MEDICAL PHYSICS GROUP
High Precision MRI based prostate radiotherapy
This project is a collaboration with the Australian-Health Research Centre and aims to develop computer techniques to utilize MRI scans directly for radiotherapy planning. Using non-rigid image registration techniques to develop pelvic anatomy MR and CT atlas to be able to segment organs and map electron densities to patient MRI scans for dose planning. This project is supported by the Cancer Council NSW and the Hunter Medical Research Institute.
Example of (a) patient MRI scan with automatically segmented organs and (b) electron densities mapped to the MR scan to create a pseudo-CT for (c) dose planning.
(a) Expert contour of prostate, and (b) automatically defined contour. Dr Dowling was recently the winner of an international prostate segmentation challenge at MICCAI in London.
Investigators: A/Prof Peter Greer, Joel Parker, Jackie Patterson, Kara Dahl, Patricia Ostwald, Prof Jim Denham, Prof Fred Menk (University of Newcastle), Dr Jason Dowling, Dr Olivier Salvado (Australian E-Health Research Centre), Dr Peter Lau (Hunter New England Health).
Students: Jonathan Lambert
Cone-beam CT for adaptive prostate planning
With cone-beam computed tomography (CBCT) scanner technology integrated with the treatment linear accelerators presents daily imaging of the patient can be performed to identify anatomy changes before each treatment. We are investigating variation in delivered dose and effectiveness of adaptive protocols. This project is supported by the Cancer Institute NSW.
(a) Prostate dose coverage on different days for the same patient, the prostate in red and the 98% isodose in green (b) Variations in dose coverage (volume of prostate covered by 98% isodose curve) measured for 12 patients.
Investigators: Joan Hatton, A/Prof Peter Greer, Prof Jim Denham, Joel Parker, Dr Colin Tang, Dr Anne Capp, Dr Philip Wright.
Real-time dosimetry for patient safety in radiation therapy
This project is a collaboration with the University of Manitoba. Aim is to develop methods to measure time-resolved dose delivery with electronic portal imaging devices (EPIDs). Applications are verification of arc-IMRT, real-time tumour tracking, accounting for intra-fraction motion, and early detection of treatment delivery errors. This project is supported by the Cancer Council NSW.
Comparison of time-resolved EPID measurement at a single point in an open field and arc-IMRT field to time-resolved ion-chamber measurements.
Investigators: A/Prof Peter Greer (University of Newcastle), Dr Boyd McCurdy, (Cancer Care Manitoba and University of Manitoba), A/Prof Zdenka Kuncic, Prof Clive Baldock (University of Sydney)
Students: Pejman Rowshanfarzad.
New EPID designs for dosimetry
Currently electronic portal imaging devices (EPID) are optimised for imaging performance and so have many problems for dosimetry applications which leads to greater uncertainties and barriers to implementation. We are investigating the dosimetric performance of an EPID modified for water-equivalent dosimetry by blocking the optical signal from the phosphor layer. Both IMRT and transit dosimetry are being studied. We are also investigating the possibility of a dual-mode imager with both optimal imaging and dosimetry capability. This project is supported by the NHMRC.
(a) Direct EPID measured dose map, (b) film measured dose map, (c) dose profile through central axis comparison, and (d) Gamma evaluation results for 3%, 3 mm tolerance values.
(a) Comparison of beam profile direct EPID and ion-chamber for transit dosimetry 15x15 cm2 field with 30 cm thick phantom, (b) head and neck phantom result.
Investigators: A/Prof Peter Greer, Dr Brian King, Prof Fred Menk (University of Newcastle), Dr Philip Vial (Liverpool Hospital), Dr Helen Gustafsson, A/Prof Zdenka Kuncic, Prof Clive Baldock (University of Sydney).
Students: Mahsheed Sabet
Improvements in EPID dosimetry
Currently electronic portal imaging devices (EPID) suffer from dosimetry artifacts due to backscatter from the support arm. We are investigating both software and hardware methods to ameliorate this effect. We have developed a model of the backscatter to predict the backscatter component of an EPID image. Experimental investigations of different thicknesses of Pb shielding and their effect on backscatter are being performed.
Picture of underside of EPID with support arm components that backscatter, and measurement of backscatter component to a large field image.
Investigators: A/Prof Peter Greer, Prof John O'Connor (University of Newcastle), Dr Boyd McCurdy (University of Manitoba)
Students: Pejman Rowshanfarzad
The aim of the current research to use miniature LiF:Mg,Cu,P TLDs (Figure (a)) to verify new treatment protocols for High Dose Rate (HDR) brachytherapy treatments and to further develop a technique to perform dose verification during actual patient treatment fractions. This latter research project is in collaboration with the Prostate Cancer Institute at St George Hospital.
(a) Picture of miniature TLD pinworms, and (b) design schematic.
Investigators: Dr Lisa Duggan