Patent ID: 8903471

Claim:
A combined radiation therapy and magnetic resonance unit, comprising: a magnetic resonance diagnosis part with an interior within which a main magnet generates a main magnet field, said interior being limited in a radial direction about an axis by the main magnet, and a radiation therapy part for irradiation of an irradiation area within the interior, said radiation therapy part comprising an electron beam accelerator which provides an electron beam directed parallel to the main magnet field; at least parts of the radiation therapy part comprising a beam deflection enclosure defining an enclosed volume entirely radially surrounding the electron beam and deflecting the electron beam in a single plane and along a two dimensional trajectory lying within said plane and toward the axis from an initial trajectory parallel to the axis, said enclosure being arranged within the interior; and said beam deflection enclosure comprising a magnetic arrangement creating first and second magnetic fields, the first magnetic field being of magnitude equal to a magnitude of the main magnet field in a region of the beam deflection enclosure, but of opposite direction, and effective to cancel the main magnet field in the region of the beam deflection enclosure, and the second magnetic field in the region of the beam deflection enclosure and directed perpendicular to said two dimensional trajectory of the electron beam throughout said two dimensional trajectory to cause the electron beam to be deflected inward into the interior and towards the axis.