examinations with expert manual semantic labels (bladder, body, bone, rectum, prostate) now released publicly for scientific use as part of this work.
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2022 |
Vasina EN, Kong N, Greer P, Baeza Ortega J, Kron T, Ludbrook JJ, et al., 'First clinical experience with real-time portal imaging-based breath-hold monitoring in tangential breast radiotherapy', Physics and Imaging in Radiation Oncology, 24 1-6 (2022) [C1]
Background and purpose: Real-time treatment monitoring with the electronic portal imaging device (EPID) can conceptually provide a more accurate assessment of the quality of deep ... [more]
Background and purpose: Real-time treatment monitoring with the electronic portal imaging device (EPID) can conceptually provide a more accurate assessment of the quality of deep inspiration breath-hold (DIBH) and patient movement during tangential breast radiotherapy (RT). A system was developed to measure two geometrical parameters, the lung depth (LD) and the irradiated width (named here skin distance, SD), along three user-selected lines in MV EPID images of breast tangents. The purpose of this study was to test the system during tangential breast RT with DIBH. Materials and methods: Measurements of LDs and SDs were carried out in real time. DIBH was guided with a commercial system using a marker block. Results from 17 patients were assessed. Mean midline LDs, <mLDs>, per tangent were compared to the planned mLDs; differences between the largest and smallest observed <mLDs> (<mSDs>) per tangent were calculated. Results: For 56% (162/288) of the tangents tested, <mLDs> were outside the tolerance window. All but one patient had at least one fraction showing this behaviour. The largest difference found between an <mLD> and its planned mLD was -16.9 mm. The accuracy of patient positioning and the quality of marker-block-based DIBH guidance contributed to the differences. Fractions with patient position verification using a single EPID image taken before treatment showed a lower rate (34%), suggesting reassessment of setup procedures. Conclusions: Real-time treatment monitoring of the internal anatomy during DIBH delivery of tangential breast RT is feasible and useful. The new system requires no additional radiation for the patient.
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2022 |
Lehmann J, Hussein M, Barry MA, Siva S, Moore A, Chu M, et al., 'SEAFARER - A new concept for validating radiotherapy patient specific QA for clinical trials and clinical practice.', Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology, 171 121-128 (2022) [C1]
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2022 |
Byrne M, Archibald-Heeren B, Hu Y, Greer P, Luo S, Aland T, 'Assessment of semi-automated stereotactic treatment planning for online adaptive radiotherapy in ethos', MEDICAL DOSIMETRY, 47 342-347 (2022) [C1]
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2022 |
Barnes M, Pomare D, Doebrich M, Standen TS, Wolf J, Greer P, Simpson J, 'Insensitivity of machine log files to MLC leaf backlash and effect of MLC backlash on clinical dynamic MLC motion: An experimental investigation.', J Appl Clin Med Phys, 23 e13660 (2022) [C1]
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2022 |
Barnes MP, Sun B, Oborn BM, Lamichhane B, Szwec S, Schmidt M, et al., 'Determination of the electronic portal imaging device pixel-sensitivity-map for quality assurance applications. Part 1: Comparison of methods.', Journal of applied clinical medical physics, 23 e13603 (2022) [C1]
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2022 |
Barnes MP, Sun B, Oborn BM, Lamichhane B, Szwec S, Schmidt M, et al., 'Determination of the electronic portal imaging device pixel-sensitivity-map for quality assurance applications. Part 2: Photon beam dependence.', Journal of applied clinical medical physics, 23 e13602 (2022) [C1]
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2022 |
Chourak H, Barateau A, Tahri S, Cadin C, Lafond C, Nunes JC, et al., 'Quality assurance for MRI-only radiation therapy: A voxel-wise population-based methodology for image and dose assessment of synthetic CT generation methods', Frontiers in Oncology, 12 (2022) [C1]
The quality assurance of synthetic CT (sCT) is crucial for safe clinical transfer to an MRI-only radiotherapy planning workflow. The aim of this work is to propose a population-ba... [more]
The quality assurance of synthetic CT (sCT) is crucial for safe clinical transfer to an MRI-only radiotherapy planning workflow. The aim of this work is to propose a population-based process assessing local errors in the generation of sCTs and their impact on dose distribution. For the analysis to be anatomically meaningful, a customized interpatient registration method brought the population data to the same coordinate system. Then, the voxel-based process was applied on two sCT generation methods: a bulk-density method and a generative adversarial network. The CT and MRI pairs of 39 patients treated by radiotherapy for prostate cancer were used for sCT generation, and 26 of them with delineated structures were selected for analysis. Voxel-wise errors in sCT compared to CT were assessed for image intensities and dose calculation, and a population-based statistical test was applied to identify the regions where discrepancies were significant. The cumulative histograms of the mean absolute dose error per volume of tissue were computed to give a quantitative indication of the error for each generation method. Accurate interpatient registration was achieved, with mean Dice scores higher than 0.91 for all organs. The proposed method produces three-dimensional maps that precisely show the location of the major discrepancies for both sCT generation methods, highlighting the heterogeneity of image and dose errors for sCT generation methods from MRI across the pelvic anatomy. Hence, this method provides additional information that will assist with both sCT development and quality control for MRI-based planning radiotherapy.
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2022 |
O'Connor LM, Dowling JA, Choi JH, Martin J, Warren-Forward H, Richardson H, et al., 'Validation of an MRI-only planning workflow for definitive pelvic radiotherapy', RADIATION ONCOLOGY, 17 (2022) [C1]
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2022 |
Calvo-Ortega JF, Greer PB, Moragues-Femenía S, Pozo-Massó M, Casals-Farran J, 'Verification of stereotactic radiosurgery plans for multiple brain metastases using a virtual phantom-based procedure', Reports of Practical Oncology and Radiotherapy, 27 449-457 (2022) [C1]
Background: The purpose of this study was to describe the use of the VIPER software for patient-specific quality assurance (PSQA) of single-isocenter multitarget (SIMT) stereotact... [more]
Background: The purpose of this study was to describe the use of the VIPER software for patient-specific quality assurance (PSQA) of single-isocenter multitarget (SIMT) stereotactic radiosurgery (SRS) plans. Materials and methods: Twenty clinical of intensity-modulated (IMRT) SIMT SRS plans were reviewed. A total of 88 brain metastases were included. Number of lesions per plan and their individual volumes ranged from 2 to 35 and from 0.03 to 32.8 cm3, respectively. Plans were designed with the Eclipse system, and delivered using a Varian CLINAC linac. SRS technique consisted of non-coplanar static-field sliding-window IMRT. Each plan was mapped onto a virtual cylindrical water phantom (VCP) in the Eclipse to calculate a 3D dose distribution (verification plan). The VIPER software reconstructed the 3D dose distribution inside the VCP from the acquired in-air electronic portal image device (EPID) images of the treatment fields. A 3D gamma analysis was used to compare the reconstructed doses to the Eclipse planned doses on the VCP. Gamma passing rates (GPRs) were calculated using 3%global/2 mm criteria and dose thresholds ranged from 10%to 90%of the maximum dose. Results: The averages (± 1 SD) of the 3D GPRs over the 20 SRS plans were: 99.9 ± 0.2%, 99.7 ± 0.3%, 99.6 ± 0.5%, 99.3 ± 0.9%,99.1 ± 1.6%, 99.0 ± 1.6%, and 98.5 ± 3.3%, for dose thresholds of 10%, 20%, 30%, 50%, 70%, 80%and 90%respectively. Conclusions: This work shows the feasibility of the VIPER software for PSQA of SIMT SRS plans, being a reliable alternative to commercially available 2D detector arrays
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2022 |
Choi JH, Asadi B, Simpson J, Dowling JA, Chalup S, Welsh J, Greer P, 'Investigation of a water equivalent depth method for dosimetric accuracy evaluation of synthetic CT', PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS, 105 (2022) [C1]
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2022 |
Richardson H, Kumar M, Tieu MT, Parker J, Dowling JA, Arm J, et al., 'Assessing the impact of magnetic resonance treatment simulation (MRSIM) on target volume delineation and dose to organs at risk for oropharyngeal radiotherapy.', J Med Radiat Sci, 69 66-74 (2022) [C1]
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2022 |
Tahri S, Barateau A, Cadin C, Chourak H, Ribault S, Nozahic F, et al., 'A high-performance method of deep learning for prostate MR-only radiotherapy planning using an optimized Pix2Pix architecture.', Phys Med, 103 108-118 (2022) [C1]
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2022 |
Ebert MA, Marcello M, Haworth A, Holloway LC, Greer P, Dowling JA, et al., 'Methodology of Voxel-Based Analysis In Regard to Shortall et al', INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 112 831-833 (2022)
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2021 |
Lim SB, Zwan BJ, Lee D, Greer PB, Lovelock DM, 'A novel quality assurance procedure for trajectory log validation using phantom-less real-time latency corrected EPID images', JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, 22 176-185 (2021) [C1]
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2021 |
Min H, Dowling J, Jameson MG, Cloak K, Faustino J, Sidhom M, et al., 'Automatic radiotherapy delineation quality assurance on prostate MRI with deep learning in a multicentre clinical trial', Physics in Medicine and Biology, 66 (2021) [C1]
Volume delineation quality assurance (QA) is particularly important in clinical trial settings where consistent protocol implementation is required, as outcomes will affect future... [more]
Volume delineation quality assurance (QA) is particularly important in clinical trial settings where consistent protocol implementation is required, as outcomes will affect future as well current patients. Currently, where feasible, this is conducted manually, which is time consuming and resource intensive. Although previous studies mostly focused on automating delineation QA on CT, magnetic resonance imaging (MRI) is being increasingly used in radiotherapy treatment. In this work, we propose to perform automatic delineation QA on prostate MRI for both the clinical target volume (CTV) and organs-at-risk (OARs) by using delineations generated by 3D Unet variants as benchmarks for QA. These networks were trained on a small gold standard atlas set and applied on a multicentre radiotherapy clinical trial dataset to generate benchmark delineations. Then, a QA stage was designed to recommend 'pass', 'minor correction' and 'major correction' for each manual delineation in the trial set by thresholding its Dice similarity coefficient to the network generated delineation. Among all 3D Unet variants explored, the Unet with anatomical gates in an AtlasNet architecture performed the best in delineation QA, achieving an area under the receiver operating characteristics curve of 0.97, 0.92, 0.89 and 0.97 for identifying unacceptable (major correction) delineations with a sensitivity of 0.93, 0.73, 0.74 and 0.90 at a specificity of 0.93, 0.86, 0.86 and 0.95 for bladder, prostate CTV, rectum and gel spacer respectively. To the best of our knowledge, this is the first study to propose automated delineation QA for a multicentre radiotherapy clinical trial with treatment planning MRI. The methods proposed in this work can potentially improve the accuracy and consistency of CTV and OAR delineation in radiotherapy treatment planning.
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2021 |
Gholizadeh N, Greer PB, Simpson J, Goodwin J, Fu C, Lau P, et al., 'Diagnosis of transition zone prostate cancer by multiparametric MRI: added value of MR spectroscopic imaging with sLASER volume selection', Journal of Biomedical Science, 28 (2021) [C1]
Background: Current multiparametric MRI (mp-MRI) in routine clinical practice has poor-to-moderate diagnostic performance for transition zone prostate cancer. The aim of this stud... [more]
Background: Current multiparametric MRI (mp-MRI) in routine clinical practice has poor-to-moderate diagnostic performance for transition zone prostate cancer. The aim of this study was to evaluate the potential diagnostic performance of novel 1H magnetic resonance spectroscopic imaging (MRSI) using a semi-localized adiabatic selective refocusing (sLASER) sequence with gradient offset independent adiabaticity (GOIA) pulses in addition to the routine mp-MRI, including T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI) and quantitative dynamic contrast enhancement (DCE) for transition zone prostate cancer detection, localization and grading. Methods: Forty-one transition zone prostate cancer patients underwent mp-MRI with an external phased-array coil. Normal and cancer regions were delineated by two radiologists and divided into low-risk, intermediate-risk, and high-risk categories based on TRUS guided biopsy results. Support vector machine models were built using different clinically applicable combinations of T2WI, DWI, DCE, and MRSI. The diagnostic performance of each model in cancer detection was evaluated using the area under curve (AUC) of the receiver operating characteristic diagram. Then accuracy, sensitivity and specificity of each model were calculated. Furthermore, the correlation of mp-MRI parameters with low-risk, intermediate-risk and high-risk cancers were calculated using the Spearman correlation coefficient. Results: The addition of MRSI to T2WI + DWI and T2WI + DWI + DCE improved the accuracy, sensitivity and specificity for cancer detection. The best performance was achieved with T2WI + DWI + MRSI where the addition of MRSI improved the AUC, accuracy, sensitivity and specificity from 0.86 to 0.99, 0.83 to 0.96, 0.80 to 0.95, and 0.85 to 0.97 respectively. The (choline + spermine + creatine)/citrate ratio of MRSI showed the highest correlation with cancer risk groups (r = 0.64, p < 0.01). Conclusion: The inclusion of GOIA-sLASER MRSI into conventional mp-MRI significantly improves the diagnostic accuracy of the detection and aggressiveness assessment of transition zone prostate cancer.
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2021 |
Young T, Dowling J, Rai R, Liney G, Greer P, Thwaites D, Holloway L, 'Effects of MR imaging time reduction on substitute CT generation for prostate MRI-only treatment planning', Physical and Engineering Sciences in Medicine, 44 799-807 (2021) [C1]
The introduction of MRI linear accelerators (MR-linacs) and the increased use of MR imaging in radiotherapy, requires improved approaches to MRI-only radiotherapy. MRI provides ex... [more]
The introduction of MRI linear accelerators (MR-linacs) and the increased use of MR imaging in radiotherapy, requires improved approaches to MRI-only radiotherapy. MRI provides excellent soft tissue visualisation but does not provide any electron density information required for radiotherapy dose calculation, instead MRI is registered to CT images to enable dose calculations. MRI-only radiotherapy eliminates registration errors and reduces patient discomfort, workload and cost. Electron density requirements may be addressed in different ways, from manually applying bulk density corrections, to more computationally intensive methods to produce substitute CT datasets (sCT), requiring additional sequences, increasing overall imaging time. Reducing MR imaging time would reduce potential artefacts from intrafraction motion and patient discomfort. The aim of this study was to assess the impact of reducing MR imaging time on a hybrid atlas-voxel sCT conversion for prostate MRI-only treatment planning, considering both anatomical and dosimetric parameters. 10 volunteers were scanned on a Siemens Skyra 3T MRI. Sequences included the 3D T2-weighted (T2-w) SPACE sequence used for sCT conversion as previously validated against CT, along with variations to this sequence in repetition time (TR), turbo factor, and combinations of these to reduce the imaging time. All scans were converted to sCT and were compared to the sCT from the original SPACE sequence, evaluating for anatomical changes and dosimetric differences for a standard prostate VMAT plan. Compared to the previously validated T2-w SPACE sequence, scan times were reduced by up to 80%. The external volume and bony anatomy were compared, with all but one sequence meeting a DICE coefficient of 0.9 or better, with the largest variations occurring at the edges of the external body volume. The generated sCT agreed with the gold standard sCT within an isocentre dose of 1% and a gamma pass rate of 99% for a 1%/1¿mm gamma tolerance for all but one sequence. This study demonstrates that the MR imaging sequence time was able to be reduced by approximately 80% with similar dosimetric results.
