Dr Danny Lee

Dr Danny Lee

Postdoctoral Research Fellow

School of Mathematical and Physical Sciences

Career Summary

Biography

Dr. Danny Lee joined the New Medical Physics Group (NewMedPhys, The University of Newcastle) in September 2017 as a postdoctoral researcher fellow funded from the NHMRC grant for Watchdog (a real-time verification imaging system) and 4D-MRI (Siemens 3T MRI) for the ideal radiation treatment for each lung and liver cancer patient.   His work broadly aims to improve the treatment of cancer patients with radiation therapy and enable high quality effective treatments.

Prior to the current position, Dr. Lee participated in several clinical projects for radiation oncology in Virginia Commonwealth University, United States and research projects related to lung and liver 4D-MRI (GE 3T MRI) and MR-guided radiotherapy (Philips 3T MRI), including real-time visual guidance, adaptive radiotherapy and radiotherapy imaging research, supervised by Prof. Jantinder Palta, Prof. Siyong Kim and Assistant Prof. Taeho Kim.

Dr. Lee received his PhD in Medical Physics from Sydney Medical School at the University of Sydney under Prof. Paul Keall and Prof. Peter Greer, working on (1) Audiovisual biofeedback respiratory guidance in MRI (GE and Siemens 3T MRI) for imaging lung cancer patient tumour motion, (2) Dynamic Keyhole as a fast MR image reconstruction for the Australian MR-LINAC project, (3) Tumour auto-segmentation on cine-MRI and (4) The image registration of breath-hold MRI and respiratory-gated MRI. Prior to his PhD, he accumulated 7 years of work experience in the IT industry at IBM and Fujitsu in Australia. He has a proven record as a senior software developer (Java, C#, C++ and Matlab) in a wide range of applications.


Qualifications

  • Doctor of Philosophy, University of Sydney

Keywords

  • Medical Physics
  • 4D-MRI
  • Breathing Motion Management
  • Lung/Liver Cancers
  • Radiation Treatment
  • Real-time Adaptive Radiotherapy
  • MRI

Languages

  • Korean (Mother)
  • English (Fluent)

Fields of Research

Code Description Percentage
090399 Biomedical Engineering not elsewhere classified 20
110313 Nuclear Medicine 20
029903 Medical Physics 60

Professional Experience

UON Appointment

Title Organisation / Department
Postdoctoral Research Fellow University of Newcastle
School of Mathematical and Physical Sciences
Australia

Professional appointment

Dates Title Organisation / Department
1/04/2016 - 31/08/2017 Postdoctoral Research Fellow Virginia Commonwealth University, Virginia Commonwealth University Health Systems
Radiation Oncology, Messagy Cancer Center
United States

Awards

Award

Year Award
2016 Travel Awards in Virginia Commonwealth University
Virginia Commonwealth University, Virginia Commonwealth University Health Systems
2015 Postgraduate Research Support Scheme (PRSS)
Sydney Medical School, The University of Sydney
2014 Cancer Research Network (CRN) Postgraduate Conference Travel Grant
Cancer Research Network
2014 Postgraduate Research Support Scheme (PRSS)
Sydney Medical School, The University of Sydney
2014 ISMRM (The International Society for Magnetic Resonance in Medicine) Educational Stipend
The International Society for Magnetic Resonance in Medicine
2013 ISMRM (The International Society for Magnetic Resonance in Medicine) Educational Stipend
The International Society for Magnetic Resonance in Medicine
2013 Australian Postgraduate Award
Sydney Medical School, The University of Sydney
2013 Postgraduate Research Support Scheme (PRSS)
Sydney Medical School, The University of Sydney
2013 Alumni Scholarship of Sydney University
Sydney Medical School, The University of Sydney
2012 University Postgraduate Award
Sydney Medical School, The University of Sydney

Prize

Year Award
2016 MC2 Award
Korean Association of Medical Physicists in North America
Edit

Publications

For publications that are currently unpublished or in-press, details are shown in italics.


Journal article (16 outputs)

Year Citation Altmetrics Link
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, (2018)

© 2018 The Royal Australian and New Zealand College of Radiologists. Introduction: In-room MRI is a promising image guidance strategy in external beam radiotherapy to acquire volu... [more]

