Spiraling contaminant electrons increase doses to surfaces outside the photon beam of an MRI-linac with a perpendicular magnetic field.

This study investigated doses from SCE for an MRI-linac comprising a 7MV linac and a 1.5T MRI scanner. Surface doses to films perpendicular to the magnetic field and 5cm from the radiation beam edge showed increased dose within the projection of the primary beam, whereas films parallel to the magnetic field and 5cm from the beam edge showed no region of increased dose. However, the dose from contaminant electrons is absorbed within a few millimeters. For large fields, the SCE dose is within the same order of magnitude as doses from scattered and leakage photons. Doses for both SCE and scattered photons decrease rapidly with decreasing beam size and increasing distance from the beam edge.
PMID: 29595150 [PubMed - as supplied by publisher]

Source: Physics in Medicine and Biology - March 29, 2018 Category: Physics Authors: Hackett SL, van Asselen B, Wolthaus JWH, Bluemink JJ, Ishakoglu K, Kok JGM, Lagendijk JJW, Raaymakers BW Tags: Phys Med Biol Source Type: research