Impact of magnetic fields on calculated AAPM TG-43 parameters for 192Ir and 60Co HDR brachytherapy sources: A Monte Carlo study.
PURPOSE
The aim of this work is to investigate the influence of an external magnetic field (MF) on The American Association of Physicists in Medicine (AAPM) No. 43 Report (TG-43) parameters for 192Ir and 60Co high dose rate (HDR) brachytherapy sources using Monte Carlo (MC) simulation methods.


MATERIALS AND METHODS
We used the Geant4 toolkit (version 10.1. p01) to simulate the geometry of 192Ir and 60Co brachytherapy sources. AAPM TG-43 parameters (the radial dose function, g(r), and the anisotropy function, F (r, θ)) of both 192Ir and 60Co sources were calculated in the presence of a magnetic field with strengths of 1.5T, 3T, and 7T in the X, Y, and Z directions in a voxelized water phantom.


RESULTS
For the 192Ir source, the calculated values g(r) and F (r, θ) remained nearly unaffected by the magnetic field for all investigated strengths. For the 60Co source, the differences for the g(r) and F (r,θ) under the 1.5T, 3T, and 7T magnetic field strengths along the direction parallel with the MF were found to be an increase of up to 5%, 15%, and 33%, respectively. However, for the directions perpendicular with the magnetic field, there was a decrease of up to 3%, 6% and 15% under 1.5T, 3T and 7T strengths, respectively.


CONCLUSION
Our results highlight the necessity of a Monte Carlo-based treatment planning system (TPS) if cobalt HDR treatments are performed under a magnetic field, especially for strengths greater than 1.5T.
['Ranjbar|Sahar|S|', 'Gholami|Somayeh|S|', 'Longo|Francesco|F|', 'Sharp|Ryan|R|', 'Meigooni|Ali S|AS|']
D000465:Algorithms D001918:Brachytherapy D003037:Cobalt Radioisotopes D003198:Computer Simulation D007496:Iridium Radioisotopes D060526:Magnetic Fields D009010:Monte Carlo Method D019047:Phantoms, Imaging
Magnetic fields HDR brachytherapy (192)Ir and (60)Co sources Geant4 simulation