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2021 |
Vasina EN, Greer P, Thwaites D, Kron T, Lehmann J, 'A system for real-time monitoring of breath-hold via assessment of internal anatomy in tangential breast radiotherapy', JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, 23 (2021) [C1]
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Nova |
2021 |
Zwan BJ, Caillet V, Booth JT, Colvill E, Fuangrod T, O'Brien R, et al., 'Toward real-time verification for MLC tracking treatments using time-resolved EPID imaging', MEDICAL PHYSICS, 48 953-964 (2021) [C1]
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Nova |
2021 |
Perkins T, Lee D, Simpson J, Greer P, Goodwin J, 'Experimental evaluation of four-dimensional Magnetic Resonance Imaging for radiotherapy planning of lung cancer', Physics and Imaging in Radiation Oncology, 17 32-35 (2021) [C1]
Radiotherapy planning for lung cancer typically requires both 3D and 4D Computed Tomography (CT) to account for respiratory related movement. 4D Magnetic Resonance Imaging (MRI) w... [more]
Radiotherapy planning for lung cancer typically requires both 3D and 4D Computed Tomography (CT) to account for respiratory related movement. 4D Magnetic Resonance Imaging (MRI) with self-navigation offers a potential alternative with greater reliability in patients with irregular breathing patterns and improved soft tissue contrast. In this study 4D-CT and a 4D-MRI Radial Volumetric Interpolated Breath-hold Examination (VIBE) sequence was evaluated with a 4D phantom and 13 patient respiratory patterns, simulating tumour motion. Quantification of motion related tumour displacement in 4D-MRI and 4D-CT found no statistically significant difference in mean motion range. The results demonstrated the potential viability of 4D-MRI for lung cancer treatment planning.
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Nova |
2021 |
Lim SB, Lee N, Zakeri K, Greer P, Fuangrod T, Coffman F, et al., 'Can the Risk of Dysphagia in Head and Neck Radiation Therapy Be Predicted by an Automated Transit Fluence Monitoring Process During Treatment? A First Comparative Study of Patient Reported Quality of Life and the Fluence-Based Decision Support Metric.', Technology in cancer research & treatment, 20 15330338211027906 (2021) [C1]
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Nova |
2021 |
O'Connor LM, Skehan K, Choi JH, Simpson J, Martin J, Warren-Forward H, et al., 'Optimisation and validation of an integrated magnetic resonance imaging-only radiotherapy planning solution', Physics and Imaging in Radiation Oncology, 20 34-39 (2021) [C1]
Background and purpose: Magnetic resonance imaging (MRI)-only treatment planning is gaining in popularity in radiation oncology, with various methods available to generate a synth... [more]
Background and purpose: Magnetic resonance imaging (MRI)-only treatment planning is gaining in popularity in radiation oncology, with various methods available to generate a synthetic computed tomography (sCT) for this purpose. The aim of this study was to validate a sCT generation software for MRI-only radiotherapy planning of male and female pelvic cancers. The secondary aim of this study was to improve dose agreement by applying a derived relative electron and mass density (RED) curve to the sCT. Method and materials: Computed tomography (CT) and MRI scans of forty patients with pelvic neoplasms were used in the study. Treatment plans were copied from the CT scan to the sCT scan for dose comparison. Dose difference at reference point, 3D gamma comparison and dose volume histogram analysis was used to validate the dose impact of the sCT. The RED values were optimised to improve dose agreement by using a linear plot. Results: The average percentage dose difference at isocentre was 1.2% and the mean 3D gamma comparison with a criteria of 1%/1 mm was 84.0% ± 9.7%. The results indicate an inherent systematic difference in the dosimetry of the sCT plans, deriving from the tissue densities. With the adapted REDmod table, the average percentage dose difference was reduced to -0.1% and the mean 3D gamma analysis improved to 92.9% ± 5.7% at 1%/1 mm. Conclusions: CT generation software is a viable solution for MRI-only radiotherapy planning. The option makes it relatively easy for departments to implement a MRI-only planning workflow for cancers of male and female pelvic anatomy.
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Nova |
2021 |
Richardson M, Skehan K, Wilton L, Sams J, Samuels J, Goodwin J, et al., 'Visualising the urethra for prostate radiotherapy planning', Journal of Medical Radiation Sciences, 68 282-288 (2021) [C1]
Introduction: The prostatic urethra is an organ at risk for prostate radiotherapy with genitourinary toxicities a common side effect. Many external beam radiation therapy protocol... [more]
Introduction: The prostatic urethra is an organ at risk for prostate radiotherapy with genitourinary toxicities a common side effect. Many external beam radiation therapy protocols call for urethral sparing, and with modulated radiotherapy techniques, the radiation dose distribution can be controlled so that maximum doses do not fall within the prostatic urethral volume. Whilst traditional diagnostic MRI sequences provide excellent delineation of the prostate, uncertainty often remains as to the true path of the urethra within the gland. This study aims to assess if a high-resolution isotropic 3D T2 MRI series can reduce inter-observer variability in urethral delineation for radiotherapy planning. Methods: Five independent observers contoured the prostatic urethra for ten patients on three data sets; a 2¿mm axial CT, a diagnostic 3¿mm axial T2 TSE MRI and a 0.9¿mm isotropic 3D T2 SPACE MRI. The observers were blinded from each other¿s contours. A Dice Similarity Coefficient (DSC) score was calculated using the intersection and union of the five observer contours vs an expert reference contour for each data set. Results: The mean DSC of the observer vs reference contours was 0.47 for CT, 0.62 for T2 TSE and 0.78 for T2 SPACE (P¿<¿0.001). Conclusions: The introduction of a 0.9¿mm isotropic 3D T2 SPACE MRI for treatment planning provides improved urethral visualisation and can lead to a significant reduction in inter-observer variation in prostatic urethral contouring.
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Nova |
2021 |
Calvo-Ortega JF, Greer PB, Hermida-López M, Moragues-Femenía S, Laosa-Bello C, Casals-Farran J, 'Validation of virtual water phantom software for pre-treatment verification of single-isocenter multiple-target stereotactic radiosurgery', Journal of Applied Clinical Medical Physics, 22 241-252 (2021) [C1]
The aim of this study was to benchmark the accuracy of the VIrtual Phantom Epid dose Reconstruction (VIPER) software for pre-treatment dosimetric verification of multiple-target s... [more]
The aim of this study was to benchmark the accuracy of the VIrtual Phantom Epid dose Reconstruction (VIPER) software for pre-treatment dosimetric verification of multiple-target stereotactic radiosurgery (SRS). VIPER is an EPID-based method to reconstruct a 3D dose distribution in a virtual phantom from in-air portal images. Validation of the VIPER dose calculation was assessed using several MLC-defined fields for a 6 MV photon beam. Central axis percent depth doses (PDDs) and output factors were measured with an ionization chamber in a water tank, while dose planes at a depth of 10¿cm in a solid flat phantom were acquired with radiochromic films. The accuracy of VIPER for multiple-target SRS plan verification was benchmarked against Monte Carlo simulations. Eighteen multiple-target SRS plans designed with the Eclipse treatment planning system were mapped to a cylindrical water phantom. For each plan, the 3D dose distribution reconstructed by VIPER within the phantom was compared with the Monte Carlo simulation, using a 3D gamma analysis. Dose differences (VIPER vs. measurements) generally within 2% were found for the MLC-defined fields, while film dosimetry revealed gamma passing rates (GPRs) =95% for a 3%/1¿mm criteria. For the 18 multiple-target SRS plans, average 3D GPRs greater than 93% and 98% for the 3%/2¿mm and 5%/2¿mm criteria, respectively. Our results validate the use of VIPER as a dosimetric verification tool for pre-treatment QA of single-isocenter multiple-target SRS plans. The method requires no setup time on the linac and results in an accurate 3D characterization of the delivered dose.
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Nova |
2021 |
Keall PJ, Sawant A, Berbeco R, Booth JT, Cho B, Cervino L, et al., 'AAPM Task Group 264: The safe clinical implementation of MLC tracking in radiotherapy', MEDICAL PHYSICS, 48 E44-E64 (2021)
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2020 |
Olaciregui-Ruiz I, Beddar S, Greer P, Jornet N, McCurdy B, Paiva-Fonseca G, et al., 'In vivo dosimetry in external beam photon radiotherapy: Requirements and future directions for research, development, and clinical practice', Physics and Imaging in Radiation Oncology, 15 108-116 (2020) [C1]
External beam radiotherapy with photon beams is a highly accurate treatment modality, but requires extensive quality assurance programs to confirm that radiation therapy will be o... [more]
External beam radiotherapy with photon beams is a highly accurate treatment modality, but requires extensive quality assurance programs to confirm that radiation therapy will be or was administered appropriately. In vivo dosimetry (IVD) is an essential element of modern radiation therapy because it provides the ability to catch treatment delivery errors, assist in treatment adaptation, and record the actual dose delivered to the patient. However, for various reasons, its clinical implementation has been slow and limited. The purpose of this report is to stimulate the wider use of IVD for external beam radiotherapy, and in particular of systems using electronic portal imaging devices (EPIDs). After documenting the current IVD methods, this report provides detailed software, hardware and system requirements for in vivo EPID dosimetry systems in order to help in bridging the current vendor-user gap. The report also outlines directions for further development and research. In vivo EPID dosimetry vendors, in collaboration with users across multiple institutions, are requested to improve the understanding and reduce the uncertainties of the system and to help in the determination of optimal action limits for error detection. Finally, the report recommends that automation of all aspects of IVD is needed to help facilitate clinical adoption, including automation of image acquisition, analysis, result interpretation, and reporting/documentation. With the guidance of this report, it is hoped that widespread clinical use of IVD will be significantly accelerated.
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Nova |
2020 |
Caillet V, Zwan B, Briggs A, Hardcastle N, Szymura K, Prodreka A, et al., 'Geometric uncertainty analysis of MLC tracking for lung SABR', PHYSICS IN MEDICINE AND BIOLOGY, 65 (2020) [C1]
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Nova |
2020 |
Puyati W, Khawne A, Barnes M, Zwan B, Greer P, Fuangrod T, 'Predictive quality assurance of a linear accelerator based on the machine performance check application using statistical process control and ARIMA forecast modeling', Journal of Applied Clinical Medical Physics, 21 73-82 (2020) [C1]
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Nova |
2020 |
Marcello M, Denham JW, Kennedy A, Haworth A, Steigler A, Greer PB, et al., 'Reduced Dose Posterior to Prostate Correlates With Increased PSA Progression in Voxel-Based Analysis of 3 Randomized Phase 3 Trials', International Journal of Radiation Oncology Biology Physics, 108 1304-1318 (2020) [C1]
Purpose: Reducing margins during treatment planning to decrease dose to healthy organs surrounding the prostate can risk inadequate treatment of subclinical disease. This study ai... [more]
Purpose: Reducing margins during treatment planning to decrease dose to healthy organs surrounding the prostate can risk inadequate treatment of subclinical disease. This study aimed to investigate whether lack of dose to subclinical disease is associated with increased disease progression by using high-quality prostate radiation therapy clinical trial data to identify anatomically localized regions where dose variation is associated with prostate-specific antigen progression (PSAP). Methods and Materials: Planned dose distributions for 683 patients of the Trans-Tasman Radiation Oncology Group 03.04 Randomized Androgen Deprivation and Radiotherapy (RADAR) trial were deformably registered onto a single exemplar computed tomography data set. These were divided into high-risk and intermediate-risk subgroups for analysis. Three independent voxel-based statistical tests, using permutation testing, Cox regression modeling, and least absolute shrinkage selection operator feature selection, were applied to identify regions where dose variation was associated with PSAP. Results from the intermediate-risk RADAR subgroup were externally validated by registering dose distributions from the RT01 (n = 388) and Conventional or Hypofractionated High Dose Intensity Modulated Radiotherapy for Prostate Cancer Trial (CHHiP) (n = 253) trials onto the same exemplar and repeating the tests on each of these data sets. Results: Voxel-based Cox regression revealed regions where reduced dose was correlated with increased prostate-specific androgen progression. Reduced dose in regions associated with coverage at the posterior prostate, in the immediate periphery of the posterior prostate, and in regions corresponding to the posterior oblique beams or posterior lateral beam boundary, was associated with increased PSAP for RADAR and RT01 patients, but not for CHHiP patients. Reduced dose to the seminal vesicle region was also associated with increased PSAP for RADAR intermediate-risk patients. Conclusions: Ensuring adequate dose coverage at the posterior prostate and immediately surrounding posterior region (including the seminal vesicles), where aggressive cancer spread may be occurring, may improve tumor control. It is recommended that particular care be taken when defining margins at the prostate posterior, acknowledging the trade-off between quality of life due to rectal dose and the preferences of clinicians and patients.
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Nova |
2020 |
Astono IP, Welsh JS, Chalup S, Greer P, 'Optimisation of 2D U-Net Model Components for Automatic Prostate Segmentation on MRI', Applied Sciences, 10 (2020) [C1]
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Nova |
2020 |
Marcello M, Denham JW, Kennedy A, Haworth A, Steigler A, Greer PB, et al., 'Relationships between rectal and perirectal doses and rectal bleeding or tenesmus in pooled voxel-based analysis of 3 randomised phase III trials.', Radiotherapy and Oncology, 150 (2020) [C1]
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Nova |
2020 |
Marcello M, Denham JW, Kennedy A, Haworth A, Steigler A, Greer PB, et al., 'Increased Dose to Organs in Urinary Tract Associates With Measures of Genitourinary Toxicity in Pooled Voxel-Based Analysis of 3 Randomized Phase III Trials', Frontiers in Oncology, 10 (2020) [C1]
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Nova |
2020 |
Keall P, Nguyen DT, O'Brien R, Hewson E, Ball H, Poulsen P, et al., 'Real-Time Image Guided Ablative Prostate Cancer Radiation Therapy: Results From the TROG 15.01 SPARK Trial', International Journal of Radiation Oncology Biology Physics, 107 530-538 (2020) [C1]
Purpose: Kilovoltage intrafraction monitoring (KIM) is a novel software platform implemented on standard radiation therapy systems and enabling real-time image guided radiation th... [more]
Purpose: Kilovoltage intrafraction monitoring (KIM) is a novel software platform implemented on standard radiation therapy systems and enabling real-time image guided radiation therapy (IGRT). In a multi-institutional prospective trial, we investigated whether real-time IGRT improved the accuracy of the dose patients with prostate cancer received during radiation therapy. Methods and Materials: Forty-eight patients with prostate cancer were treated with KIM-guided SABR with 36.25 Gy in 5 fractions. During KIM-guided treatment, the prostate motion was corrected for by either beam gating with couch shifts or multileaf collimator tracking. A dose reconstruction method was used to evaluate the dose delivered to the target and organs at risk with and without real-time IGRT. Primary outcome was the effect of real-time IGRT on dose distributions. Secondary outcomes included patient-reported outcomes and toxicity. Results: Motion correction occurred in =1 treatment for 88% of patients (42 of 48) and 51% of treatments (121 of 235). With real-time IGRT, no treatments had prostate clinical target volume (CTV) D98% dose 5% less than planned. Without real-time IGRT, 13 treatments (5.5%) had prostate CTV D98% doses 5% less than planned. The prostate CTV D98% dose with real-time IGRT was closer to the plan by an average of 1.0% (range, ¿2.8% to 20.3%). Patient outcomes showed no change in the 12-month patient-reported outcomes compared with baseline and no grade =3 genitourinary or gastrointestinal toxicities. Conclusions: Real-time IGRT is clinically effective for prostate cancer SABR.
