HIT is the world’s first heavy ion treatment facility with a 360° rotating beam delivery system – the gantry. In conventional radiation therapy with photons, mobile radiation sources have already been used very successfully in clinical applications for decades. Proton facilities also use gantries.
The gantry at HIT is a gigantic steel construction. It is 25 meters long, 13 meters in diameter and weighs 670 tons, of which 600 tons can be rotated with submillimeter precision.
The particle beam technology of the gantry and the HIT facility in general was developed by the GSI Helmholtz Center for Heavy Iron Research in Darmstadt. The rotating structure was built by MT Aerospace, the global leader in satellite and telescope construction. The tech-nology for treating the patients was developed in the context of a cooperation between Siemens Healthcare and the experts at HIT-Betriebs GmbH. Today, a team of physicists, technicians and software specialists at Heidelberg University Hospital’s HIT-Betriebs GmbH is responsible for operations and technical refinement.
The gantry works extremely precisely. The beam reaches the patients at up to 75% of the speed of light, can penetrate up to 30 centimeters into the tissue and still deviates from the target by no more than one millimeter.
With HIT’s gantry a tumor can be irradiated with heavy ions (carbon, helium, oxygen) and protons (hydrogen) from any angle. In addition, the robot-based treatment table is adjusta-ble in six ways. Combining these two movements enables an infinite number of beam en-trance angles to be realized for the beam delivery. This means that the individual pencil beams are superimposed in the tumor and accumulate to deliver the total dose at this site only. For this purpose, the raster scanning method was integrated into the HIT gantry. This extremely accurate irradiation method scans the tumor, millimeter by millimeter. In this way, healthy tissue is ideally spared and receives only a fraction of the tumor dose. Especial-ly if the tumor has a complicated location in the proximity of highly radiation-sensitive or-gans such as the intestines or the optic nerve, the burden on these organs can be minimized by selection of particularly favorable beam entrance angles.