Development of an EGSnrc Multi-Leaf Collimator Component Module and Treatment Head Model for a Low-Field MRI Linear Accelerator
Recommended Citation
Etienne T, Kim J, Thind K, and Chetty IJ. Development of an EGSnrc multi-leaf collimator component module and treatment head model for a low-field MRI linear accelerator. Med Phys 2024.
Document Type
Article
Publication Date
10-10-2024
Publication Title
Medical physics
Abstract
BACKGROUND: Monte Carlo (MC) modeling of MR-guided radiotherapy (MRgRT) treatment machines enables the characterization of photon/electron interactions in the presence of a magnetic field. The EGSnrc MC code system is a well-established system for radiation dose calculations. The multi-leaf collimator (MLC) component modules presently available within the EGSnrc MC code system do not include a model of the double-focused MLC available on a low-field (0.35T) MRI linear accelerator (MR linac). PURPOSE: Here we developed and validated a new component module (CM) for the low-field MRgRT MLC using the EGSnrc/BEAMnrc/DOSXYZnrc code system. We performed detailed modeling of the treatment head and validated the model using measurements and calculations from the vendor-specific treatment planning system (TPS).
METHODS: The detailed geometry of the low-field MR linac MLC and other treatment head structures were modeled using BEAMnrc. Comparisons of DOSXYZnrc simulated dose against measurements and the low-field MR linac TPS for a variety of AAPM TG-53 task group report suggested square and shaped fields, as well as a step-and-shoot intensity-modulated radiotherapy (IMRT) plan, are presented.
RESULTS: Our model agrees with both measured and TPS calculated data on average within 2%/2 mm (dose/DTA) criterion for square field profiles. Output factors agreed within 1% for field sizes down to 2.49 × 2.49 cm(2) and within 2% of TPS data for the smallest field size of 0.83 × 0.83 cm(2). Shaped field and IMRT MC calculations agreed with measured and TPS data such that the gamma pass rates (3%/2 mm) were 99.5% and (3%/3 mm) 96.2%, respectively.
CONCLUSIONS: We developed and validated an MLC CM (SYNCVRMLC) for the low-field MR linac using the EGSnrc MC code systems. This new CM will facilitate MC computation of fluence and dose distributions using BEAMnrc/DOSXYZnrc for patients treated on the low-field MR linac.
PubMed ID
39388092
ePublication
ePub ahead of print