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Nova |
2020 |
Hewson EA, Nguyen DT, O'Brien R, Poulsen PR, Booth JT, Greer P, et al., 'Is multileaf collimator tracking or gating a better intrafraction motion adaptation strategy? An analysis of the TROG 15.01 stereotactic prostate ablative radiotherapy with KIM (SPARK) trial', RADIOTHERAPY AND ONCOLOGY, 151 234-241 (2020)
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2020 |
Gholizadeh N, Pundavela J, Nagarajan R, Dona A, Quadrelli S, Biswas T, et al., 'Nuclear magnetic resonance spectroscopy of human body fluids and in vivo magnetic resonance spectroscopy: Potential role in the diagnosis and management of prostate cancer', Urologic Oncology: Seminars and Original Investigations, 38 150-173 (2020) [C1]
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Nova |
2020 |
Gholizadeh N, Simpson J, Ramadan S, Denham J, Lau P, Siddique S, et al., 'Voxel-based supervised machine learning of peripheral zone prostate cancer using noncontrast multiparametric MRI', Journal of Applied Clinical Medical Physics, 21 179-191 (2020) [C1]
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Nova |
2020 |
Verhaegen F, Fonseca GP, Johansen JG, Beaulieu L, Beddar S, Greer P, et al., 'Future directions of in vivo dosimetry for external beam radiotherapy and brachytherapy', PHYSICS & IMAGING IN RADIATION ONCOLOGY, 16 18-19 (2020)
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2020 |
Oultram S, Dempsey S, Greer P, Clapham M, 'Comparing Breast Conservation Surgery Seromas Contoured by Radiation Therapists versus those Contoured by a Radiation Oncologist in Radiation Therapy Planning for Early-Stage Breast Cancer', Journal of Medical Imaging and Radiation Sciences, 51 108-116 (2020) [C1]
Introduction: In the management of early-stage breast cancer using radiation therapy, computed tomography (CT) simulation is used to identify the breast conservation surgery (BCS)... [more]
Introduction: In the management of early-stage breast cancer using radiation therapy, computed tomography (CT) simulation is used to identify the breast conservation surgery (BCS) seroma as a proxy for the tumour bed. The delineation or contouring of the seroma is generally a task performed by a radiation oncologist (RO). With increasing patient numbers and other demands placed on ROs, the scope of practice for radiation therapists (RTs) is continually expanding, and the need for skills transfer from one profession to another has been investigated in recent years. This study aims to compare the BCS seroma volumes contoured by RTs with those contoured by ROs to add evidence in support of expanding the RTs' role in the treatment planning process in the management of early-stage breast cancer. Methods: A study was undertaken using the CT-simulation (CT-sim) data sets of patients with early-stage breast cancer treated in 2013. The CT-sim data sets had BCS seromas contoured by 1 of 5 ROs as part of routine clinical management. This study involved 4 RTs who each used the patient information to identify and contour breast seromas on 50 deidentified CT-sim data sets. Metrics used to compare RT versus RO contours included volume size, overlap between volumes, and geographical distance from the centre of volumes. Results: There were 50 CT-sim data sets with 1 RO contour and 4 RT contours analysed. The contour volumes of the 4 RTs and the ROs were assessed. Although there were 50 CT-sim data sets presented to each RT, analysis was carried out on 45, 43, 46, and 45 CT-sim data sets. There were no comparisons made where contours were not delineated. The contour volumes of the 4 RTs and the ROs were assessed with an interclass correlation coefficient, with a result of excellent reliability (0.975, 95% [0.963, 0.985]). The DICE similarity coefficient was used to compare the overlap of each RT contour with the RO contour; the results were favourable with mean (95% CI) DSCs 0.685, 0.640, 0.678, and 0.681, respectively. Comparing the RT and RO geographical centre of the seroma volumes, good to excellent reliability between the RTs and ROs was demonstrated (95% CI mean RO vs RT distances (mm): 3.75, 4.99, 7.71, and 3.39). There was no statistically significant difference between the distances (P = 0.65). Conclusion: BCS seromas contoured by RTs compared well with those contoured by an RO. This research has provided further evidence to support RTs in assuming additional contouring responsibilities in radiation therapy planning for patients with early-stage breast cancer.
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Nova |
2019 |
Greer P, Martin J, Sidhom M, Hunter P, Pichler P, Choi JH, et al., 'A Multi-center Prospective Study for Implementation of an MRI-Only Prostate Treatment Planning Workflow', FRONTIERS IN ONCOLOGY, 9 (2019) [C1]
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Nova |
2019 |
Largent A, Barateau A, Nunes J-C, Mylona E, Castelli J, Lafond C, et al., 'Comparison of Deep Learning-Based and Patch-Based Methods for Pseudo-CT Generation in MRI-Based Prostate Dose Planning', INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 105 1137-1150 (2019) [C1]
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Nova |
2019 |
Miri N, Vial P, Greer PB, 'Remote dosimetric auditing of clinical trials: The need for vendor specific models to convert images to dose', Journal of Applied Clinical Medical Physics, 20 175-183 (2019) [C1]
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Nova |
2019 |
Roach D, Holloway LC, Jameson MG, Dowling JA, Kennedy A, Greer PB, et al., 'Multi-observer contouring of male pelvic anatomy: Highly variable agreement across conventional and emerging structures of interest', JOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, 63 264-271 (2019) [C1]
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Nova |
2019 |
Kennedy A, Dowling J, Greer PB, Holloway L, Jameson MG, Roach D, et al., 'Similarity clustering-based atlas selection for pelvic CT image segmentation', Medical Physics, 46 2243-2250 (2019) [C1]
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Nova |
2019 |
Largent A, Nunes J-C, Saint-Jalmes H, Baxter J, Greer P, Dowling J, et al., 'Pseudo-CT Generation For MRI-Only Radiotherapy: Comparative Study Between A Generative Adversarial Network, A U-Net Network, A Patch-Based, And An Atlas Based Methods', 2019 IEEE 16th International Symposium On Biomedical Imaging (ISBI 2019), 1109-1113 (2019)
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Nova |
2019 |
Martin J, Keall P, Siva S, Greer P, Christie D, Moore K, et al., 'TROG 18.01 phase III randomised clinical trial of the Novel Integration of New prostate radiation schedules with adJuvant Androgen deprivation: NINJA study protocol', BMJ OPEN, 9 (2019)
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2019 |
Lim SB, Tsai CJ, Yu Y, Greer P, Fuangrod T, Hwang K, et al., 'Investigation of a Novel Decision Support Metric for Head and Neck Adaptive Radiation Therapy Using a Real-Time In Vivo Portal Dosimetry System', TECHNOLOGY IN CANCER RESEARCH & TREATMENT, 18 (2019)
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2019 |
Choi JH, Lee D, O'Connor L, Chalup S, Welsh JS, Dowling J, Greer PB, 'Bulk Anatomical Density Based Dose Calculation for Patient-Specific Quality Assurance of MRI-Only Prostate Radiotherapy', Frontiers in Oncology, 9 (2019) [C1]
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Nova |
2019 |
Gholizadeh N, Greer PB, Simpson J, Fu C, Al-iedani O, Lau P, et al., 'Supervised risk predictor of central gland lesions in prostate cancer using
Background: Due to the histological heterogeneity of the central gland, accurate detection of central gland prostate cancer remains a challenge. Purpose: To evaluate the efficacy ... [more]
Background: Due to the histological heterogeneity of the central gland, accurate detection of central gland prostate cancer remains a challenge. Purpose: To evaluate the efficacy of in vivo 3D 1H MR spectroscopic imaging (3D 1H MRSI) with a semi-localized adiabatic selective refocusing (sLASER) sequence and gradient-modulated offset-independent adiabatic (GOIA) pulses for detection of central gland prostate cancer. Additionally four risk models were developed to differentiate 1) normal vs. cancer, 2) low- vs. high-risk cancer, 3) low- vs. intermediate-risk cancer, and 4) intermediate- vs. high-risk cancer voxels. Study Type: Prospective. Subjects: Thirty-six patients with biopsy-proven central gland prostate cancer. Field Strength/Sequence: 3T MRI / 3D 1H MRSI using GOIA-sLASER. Assessment: Cancer and normal regions of interest (ROIs) were selected by an experienced radiologist and 1H MRSI voxels were placed within the ROIs to calculate seven metabolite signal ratios. Voxels were split into two subsets, 80% for model training and 20% for testing. Statistical Tests: Four support vector machine (SVM) models were built using the training dataset. The accuracy, sensitivity, and specificity for each model were calculated for the testing dataset. Results: High-quality MR spectra were obtained for the whole central gland of the prostate. The normal vs. cancer diagnostic model achieved the highest predictive performance with an accuracy, sensitivity, and specificity of 96.2%, 95.8%, and 93.1%, respectively. The accuracy, sensitivity, and specificity of the low- vs. high-risk cancer and low- vs. intermediate-risk cancer models were 82.5%, 89.2%, 70.2%, and 73.0%, 84.7%, 60.8%, respectively. The intermediate- vs. high-risk cancer model yielded an accuracy, sensitivity, and specificity lower than 55%. Data Conclusion: The GOIA-sLASER sequence with an external phased-array coil allows for fast assessment of central gland prostate cancer. The classification offers a promising diagnostic tool for discriminating normal vs. cancer, low- vs. high-risk cancer, and low- vs. intermediate-risk cancer. Level of Evidence: 2. Technical Efficacy: Stage 2. J. Magn. Reson. Imaging 2019;50:1926¿1936.
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Nova |
2019 |
Largent A, Barateau A, Nunes J-C, Lafond C, Greer PB, Dowling JA, et al., 'Pseudo-CT Generation for MRI-Only Radiation Therapy Treatment Planning: Comparison Among Patch-Based, Atlas-Based, and Bulk Density Methods', INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 103 479-490 (2019) [C1]
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Nova |
2019 |
Hewson EA, Nguyen DT, O Brien R, Kim JH, Montanaro T, Moodie T, et al., 'The accuracy and precision of the KIM motion monitoring system used in the multi-institutional TROG 15.01 Stereotactic Prostate Ablative Radiotherapy with KIM (SPARK) trial', Medical Physics, 46 4725-4737 (2019) [C1]
Purpose: Kilovoltage intrafraction monitoring (KIM) allows for real-time image guidance for tracking tumor motion in six-degrees-of-freedom (6DoF) on a standard linear accelerator... [more]
Purpose: Kilovoltage intrafraction monitoring (KIM) allows for real-time image guidance for tracking tumor motion in six-degrees-of-freedom (6DoF) on a standard linear accelerator. This study assessed the geometric accuracy and precision of KIM used to guide patient treatments in the TROG 15.01 multi-institutional Stereotactic Prostate Ablative Radiotherapy¿with KIM trial and investigated factors affecting accuracy and precision. Methods: Fractions from 44 patients with prostate cancer treated using KIM-guided SBRT were analyzed across four institutions, on two different linear accelerator models and two different beam models (6 MV¿and 10¿MV FFF). The geometric accuracy and precision of KIM was assessed from over 33¿000¿images (translation) and over 9000 images (rotation) by comparing the real-time measured motion to retrospective kV/MV triangulation. Factors potentially affecting accuracy, including contrast-to-noise ratio (CNR) of kV images and incorrect marker segmentation, were also investigated. Results: The geometric accuracy and precision did not depend on treatment institution, beam model or motion magnitude, but was correlated with gantry angle. The centroid geometric accuracy and precision of the KIM system for SABR prostate treatments was 0.0¿±¿0.5, 0.0¿±¿0.4 and 0.1¿±¿0.3¿mm for translation, and¿-0.1¿±¿0.6°, -0.1¿±¿1.4° and¿-0.1¿±¿1.0° for rotation in the AP, LR and SI directions respectively. Centroid geometric error exceeded 2¿mm for 0.05% of this dataset. No significant relationship was found between large geometric error and CNR or marker segmentation correlation. Conclusions: This study demonstrated the ability of KIM to locate the prostate with accuracy below other uncertainties in radiotherapy treatments, and the feasibility for KIM to be implemented across multiple institutions.
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2019 |
Kaur G, Lehmann J, Greer P, Simpson J, 'Assessment of the accuracy of truebeam intrafraction motion review (IMR) system for prostate treatment guidance', AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE, 42 585-598 (2019) [C1]
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Nova |
2019 |
Pryor D, Sidhom M, Arumugam S, Bucci J, Gallagher S, Smart J, et al., 'Phase 2 Multicenter Study of Gantry-Based Stereotactic Radiotherapy Boost for Intermediate and High Risk Prostate Cancer (PROMETHEUS)', FRONTIERS IN ONCOLOGY, 9 (2019) [C1]
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Nova |
2019 |
Gholizadeh N, Fuangrod T, Greer PB, Lau P, Ramadan S, Simpson J, 'An inter-centre statistical scale standardisation for quantitatively evaluating prostate tissue on T2-weighted MRI', Australasian Physical and Engineering Sciences in Medicine (APES), 42 137-147 (2019) [C1]
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Nova |
2019 |
Gholizadeh N, Greer PB, Simpson J, Denham J, Lau P, Dowling J, et al., 'Characterization of prostate cancer using diffusion tensor imaging: a new perspective', European Journal of Radiology, 110 112-120 (2019) [C1]
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Nova |
2018 |
Siciarz P, McCurdy B, Alshafa F, Greer P, Hatton J, Wright P, 'Evaluation of CT to CBCT non-linear dense anatomical block matching registration for prostate patients', Biomedical Physics and Engineering Express, 4 (2018)
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2018 |
Paganelli C, Lee D, Kipritidis J, Whelan B, Greer PB, Baroni G, et al., 'Feasibility study on 3D image reconstruction from 2D orthogonal cine-MRI for MRI-guided radiotherapy', JOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, 62 389-400 (2018) [C1]
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Nova |
2018 |
Barnes MP, Menk FW, Lamichhane BP, Greer PB, 'A proposed method for linear accelerator photon beam steering using EPID', JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, 19 591-597 (2018) [C1]
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Nova |
2018 |
Lee D, Greer PB, Paganelli C, Ludbrook JJ, Kim T, Keall P, 'Audiovisual biofeedback improves the correlation between internal/external surrogate motion and lung tumor motion', MEDICAL PHYSICS, 45 1009-1017 (2018) [C1]
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Nova |
2018 |
Keall PJ, Colvill E, O'Brien R, Caillet V, Eade T, Kneebone A, et al., 'Electromagnetic-Guided MLC Tracking Radiation Therapy for Prostate Cancer Patients: Prospective Clinical Trial Results', INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 101 387-395 (2018) [C1]
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Nova |
2018 |
Kennedy A, Dowling J, Greer PB, Ebert MA, 'Estimation of Hounsfield unit conversion parameters for pelvic CT images', AUSTRALASIAN PHYSICAL & ENGINEERING SCIENCES IN MEDICINE, 41 739-745 (2018) [C1]
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Nova |
2018 |
Owrangi AM, Greer PB, Glide-Hurst CK, 'MRI-only treatment planning: benefits and challenges', PHYSICS IN MEDICINE AND BIOLOGY, 63 (2018) [C1]
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Nova |
2018 |
Hanlon MC, Ludbrook J, Jovanovic K, Greer P, Martin JM, 'Fostering a culture of research within a clinical radiation oncology department', Journal of Medical Imaging and Radiation Oncology, 62 102-108 (2018) [C1]
Introduction: Support and investment in increasing a research-active culture in clinical practice needs to be translated at the department and hospital levels as well as regional,... [more]
Introduction: Support and investment in increasing a research-active culture in clinical practice needs to be translated at the department and hospital levels as well as regional, state and national levels. We aimed to improve the research culture of our department, to enable more clinical staff to become more research competent and research active. Methods: We describe and discuss the appointment of a Director of Research and a Research Coordinator into our already-research-active department and the interactions at the research¿clinical interface. By identifying barriers and instituting enablers which ameliorate their effect, we explore how a clinical department can utilize the resources already available with the goal of developing a more confident and competent clinician-researcher culture as measured by a range of research metrics. Results: We observed an improved research culture within our department. Our department's improved research culture was reflected by increased numbers of peer-reviewed publications (of 30%), research students/supervisions (of 60%) and engagement of external speakers. We also observed double the number of first-authored peer-reviewed articles and a growth in conference presentations, posters and speaker invitations/awards. In the majority of the research performance metrics tracked, there was a steady improvement noted over the four years monitored. Conclusions: By responding to the barriers of staff (such as time, expertise and ideas) with structural and personal enablers, as well as funded resources, it is possible to develop research capacity and confidence in a clinical setting.
