Dosimetry Analysis of the Chang Gung Memorial Hospital Proton Radiosurgery System

In 2008, the Chang Gung Memorial Hospital (CGMH) signed a contract with Sumitomo Heavy Industries, Inc. to introduce the most advanced proton therapy facility into Taiwan. In this facility, four gantry treatment rooms (G1-4) will be constructed. Among them, G1/G2 will adopt the single scattering/wobbling technique and G3/G4 the pencil beam scanning (PBS) technique for beam delivery. Proton radiosurgery is a special treatment technique currently available only in few proton centers in the world and most of them were established on single or double scattering systems. Currently the CGMH commission team is evaluating whether to establish their proton radiosurgery system on the G1 wobbling or the G3 PBS nozzle. Based on beam transport theory and currently available beam data, the G3 nozzle has dosimetry advantage over the G1 nozzle. However, whether this is the best decision requires further study to confirm. This study will try to build one Monte Carlo dose simulation module and one analytical dose calculation program to simulate radiosurgery beam dosimetry properties established in the G1 and G3 nozzles so that pros and cons of their application can be analyzed. The Monte Carlo technique will be based on the PTSIM framework to simulate beam transport through the nozzle and the patient so that beam characteristics and dose distribution inside patients can be obtained. The analytical dose algorithm will be built on measured depth dose distribution and multiple Coulomb scattering of Highland. In addition, the dose calculation algorithm of the CGMH commercial Eclipse treatment planning system suffers from its theoretical assumption of charged particle equilibrium (CPE) and thus have a lower calculation limit of field sizes around 3 cm. This study proposes to adopt the small field dose calculation theory developed by Massachusetts General Hospital (MGH) into the analytical dose calculation program so that the low calculation limit can be extended down to around 1 cm.

Project ID:PC10408-2480
External Project ID:MOST104-2314-B182-041