A system for positioning and repositioning of a portion of a patient's body with respect to a treatment or imaging machine includes multiple cameras to view the body and the machine. Index markers, either light-emitting, passive, geometric shapes, or natural landmarks, are identified and located by the cameras in 3D space. In one embodiment, such reference or index markers are in a determinable relationship to analogous markers used during previous image scanning of the patient. Anatomical targets determined from image scanning can be located relative to reference positions associated with the treatment or diagnostic machine. Several forms of camera, index markers, methods and systems accommodate different clinical uses. X-ray imaging of the patient further refines anatomical target positioning relative to the treatment or diagnostic imaging reference point. Movements of the patient based on comparative analysis of imaging determined anatomical targets relative to reference points on treatment or diagnostic apparatus are controlled by the system and process of the invention.