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Nova |
2018 |
Arabi H, Dowling JA, Burgos N, Han X, Greer PB, Koutsouvelis N, Zaidi H, 'Comparative study of algorithms for synthetic CT generation from MRI: Consequences for MRI-guided radiation planning in the pelvic region', Medical Physics, 45 5218-5233 (2018) [C1]
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Nova |
2018 |
Barnes MP, Pomare D, Menk FW, Moraro B, Greer PB, 'Evaluation of the truebeam machine performance check (MPC): OBI X-ray tube alignment procedure', Journal of Applied Clinical Medical Physics, 19 68-78 (2018) [C1]
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Nova |
2018 |
Roach D, Jameson MG, Dowling JA, Ebert MA, Greer PB, Kennedy AM, et al., 'Correlations between contouring similarity metrics and simulated treatment outcome for prostate radiotherapy', PHYSICS IN MEDICINE AND BIOLOGY, 63 (2018) [C1]
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Nova |
2018 |
Miri N, Legge K, Colyvas K, Lehmann J, Vial P, Moore A, et al., 'A remote EPID-based dosimetric TPS-planned audit of centers for clinical trials: outcomes and analysis of contributing factors', RADIATION ONCOLOGY, 13 (2018) [C1]
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Nova |
2017 |
Miri N, Lehmann J, Legge K, Vial P, Greer PB, 'Virtual EPID standard phantom audit (VESPA) for remote IMRT and VMAT credentialing', PHYSICS IN MEDICINE AND BIOLOGY, 62 4293-4299 (2017) [C1]
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Nova |
2017 |
Zwan BJ, Barnes MP, Hindmarsh J, Lim SB, Lovelock DM, Fuangrod T, et al., 'Commissioning and quality assurance for VMAT delivery systems: An efficient time-resolved system using real-time EPID imaging: An', Medical Physics, 44 3909-3922 (2017) [C1]
Purpose: An ideal commissioning and quality assurance (QA) program for Volumetric Modulated Arc Therapy (VMAT) delivery systems should assess the performance of each individual dy... [more]
Purpose: An ideal commissioning and quality assurance (QA) program for Volumetric Modulated Arc Therapy (VMAT) delivery systems should assess the performance of each individual dynamic component as a function of gantry angle. Procedures within such a program should also be time-efficient, independent of the delivery system and be sensitive to all types of errors. The purpose of this work is to develop a system for automated time-resolved commissioning and QA of VMAT control systems which meets these criteria. Methods: The procedures developed within this work rely solely on images obtained, using an electronic portal imaging device (EPID) without the presence of a phantom. During the delivery of specially designed VMAT test plans, EPID frames were acquired at 9.5 Hz, using a frame grabber. The set of test plans was developed to individually assess the performance of the dose delivery and multileaf collimator (MLC) control systems under varying levels of delivery complexities. An in-house software tool was developed to automatically extract features from the EPID images and evaluate the following characteristics as a function of gantry angle: dose delivery accuracy, dose rate constancy, beam profile constancy, gantry speed constancy, dynamic MLC positioning accuracy, MLC speed and acceleration constancy, and synchronization between gantry angle, MLC positioning and dose rate. Machine log files were also acquired during each delivery and subsequently compared to information extracted from EPID image frames. Results: The largest difference between measured and planned dose at any gantry angle was 0.8% which correlated with rapid changes in dose rate and gantry speed. For all other test plans, the dose delivered was within 0.25% of the planned dose for all gantry angles. Profile constancy was not found to vary with gantry angle for tests where gantry speed and dose rate were constant, however, for tests with varying dose rate and gantry speed, segments with lower dose rate and higher gantry speed exhibited less profile stability. MLC positional accuracy was not observed to be dependent on the degree of interdigitation. MLC speed was measured for each individual leaf and slower leaf speeds were shown to be compensated for by lower dose rates. The test procedures were found to be sensitive to 1 mm systematic MLC errors, 1 mm random MLC errors, 0.4 mm MLC gap errors and synchronization errors between the MLC, dose rate and gantry angle controls systems of 1. In general, parameters measured by both EPID and log files agreed with the plan, however, a greater average departure from the plan was evidenced by the EPID measurements. Conclusion: QA test plans and analysis methods have been developed to assess the performance of each dynamic component of VMAT deliveries individually and as a function of gantry angle. This methodology relies solely on time-resolved EPID imaging without the presence of a phantom and has been shown to be sensitive to a range of delivery errors. The procedures developed in this work are both comprehensive and time-efficient and can be used for streamlined commissioning and QA of VMAT delivery systems.
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Nova |
2017 |
Hussein M, Clementel E, Eaton DJ, Greer PB, Haworth A, Ishikura S, et al., 'A virtual dosimetry audit - Towards transferability of gamma index analysis between clinical trial QA groups', RADIOTHERAPY AND ONCOLOGY, 125 398-404 (2017) [C1]
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Nova |
2017 |
Wyatt J, Dowling JA, Kelly CG, McKenna J, Johnstone E, Speight R, et al., 'Investigating the generalisation of an atlas-based synthetic-CT algorithm to another centre and MR scanner for prostate MR-only radiotherapy.', Physics in Medicine and Biology, 62 N548-N560 (2017) [C1]
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Nova |
2017 |
Ghose S, Greer PB, Sun J, Pichler P, Rivest-Henault D, Mitra J, et al., 'Regression and statistical shape model based substitute CT generation for MRI alone external beam radiation therapy from standard clinical MRI sequences.', Phys Med Biol, 62 8566-8580 (2017) [C1]
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Nova |
2017 |
Legge K, Nguyen D, Ng JA, Wilton L, Richardson M, Booth J, et al., 'Real-time intrafraction prostate motion during linac based stereotactic radiotherapy with rectal displacement.', Journal of applied clinical medical physics, 18 130-136 (2017) [C1]
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Nova |
2017 |
Lee D, Greer PB, Lapuz C, Ludbrook J, Hunter P, Arm J, et al., 'Audiovisual biofeedback guided breath-hold improves lung tumor position reproducibility and volume consistency', Advances in Radiation Oncology, 2 354-362 (2017) [C1]
Purpose Respiratory variation can increase the variability of tumor position and volume, accounting for larger treatment margins and longer treatment times. Audiovisual biofeedbac... [more]
Purpose Respiratory variation can increase the variability of tumor position and volume, accounting for larger treatment margins and longer treatment times. Audiovisual biofeedback as a breath-hold technique could be used to improve the reproducibility of lung tumor positions at inhalation and exhalation for the radiation therapy of mobile lung tumors. This study aimed to assess the impact of audiovisual biofeedback breath-hold (AVBH) on interfraction lung tumor position reproducibility and volume consistency for respiratory-gated lung cancer radiation therapy. Methods Lung tumor position and volume were investigated in 9 patients with lung cancer who underwent a breath-hold training session with AVBH before 2 magnetic resonance imaging (MRI) sessions. During the first MRI session (before treatment), inhalation and exhalation breath-hold 3-dimensional MRI scans with conventional breath-hold (CBH) using audio instructions alone and AVBH were acquired. The second MRI session (midtreatment) was repeated within 6 weeks after the first session. Gross tumor volumes (GTVs) were contoured on each dataset. CBH and AVBH were compared in terms of tumor position reproducibility as assessed by GTV centroid position and position range (defined as the distance of GTV centroid position between inhalation and exhalation) and tumor volume consistency as assessed by GTV between inhalation and exhalation. Results Compared with CBH, AVBH improved the reproducibility of interfraction GTV centroid position by 46% (P = .009) from 8.8 mm to 4.8 mm and GTV position range by 69% (P = .052) from 7.4 mm to 2.3 mm. Compared with CBH, AVBH also improved the consistency of intrafraction GTVs by 70% (P = .023) from 7.8 cm3 to 2.5 cm3. Conclusions This study demonstrated that audiovisual biofeedback can be used to improve the reproducibility and consistency of breath-hold lung tumor position and volume, respectively. These results may provide a pathway to achieve more accurate lung cancer radiation treatment in addition to improving various medical imaging and treatments by using breath-hold procedures.
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Nova |
2017 |
Koivula L, Kapanen M, Seppala T, Collan J, Dowling JA, Greer PB, et al., 'Intensity-based dual model method for generation of synthetic CT images from standard T2-weighted MR images - Generalized technique for four different MR scanners', RADIOTHERAPY AND ONCOLOGY, 125 411-419 (2017) [C1]
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Nova |
2017 |
Keall P, Doan TN, O'Brien R, Booth J, Greer P, Poulsen P, et al., 'Stereotactic prostate adaptive radiotherapy utilising kilovoltage intrafraction monitoring: the TROG 15.01 SPARK trial', BMC CANCER, 17 (2017)
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2017 |
Barnes MP, Greer PB, 'Evaluation of the TrueBeam machine performance check (MPC) beam constancy checks for flattened and flattening filter-free (FFF) photon beams', JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, 18 139-150 (2017) [C1]
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Nova |
2017 |
Barnes MP, Greer PB, 'Evaluation of the truebeam machine performance check (MPC): mechanical and collimation checks', JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, 18 56-66 (2017) [C1]
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Nova |
2017 |
Barnes MP, Greer PB, 'Evaluation of the truebeam machine performance check (MPC) geometric checks for daily IGRT geometric accuracy quality assurance', JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS, 18 200-206 (2017) [C1]
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Nova |
2017 |
Nguyen DT, O'Brien R, Kim J-H, Huang C-Y, Wilton L, Greer P, et al., 'The first clinical implementation of a real-time six degree of freedom target tracking system during radiation therapy based on Kilovoltage Intrafraction Monitoring (KIM)', RADIOTHERAPY AND ONCOLOGY, 123 37-42 (2017) [C1]
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Nova |
2017 |
Fuangrod T, Greer PB, Zwan BJ, Barnes MP, Lehmann J, 'A novel and independent method for time-resolved gantry angle quality assurance for VMAT', Journal of Applied Clinical Medical Physics, 18 134-142 (2017) [C1]
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Nova |
2017 |
Miri N, Lehmann J, Legge K, Zwan BJ, Vial P, Greer PB, 'Remote dosimetric auditing for intensity modulated radiotherapy: A pilot study', Physics and Imaging in Radiation Oncology, 4 26-31 (2017)
Background and Purpose: Electronic portal imaging devices (EPIDs) can be used to reconstruct dose inside a virtual phantom. This work aims to study the feasibility of using this m... [more]
Background and Purpose: Electronic portal imaging devices (EPIDs) can be used to reconstruct dose inside a virtual phantom. This work aims to study the feasibility of using this method for remote dosimetry auditing of clinical trials. Materials and Methods: Six centres participated in an intensity modulated radiotherapy (IMRT) pilot study of this new audit approach. Each centre produced a head and neck (HN) and post-prostatectomy (PP) trial plan and transferred the plans to virtual phantoms to calculate a reference dose distribution. They acquired in-air images of the treatment fields along with calibration images using their EPID. These data were sent to the central site where the images were converted to 2D field-by-field doses in a flat virtual water phantom and to 3D combined field doses in a cylindrical virtual phantom for comparison with corresponding reference dose distributions. Additional test images were used to assess the accuracy of the method when using different EPIDs. Results: Field-by-field 2D analysis yielded mean gamma pass-rates of 99.6% (±0.3%) and 99.6% (±0.6%) for HN and PP plans respectively (3%/3 mm, doses greater than 10% global max). 3D combined field analysis gave mean pass-rates of 97.9% (±2.6%) and 97.9% (±1.8%) for the HN and PP plans. Dosimetry tests revealed some field size limitations of the EPIDs. Conclusions: The remote auditing methodology using EPIDs is feasible and potentially an inexpensive method.
