The ProBeam Energy Selection System (ESS) is a proton beam modification system, converting the fixed energy from the cyclotron to the desired treatment energy. In this way the ESS aids in verifying optimal treatment precision. The ESS is designed specifically for delivery of pencil beam scanning and the precision it offers.
The energy for each spot is prescribed in the treatment planning, and the integrated ProBeam system delivers the prescribed dose per spot to the treatment area. There is a dosimeter integrated into the nozzle that measures each spot before delivering the next to optimize dose rate and overall conformity.