狈补尘别:听Peter Watson, MSc
Level at MPU:听PhD
贰尘补颈濒:听peter.watson [at] mail.mcgill.ca
厂耻辫别谤惫颈蝉辞谤(蝉):听Dr. Jan Seuntjens
Research interests:听Kilovoltage dosimetry, Intraoperative radiotherapy, Electronic brachytherapy
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Research summary
The INTRABEAM system (Carl Zeiss, Germany) is a miniature x-ray source for use in intraoperative听radiotherapy and brachytherapy. Currently, this source is calibrated in a relative way using an indirect听measurement of absorbed dose (energy per unit mass). The absolute primary standard for measuring听absorbed dose from ionizing radiation is calorimetry, whereby dose is measured directly via听temperature change of a medium. Thus, the ideal calibration technique for miniature x-ray sources听would be calorimetry-based. The purpose of this project is to evaluate the current dosimetry formalism听of the INTRABEAM system, and to develop a calorimetry-based absorbed dose protocol for these听sources.听
A monte carlo model of the INTRABEAM source has been developed and validated in-air using the听EGSnrc particle transport code. Using this model, ionization chamber correction and conversion听factors can be accurately calculated for the INTRABEAM source, and compared with accepted values.听Next, the feasibility of performing a calorimetric dose measurement with the INTRABEAM source will听be investigated. A protoype calorimeter will then be constructed, and characterised in terms of听stability and noise. Once characterised, dose measurements with the calorimeter will be performed and听compared with ionization chamber and radiochromic film measurements.听The establishment of a calorimetry-based dose protocol for miniature x-ray sources, such as the听INTRABEAM system, would help reduce dosimetric uncertainties. This increased confidence in听delivered dose would allow for direct comparison between INTRABEAM and other existing听commercial miniature x-ray devices. It would also assist with investigating the use of INTRABEAM at听different cancer sites in the body, and for combining INTRABEAM treatments with external beam听radiotherapy. Most importantly, reducing the uncertainty of delivered dose will ultimately lead to听improving patient outcome.
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Key publications
- Watson, P., Mainegra-Hing, E., Tomic, N., & Seuntjens, J. (2015). Implementation of an efficient Monte Carlo calculation for CBCT scatter correction: phantom study. Journal Of Applied Clinical Medical Physics, 16(4). doi:10.1120/jacmp.v16i4.5393
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Awards
平特五不中 Physics Graduate Fellowship (2013)
Research Institute of the MUHC Studentship (2011)
NSERC Undergraduate Research Award (declined) (2006)