The entire rotating unit of the Clinac that emits the treatment beam. The upper part of the gantry includes the linear accelerator and electron gun, while the lower part contains a counterweight or a retractable beam stopper. The entire rotating unit of the HET Clinac that emits the treatment beam. The upper part of the gantry includes the linear accelerator and electron gun, while the lower part contains a counterweight and the MV Imager platform.