© 2018 The Royal Australian and New Zealand College of Radiologists. Introduction: In-room MRI is a promising image guidance strategy in external beam radiotherapy to acquire volumetric information for moving targets. However, limitations in spatio-temporal resolution led several authors to use 2D orthogonal images for guidance. The aim of this work is to present a method to concurrently compensate for non-rigid tumour motion and provide an approach for 3D reconstruction from 2D orthogonal cine-MRI slices for MRI-guided treatments. Methods: Free-breathing sagittal/coronal interleaved 2D cine-MRI were acquired in addition to a pre-treatment 3D volume in two patients. We performed deformable image registration (DIR) between cine-MRI slices and corresponding slices in the pre-treatment 3D volume. Based on an extrapolation of the interleaved 2D motion fields, the 3D motion field was estimated and used to warp the pre-treatment volume. Due to the lack of a ground truth for patients, the method was validated on a digital 4D lung phantom. Results: On the phantom, the 3D reconstruction method was able to compensate for tumour motion and compared favourably to the results of previously adopted strategies. The difference in the 3D motion fields between the phantom and the extrapolated motion was 0.4 ± 0.3 mm for tumour and 0.8 ± 1.5 mm for whole anatomy, demonstrating feasibility of performing a 3D volumetric reconstruction directly from 2D orthogonal cine-MRI slices. Application of the method to patient data confirmed the feasibility of utilizing this method in real world scenarios. Conclusion: Preliminary results on phantom and patient cases confirm the feasibility of the proposed approach in an MRI-guided scenario, especially for non-rigid tumour motion compensation.

DOI 10.1111/1754-9485.12713
Co-authors Peter Greer
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]
DOI 10.1002/mp.12758
Co-authors Peter Greer
2018 Paganelli C, Kipritidis J, Lee D, Baroni G, Keall P, Riboldi M, 'Image-based retrospective 4D MRI in external beam radiotherapy: A comparative study with a digital phantom', Medical Physics, (2018)

© 2018 American Association of Physicists in Medicine. Purpose: Several image-based retrospective sorting methods of 4D magnetic resonance imaging (4D MRI) have been proposed for ... [more]

© 2018 American Association of Physicists in Medicine. Purpose: Several image-based retrospective sorting methods of 4D magnetic resonance imaging (4D MRI) have been proposed for respiratory motion reconstruction in external beam radiotherapy. However, the optimal strategy for providing accurate and artifact-free 4D MRI, ideally corresponding to an average breathing cycle, is not yet defined. This study presents a proactive comparison of three published image-based sorting methods, to define a groundwork for benchmarking in 4D MRI. Methods: Three published 4D MRI methods were selected for image retrospective sorting: body area, mutual information, and navigator slice. The three image-based methods were compared against a conventional retrospective sorting method based on an external surrogate. Comparisons were performed by means of an MRI digital phantom, derived from the XCAT CT phantom generated with different patient-derived signals, for a total of 12 cases. Specific multislice MRI acquisitions were simulated for slice sorting and sagittal, coronal, and axial orientations were tested. An average 4D cycle was generated as ground truth. Results: Individual and grouped patient analyses showed better performance of the navigator slice and mutual information in amplitude binning with respect to the body area strategy. Binning artifacts were reduced on the diaphragm with the slice navigator method due to the acquired internal information. Tumor motion description accurately matched the ground truth in the mutual information strategy with amplitude binning. The body area method followed the performance of the external surrogate and presented larger errors, since was not correlated with the internal anatomy. Sagittal and coronal orientations reported lower errors than axial slicing. Individual analysis showed the need of a patient-specific evaluation for the selection of the best method. Conclusions: A comparison between three different image-based retrospective sorting methods for 4D MRI is proposed, providing guidelines for benchmark definition in MRI-guided radiotherapy.

DOI 10.1002/mp.12965
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]

© 2017 The Authors on behalf of the American Society for Radiation Oncology Purpose Respiratory variation can increase the variability of tumor position and volume, accounting for... [more]

© 2017 The Authors on behalf of the American Society for Radiation Oncology 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 cm 3 to 2.5 cm 3 . 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.

DOI 10.1016/j.adro.2017.03.002
Co-authors Peter Greer
2017 Lee D, Kim S, Palta JR, Kim T, 'Technical note: real-time web-based wireless visual guidance system for radiotherapy', Australasian Physical and Engineering Sciences in Medicine, 40 463-469 (2017)

© 2017, Australasian College of Physical Scientists and Engineers in Medicine. Describe a Web-based wireless visual guidance system that mitigates issues associated with hard-wire... [more]

© 2017, Australasian College of Physical Scientists and Engineers in Medicine. Describe a Web-based wireless visual guidance system that mitigates issues associated with hard-wired audio-visual aided patient interactive motion management systems that are cumbersome to use in routine clinical practice. Web-based wireless visual display duplicates an existing visual display of a respiratory-motion management system for visual guidance. The visual display of the existing system is sent to legacy Web clients over a private wireless network, thereby allowing a wireless setting for real-time visual guidance. In this study, active breathing coordinator (ABC) trace was used as an input for visual display, which captured and transmitted to Web clients. Virtual reality goggles require two (left and right eye view) images for visual display. We investigated the performance of Web-based wireless visual guidance by quantifying (1) the network latency of visual displays between an ABC computer display and Web clients of a laptop, an iPad mini 2 and an iPhone 6, and (2) the frame rate of visual display on the Web clients in frames per second (fps). The network latency of visual display between the ABC computer and Web clients was about 100¿ms and the frame rate was 14.0¿fps (laptop), 9.2¿fps (iPad mini 2) and 11.2¿fps (iPhone 6). In addition, visual display for virtual reality goggles was successfully shown on the iPhone 6 with 100¿ms and 11.2¿fps. A high network security was maintained by utilizing the private network configuration. This study demonstrated that a Web-based wireless visual guidance can be a promising technique for clinical motion management systems, which require real-time visual display of their outputs. Based on the results of this study, our approach has the potential to reduce clutter associated with wired-systems, reduce space requirements, and extend the use of medical devices from static usage to interactive and dynamic usage in a radiotherapy treatment vault.