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2017 |
Legge K, Greer PB, Keall PJ, Booth JT, Arumugam S, Moodie T, et al., 'Technical note: TROG 15.01 SPARK trial multi-institutional imaging dose measurement', Journal of Applied Clinical Medical Physics, 18 358-363 (2017) [C1]
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Nova |
2017 |
Legge K, Greer PB, O'Connor DJ, Wilton L, Richardson M, Hunter P, et al., 'Real-time in vivo rectal wall dosimetry using MOSkin detectors during linac based stereotactic radiotherapy with rectal displacement', RADIATION ONCOLOGY, 12 (2017) [C1]
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Nova |
2017 |
Fuangrod T, Greer PB, Simpson J, Zwan BJ, Middleton RH, 'A method for evaluating treatment quality using in vivo EPID dosimetry and statistical process control in radiation therapy', INTERNATIONAL JOURNAL OF HEALTH CARE QUALITY ASSURANCE, 30 90-102 (2017) [C1]
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Nova |
2016 |
Lee D, Greer PB, Pollock S, Kim T, Keall P, 'Quantifying the accuracy of the tumor motion and area as a function of acceleration factor for the simulation of the dynamic keyhole magnetic resonance imaging method', Medical Physics, 43 2639-2648 (2016) [C1]
Purpose: The dynamic keyhole is a newMRimage reconstruction method for thoracic and abdominal MR imaging. To date, this method has not been investigated with cancer patient magnet... [more]
Purpose: The dynamic keyhole is a newMRimage reconstruction method for thoracic and abdominal MR imaging. To date, this method has not been investigated with cancer patient magnetic resonance imaging (MRI) data. The goal of this study was to assess the dynamic keyhole method for the task of lung tumor localization using cine-MR images reconstructed in the presence of respiratory motion. Methods: The dynamic keyhole method utilizes a previously acquired a library of peripheral k-space datasets at similar displacement and phase (where phase is simply used to determine whether the breathing is inhale to exhale or exhale to inhale) respiratory bins in conjunction with central k-space datasets (keyhole) acquired. External respiratory signals drive the process of sorting, matching, and combining the two k-space streams for each respiratory bin, thereby achieving faster image acquisition without substantial motion artifacts. This study was the first that investigates the impact of k-space undersampling on lung tumor motion and area assessment across clinically available techniques (zero-filling and conventional keyhole). In this study, the dynamic keyhole, conventional keyhole and zero-filling methods were compared to full k-space dataset acquisition by quantifying (1) the keyhole size required for central k-space datasets for constant image quality across sixty four cine-MRI datasets from nine lung cancer patients, (2) the intensity difference between the original and reconstructed images in a constant keyhole size, and (3) the accuracy of tumor motion and area directly measured by tumor autocontouring. Results: For constant image quality, the dynamic keyhole method, conventional keyhole, and zerofilling methods required 22%, 34%, and 49% of the keyhole size (P < 0.0001), respectively, compared to the full k-space image acquisition method. Compared to the conventional keyhole and zero-filling reconstructed images with the keyhole size utilized in the dynamic keyhole method, an average intensity difference of the dynamic keyhole reconstructed images (P < 0.0001) was minimal, and resulted in the accuracy of tumor motion within 99.6% (P < 0.0001) and the accuracy of tumor area within 98.0% (P < 0.0001) for lung tumor monitoring applications. Conclusions: This study demonstrates that the dynamic keyhole method is a promising technique for clinical applications such as image-guided radiation therapy requiring the MR monitoring of thoracic tumors. Based on the results from this study, the dynamic keyhole method could increase the imaging frequency by up to a factor of five compared with full k-space methods for real-time lung tumor MRI.
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Nova |
2016 |
Barnes MP, Greer PB, 'Time-resolved beam symmetry measurement for VMAT commissioning and quality assurance.', J Appl Clin Med Phys, 17 220-230 (2016)
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Nova |
2016 |
Barnes MP, Rowshanfarzad P, Greer PB, 'VMAT linear accelerator commissioning and quality assurance: dose control and gantry speed tests.', J Appl Clin Med Phys, 17 246-261 (2016)
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2016 |
Lee D, Greer PB, Ludbrook J, Arm J, Hunter P, Pollock S, et al., 'Audiovisual Biofeedback Improves Cine-Magnetic Resonance Imaging Measured Lung Tumor Motion Consistency', INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 94 628-636 (2016) [C1]
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Nova |
2016 |
Zwan BJ, Barnes MP, Fuangrod T, Stanton CJ, O'Connor DJ, Keall PJ, Greer PB, 'An EPID-based system for gantry-resolved MLC quality assurance for VMAT.', J Appl Clin Med Phys, 17 1-18 (2016)
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2016 |
Miri N, Keller P, Zwan BJ, Greer P, 'EPID-based dosimetry to verify IMRT planar dose distribution for the aS1200 EPID and FFF beams.', Journal of applied clinical medical physics, 17 292-304 (2016)
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2016 |
Fuangrod T, Greer PB, Woodruff HC, Simpson J, Bhatia S, Zwan B, et al., 'Investigation of a real-time EPID-based patient dose monitoring safety system using site-specific control limits', RADIATION ONCOLOGY, 11 (2016) [C1]
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Nova |
2016 |
Seregni M, Paganelli C, Lee D, Greer PB, Baroni G, Keall PJ, Riboldi M, 'Motion prediction in MRI-guided radiotherapy based on interleaved orthogonal cine-MRI', Physics in Medicine and Biology, 61 872-887 (2016) [C1]
In-room cine-MRI guidance can provide non-invasive target localization during radiotherapy treatment. However, in order to cope with finite imaging frequency and system latencies ... [more]
In-room cine-MRI guidance can provide non-invasive target localization during radiotherapy treatment. However, in order to cope with finite imaging frequency and system latencies between target localization and dose delivery, tumour motion prediction is required. This work proposes a framework for motion prediction dedicated to cine-MRI guidance, aiming at quantifying the geometric uncertainties introduced by this process for both tumour tracking and beam gating. The tumour position, identified through scale invariant features detected in cine-MRI slices, is estimated at high-frequency (25 Hz) using three independent predictors, one for each anatomical coordinate. Linear extrapolation, auto-regressive and support vector machine algorithms are compared against systems that use no prediction or surrogate-based motion estimation. Geometric uncertainties are reported as a function of image acquisition period and system latency. Average results show that the tracking error RMS can be decreased down to a [0.2; 1.2] mm range, for acquisition periods between 250 and 750 ms and system latencies between 50 and 300 ms. Except for the linear extrapolator, tracking and gating prediction errors were, on average, lower than those measured for surrogate-based motion estimation. This finding suggests that cine-MRI guidance, combined with appropriate prediction algorithms, could relevantly decrease geometric uncertainties in motion compensated treatments.
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Nova |
2016 |
Chandra SS, Dowling JA, Greer PB, Martin J, Wratten C, Pichler P, et al., 'Fast automated segmentation of multiple objects via spatially weighted shape learning', Physics in Medicine and Biology, 61 8070-8084 (2016) [C1]
Active shape models (ASMs) have proved successful in automatic segmentation by using shape and appearance priors in a number of areas such as prostate segmentation, where accurate... [more]
Active shape models (ASMs) have proved successful in automatic segmentation by using shape and appearance priors in a number of areas such as prostate segmentation, where accurate contouring is important in treatment planning for prostate cancer. The ASM approach however, is heavily reliant on a good initialisation for achieving high segmentation quality. This initialisation often requires algorithms with high computational complexity, such as three dimensional (3D) image registration. In this work, we present a fast, self-initialised ASM approach that simultaneously fits multiple objects hierarchically controlled by spatially weighted shape learning. Prominent objects are targeted initially and spatial weights are progressively adjusted so that the next (more difficult, less visible) object is simultaneously initialised using a series of weighted shape models. The scheme was validated and compared to a multi-atlas approach on 3D magnetic resonance (MR) images of 38 cancer patients and had the same (mean, median, inter-rater) Dice's similarity coefficients of (0.79, 0.81, 0.85), while having no registration error and a computational time of 12-15 min, nearly an order of magnitude faster than the multi-atlas approach.
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Nova |
2016 |
Kron T, Lehmann J, Greer PB, 'Dosimetry of ionising radiation in modern radiation oncology', PHYSICS IN MEDICINE AND BIOLOGY, 61 R167-R205 (2016) [C1]
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Nova |
2016 |
Ghose S, Mitra J, Rivest-Hénault D, Fazlollahi A, Stanwell P, Pichler P, et al., 'MRI-alone radiation therapy planning for prostate cancer: Automatic fiducial marker detection', Medical Physics, 43 2218-2228 (2016) [C1]
Purpose: The feasibility of radiation therapy treatment planning using substitute computed tomography (sCT) generated from magnetic resonance images (MRIs) has been demonstrated b... [more]
Purpose: The feasibility of radiation therapy treatment planning using substitute computed tomography (sCT) generated from magnetic resonance images (MRIs) has been demonstrated by a number of research groups. One challenge with an MRI-alone workflow is the accurate identification of intraprostatic gold fiducial markers, which are frequently used for prostate localization prior to each dose delivery fraction. This paper investigates a template-matching approach for the detection of these seeds in MRI. Methods: Two different gradient echo T1 and T2* weighted MRI sequences were acquired from fifteen prostate cancer patients and evaluated for seed detection. For training, seed templates from manual contours were selected in a spectral clustering manifold learning framework. This aids in clustering "similar" gold fiducial markers together. The marker with the minimum distance to a cluster centroid was selected as the representative template of that cluster during training. During testing, Gaussian mixture modeling followed by a Markovian model was used in automatic detection of the probable candidates. The probable candidates were rigidly registered to the templates identified from spectral clustering, and a similarity metric is computed for ranking and detection. Results: A fiducial detection accuracy of 95% was obtained compared to manual observations. Expert radiation therapist observers were able to correctly identify all three implanted seeds on 11 of the 15 scans (the proposed method correctly identified all seeds on 10 of the 15). Conclusions: An novel automatic framework for gold fiducial marker detection in MRI is proposed and evaluated with detection accuracies comparable to manual detection. When radiation therapists are unable to determine the seed location in MRI, they refer back to the planning CT (only available in the existing clinical framework); similarly, an automatic quality control is built into the automatic software to ensure that all gold seeds are either correctly detected or a warning is raised for further manual intervention.
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Nova |
2015 |
Loh J, Baker K, Sridharan S, Greer P, Wratten C, Capp A, et al., 'Infections after fiducial marker implantation for prostate radiotherapy: are we underestimating the risks?', RADIATION ONCOLOGY, 10 (2015) [C1]
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Nova |
2015 |
Van Uytven E, Van Beek T, McCowan PM, Chytyk-Praznik K, Greer PB, McCurdy BMC, 'Validation of a method for in vivo 3D dose reconstruction for IMRT and VMAT treatments using on-treatment EPID images and a model-based forward-calculation algorithm', Medical Physics, 42 6945-6954 (2015) [C1]
Purpose: Radiation treatments are trending toward delivering higher doses per fraction under stereotactic radiosurgery and hypofractionated treatment regimens. There is a need for... [more]
Purpose: Radiation treatments are trending toward delivering higher doses per fraction under stereotactic radiosurgery and hypofractionated treatment regimens. There is a need for accurate 3D in vivo patient dose verification using electronic portal imaging device (EPID) measurements. This work presents a model-based technique to compute full three-dimensional patient dose reconstructed from on-treatment EPID portal images (i.e., transmission images). Methods: EPID dose is converted to incident fluence entering the patient using a series of steps which include converting measured EPID dose to fluence at the detector plane and then back-projecting the primary source component of the EPID fluence upstream of the patient. Incident fluence is then recombined with predicted extra-focal fluence and used to calculate 3D patient dose via a collapsed-cone convolution method. This method is implemented in an iterative manner, although in practice it provides accurate results in a single iteration. The robustness of the dose reconstruction technique is demonstrated with several simple slab phantom and nine anthropomorphic phantom cases. Prostate, head and neck, and lung treatments are all included as well as a range of delivery techniques including VMAT and dynamic intensity modulated radiation therapy (IMRT). Results: Results indicate that the patient dose reconstruction algorithm compares well with treatment planning system computed doses for controlled test situations. For simple phantom and square field tests, agreement was excellent with a 2%/2 mm 3D chi pass rate .98.9%. On anthropomorphic phantoms, the 2%/2 mm 3D chi pass rates ranged from 79.9% to 99.9% in the planning target volume (PTV) region and 96.5% to 100% in the low dose region (>20% of prescription, excluding PTV and skin build-up region). Conclusions: An algorithm to reconstruct delivered patient 3D doses from EPID exit dosimetry measurements was presented. The method was applied to phantom and patient data sets, as well as for dynamic IMRT and VMAT delivery techniques. Results indicate that the EPID dose reconstruction algorithm presented in this work is suitable for clinical implementation.
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Nova |
2015 |
Herschtal A, te Marvelde L, Mengersen K, Hosseinifard Z, Foroudi F, Devereux T, et al., 'Calculating radiotherapy margins based on Bayesian modelling of patient specific random errors', PHYSICS IN MEDICINE AND BIOLOGY, 60 1793-1805 (2015) [C1]
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Nova |
2015 |
Dowling JA, Sun J, Pichler P, Rivest-Hénault D, Ghose S, Richardson H, et al., 'Automatic substitute computed tomography generation and contouring for magnetic resonance imaging (MRI)-alone external beam radiation therapy from standard MRI sequences', International Journal of Radiation Oncology Biology Physics, 93 1144-1153 (2015) [C1]
Purpose To validate automatic substitute computed tomography CT (sCT) scans generated from standard T2-weighted (T2w) magnetic resonance (MR) pelvic scans for MR-Sim prostate trea... [more]
Purpose To validate automatic substitute computed tomography CT (sCT) scans generated from standard T2-weighted (T2w) magnetic resonance (MR) pelvic scans for MR-Sim prostate treatment planning. Patients and Methods A Siemens Skyra 3T MR imaging (MRI) scanner with laser bridge, flat couch, and pelvic coil mounts was used to scan 39 patients scheduled for external beam radiation therapy for localized prostate cancer. For sCT generation a whole-pelvis MRI scan (1.6 mm 3-dimensional isotropic T2w SPACE [Sampling Perfection with Application optimized Contrasts using different flip angle Evolution] sequence) was acquired. Three additional small field of view scans were acquired: T2w, T2*w, and T1w flip angle 80° for gold fiducials. Patients received a routine planning CT scan. Manual contouring of the prostate, rectum, bladder, and bones was performed independently on the CT and MR scans. Three experienced observers contoured each organ on MRI, allowing interobserver quantification. To generate a training database, each patient CT scan was coregistered to their whole-pelvis T2w using symmetric rigid registration and structure-guided deformable registration. A new multi-atlas local weighted voting method was used to generate automatic contours and sCT results. Results The mean error in Hounsfield units between the sCT and corresponding patient CT (within the body contour) was 0.6 ± 14.7 (mean ± 1 SD), with a mean absolute error of 40.5 ± 8.2 Hounsfield units. Automatic contouring results were very close to the expert interobserver level (Dice similarity coefficient): prostate 0.80 ± 0.08, bladder 0.86 ± 0.12, rectum 0.84 ± 0.06, bones 0.91 ± 0.03, and body 1.00 ± 0.003. The change in monitor units between the sCT-based plans relative to the gold standard CT plan for the same dose prescription was found to be 0.3% ± 0.8%. The 3-dimensional ¿ pass rate was 1.00 ± 0.00 (2 mm/2%). Conclusions The MR-Sim setup and automatic sCT generation methods using standard MR sequences generates realistic contours and electron densities for prostate cancer radiation therapy dose planning and digitally reconstructed radiograph generation.
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Nova |
2015 |
Paganelli C, Lee D, Greer PB, Baroni G, Riboldi M, Keall P, 'Quantification of lung tumor rotation with automated landmark extraction using orthogonal cine MRI images', Physics in Medicine and Biology, 60 7165-7178 (2015) [C1]
The quantification of tumor motion in sites affected by respiratory motion is of primary importance to improve treatment accuracy. To account for motion, different studies analyze... [more]
The quantification of tumor motion in sites affected by respiratory motion is of primary importance to improve treatment accuracy. To account for motion, different studies analyzed the translational component only, without focusing on the rotational component, which was quantified in a few studies on the prostate with implanted markers. The aim of our study was to propose a tool able to quantify lung tumor rotation without the use of internal markers, thus providing accurate motion detection close to critical structures such as the heart or liver. Specifically, we propose the use of an automatic feature extraction method in combination with the acquisition of fast orthogonal cine MRI images of nine lung patients. As a preliminary test, we evaluated the performance of the feature extraction method by applying it on regions of interest around (i) the diaphragm and (ii) the tumor and comparing the estimated motion with that obtained by (i) the extraction of the diaphragm profile and (ii) the segmentation of the tumor, respectively. The results confirmed the capability of the proposed method in quantifying tumor motion. Then, a point-based rigid registration was applied to the extracted tumor features between all frames to account for rotation. The median lung rotation values were -0.6 ± 2.3° and -1.5 ± 2.7° in the sagittal and coronal planes respectively, confirming the need to account for tumor rotation along with translation to improve radiotherapy treatment.
