A target positioner including a radiation source disposed in a source
housing, the radiation source adapted to emit a radiation beam, a target
holder adapted to be attached to and generally immobilize a target organ,
the target holder being rotatingly attached to a bearing assembly, a
patient support table for supporting a patient thereon, a rotator for
turning the patient support table about a rotation axis, and a source arm
fixedly attached at one portion thereof to the source housing and at
another portion thereof to the bearing assembly, such that when the
target holder is attached to a target organ and the rotator turns the
patient support table about the rotation axis, the target holder
constrains the target organ from translating with respect to the
radiation source and the source housing, and wherein the target holder
permits the target organ to rotate by means of the bearing assembly
relative to the source housing while experiencing slight translations
with respect to the patient support table, so that the radiation beam
emanating from the radiation source impinges upon the target organ at a
plurality of angles irrespective of the misalignments between the
radiation beam and the patient support table and between the patient
support table and the target organ.