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First Monte Carlo beam model for ultra-high dose rate radiotherapy with a compact electron LINAC
Tianyuan Dai1,2, Austin M Sloop1, Mahbubur R Rahman3
1Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA.
Medical Physics
|March 17, 2024
Summary
A validated Monte Carlo model for the ultra-high dose rate (UHDR) Mobetron electron beam was developed. This model enables accurate dose calculations for preclinical research and clinical trials in FLASH radiotherapy.
Area of Science:
- Medical Physics
- Radiation Oncology
Background:
- Ultra-high dose rate (UHDR) FLASH radiotherapy is a rapidly advancing field.
- Dedicated UHDR electron devices are crucial for current FLASH research.
Purpose of the Study:
- To develop and validate the first Monte Carlo (MC) electron beam model for the UHDR-capable Mobetron (FLASH-IQ).
- To establish a platform for dose calculation and treatment planning in preclinical and clinical FLASH-RT research.
Main Methods:
- Implemented the Mobetron beamline geometry in the Geant4-based GAMOS MC toolkit.
- Tuned electron source characteristics (energy spectrum, beamline parameters) to match commissioning data (PDDs, lateral profiles).
- Validated the MC model by comparing calculated PDDs and profiles against EBT-XD film measurements.
Main Results:
- The 9 MeV electron FLASH beams were accurately represented by a Gaussian energy spectrum (mean 9.9 MeV, variance 0.2 MeV).
- MC model showed good agreement with commissioning data (discrepancy < 3%) and achieved high gamma pass rates (e.g., 98.7% for PDDs with 2mm/2% criteria).
Conclusions:
- A validated MC beam model for the UHDR Mobetron is now available.
- This model supports direct dose calculation and treatment planning for FLASH-RT.
- Facilitates translational and clinical FLASH-RT trials on the Mobetron FLASH-IQ platform.
