System for MRI Guided Radiotherapy

Johan Overweg¹, Bas Raaymakers², Jan Lagendijk², Kevin Brown³

The abstract presents key features of an MRI system for MRI guided radiotherapy. The Linac-based radiation source is located on the outside of a cylindrical high-field MR scanner, radiating through the magnet's cryostat. The coil designs of main magnet and gradient coil provide a gap in the midplane of sufficient width to allow the beam to pass through. Magnetic interaction with the Linac is minimized by modification of the magnets active shielding configuration so that a ring-shaped low field ring is obtained at the location of the field-sensitive parts of the accelerator.