Compensating for the impact of non-stationary spherical air cavities on IMRT dose delivery in transverse magnetic fields

摘要

With the development of the 1.5 T MRI linear accelerator and the clinical introduction of the 0.35 T ViewRay (TM) system, delivering intensity-modulated radiotherapy (IMRT) in a transverse magnetic field becomes increasingly important. When delivering dose in the presence of a transverse magnetic field, one of the most prominent phenomena occurs around air cavities: the electron return effect (ERE). For stationary, spherical air cavities which are centrally located in the phantom, the ERE can be compensated by using opposing beams configurations in combination with IMRT.