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MO‐G‐BRF‐09: Investigating Magnetic Field Dose Effects in Mice: A Monte Carlo Study
Author(s) -
Rubinstein A,
Guindani M,
Followill D,
Melancon A,
Hazle J,
Court L
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4889201
Subject(s) - monte carlo method , imaging phantom , magnetic field , magnetostatics , beam (structure) , linear particle accelerator , nuclear medicine , dosimetry , materials science , physics , computational physics , nuclear magnetic resonance , medicine , optics , mathematics , statistics , quantum mechanics
Purpose: In MRI‐linac treatments, radiation dose distributions are affected by magnetic fields, especially at high‐density/low‐density interfaces. Radiobiological consequences of magnetic field dose effects are presently unknown; therefore, preclinical studies are needed to ensure the safe clinical use of MRI‐linacs. This study investigates the optimal combination of beam energy and magnetic field strength needed for preclinical murine studies. Methods: The Monte Carlo code MCNP6 was used to simulate the effects of a magnetic field when irradiating a mouse‐sized lung phantom with a 1.0cmx1.0cm photon beam. Magnetic field effects were examined using various beam energies (225kVp, 662keV[Cs‐137], and 1.25MeV[Co‐60]) and magnetic field strengths (0.75T, 1.5T, and 3T). The resulting dose distributions were compared to Monte Carlo results for humans with various field sizes and patient geometries using a 6MV/1.5T MRI‐linac. Results: In human simulations, the addition of a 1.5T magnetic field caused an average dose increase of 49% (range:36%–60%) to lung at the soft tissue‐to‐lung interface and an average dose decrease of 30% (range:25%–36%) at the lung‐to‐soft tissue interface. In mouse simulations, the magnetic fields had no effect on the 225kVp dose distribution. The dose increases for the Cs‐137 beam were 12%, 33%, and 49% for 0.75T, 1.5T, and 3.0T magnetic fields, respectively while the dose decreases were 7%, 23%, and 33%. For the Co‐60 beam, the dose increases were 14%, 45%, and 41%, and the dose decreases were 18%, 35%, and 35%. Conclusion: The magnetic field dose effects observed in mouse phantoms using a Co‐60 beam with 1.5T or 3T fields and a Cs‐137 beam with a 3T field compare well with those seen in simulated human treatments with an MRI‐linac. These irradiator/magnet combinations are suitable for preclinical studies investigating potential biological effects of delivering radiation therapy in the presence of a magnetic field. Partially funded by Elekta.