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Characterizing a proton beam scanning system for Monte Carlo dose calculation in patients
C Grassberger1, Anthony Lomax, H Paganetti
1Department of Radiation Oncology, Massachusetts General Hospital & Harvard Medical School, Boston MA 02114, USA. Centre for Proton Radiotherapy, Paul Scherrer Institut, 5232 Villigen-PSI, Switzerland.
Physics in Medicine and Biology
|December 31, 2014
Summary
Accurate proton radiation characterization for Monte Carlo dose calculations is feasible using only depth dose and spot size data. This method enables precise patient treatment simulations, though full head simulations are needed for out-of-field effects.
Area of Science:
- Medical Physics
- Radiation Oncology
- Computational Dosimetry
Background:
- Accurate Monte Carlo (MC) dose calculations are crucial for active scanning proton therapy.
- Characterizing the proton radiation field at the treatment head exit is essential for MC simulations.
- Current methods may not fully capture beamline specifics, potentially impacting dose accuracy.
Purpose of the Study:
- To demonstrate the feasibility of accurately characterizing proton radiation fields for MC dose calculations.
- To show this characterization can rely solely on measured depth dose curves and spot size.
- To calibrate MC codes for patient treatments at different institutions.
Main Methods:
- Calibrated a Monte Carlo code to beamlines at Massachusetts General Hospital (MGH) and Paul Scherrer Institute (PSI).
- Used measured depth dose curves and spot size data for calibration.
- Employed an analytical Bragg peak model to determine range-dependent energy spread.
Main Results:
- Simulations using parameterized phase space at MGH treatment head exit were adequate for patient simulations.
- Secondary particle production was generally below 0.2% of primary fluence.
- Full treatment head simulations are necessary for accurate low-dose penumbra and out-of-field effect studies.
- Simulated and measured depth dose curves agreed within 0.5 mm.
Conclusions:
- A feasible method for characterizing proton radiation fields using limited measurements was established.
- The approach allows for accurate MC dose calculations in active scanning proton therapy.
- This technique can be applied to investigate discrepancies in patient-specific treatments across different anatomical sites.
