Research Masterclass in Radiotherapy Physics 2017

How to deal with Lorentz forces on scatter electrons • The trajectories of scattered electrons will curve in a magnetic field • This effect is most prominent at the interface between tissue and air (‘Electron Return Effect’)

Options 1. Minimize the B 0 field 2. irradiate parallel to the B 0 field 3. choose clever beam geometries 4. Accept and incorporate in dose calculation (Monte Carlo)

Raaijmakers et al. Phys. Med. Biol. 50, 1363 (2005);