Apparatus for radiation therapy combines a patient table, an MRI and a radiation treatment apparatus mounted in a common treatment room with the MR magnet movable through a radiation shielded door to an imaging position. An initial MR image and an initial X-ray image is used to generate an RT program for the patient to be carried out in a plurality of separate treatment steps. Before carrying out the procedure, a registration step is performed using a phantom by which X-ray images are registered relative to MR images to generate a transformation algorithm required to align the MR images of the part of the patient relative to the X-ray images. Prior to each separate treatment step a current MR image of the part of the patient is obtained and the transformation algorithm data is used from the current MR image is used in guiding the RT treatment step.
