Systems and methods of tracking location of an internal bodily structure of a patient in a radiation treatment room, including a fiducial marker having a unique center point, an offset structure detachably connected to the fiducial marker, the offset structure having unique three dimensional offset coordinates relative to the center point, a means for detachably mounting the offset structure to the patient, an imaging unit to measure location information of the offset structure relative to a target internal bodily structure of the patient, and a detection unit to detect location information of the offset structure and to calculate an offset distance between the target internal bodily structure and the center point.