DOI 10.1007/s13246-017-0548-0
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]

� 2016 American Association of Physicists in Medicine. Purpose: The dynamic keyhole is a newMRimage reconstruction method for thoracic and abdominal MR imaging. To date, this me... [more]

� 2016 American Association of Physicists in Medicine. 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, matchi ng, 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.

DOI 10.1118/1.4947508
Citations Scopus - 4Web of Science - 3
Co-authors Peter Greer
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]
DOI 10.1016/j.ijrobp.2015.11.017
Citations Scopus - 10Web of Science - 10
Co-authors Peter Greer
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]

© 2016 Institute of Physics and Engineering in Medicine. In-room cine-MRI guidance can provide non-invasive target localization during radiotherapy treatment. However, in order to... [more]

© 2016 Institute of Physics and Engineering in Medicine. 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.

DOI 10.1088/0031-9155/61/2/872
Citations Scopus - 17Web of Science - 19
Co-authors Peter Greer
2016 Pollock S, Kipritidis J, Lee D, Bernatowicz K, Keall P, 'The impact of breathing guidance and prospective gating during thoracic 4DCT imaging: An XCAT study utilizing lung cancer patient motion', Physics in Medicine and Biology, 61 6485-6501 (2016)

� 2016 Institute of Physics and Engineering in Medicine. Two interventions to overcome the deleterious impact irregular breathing has on thoracic-abdominal 4D computed tomograph... [more]

� 2016 Institute of Physics and Engineering in Medicine. Two interventions to overcome the deleterious impact irregular breathing has on thoracic-abdominal 4D computed tomography (4DCT) are (1) facilitating regular breathing using audiovisual biofeedback (AVB), and (2) prospective respiratory gating of the 4DCT scan based on the real-time respiratory motion. The purpose of this study was to compare the impact of AVB and gating on 4DCT imaging using the 4D eXtended cardiac torso (XCAT) phantom driven by patient breathing patterns. We obtained simultaneous measurements of chest and abdominal walls, thoracic diaphragm, and tumor motion from 6 lung cancer patients under two breathing conditions: (1) AVB, and (2) free breathing. The XCAT phantom was used to simulate 4DCT acquisitions in cine and respiratory gated modes. 4DCT image quality was quantified by artefact detection (NCC diff ), mean square error (MSE), and Dice similarity coefficient of lung and tumor volumes (DSC lung , DSC tumor ). 4DCT acquisition times and imaging dose were recorded. In cine mode, AVB improved NCC diff , MSE, DSC lung , and DSC tumor by 20% (p = 0.008), 23% (p < 0.001), 0.5% (p < 0.001), and 4.0% (p < 0.003), respectively. In respiratory gated mode, AVB improved NCC diff , MSE, and DSC lung by 29% (p < 0.001), 34% (p < 0.001), 0.4% (p < 0.001), respectively. AVB increased the cine acquisitions by 15 s and reduced respiratory gated acquisitions by 31 s. AVB increased imaging dose in cine mode by 10%. This was the first study to quantify the impact of breathing guidance and respiratory gating on 4DCT imaging. With the exception of DSC tumor in respiratory gated mode, AVB significantly improved 4DCT image analysis metrics in both cine and respiratory gated modes over free breathing. The results demonstrate that AVB and respirat ory-gating can be beneficial interventions to improve 4DCT for cancer radiation therapy, with the biggest gains achieved when these interventions are used simultaneously.

DOI 10.1088/0031-9155/61/17/6485
Citations Scopus - 6
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]

© 2015 Institute of Physics and Engineering in Medicine. The quantification of tumor motion in sites affected by respiratory motion is of primary importance to improve treatment a... [more]

© 2015 Institute of Physics and Engineering in Medicine. 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.