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Nova |
2015 |
Rivest-Hénault D, Dowson N, Greer PB, Fripp J, Dowling JA, 'Robust inverse-consistent affine CT-MR registration in MRI-assisted and MRI-alone prostate radiation therapy', Medical Image Analysis, 23 56-69 (2015) [C1]
Background: CT-MR registration is a critical component of many radiation oncology protocols. In prostate external beam radiation therapy, it allows the propagation of MR-derived c... [more]
Background: CT-MR registration is a critical component of many radiation oncology protocols. In prostate external beam radiation therapy, it allows the propagation of MR-derived contours to reference CT images at the planning stage, and it enables dose mapping during dosimetry studies. The use of carefully registered CT-MR atlases allows the estimation of patient specific electron density maps from MRI scans, enabling MRI-alone radiation therapy planning and treatment adaptation. In all cases, the precision and accuracy achieved by registration influences the quality of the entire process.Problem: Most current registration algorithms do not robustly generalize and lack inverse-consistency, increasing the risk of human error and acting as a source of bias in studies where information is propagated in a particular direction, e.g. CT to MR or vice versa. In MRI-based treatment planning where both CT and MR scans serve as spatial references, inverse-consistency is critical, if under-acknowledged.Purpose: A robust, inverse-consistent, rigid/affine registration algorithm that is well suited to CT-MR alignment in prostate radiation therapy is presented.Method: The presented method is based on a robust block-matching optimization process that utilises a half-way space definition to maintain inverse-consistency. Inverse-consistency substantially reduces the influence of the order of input images, simplifying analysis, and increasing robustness. An open source implementation is available online at http://aehrc.github.io/Mirorr/.Results: Experimental results on a challenging 35 CT-MR pelvis dataset demonstrate that the proposed method is more accurate than other popular registration packages and is at least as accurate as the state of the art, while being more robust and having an order of magnitude higher inverse-consistency than competing approaches.Conclusion: The presented results demonstrate that the proposed registration algorithm is readily applicable to prostate radiation therapy planning.
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2015 |
Sun J, Dowling JA, Pichler P, Parker J, Martin J, Stanwell P, et al., 'Investigation on the performance of dedicated radiotherapy positioning devices for MR scanning for prostate planning', Journal of Applied Clinical Medical Physics, 16 4-13 (2015) [C1]
The purpose of this study was to investigate performance of the couch and coil mounts designed for MR-simulation prostate scanning using data from ten volunteers. Volunteers were ... [more]
The purpose of this study was to investigate performance of the couch and coil mounts designed for MR-simulation prostate scanning using data from ten volunteers. Volunteers were scanned using the standard MR scanning protocol with the MR coil directly strapped on the external body and the volunteer lying on the original scanner table. They also were scanned using a MR-simulation table top and pelvic coil mounts. MR images from both setups were compared in terms of body contour variation and image quality effects within particular organs of interest. Six-field conformal plans were generated on the two images with assigned bulk density for dose calculation. With the MR-simulation devices, the anterior skin deformation was reduced by up to 1.7 cm. The hard tabletop minimizes the posterior body deformation which can be up to 2.3 cm on the standard table, depending on the weight of volunteer. The image signal-to-noise ratio reduced by 14% and 25% on large field of view (FOV) and small FOV images, respectively, after using the coil mount; the prostate volume contoured on two images showed difference of 1.05 ± 0.66 cm3. The external body deformation caused a mean dose reduction of 0.6 ± 0.3 Gy, while the coverage reduced by 22% ± 13% and 27% ± 6% in V98 and V100, respectively. A dedicated MR simulation setup for prostate radiotherapy is essential to ensure the agreement between planning anatomy and treatment anatomy. The image signal was reduced after applying the coil mount, but no significant effect was found on prostate contouring.
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2015 |
Sun J, Dowling J, Pichler P, Menk F, Rivest-Henault D, Lambert J, et al., 'MRI simulation: End-to-end testing for prostate radiation therapy using geometric pelvic MRI phantoms', Physics in Medicine and Biology, 60 3097-3109 (2015) [C1]
To clinically implement MRI simulation or MRI-alone treatment planning requires comprehensive end-to-end testing to ensure an accurate process. The purpose of this study was to de... [more]
To clinically implement MRI simulation or MRI-alone treatment planning requires comprehensive end-to-end testing to ensure an accurate process. The purpose of this study was to design and build a geometric phantom simulating a human male pelvis that is suitable for both CT and MRI scanning and use it to test geometric and dosimetric aspects of MRI simulation including treatment planning and digitally reconstructed radiograph (DRR) generation. A liquid filled pelvic shaped phantom with simulated pelvic organs was scanned in a 3T MRI simulator with dedicated radiotherapy couch-top, laser bridge and pelvic coil mounts. A second phantom with the same external shape but with an internal distortion grid was used to quantify the distortion of the MR image. Both phantoms were also CT scanned as the gold-standard for both geometry and dosimetry. Deformable image registration was used to quantify the MR distortion. Dose comparison was made using a seven-field IMRT plan developed on the CT scan with the fluences copied to the MR image and recalculated using bulk electron densities. Without correction the maximum distortion of the MR compared with the CT scan was 7.5 mm across the pelvis, while this was reduced to 2.6 and 1.7 mm by the vendor's 2D and 3D correction algorithms, respectively. Within the locations of the internal organs of interest, the distortion was <1.5 and <1 mm with 2D and 3D correction algorithms, respectively. The dose at the prostate isocentre calculated on CT and MRI images differed by 0.01% (1.1 cGy). Positioning shifts were within 1 mm when setup was performed using MRI generated DRRs compared to setup using CT DRRs. The MRI pelvic phantom allows end-to-end testing of the MRI simulation workflow with comparison to the gold-standard CT based process. MRI simulation was found to be geometrically accurate with organ dimensions, dose distributions and DRR based setup within acceptable limits compared to CT.
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2015 |
Whelan B, Kumar S, Dowling J, Begg J, Lambert J, Lim K, et al., 'Utilising pseudo-CT data for dose calculation and plan optimization in adaptive radiotherapy', Australasian Physical and Engineering Sciences in Medicine, (2015) [C1]
© 2015 Australasian College of Physical Scientists and Engineers in Medicine To quantify the dose calculation error and resulting optimization uncertainty caused by performing inv... [more]
© 2015 Australasian College of Physical Scientists and Engineers in Medicine To quantify the dose calculation error and resulting optimization uncertainty caused by performing inverse treatment planning on inaccurate electron density data (pseudo-CT) as needed for adaptive radiotherapy and Magnetic Resonance Imaging (MRI) based treatment planning. Planning Computer Tomography (CT) data from 10 cervix cancer patients was used to generate 4 pseudo-CT data sets. Each pseudo-CT was created based on an available method of assigning electron density to an anatomic image. An inversely modulated radiotherapy (IMRT) plan was developed on each planning CT. The dose calculation error caused by each pseudo-CT data set was quantified by comparing the dose calculated each pseudo-CT data set with that calculated on the original planning CT for the same IMRT plan. The optimization uncertainty introduced by the dose calculation error was quantified by re-optimizing the same optimization parameters on each pseudo-CT data set and comparing against the original planning CT. Dose differences were quantified by assessing the Equivalent Uniform Dose (EUD) for targets and relevant organs at risk. Across all pseudo-CT data sets and all organs, the absolute mean dose calculation error was 0.2 Gy, and was within 2 % of the prescription dose in 98.5 % of cases. Then absolute mean optimisation error was 0.3 Gy EUD, indicating that that inverse optimisation is impacted by the dose calculation error. However, the additional uncertainty introduced to plan optimisation is small compared the sources of variation which already exist. Use of inaccurate electron density data for inverse treatment planning results in a dose calculation error, which in turn introduces additional uncertainty into the plan optimization process. In this study, we showed that both of these effects are clinically acceptable for cervix cancer patients using four different pseudo-CT data sets. Dose calculation and inverse optimization on pseudo-CT is feasible for this patient cohort.
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2015 |
Fuangrod T, Rowshanfarzad P, Greer PB, Middleton RH, 'A cine-EPID based method for jaw detection and quality assurance for tracking jaw in IMRT/VMAT treatments', Physica Medica, 31 16-24 (2015) [C1]
A new tool with the potential to verify and track jaw position during delivery has been developed. The method should be suitable for independent quality assurance for jaw position... [more]
A new tool with the potential to verify and track jaw position during delivery has been developed. The method should be suitable for independent quality assurance for jaw position during jaw tracking dynamic IMRT and VMAT treatments. The jaw detection and tracking algorithm developed consists of five main steps. Firstly, the image is enhanced by removing a normalised predicted EPID image (that does not include the collimator transmission) from each cine EPID image. Then, using a histogram clustering technique a global intensity threshold level was determined. This threshold level was used to classify each pixel of the image as either under the jaws or under the MLC. Additionally, the collimator angle was automatically detected and used to rotate the image to vertical direction. Finally, this rotation allows the jaw positions to be determined using vertical and horizontal projection profiles. Nine IMRT fields (with static jaws) and a single VMAT clinical field (with dynamic jaws) were tested by determining the root mean square difference between planned and detected jaw positions. The test results give a detection accuracy of ±1mm RMS error for static jaw IMRT treatments and ±1.5mm RMS error for the dynamic jaw VMAT treatment. This method is designed for quality assurance and verification in modern radiation therapy; to detect the position of static jaws or verify the position of tracking jaws in more complex treatments. This method uses only information extracted from EPID images and it is therefore independent from the linear accelerator.
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Nova |
2015 |
Sun J, Barnes M, Dowling J, Menk F, Stanwell P, Greer PB, 'An open source automatic quality assurance (OSAQA) tool for the ACR MRI phantom.', Australas Phys Eng Sci Med, 38 39-46 (2015) [C1]
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Nova |
2015 |
Woodruff HC, Fuangrod T, Van Uytven E, McCurdy BMC, Van Beek T, Bhatia S, Greer PB, 'First Experience with Real-Time EPID-Based Delivery Verification during IMRT and VMAT Sessions', International Journal of Radiation Oncology Biology Physics, 93 516-522 (2015) [C1]
Purpose Gantry-mounted megavoltage electronic portal imaging devices (EPIDs) have become ubiquitous on linear accelerators. WatchDog is a novel application of EPIDs, in which the ... [more]
Purpose Gantry-mounted megavoltage electronic portal imaging devices (EPIDs) have become ubiquitous on linear accelerators. WatchDog is a novel application of EPIDs, in which the image frames acquired during treatment are used to monitor treatment delivery in real time. We report on the preliminary use of WatchDog in a prospective study of cancer patients undergoing intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) and identify the challenges of clinical adoption. Methods and Materials At the time of submission, 28 cancer patients (head and neck, pelvis, and prostate) undergoing fractionated external beam radiation therapy (24 IMRT, 4 VMAT) had =1 treatment fraction verified in real time (131 fractions or 881 fields). EPID images acquired continuously during treatment were synchronized and compared with model-generated transit EPID images within a frame time (~0.1 s). A ¿ comparison was performed to cumulative frames to gauge the overall delivery quality, and the resulting pass rates were reported graphically during treatment delivery. Every frame acquired (500-1500 per fraction) was saved for postprocessing and analysis. Results The system reported the mean ± standard deviation in real time ¿ 91.1% ± 11.5% (83.6% ± 13.2%) for cumulative frame ¿ analysis with 4%, 4 mm (3%, 3 mm) criteria, global over the integrated image. Conclusions A real-time EPID-based radiation delivery verification system for IMRT and VMAT has been demonstrated that aims to prevent major mistreatments in radiation therapy.
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2014 |
Sun J, Pichler P, Dowling J, Menk F, Stanwell P, Arm J, Greer PB, 'MR simulation for prostate radiation therapy: Effect of coil mounting position on image quality', British Journal of Radiology, 87 (2014) [C1]
Methods: A custom-designed pelvic-shaped phantom was scanned by systematically increasing the anterior body-tocoil (BTC) distance from 30 to 90mm. The image quality near the organ... [more]
Methods: A custom-designed pelvic-shaped phantom was scanned by systematically increasing the anterior body-tocoil (BTC) distance from 30 to 90mm. The image quality near the organs of interest was determined in order to characterize the relationship between image quality and BTC distance at the critical organ structures. The half intensity reduction (HIR) was calculated to determine the sensitivity of each organ structure to the BTC distance change.
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2014 |
Rivest-Hénault D, Ghose S, Pluim JPW, Greer PB, Fripp J, Dowling JA, 'Fast multiatlas selection using composition of transformations for radiation therapy planning', Medical Computer Vision: Algorithms for Big Data. International Workshop, MCV 2014 Held in Conjunction with MICCAI 2014 Cambridge, MA, USA, September 18, 2014 Revised Selected Papers, 8848 105-115 (2014) [E1]
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Nova |
2014 |
Fuangrod T, Woodruff HC, Rowshanfarzad P, O'Connor DJ, Middleton RH, Greer PB, 'An independent system for real-time dynamic multileaf collimation trajectory verification using EPID', PHYSICS IN MEDICINE AND BIOLOGY, 59 61-81 (2014) [C1]
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Nova |
2014 |
Zwan BJ, King BW, O'Connor DJ, Greer PB, 'Dose-to-water conversion for the backscatter-shielded EPID: a frame-based method to correct for EPID energy response to MLC transmitted radiation.', Med Phys, 41 081716 (2014) [C1]
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Nova |
2014 |
Sabet M, Rowshanfarzad P, Menk FW, Greer PB, 'Transit dosimetry in dynamic IMRT with an a-Si EPID', MEDICAL & BIOLOGICAL ENGINEERING & COMPUTING, 52 579-588 (2014) [C1]
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Nova |
2014 |
Rivest-Hénault D, Dowson N, Greer P, Dowling J, 'Inverse-consistent rigid registration of CT and MR for MR-based planning and adaptive prostate radiation therapy', Journal of Physics: Conference Series, 489 (2014)
MRI-alone treatment planning and adaptive MRI-based prostate radiation therapy are two promising techniques that could significantly increase the accuracy of the curative dose del... [more]
MRI-alone treatment planning and adaptive MRI-based prostate radiation therapy are two promising techniques that could significantly increase the accuracy of the curative dose delivery processes while reducing the total radiation dose. State-of-the-art methods rely on the registration of a patient MRI with a MR-CT atlas for the estimation of pseudo-CT [5]. This atlas itself is generally created by registering many CT and MRI pairs. Most registration methods are not symmetric, but the order of the images influences the result [8]. The computed transformation is therefore biased, introducing unwanted variability. This work examines how much a symmetric algorithm improves the registration. Methods: A robust symmetric registration algorithm is proposed that simultaneously optimises a half space transform and its inverse. During the registration process, the two input volumetric images are transformed to a common position in space, therefore minimising any computational bias. An asymmetrical implementation of the same algorithm was used for comparison purposes. Results: Whole pelvis MRI and CT scans from 15 prostate patients were registered, as in the creation of MR-CT atlases. In each case, two registrations were performed, with different input image orders, and the transformation error quantified. Mean residuals of 0.63±0.26 mm (translation) and (8.7±7.3) × 10-3 rad (rotation) were found for the asymmetrical implementation with corresponding values of 0.038±0.039 mm and (1.6 ± 1.3) × 10-3 rad for the proposed symmetric algorithm, a substantial improvement. Conclusions: The increased registration precision will enhance the generation of pseudo-CT from MRI for atlas based MR planning methods. © Published under licence by IOP Publishing Ltd.
