Radiation therapy of a lesion in a part of a patient is carried out by maintaining the patient on a patient support table in fixed position using an immobilization device while the table is rotated between a magnetic resonance imaging system, a CT imaging system for generating a 360 degree scanned image of the patient at the location of the lesion and the radiation therapy system for generating a beam of radiation for treatment of the lesion and for scanning the beam 360 degrees around the lesion. The MR image locates the lesion and the CT system is used to calculate the treatment. Registration between the MR image, the CT image and the radiation treatment is provided by the fixed position of the part of the patient on the table which is held fixed using an immobilization system suitable for the part concerned which may include a molded head mask where the head is involved.