DOI 10.1088/0031-9155/60/18/7165
Citations Scopus - 5Web of Science - 5
Co-authors Peter Greer
2014 Lee D, Pollock S, Whelan B, Keall P, Kim T, 'Dynamic keyhole: A novel method to improve MR images in the presence of respiratory motion for real-time MRI', Medical Physics, 41 (2014)

Purpose: In this work, the authors present a novel magnetic resonance imaging reconstruction method to improve the quality of MR images in the presence of respiratory motion for r... [more]

Purpose: In this work, the authors present a novel magnetic resonance imaging reconstruction method to improve the quality of MR images in the presence of respiratory motion for real-time thoracic image-guided radiotherapy. Methods: This new reconstruction method is called dynamic keyhole and utilizes a library of previously acquired, peripheral k-space datasets from the same (or similar) respiratory state in conjunction with central k-space datasets acquired in real-time. Internal or external respiratory signals are utilized to sort, match, and combine the two separate peripheral and central k-space datasets with respect to respiratory displacement, thereby reducing acquisition time and improving image quality without respiratory-related artifacts. In this study, the dynamic keyhole, conventional keyhole, and zero-filling methods were compared to full k-space acquisition (ground truth) for 60 coronal datasets acquired from 15 healthy human subjects. Results: For the same image-quality difference from the ground-truth image, the dynamic keyhole method reused 79% of the prior peripheral phase-encoding lines, while the conventional keyhole reused 73% and zero-filling 63% (p-value < 0.0001), corresponding to faster acquisition speed of dynamic keyhole for real-time imaging applications. Conclusions: This study demonstrates that the dynamic keyhole method is a promising technique for clinical applications such as image-guided radiotherapy requiring real-time MR monitoring of the thoracic region. Based on the results from this study, the dynamic keyhole method could increase the temporal resolution by a factor of five compared with full k-space methods. © 2014 American Association of Physicists in Medicine.

DOI 10.1118/1.4883882
Citations Scopus - 3
2014 Steel H, Pollock S, Lee D, Keall P, Kim T, 'The internal-external respiratory motion correlation is unaffected by audiovisual biofeedback', Australasian Physical and Engineering Sciences in Medicine, 37 97-102 (2014)

This study evaluated if an audiovisual (AV) biofeedback causes variation in the level of external and internal correlation due to its interactive intervention in natural breathing... [more]

This study evaluated if an audiovisual (AV) biofeedback causes variation in the level of external and internal correlation due to its interactive intervention in natural breathing. The internal (diaphragm) and external (abdominal wall) respiratory motion signals of 15 healthy human subjects under AV biofeedback and free breathing (FB) were analyzed and measures of correlation and regularity taken. Regularity metrics (root mean square error and spectral power dispersion metric) were obtained and the correlation between these metrics and the internal and external correlation was investigated. For FB and AV biofeedback assisted breathing the mean correlations found between internal and external respiratory motion were 0.96 ± 0.02 and 0.96 ± 0.03, respectively. This means there is no evidence to suggest (p-value = 0.88) any difference in the correlation between internal and external respiratory motion with the use of AV biofeedback. Our results confirmed the hypothesis that the internal-external correlation with AV biofeedback is the same as for free breathing. Should this correlation be maintained for patients, AV biofeedback can be implemented in the clinic with confidence as regularity improvements using AV biofeedback with an external signal will be reflected in increased internal motion regularity. © 2014 Australasian College of Physical Scientists and Engineers in Medicine.

DOI 10.1007/s13246-014-0247-z
Citations Scopus - 6
2014 Kim T, Pooley R, Lee D, Keall P, Lee R, Kim S, 'Quasi-breath-hold (QBH) Biofeedback in Gated 3D Thoracic MRI: Feasibility Study', Progress in Medical Physics, 25 72-72 (2014)
DOI 10.14316/pmp.2014.25.2.72
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]
DOI 10.1088/1742-6596/489/1/012033
Citations Scopus - 7Web of Science - 5
Co-authors Peter Greer
2013 Pollock S, Lee D, Keall P, Kim T, 'Audiovisual biofeedback improves motion prediction accuracy', Medical Physics, 40 (2013)

Purpose: The accuracy of motion prediction, utilized to overcome the system latency of motion management radiotherapy systems, is hampered by irregularities present in the patient... [more]

Purpose: The accuracy of motion prediction, utilized to overcome the system latency of motion management radiotherapy systems, is hampered by irregularities present in the patients' respiratory pattern. Audiovisual (AV) biofeedback has been shown to reduce respiratory irregularities. The aim of this study was to test the hypothesis that AV biofeedback improves the accuracy of motion prediction. Methods: An AV biofeedback system combined with real-time respiratory data acquisition and MR images were implemented in this project. One-dimensional respiratory data from (1) the abdominal wall (30 Hz) and (2) the thoracic diaphragm (5 Hz) were obtained from 15 healthy human subjects across 30 studies. The subjects were required to breathe with and without the guidance of AV biofeedback during each study. The obtained respiratory signals were then implemented in a kernel density estimation prediction algorithm. For each of the 30 studies, five different prediction times ranging from 50 to 1400 ms were tested (150 predictions performed). Prediction error was quantified as the root mean square error (RMSE); the RMSE was calculated from the difference between the real and predicted respiratory data. The statistical significance of the prediction results was determined by the Students t-test. Results: Prediction accuracy was considerably improved by the implementation of AV biofeedback. Of the 150 respiratory predictions performed, prediction accuracy was improved 69 (103150) of the time for abdominal wall data, and 78 (117150) of the time for diaphragm data. The average reduction in RMSE due to AV biofeedback over unguided respiration was 26 (p 0.001) and 29 (p 0.001) for abdominal wall and diaphragm respiratory motion, respectively. Conclusions: This study was the first to demonstrate that the reduction of respiratory irregularities due to the implementation of AV biofeedback improves prediction accuracy. This would result in increased efficiency of motion management techniques affected by system latencies used in radiotherapy. © 2013 American Association of Physicists in Medicine.