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2014 |
Ghose S, Holloway L, Lim K, Chan P, Veera J, Vinod SK, et al., 'A review of segmentation and deformable registration methods applied to adaptive cervical cancer radiation therapy treatment planning', Artificial Intelligence in Medicine, (2014) [C1]
Objective: Manual contouring and registration for radiotherapy treatment planning and online adaptation for cervical cancer radiation therapy in computed tomography (CT) and magne... [more]
Objective: Manual contouring and registration for radiotherapy treatment planning and online adaptation for cervical cancer radiation therapy in computed tomography (CT) and magnetic resonance images (MRI) are often necessary. However manual intervention is time consuming and may suffer from inter or intra-rater variability. In recent years a number of computer-guided automatic or semi-automatic segmentation and registration methods have been proposed. Segmentation and registration in CT and MRI for this purpose is a challenging task due to soft tissue deformation, inter-patient shape and appearance variation and anatomical changes over the course of treatment. The objective of this work is to provide a state-of-the-art review of computer-aided methods developed for adaptive treatment planning and radiation therapy planning for cervical cancer radiation therapy. Methods: Segmentation and registration methods published with the goal of cervical cancer treatment planning and adaptation have been identified from the literature (PubMed and Google Scholar). A comprehensive description of each method is provided. Similarities and differences of these methods are highlighted and the strengths and weaknesses of these methods are discussed. A discussion about choice of an appropriate method for a given modality is provided. Results: In the reviewed papers a Dice similarity coefficient of around 0.85 along with mean absolute surface distance of 2-4. mm for the clinically treated volume were reported for transfer of contours from planning day to the treatment day. Conclusions: Most segmentation and non-rigid registration methods have been primarily designed for adaptive re-planning for the transfer of contours from planning day to the treatment day. The use of shape priors significantly improved segmentation and registration accuracy compared to other models.
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Nova |
2014 |
McCowan PM, Rickey DW, Rowshanfarzad P, Greer PB, Ansbacher W, McCurdy BM, 'An investigation of gantry angle data accuracy for cine-mode EPID images acquired during arc IMRT', Journal of Applied Clinical Medical Physics, 15 187-201 (2014) [C1]
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Nova |
2014 |
Monville ME, Kuncic Z, Greer PB, 'Simulation of real-time EPID images during IMRT using Monte-Carlo', PHYSICA MEDICA-EUROPEAN JOURNAL OF MEDICAL PHYSICS, 30 326-330 (2014) [C1]
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Nova |
2014 |
Dowling JA, Burdett N, Greer PB, Sun J, Parker J, Pichler P, et al., 'Automatic Atlas Based Electron Density and Structure Contouring for MRI-based Prostate Radiation Therapy on the Cloud', Journal of Physics: Conference Series, 489 (2014) [E1]
Our group have been developing methods for MRI-alone prostate cancer radiation therapy treatment planning. To assist with clinical validation of the workflow we are investigating ... [more]
Our group have been developing methods for MRI-alone prostate cancer radiation therapy treatment planning. To assist with clinical validation of the workflow we are investigating a cloud platform solution for research purposes. Benefits of cloud computing can include increased scalability, performance and extensibility while reducing total cost of ownership. In this paper we demonstrate the generation of DICOM-RT directories containing an automatic average atlas based electron density image and fast pelvic organ contouring from whole pelvis MR scans. © Published under licence by IOP Publishing Ltd.
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2014 |
Lee D, Greer PB, Arm J, Keall P, Kim T, 'Audiovisual biofeedback improves image quality and reduces scan time for respiratory-gated 3D MRI', Journal of Physics: Conference Series, 489 1-4 (2014) [C1]
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Nova |
2014 |
Blake SJ, McNamara AL, Vial P, Holloway L, Greer PB, Kuncic Z, 'Monte Carlo simulation of the transit dosimetric response of an a-Si electronic portal imaging device', Journal of Physics: Conference Series, 489 1-6 (2014) [C1]
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Nova |
2014 |
Monville ME, Kuncic Z, Greer PB, 'An improved Monte-Carlo model of the Varian EPID separating support arm and rear-housing backscatter', XVII INTERNATIONAL CONFERENCE ON THE USE OF COMPUTERS IN RADIATION THERAPY (ICCR 2013), 489 (2014) [E1]
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2014 |
Rivest-Hénault D, Greer P, Fripp J, Dowling J, 'Structure-guided nonrigid registration of CT-MR pelvis scans with large deformations in MR-based image guided radiation therapy', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 8361 LNCS 65-73 (2014)
Multimodal registration of CT and MR scans is a required step in leading edge adaptive MR-based image guided radiation therapy protocols. Yet, anatomical changes limit the precisi... [more]
Multimodal registration of CT and MR scans is a required step in leading edge adaptive MR-based image guided radiation therapy protocols. Yet, anatomical changes limit the precision of the registration process and therefore that of the whole intervention. In prostate radiation therapy, the difference in bladder and rectum filling can significantly displace both the targeted area and the organs at risk. Here, we describe a method that integrates an image-based similarity criterion with the anatomical information from manual contours to guide the registration process toward an accurate solution. Whole pelvis CT and MR scans of 33 patients have been nonrigidly registered, and the proposed method leads to an average improvement of 0.17 DSC when compared to a baseline nonrigid registrations. The increased accuracy will thus enhance an MR-based prostate radiation therapy protocol. © 2014 Springer International Publishing.
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2013 |
Blake SJ, Vial P, Holloway L, Greer PB, McNamara AL, Kuncic Z, 'Characterization of optical transport effects on EPID dosimetry using Geant4', MEDICAL PHYSICS, 40 (2013) [C1]
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Nova |
2013 |
Woodruff HC, Fuangrod T, Rowshanfarzad P, McCurdy BMC, Greer PB, 'Gantry-angle resolved VMAT pretreatment verification using EPID image prediction', MEDICAL PHYSICS, 40 (2013) [C1]
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Nova |
2013 |
Blake SJ, McNamara AL, Deshpande S, Holloway L, Greer PB, Kuncic Z, Vial P, 'Characterization of a novel EPID designed for simultaneous imaging and dose verification in radiotherapy', MEDICAL PHYSICS, 40 (2013) [C1]
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Nova |
2013 |
Fuangrod T, Woodruff HC, Van Uytven E, McCurdy BMC, Kuncic Z, O'Connor DJ, Greer PB, 'A system for EPID-based real-time treatment delivery verification during dynamic IMRT treatment', Medical Physics, 40 (2013) [C1]
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Nova |
2013 |
Chytyk-Praznik K, VanUytven E, vanBeek TA, Greer PB, McCurdy BMC, 'Model-based prediction of portal dose images during patient treatment', Medical Physics, 40 (2013) [C1]
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Nova |
2013 |
King BW, Greer PB, 'A method for removing arm backscatter from EPID images', Medical Physics, 40 (2013) [C1]
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Nova |
2013 |
Ghose S, Holloway L, Lim K, Chan P, Veera J, Vinod SK, et al., 'A survey of cervix segmentation methods in magnetic resonance images', Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 8198 LNCS 290-298 (2013) [C1]
Radiotherapy is an effective therapy in the treatment of cervix cancer. However tumor and normal tissue motion and shape deformation of the cervix, the bladder and the rectum over... [more]
Radiotherapy is an effective therapy in the treatment of cervix cancer. However tumor and normal tissue motion and shape deformation of the cervix, the bladder and the rectum over the course of the treatment can limit the efficacy of radiotherapy and safe delivery of the dose. A number of studies have presented the potential benefits of adaptive radiotherapy for cervix cancer with high soft tissue contrast magnetic resonance images. To enable practical implementation of adaptive radiotherapy for the cervix, computer aided segmentation is necessary. Accurate computer aided automatic or semi-automatic segmentation of the cervix is a challenging task due to inter patient shape variation, soft tissue deformation, organ motion, and anatomical changes during the course of the treatment. This article reviews the methods developed for cervix segmentation in magnetic resonance images. The objective of this work is to present different methods for cervix segmentation in the literature highlighting their similarities, differences, strengths and weaknesses. © 2013 Springer-Verlag.
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2013 |
Singh J, Greer PB, White MA, Parker J, Patterson J, Tang CI, et al., 'Treatment-Related Morbidity in Prostate Cancer: A Comparison of 3-Dimensional Conformal Radiation Therapy With and Without Image Guidance Using Implanted Fiducial Markers', INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 85 1018-1023 (2013) [C1]
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2013 |
Thwaites D, Baldock C, Price L, Starkey E, Whitaker M, Greer P, et al., 'Journal of Physics: Conference Series - Preface', Journal of Physics: Conference Series, 444 (2013)
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2013 |
Woodruff HC, Greer PB, '3D Dose reconstruction: Banding artefacts in cine mode EPID images during VMAT delivery', Journal of Physics: Conference Series, 444 012042 (2013) [E1]
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Nova |
2012 |
Rowshan Farzad P, Sabet M, O'Connor JD, Greer PB, 'Investigation of the sag in linac secondary collimator and MLC carriage during arc deliveries', Physics in Medicine and Biology, 57 N209-N224 (2012) [C1]
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Nova |
2012 |
Herschtal A, Foroudi F, Greer PB, Eade TN, Hindson BR, Kron T, 'Finding the optimal statistical model to describe target motion during radiotherapy delivery-a Bayesian approach', Physics in Medicine and Biology, 57 2743-2755 (2012) [C1]
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Nova |
2012 |
Sabet M, Rowshan Farzad P, Vial P, Menk FW, Greer PB, 'Transit dosimetry in IMRT with an a-Si EPID in direct detection configuration', Physics in Medicine and Biology, 57 N295-N306 (2012) [C1]
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Nova |
2012 |
King BW, Morf D, Greer PB, 'Development and testing of an improved dosimetry system using a backscatter shielded electronic portal imaging device', Medical Physics, 39 2839-2847 (2012) [C1]
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Nova |
2012 |
Chandra SS, Dowling JA, Shen K-K, Raniga P, Pluim JPW, Greer PB, et al., 'Patient specific prostate segmentation in 3-D magnetic resonance images', IEEE Transactions on Medical Imaging, 31 1955-1964 (2012) [C1]
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Nova |
2012 |
Rowshan Farzad P, Sabet M, O'Connor JD, Greer PB, 'Improvement of Varian a-Si EPID dosimetry measurements using a lead-shielded support-arm', Medical Dosimetry, 37 145-151 (2012) [C1]
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Nova |
2012 |
Rowshan Farzad P, Sabet M, O'Connor JD, Greer PB, 'Impact of backscattered radiation from the bunker structure on EPID dosimetry', Journal of Applied Clinical Medical Physics, 13 91-100 (2012) [C1]
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Nova |
2012 |
Rowshan Farzad P, Sabet M, O'Connor JD, McCowan PM, McCurdy BMC, Greer PB, 'Gantry angle determination during arc IMRT: evaluation of a simple EPID-based technique and two commercial inclinometers', Journal of Applied Clinical Medical Physics, 13 203-214 (2012) [C1]
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Nova |
2012 |
Rowshan Farzad P, Sabet M, O'Connor JD, McCowan PM, McCurdy BMC, Greer PB, 'Detection and correction for EPID and gantry sag during arc delivery using cine EPID imaging', Medical Physics, 39 623-635 (2012) [C1]
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Nova |
2012 |
Rowshan Farzad P, Sabet M, Barnes MP, O'Connor JD, Greer PB, 'EPID-based verification of the MLC performance for dynamic IMRT and VMAT', Medical Physics, 39 6192-6207 (2012) [C1]
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Nova |
2012 |
Dowling JA, Lambert JA, Parker J, Salvado O, Fripp J, Capp A, et al., 'An atlas-based electron density mapping method for Magnetic Resonance Imaging (MRI)-Alone treatment planning and adaptive MRI-Based prostate radiation therapy', International Journal of Radiation Oncology Biology Physics, 83 E5-E11 (2012) [C1]
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Nova |
2011 |
Rowshan Farzad P, Sabet M, O'Connor JD, Greer PB, 'Isocenter verification for linac-based stereotactic radiation therapy: review of principles and techniques', Journal of Applied Clinical Medical Physics, 12 12 (2011) [C1]
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2011 |
Chandra S, Dowling J, Shen K, Pluim J, Greer PB, Salvado O, Fripp J, 'Automatic segmentation of the prostate in 3D magnetic resonance images using case specific deformable models', Proceedings: 2011 International Conference on Digital Image Computing: Techniques and Applications, DICTA 2011, 7-12 (2011) [E1]
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2011 |
Dowling JA, Fripp J, Chandra S, Pluim JPW, Lambert JA, Parker J, et al., 'Fast automatic multi-atlas segmentation of the prostate from 3D MR images', International Workshop on Prostate Cancer Imaging: Image Analysis and Image-Guided Interventions Proceedings (LNCS 6963), 10-21 (2011) [E1]
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Nova |
2011 |
Greer PB, Dowling JA, Lambert JA, Fripp J, Parker J, Denham J, et al., 'A magnetic resonance imaging-based workflow for planning radiation therapy for prostate cancer', Medical Journal of Australia, 194 S24-S27 (2011) [C1]
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Nova |
2011 |
Rowshan Farzad P, Sabet M, O'Connor JD, Greer PB, 'Verification of the linac isocenter for stereotactic radiosurgery using cine-EPID imaging and arc delivery', Medical Physics, 38 3963-3970 (2011) [C1]
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Nova |
2011 |
Gustafsson H, Vial P, Kuncic Z, Baldock C, Denham J, Greer PB, 'Direct dose to water dosimetry for pretreatment IMRT verification using a modified EPID', Medical Physics, 38 6257-6264 (2011) [C1]
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Nova |
2011 |
Hatton J, Greer PB, Tang C, Wright P, Capp A, Gupta S, et al., 'Does the planning dose-volume histogram represent treatment doses in image-guided prostate radiation therapy? Assessment with cone-beam computerised tomography scans', Radiotherapy and Oncology, 98 162-168 (2011) [C1]
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Nova |
2011 |
Lambert JA, Greer PB, Menk FW, Patterson J, Parker J, Dahl K, et al., 'MRI-guided prostate radiation therapy planning: Investigation of dosimetric accuracy of MRI-based dose planning', Radiotherapy and Oncology, 98 330-334 (2011) [C1]
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Nova |
2011 |
King BW, Clews L, Greer PB, 'Long-term two-dimensional pixel stability of EPIDs used for regular linear accelerator quality assurance', Australasian Physical & Engineering Sciences in Medicine, 34 459-466 (2011) [C1]
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Nova |
2010 |
