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Magnetic fields with photon beams: Dose calculation using electron multiple‐scattering theory
Author(s) -
Jette David
Publication year - 2000
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 - 10.1118/1.1286554
Subject(s) - physics , electron , photon , monte carlo method , compton scattering , scattering , magnetic field , monte carlo method for photon transport , computational physics , dosimetry , beam (structure) , pair production , atomic physics , nuclear physics , optics , dynamic monte carlo method , quantum mechanics , statistics , mathematics , direct simulation monte carlo , medicine , radiology
Strong transverse magnetic fields can produce large dose enhancements and reductions in localized regions of a patient under irradiation by a photon beam. We have developed a new equation of motion for the transport of charged particles in an arbitrary magnetic field, incorporating both energy loss and multiple scattering. Key to modeling the latter process is a new concept, that of “typical scattered particles.” The formulas which we have arrived at are particularly applicable to the transport of, and deposition of energy by, Compton electrons and pair‐production electrons and positrons generated within a medium by a photon beam, and we have shown qualitatively how large dose enhancements and reductions can occur. A companion article examines this dose modification effect through systematic Monte Carlo simulations.