DOI 10.1118/1.4794497
Citations Scopus - 14
2012 Kim T, Pollock S, Lee D, O'Brien R, Keall P, 'Audiovisual biofeedback improves diaphragm motion reproducibility in MRI', Medical Physics, 39 6921-6928 (2012)

Purpose: In lung radiotherapy, variations in cycle-to-cycle breathing results in four-dimensional computed tomography imaging artifacts, leading to inaccurate beam coverage and tu... [more]

Purpose: In lung radiotherapy, variations in cycle-to-cycle breathing results in four-dimensional computed tomography imaging artifacts, leading to inaccurate beam coverage and tumor targeting. In previous studies, the effect of audiovisual (AV) biofeedback on the external respiratory signal reproducibility has been investigated but the internal anatomy motion has not been fully studied. The aim of this study is to test the hypothesis that AV biofeedback improves diaphragm motion reproducibility of internal anatomy using magnetic resonance imaging (MRI). Methods: To test the hypothesis 15 healthy human subjects were enrolled in an ethics-Approved AV biofeedback study consisting of two imaging sessions spaced ~1 week apart. Within each session MR images were acquired under free breathing and AV biofeedback conditions. The respiratory signal to the AV biofeedback system utilized optical monitoring of an external marker placed on the abdomen. Synchronously, serial thoracic 2D MR images were obtained to measure the diaphragm motion using a fast gradient-recalled-echo MR pulse sequence in both coronal and sagittal planes. The improvement in the diaphragm motion reproducibility using the AV biofeedback system was quantified by comparing cycle-to-cycle variability in displacement, respiratory period, and baseline drift. Additionally, the variation in improvement between the two sessions was also quantified. Results: The average root mean square error (RMSE) of diaphragm cycle-to-cycle displacement was reduced from 2.6 mm with free breathing to 1.6 mm (38 reduction) with the implementation of AV biofeedback (p-value 0.0001). The average RMSE of the respiratory period was reduced from 1.7 s with free breathing to 0.3 s (82 reduction) with AV biofeedback (p-value 0.0001). Additionally, the average baseline drift obtained using a linear fit was reduced from 1.6 mmmin with free breathing to 0.9 mmmin (44 reduction) with AV biofeedback (p-value 0.012). The diaphragm motion reproducibility improvements with AV biofeedback were consistent with the abdominal motion reproducibility that was observed from the external marker motion variation. Conclusions: This study was the first to investigate the potential of AV biofeedback to improve the motion reproducibility of internal anatomy using MRI. The study demonstrated the significant improvement in diaphragm motion reproducibility using AV biofeedback combined with MRI. This system can potentially provide clinically beneficial motion management of internal anatomy in MRI and radiotherapy. © 2012 American Association of Physicists in Medicine.

DOI 10.1118/1.4761866
Citations Scopus - 28
Show 13 more journal articles

Conference (23 outputs)