Ansbacher W, Swift C-L, Greer PB, 'An evaluation of cine-mode 3D portal image dosimetry for volumetric modulated arc therapy', Journal of Physics: Conference Series, 012022 (2010) [E1]
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Nova |
2010 |
Dowling J, Lambert JA, Parker J, Greer PB, Fripp J, Denham J, et al., 'Automatic MRI atlas-based external beam radiation therapy treatment planning for prostate cancer', Prostate Cancer Imaging: Computer-Aided Diagnosis, Prognosis, and Intervention International Workshop, Held in Conjunction with MICCAI 2010, Beijing,China, September 24, 2010. Proceedings, 25-33 (2010) [E1]
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2010 |
Rowshan Farzad P, McCurdy BMC, Sabet M, Lee CG, O'Connor JD, Greer PB, 'Measurement and modeling of the effect of support arm backscatter on dosimetry with a Varian EPID', Medical Physics, 37 2269-2278 (2010) [C1]
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Nova |
2010 |
Sabet M, Menk FW, Greer PB, 'Evaluation of an a-Si EPID in direct detection configuration as a water-equivalent dosimeter for transit dosimetry', Medical Physics, 37 1459-1467 (2010) [C1]
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Nova |
2010 |
Rowshan Farzad P, Sabet M, O'Connor JD, Greer PB, 'Reduction of the effect of non-uniform backscatter from an E-type support arm of a Varian a-Si EPID used for dosimetry', Physics in Medicine and Biology, 55 6617-6632 (2010) [C1]
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Nova |
2009 |
Tang C, Stanwell PT, Ourselin S, Salvado O, Dowling J, Bourgeat P, et al., 'Nonrigid correction of interleaving artefacts in pelvic MRI', Proceedings of SPIE Medical Imaging, 7259 1-10 (2009) [E1]
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2009 |
Ebert MA, Kenny J, Greer PB, 'Experience converting an RT department to full CT simulation: Technical issues identified during commissioning of a wide-bore scanner', Journal of Medical Imaging and Radiation Oncology, 53 325-330 (2009) [C1]
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Nova |
2009 |
Hatton J, McCurdy B, Greer PB, 'Cone beam computerized tomography: The effect of calibration of the Hounsfield unit number to electron density on dose calculation accuracy for adaptive radiation therapy', Physics in Medicine and Biology, 54 N329-N346 (2009) [C1]
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Nova |
2009 |
Gardner JK, Clews L, Gordon JJ, Wang S, Greer PB, Siebers JV, 'Comparison of sources of exit fluence variation for IMRT', Physics in Medicine and Biology, 54 N451-N458 (2009) [C1]
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Nova |
2009 |
Vial P, Gustafsson H, Oliver L, Baldock C, Greer PB, 'Direct-detection EPID dosimetry: Investigation of a potential clinical configuration for IMRT verification', Physics in Medicine and Biology, 54 7151-7169 (2009) [C1]
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Nova |
2009 |
McCurdy BMC, Greer PB, 'Dosimetric properties of an amorphous-silicon EPID used in continuous acquisition mode for application to dynamic and arc IMRT', Medical Physics, 36 3028-3039 (2009) [C1]
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Nova |
2009 |
Greer PB, Cadman P, Lee CG, Bzdusek K, 'An energy fluence-convolution model for amorphous silicon EPID dose prediction', Medical Physics, 36 547-555 (2009) [C1]
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Nova |
2009 |
Lee CG, Menk FW, Cadman P, Greer PB, 'A simple approach to using an amorphous silicon EPID to verify IMRT planar dose maps', Medical Physics, 36 984-992 (2009) [C1]
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Nova |
2009 |
Wang S, Gardner JK, Gordon JJ, Li W, Clews L, Greer PB, Siebers JV, 'Monte Carlo-based adaptive EPID dose kernel accounting for different field size responses of imagers', Medical Physics, 36 3582-3595 (2009) [C1]
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Nova |
2009 |
Clews L, Greer PB, 'An EPID based method for efficient and precise asymmetric jaw alignment quality assurance', Medical Physics, 36 5488-5496 (2009) [C1]
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Nova |
2009 |
Gustafsson H, Vial P, Kuncic Z, Baldock C, Greer PB, 'EPID dosimetry: Effect of different layers of materials on absorbed dose response', Medical Physics, 36 5665-5674 (2009) [C1]
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Nova |
2009 |
Haworth A, Kearvell R, Greer PB, Hooton B, Denham J, Lamb D, et al., 'Assuring high quality treatment delivery in clinical trials: Results from the Trans-Tasman Radiation Oncology Group (TROG) study 03.04 'RADAR' set-up accuracy study', Radiotherapy and Oncology, 90 299-306 (2009) [C1]
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Nova |
2009 |
Denham J, Kumar M, Gleeson PS, Lamb DS, Joseph D, Atkinson C, et al., 'Recognizing false biochemical failure calls after radiation with or without neo-adjuvant androgen deprivation for prostate cancer', International Journal of Radiation Oncology Biology Physics, 74 404-411 (2009) [C1]
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Nova |
2009 |
Denham J, Steigler A, Kumar M, Lamb DS, Joseph D, Spry NA, et al., 'Measuring time to biochemical failure in the Trog 96.01 trial: When should the clock start ticking?', International Journal of Radiation Oncology Biology Physics, 75 1008-1012 (2009) [C1]
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Nova |
2009 |
McCurdy BMC, Greer PB, 'Dosimetric properties of an amorphous-silicon EPID used in continuous acquisition mode for application to dynamic and arc IMRT.', Med Phys, 36 3028-3039 (2009)
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2008 |
Denham J, Steigler A, Wilcox C, Lamb DS, Joseph D, Atkinson C, et al., 'Time to biochemical failure and prostate-specific antigen doubling time as surrogates for prostate cancer-specific mortality: evidence from the TROG 96.01 randomised controlled trial', Lancet Oncology, 9 1058-1068 (2008) [C1]
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Nova |
2008 |
Greer PB, Dahl K, Ebert MA, White M, Wratten C, Ostwald PM, et al., 'Assessment of a daily online implanted fiducial marker-guided prostate radiotherapy process', Journal of Medical Imaging and Radiation Oncology, 52 517-524 (2008) [C1]
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Nova |
2008 |
Greer PB, Dahl K, Ebert MA, Wratten C, White M, Denham J, 'Comparison of prostate set-up accuracy and margins with off-line bony anatomy corrections and online implanted fiducial-based corrections', Journal of Medical Imaging and Radiation Oncology, 52 511-516 (2008) [C1]
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Nova |
2008 |
Vial P, Greer PB, Hunt P, Oliver L, Baldock C, 'The impact of MLC transmitted radiation on EPID dosimetry for dynamic MLC beams', Medical Physics, 35 1267-1277 (2008) [C1]
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Nova |
2008 |
Vial P, Greer PB, Oliver L, Baldock C, 'Initial evaluation of a commercial EPID modified to a novel direct-detection configuration for radiotherapy dosimetry', Medical Physics, 35 4362-4374 (2008) [C1]
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Nova |
2008 |
Vial P, Hunt P, Greer PB, Oliver L, Baldock C, 'Software tool for portal dosimetry research', Australasian Physical & Engineering Sciences in Medicine, 31 216-222 (2008) [C1]
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Nova |
2008 |
Ebert MA, Lambert JA, Greer PB, 'CT-ED conversion on a GE Lightspeed-RT scanner: Influence of scanner settings', Australasian Physical and Engineering Sciences in Medicine, 31 154-159 (2008) [C1]
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Nova |
2007 |
Greer PB, Barnes MP, 'Investigation of an amorphous silicon EPID for measurement and quality assurance of enhanced dynamic wedge', Physics in Medicine and Biology, 52 1075-1087 (2007) [C1]
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Nova |
2007 |
Greer PB, 'Off-axis dose response characteristics of an amorphous silicon electronic portal imaging device', Medical Physics, 34 3815-3824 (2007) [C1]
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Nova |
2007 |
Greer PB, Vial P, Oliver L, Baldock C, 'Experimental investigation of the response of an amorphous silicon EPID to intensity modulated radiotherapy beams', Medical Physics, 34 4389-4398 (2007) [C1]
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Nova |
2006 |
Vial P, Oliver L, Greer PB, Baldock C, 'An experimental investigation into the radiation field offset of a dynamic multileaf collimator', Physics in Medicine and Biology, 51 5517-5538 (2006) [C1]
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Nova |
2005 |
Greer PB, 'Correction of pixel sensitivity variation and off-axis response for amorphous silicon EPID dosimetry', Medical Physics, 32 3558-3578 (2005) [C1]
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Nova |
2005 |
Ludbrook JJS, Greer PB, Blood P, D'Yachkova Y, Coldman A, Beckham WA, et al., 'Correction Of Systematic Setup Errors in Prostate Radiation Therapy: How Many Images to Perform?', Medical Dosimetry, 30 76-84 (2005) [C1]
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2003 |
Greer PB, Beckham WA, 'Improving the resolution of intensity modulated delivery by reducing the MLC leaf sampling distance', Medical Physics, 30 2793-2801 (2003) [C1]
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Nova |
2003 |
Greer PB, Popescue CC, 'Dosimetric properties of an amorphous silicon electronic portal imaging device for verification of dynamic intensity modulated radiation therapy', Medical Physics, 30 1618-1627 (2003) [C1]
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Nova |
2003 |
Greer PB, Beckham WA, 'The effect of leaf width and sampling distance on the ''stair-stepping'' of field borders defined by multileaf collimators', Australasian Physical and Engineering Sciences in Medicine, 26 44-51 (2003) [C1]
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2002 |
Greer PB, Donaldson WA, 'Synthetic studies directed toward the phorboxazoles: preparation of the C3-C15 bisoxane segment and two stereoisomers', TETRAHEDRON, 58 6009-6018 (2002)
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2000 |
Greer PB, van Doorn T, 'Evaluation of an algorithm for the assessment of the MTF using an edge method', MEDICAL PHYSICS, 27 2048-2059 (2000)
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2000 |
Greer PB, van Doom T, 'A design for a dual assembly multileaf collimator', MEDICAL PHYSICS, 27 2242-2255 (2000)
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2000 |
Greer PB, Donaldson WA, 'Phorboxazole synthetic studies: the C3-C15 bis-oxane segment', TETRAHEDRON LETTERS, 41 3801-3803 (2000)
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1998 |
Greer PB, Jose CC, Matthews JHL, 'Set-up variation of patients treated with radiotherapy to the prostate measured with an electronic portal imaging device', Australasian Radiology, 42 207-212 (1998)
The set-up variation of 11 patients treated supine with radical radiotherapy for carcinoma of the prostate was measured with an electronic portal imaging device to determine the a... [more]
The set-up variation of 11 patients treated supine with radical radiotherapy for carcinoma of the prostate was measured with an electronic portal imaging device to determine the adequacy of set-up techniques and current margins, as well as the need for immobilization. During the treatments 172 images of the anterior fields and 159 images of the left- lateral fields were taken and the errors in treatment placement were measured by template matching. The variation in the superior-inferior direction was small, 1.4-1.6 mm (1 SD), while the medio-lateral variation was 2.8 mm (1 SD). The anterior-posterior variation was largest, 4.6 mm (1 SD) with an offset of 3.3 mm anterior. This anterior offset and large anterior-posterior variation suggests that set-up techniques were not optimal for this direction. The 1 cm margin used was adequate for set-up variation except in a small number of cases, which was mainly due to the anterior trend. Random (treatment-to-treatment) variations were small (1.1-2.3 mm; 1 SD), indicating that immobilization would result in only modest improvement in reproducibility for these supine patients.
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1998 |
Greer PB, Mortensen TM, Rad DT, Jose CC, 'Comparison of two methods for anterior-posterior isocenter localization in pelvic radiotherapy using electronic portal imaging', INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 41 1193-1199 (1998)
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1997 |
Greer PB, Mortensen TM, 'Anterior-posterior treatment localization in pelvic radiotherapy: Tattoos or fixed couch-to-isocentre distance', Medical Dosimetry, 22 43-46 (1997)
The methods of determining the anterior-posterior isocentre location in pelvic radiotherapy are either by aligning lateral localization lasers to tattoo marks on skin, or by setti... [more]
The methods of determining the anterior-posterior isocentre location in pelvic radiotherapy are either by aligning lateral localization lasers to tattoo marks on skin, or by setting a constant daily couch-to-isocentre distance. While using the former method the day-to-day vertical couch movement was recorded and combined with measurements of day-to-day anterior- posterior patient movement made with an electronic portal imaging device to determine whether couch vertical movement contributes to anterior-posterior setup variation. Seven unimmobilized patients were studied, four supine prostate and three prone rectum patients. The two motions were found to be highly correlated (correlation coefficient = 0.82) which supports the constant couch-to-isocentre distance approach. When the day-to-day couch vertical movement was subtracted from the anterior-posterior movement results the setup variation was reduced in six of the seven patients.
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1996 |
Greer PB, 'Image timing and detector performance of a matrix ion-chamber electronic portal imaging device', Australasian Physical and Engineering Sciences in Medicine, 19 264-269 (1996)
Image timing and input/output characteristics of a Varian PortalVision¿ matrix liquid ion-chamber electronic portal imaging device (EPID) used with a Varian CL2100C/D linear accel... [more]
Image timing and input/output characteristics of a Varian PortalVision¿ matrix liquid ion-chamber electronic portal imaging device (EPID) used with a Varian CL2100C/D linear accelerator were investigated to examine the variation in image timing and detector performance with acquisition mode. Contrast-detail curves showed that the input/output results were indicative of the image quality variation with acquisition mode. Overall for this accelerator/EPID arrangement the 500 MU/min repetition rate gives the best image quality for the 6 MV and 18 MV acquisition modes.
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1994 |
Hodgkinson IJ, Greer PB, Molteno AC, 'Point-spread function for light scattered in the human ocular fundus.', Journal of the Optical Society of America. A, Optics, image science, and vision, 11 479-486 (1994)
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1994 |
HODGKINSON IJ, GREER PB, MOLTENO ACB, 'PAINT-SPREAD FUNCTION FOR LIGHT SCATTERED IN THE HUMAN OCULAR FUNDUS', JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION, 11 479-486 (1994)
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1993 |
NEUBERT ME, KEAST SS, EZENYILIMBA MC, GREER PB, JONES WC, LEONHARDT D, SHENOUDA I, 'THE EFFECT OF CARBONYL-CONTAINING TERMINAL CHAINS ON MESOMORPHIC PROPERTIES IN 4,4'-DISUBSTITUTED PHENYLBENZOATES AND THIOBENZOATES .8. PHENYLBENZOATES CONTAINING 2 CARBONYL-CONTAINING TERMINAL CHAINS', MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 237 47-68 (1993)
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1993 |
Greer PB, Molteno ACB, Hodgkinson IJ, 'Reflected line spread function of the human ocular fundus', Australasian Physical and Engineering Sciences in Medicine, 16 168-173 (1993)
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