Overview
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Lung cancer is a leading cause of cancer-related death in both men and women. It is estimated that 50 - 60% of patients will require radiotherapy at least once during the treatment of their disease. Crucial to the success of any radiotherapy treatment is an accurate knowledge of the absorbed dose (energy imparted by the ionising radiation per unit mass) received by the patient. This usually is obtained by performing a dose calculation and it is important for prescribing the appropriate treatment and predicting clinical outcomes for the patient. The calculation of the absorbed dose to the patient is relatively straightforward for the primary radiation but calculation of the absorbed dose due to scattered radiation is a more complex problem, particularly in and around tissue inhomogeneities such as lung and bone. Recent algorithm improvements in the treatment planning system such as the Anisotropic Analytical Algorithm (AAA, Varian Medical Systems) have improved the accuracy of the dose calculation but validation in actual patient geometries is difficult. Monte-Carlo simulation of the treatment can be used as a gold standard to assess dose calculation accuracy in the patient.
The project aims to test the accuracy of the dose calculation algorithms for lung cancer radiotherapy patients that are currently used in a clinical treatment planning system (TPS). Monte-Carlo (MC) simulations of patient treatments will be performed and the MC dose distribution compared with that calculated using the TPS to directly assess the accuracy.
Recent work at QUT and the Princess Alexandra Hospital has produced commissioned Monte-Carlo models of the Elekta Synergy linear accelerators. Software has also been developed that allows the information for each patient's unique treatment plan to be transferred from the TPS ready for simulation by the EGSnrc/BEAMnrc Monte-Carlo code. Lung radiotherapy treatments frequently use devices called wedges that are applied to one or more of the treatment fields to enable delivery of a more uniform dose distribution across the tumour volume within the lung. The first stage of this project will involve commissioning Monte-Carlo models of the wedges by comparing the simulated with measured wedge field dosimetry. Once this is complete the project will progress to carrying out Monte-Carlo simulations of a number of patient treatments. The simulated dose distributions can then be compared with the dose distribution calculated by the clinical treatment planning system. The accuracy of the calculated dose delivered to the tumour volume and organs at risk such as normal healthy lung tissue, the oesophagus and the heart will be assessed. The project will require close collaboration with clinical radiation oncology medical physicists at the Princess Alexandra Hospital and involve gaining experience and understanding of clinical radiotherapy treatment planning systems and Monte-Carlo computer simulations.
References:
- A.L Boyer, M. Goitein, A.J. Lomax and E.S. Pedroni Radiation in the Treatment of Cancer Physics Today, September 2002, p. 34-36
- F. Verhaegen and J. Seuntjens Monte-Carlo Modelling of External Radiotherapy Photon Beams, Physics in Medicine and Biology, Vol 48, p. R107-R164 (2003)
- N. Papanikolaou and S. Stathakis. Dose-calculation algorithms in the context of inhomogeneity corrections for high energy photon beams. Med. Phys. Vol 36 (10) p4765 (2009)
- Study level
- Honours
- Supervisors
- QUT External Paul Charles (Princess Alexandra Hospital)
- Organisational unit
Science and Engineering Faculty
- Research area
- Contact
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Please contact the supervisor.
Dr Andrew Fielding