Year Citation Altmetrics Link
2017 Paganelli C, Albertini S, Iudicello F, Whelan B, Kipritidis J, Lee D, et al., 'OC-0302: Dosimetric evaluation of a global motion model for MRI-guided radiotherapy', Radiotherapy and Oncology (2017)
DOI 10.1016/S0167-8140(17)30744-2
2017 Lewis B, Lee D, Kim S, Kim T, 'Implementation of Volumetric Dynamic Keyhole (VDK) Using Normalized Mutual Information Through Respiratory-Phase Matching', MEDICAL PHYSICS (2017)
2017 Lee D, Kim S, Palta J, Kim T, 'Real-Time Web-Based Wireless Visual Guidance System for Radiotherapy', MEDICAL PHYSICS (2017)
2017 Lee D, Kim T, Lewis B, Kapoor P, Datsang R, Kim S, et al., 'Seed Localization in MR-Assisted CT-Based LDR Post-Implant Plan', MEDICAL PHYSICS (2017)
2017 Oh S, Lee D, Leong B, Wu Y, Kim S, Kim T, 'An Automated Method for the Verification and Quality Assurance of Treatment Planning Systems', MEDICAL PHYSICS (2017)
2017 Mueller M, Paganelli C, Lee D, Keall P, 'Real-Time Pseudo-CT Creation From Orthogonal Two Dimensional Cinematic MRI for Tumor Tracking', MEDICAL PHYSICS (2017)
2017 Ostyn M, Lee D, Kim S, Kim T, 'A Novel Assisted Breath Hold System for Involuntary Breath Hold in Radiotherapy', MEDICAL PHYSICS (2017)
2017 Lee D, Kim S, Palta J, Keall P, Kim T, 'A Novel Dynamic Profile-Driven 4D-MRI Reconstruction Method', MEDICAL PHYSICS (2017)
2017 Lee D, Lewis B, Kim S, Palta J, Kim T, 'Feasibility Study: Auto-Triggered Consecutive-Short-Breath-Hold Control with ABC in Cancer Radiotherapy', MEDICAL PHYSICS (2017)
2016 Lee D, Greer P, Lapuz C, Ludbrook J, Pollock S, Kim T, Keall P, 'MO-FG-CAMPUS-JeP2-02: Audiovisual Biofeedback Guided Respiratory-Gated MRI: An Investigation of Tumor Definition and Scan Time for Lung Cancer.', Med Phys, United States (2016)
DOI 10.1118/1.4957355
Co-authors Peter Greer
2016 Pollock S, Kipritidis J, Lee D, Bernatowicz K, Keall P, 'OC-0158: Impact of breathing guidance and prospective gating on 4DCT image quality: a digital phantom study', Radiotherapy and Oncology (2016)
DOI 10.1016/S0167-8140(16)31407-4
2015 Lee D, Greer P, Lapuz C, Ludbrook J, Pollock S, Kim T, Keall P, 'Audiovisual Biofeedback Improves Breath-Hold Lung Tumor Position Reproducibility Measured with 4D MRI', Medical Physics, Anaheim, CA (2015) [E3]
DOI 10.1118/1.4924322
Co-authors Peter Greer
2015 Paganelli C, Lee D, Kipritidis J, Greer P, Riboldi M, Keall P, '3D Reconstruction From 2D CineMRI Orthogonal Slices: A Feasibility Study', MEDICAL PHYSICS (2015) [E3]
Co-authors Peter Greer
2015 Pollock S, Kipritidis J, Lee D, Bernatowicz K, Keall P, 'SU-E-J-158: Audiovisual Biofeedback Reduces Image Artefacts in 4DCT: A Digital Phantom Study', Medical Physics (2015)
DOI 10.1118/1.4924243
2015 Lee D, Greer P, Ludbrook J, Paganelli C, Pollock S, Kim T, Keall P, 'SU-E-J-235: Audiovisual Biofeedback Improves the Correlation Between Internal and External Respiratory Motion', Medical Physics (2015)
DOI 10.1118/1.4924321
2015 Pollock S, Kipritidis J, Lee D, Bernatowicz K, Keall P, 'PO-0966: Audiovisual biofeedback breathing training during thoracic 4DCT imaging: a digital phantom study', Radiotherapy and Oncology (2015)
DOI 10.1016/S0167-8140(15)40958-2
2014 Lee D, Greer P, Arm J, Hunter P, Pollock S, Makhija K, et al., 'SU-E-J-29: Audiovisual Biofeedback Improves Tumor Motion Consistency for Lung Cancer Patients.', Med Phys, United States (2014)
DOI 10.1118/1.4888080
Co-authors Peter Greer
2014 Lee D, Greer P, Pollock S, Whelan B, Kim T, Keall P, 'WE-G-18C-08: Real Time Tumor Imaging Using a Novel Dynamic Keyhole MRI Reconstruction Technique.', Med Phys, United States (2014)
DOI 10.1118/1.4889527
Co-authors Peter Greer
2013 Pollock S, Lee D, Kim T, Yamamoto T, Loo B, Yang J, Keall P, 'SU-E-J-142: Respiratory Guidance for Lung Cancer Patients: An Investigation of Audiovisual Biofeedback Training and Effectiveness', Medical Physics (2013)

Purpose: Irregular breathing can exacerbate errors in medical imaging and radiotherapy. The audiovisual biofeedback (AV) system has been proposed to facilitate regular patient res... [more]

