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.