Benchmarking a GATE/Geant4 Monte Carlo model for proton beams in magnetic fields
Fatima Padilla-Cabal1,2, Jose Alejandro Fragoso3, Andreas Franz Resch1,2
1Department of Radiotherapy, Medical University of Vienna/AKH, Vienna, Austria.
Medical Physics
|October 30, 2019
Summary
A new Monte Carlo (MC) model accurately simulates proton beam behavior in magnetic resonance guidance for proton therapy (MRPT). This validated model is crucial for precise dose calculations and treatment planning in MRPT.
Area of Science:
- Medical Physics
- Radiation Oncology
- Computational Physics
Background:
- Magnetic resonance guidance in proton therapy (MRPT) promises improved treatment outcomes.
- Integrating magnetic fields into proton therapy presents significant challenges in dosimetry, treatment planning, and dose delivery due to beam deflection and Bragg peak shifts.
Purpose of the Study:
- To develop and validate a Monte Carlo (MC) beam model for accurate dose calculation in MRPT under static magnetic fields up to 1 Tesla.
- To predict and compensate for the effects of magnetic fields on proton beam trajectories and Bragg peak positions.
Main Methods:
- Simulated proton beam interactions with magnetic fields using the GATE/Geant4 toolkit, implementing custom 3D magnetic field transport.
- Validated the model through experiments using a proton pencil beam scanning system and a dipole magnet, measuring dose with Gafchromic EBT3 films in homogeneous and heterogeneous phantoms.
- Corrected for EBT3 film LET quenching and compared planar dose distributions, lateral deflections, and spot sizes against MC predictions.
Main Results:
- MC-predicted proton beam deflections agreed with experimental measurements within 4 mm.
- Differences in beam width (FWHM) between calculations and measurements were less than 2 mm.
- In-depth dose profiles in homogeneous phantoms showed range and average dose differences below 0.2 mm and 1.2%, respectively. Agreements within 1 mm were observed for beam positions and widths in heterogeneous phantoms.
Conclusions:
- A validated GATE/Geant4 MC beam model for proton transport in magnetic fields up to 1 T was successfully developed.
- The model's accuracy was confirmed for single energy beams and spread-out Bragg peaks (SOBP) in both homogeneous and heterogeneous phantoms.
- This MC model is expected to significantly aid treatment planning and quality assurance for MRPT.
Related Concept Videos
01:24Potential Due to a Magnetized Object
737
Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...
The vector...
737
01:22Motion Of A Charged Particle In A Magnetic Field
6.6K
A charged particle experiences a force when moving through a magnetic field. Consider the field to be uniform and the charged particle to move perpendicular to it. If the field is in a vacuum, the magnetic field is the dominant factor determining the motion. Since the magnetic force is perpendicular to the direction of motion, a charged particle follows a curved path. The particle continues to follow this curved path until it forms a complete circle. Another way to look at this is that the...
6.6K