Purpose: Irregular breathing can exacerbate errors in medical imaging and radiotherapy. The audiovisual biofeedback (AV) system has been proposed to facilitate regular patient respiration. The purpose of this work was to identify predictive factors from two lung cancer studies to extract information regarding each study's results and conduct to determine how to produce maximal respiratory guidance effectiveness for future studies. Methods: An analysis of respiratory regularity was performed on respiratory traces from two AV biofeedback lung cancer studies: one from a recent study performed at Stanford (Stanford study) and another, retrospectively, using data from George, et al (2006) (VCU study). Stanford study: 10 lung cancer patients, each had their external respiratory motion monitored whilst they breathed both with and without the guidance of AV biofeedback. VCU study: 24 lung cancer patients. Each patient participated in up to 5 study sessions, received training with the AV biofeedback system and shorter study sessions. Breathing regularity was quantified as the root mean square error (RMSE) of displacement and period. Results: The VCU study demonstrated AV biofeedback to be effective in producing regular respiration over free breathing (reduction in RMSE of 20% (p < 0.001) and 14% (p = 0.06) for displacement and period, respectively). However, the Stanford study did not (no reduction in RMSE displacement and reduction of RMSE in period by 31% (p = 0.17)). Distinguishing features in the conduct between these two studies was the AV biofeedback training, and the repeated and shorter sessions provided in the VCU study. Conclusion: This is the first study to retrospectively analyze the conduct and results from AV biofeedback studies and demonstrate the importance of patient familiarity and training with the AV biofeedback system. This will be used to develop ideal training and information for patients to maximize the efficiency of future AV biofeedback sessions. This work was supported by Sydney Medical School New Staff/Early; Career Researcher Scheme grant, NIH/NCI R01CA93626 and an NHMRC Australia Fellowship. © 2013, American Association of Physicists in Medicine. All rights reserved.

DOI 10.1118/1.4814354
Citations Scopus - 4
2013 Kim T, Lee D, Keall P, Lee R, Kim S, 'WE-C-116-05: Residual Respiratory Motion Management Within a Gating Window Using Quasi-Breath-Hold (QBH) Biofeedback', Medical Physics (2013)

Purpose: The aim of the project is to test the hypothesis that quasi-breath-hold (QBH) biofeedback improves the residual respiratory motion management within a gating window, redu... [more]

Purpose: The aim of the project is to test the hypothesis that quasi-breath-hold (QBH) biofeedback improves the residual respiratory motion management within a gating window, reducing respiratory motion artifacts in gated 3D thoracic MR images. Methods: A QBH biofeedback system has been employed with gated 3D thoracic MRI acquisitions. The QBH biofeedback system utilized (1) the external marker position on the abdomen using an RPM system (Real-time Position Management, Varian) to audio-visually guide a human subject for 2s breath-hold at 90% exhalation position in each respiratory cycle and (2) the gated T2 weighted SPACE MR pulse sequence of 3 T Siemens MRI for 3D thoracic imaging. The improvement in the upper liver breath-hold motion reproducibility within the gating window using the QBH biofeedback system has been assessed for a group of volunteers. Each subject underwent two imaging sessions for the assessments of the residual respiratory motion management within the gating window and respiratory motion artifacts in 3D thoracic MRI both with/without QBH biofeedback. Results: The residual upper liver motion within the gating window during MR acquisitions (~6 minutes) has been considerably reduced using QBH biofeedback, resulting in the reduction of respiratory motion artifacts in lungs and liver of 3D thoracic MR images. Additionally, average RMSE (root mean square error) of abdomen displacement obtained from the RPM has been reduced from 2.3mm of free breathing to 0.8mm of QBH biofeedback breathing: 65% of average displacement error reduction with QBH biofeedback. Conclusion: The study demonstrated the improvement of the upper liver breath-hold motion reproducibility using QBH biofeedback during 3D thoracic MR imaging. This system can provide clinically applicable motion management of the internal anatomy for gated radiotherapy. © 2013, American Association of Physicists in Medicine. All rights reserved.

DOI 10.1118/1.4815567
2012 Pollock S, Lee D, Keall P, Kim T, 'WE-G-213CD-07: Enhancing Respiratory Motion Prediction Accuracy Using Audiovisual (AV) Biofeedback', Medical Physics (2012)

Purpose: Prediction of respiratory-related tumor motion is hampered by irregularities present in the patient breathing patterns. Audiovisual (AV) biofeedback reduces irregularitie... [more]

Purpose: Prediction of respiratory-related tumor motion is hampered by irregularities present in the patient breathing patterns. Audiovisual (AV) biofeedback reduces irregularities, thereby producing a less complex breathing pattern. The aim of this project is to improve respiratory motion prediction accuracy using an AV biofeedback system. Methods: An AV biofeedback system combined with real-time MRI was implemented in this project (4 human subjects across 5 studies (one subject had both an initial and follow-up study)). The AV biofeedback system consists of external marker positioned on the abdomen of human subjects, being tracked using an RPM system (Real-time Position Management, Varian) to guide the subject's breathing. Acquired respiratory data has been used as input for motion prediction through a dynamic multi-leaf collimator (DMLC) simulator developed by Prof. Keall. The prediction algorithm utilized was a kernel density estimation-based real-time prediction algorithm. A variety of prediction parameters were tested to determine optimum prediction performance. Prediction parameters adjusted were the delay time (DT) and training examples (TE); the parameters tested here were: DT/TE = 2500/1500, 2500/100, 1000/250, 500/250; Given that the data sampling rate was kept at 30 Hz, the resultant prediction training window lengths were 49.5, 8.25, 3.3 and 3.3seconds respectively. Results: The mean difference between measured and predicted data for free breathing was 1.98±2.32mm; and 0.65±0.65mm for when AV biofeedback was implemented (reduction of error of 67%). The most accurate prediction results were attained using the parameters: DT/TE = 500 ms/250. Conclusions: This study demonstrates the improvement of respiratory motion prediction accuracy when AV biofeedback is implemented to produce a more regular breathing pattern. © 2012, American Association of Physicists in Medicine. All rights reserved.

