Room: Exhibit Hall | Forum 4
Purpose: To report our experience of commissioning the first Mevion HYPERSCAN PBS proton system; to quantify the proton beam characteristics of this dramatically unique proton system; and to report our initial experience on treatment plans based on such unique beam properties
Methods: The Mevion HYPERSCAN is the first single-room proton system with a superconducting synchrocyclotron mounted on a rotating gantry. It builds the scanning magnets, the beam monitoring dosimetry system, the Energy Selector (ES) and the spot trimming Adaptive Aperture (AA) into a nozzle of only 2-m in length. Bragg Peak curves for spot maps as well as single spot beams, and single spot profiles were acquired. Performance of the AA was evaluated by spot maps of various sizes with and without the AA. Performance of the EE was evaluated using Bragg peaks produced by various combinations of energy selection plates.
Results: The sigmas of spots in air varied from 0.37 cm to 1.74 cm from 227 MeV to 64 MeV at the ISO plane. The percent depth dose for both single spot and spot maps yielded a constant Bragg peak width of 8.4 mm at 80%-to-80%) and distal 80%-20% fall-off of 4.5 mm. The Adaptive Aperture can effectively reduce the penumbra by 0.2 cm for the highest energy of 227 MeV to 1 cm for the 64 MeV beam. The ES has a fast energy switching time of 50 ms.
Conclusion: The HYPERSCAN system has beam characteristics significantly different from that of other proton systems. The AA, which is the first such penumbra trimming device built on a PBS proton system, can effectively sharpen proton spots to achieve faster lateral dose fall off. The ES achieves the fastest energy switching time.
Not Applicable / None Entered.