DOI 10.1118/1.4736208
2012 Lee D, Pollock S, Keall P, Kim T, 'WE-G-217A-03: Respiratory-Related External/Internal Motion Based MR Image Reconstruction Using Dynamic Keyhole for Real-Time Tumor Monitoring', Medical Physics (2012)

Purpose: It is aim to test the hypothesis that a dynamic keyhole MRI reconstruction technique using external/internal respiratory surrogate position reduces acquisition time while... [more]

Purpose: It is aim to test the hypothesis that a dynamic keyhole MRI reconstruction technique using external/internal respiratory surrogate position reduces acquisition time while retaining image quality for real-time tumor monitoring, compared to the conventional keyhole technique. Methods: 46 thoracic MRI studies with 13 healthy human subjects have been acquired using a 3T GE MRI. Acquired MR images were reconstructed using zero-filling, conventional keyhole and the proposed respiratory motion based dynamic keyhole techniques; resultant images were then compared for image quality. Undersampled k-space rate in the phase encoding direction was determined based on the difference between the original image and the reconstructed image. The position of abdominal muscles and diaphragm were used to determine any excess data that exists in the overlaid temporal data. In addition, the feasibility of the dynamic keyhole method was applied using lung tumor MR images. Results: The result from dynamic keyhole using respiratory motion demonstrated significant improvement compared with the zero-filling and conventional keyhole methods. Firstly, the dynamic keyhole method using external respiratory motion had an overlaid average of 79.7% (204 lines) of 256 lines from 46 datasets, compared to 63.9% in zero-filling and 74.3% in conventional keyhole. Secondly, dynamic keyhole method using internal diaphragm motion had an overlaid average of 84.5% (216 lines) of 256 lines from all datasets compared to 67.1% and 77.8% or zero-filling and conventional keyhole, respectively. Lastly, dynamic keyhole has been validated with one dataset involving lung tumor MR images. Image blurring artifacts and inferior resolution were not present in the final MR images using dynamic keyhole. Conclusions: Dynamic keyhole method using respiratory external/internal surrogate motion has been proposed to reconstruct MR images without image artifacts and with superior resolution. This method is applicable to MR images targeting lungs and other organs affected by respiratory motion for real-time tumor motion monitoring. © 2012, American Association of Physicists in Medicine. All rights reserved.

DOI 10.1118/1.4736222
2012 Kim T, Pollock S, Lee D, Keall P, 'Audiovisual Biofeedback Improves Anatomical Position Management in Breath-hold', International Journal of Radiation Oncology*Biology*Physics (2012)
DOI 10.1016/j.ijrobp.2012.07.561
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Thesis / Dissertation (1 outputs)

Year Citation Altmetrics Link
2016 Lee DK, Magnetic resonance imaging of lung cancer in the presence of respiratory motion: Dynamic keyhole and audio visual biofeedback, University of Sydney (2016)
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Research Projects

WatchDog 2.0 2017 - 2020

WatchDog (A real-time verification imaging system during radiation treatment): Improving patient safety in radiation therapy with the Watchdog real-time treatment delivery verification system - Funded by NHMRC (National Health & Medical Research Council) - Prof. Peter Greer.


Liver and Lung 4D-MRI 2017 - 2019

Liver and Lung 4D-MRI

This project is to investigate the performance of two 4D-MRI methods for two distinct body sites; lung and liver. To assess the clinical benefit of 4D-MRI compared to the current standard (4D-CT), tumours are delineated on 4D-CT and 4D-MR images, required for evaluating tumour delineation efficiency and tumour motion range accuracy. In addition, a treatment planning study is included to assess the potential clinical benefit of 4D-MRI in dose delivered to tumour and healthy tissues resulting from changes in tumour margins due to the correction of tumor volume and motion range.


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Research Collaborations

The map is a representation of a researchers co-authorship with collaborators across the globe. The map displays the number of publications against a country, where there is at least one co-author based in that country. Data is sourced from the University of Newcastle research publication management system (NURO) and may not fully represent the authors complete body of work.

Country Count of Publications
Australia 23
United States 10
Italy 6
Germany 2
Switzerland 1
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Dr Danny Lee

Position

Postdoctoral Research Fellow
School of Mathematical and Physical Sciences
Faculty of Science

Contact Details

Email danny.lee@newcastle.edu.au
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