Evaluation of a Digital Tracking Calorimeter for In-Situ Range Verification during Particle Therapy

When protons or heavier ions are used for radiation treatment, it is paramount to assure quality by performing range verification during or right after treatment. This work presents, for the first time, a feasibility study for proton therapy range verification based on secondary charged particles using the digital tracking calorimeter designed by the Bergen pCT collaboration. Additionally, we compare the precision achievable with protons and carbon ions, by applying regression models to predict the beam range with Monte Carlo-simulated data. The simulated treatment scenario contains a water cuboid phantom of different thicknesses, with protons and carbon ions as treatment modality at different medically relevant energy levels. Results show that the error for carbon ions is lower despite having 100 times fewer primaries simulated, due to the much higher readout yield. The lowest mean absolute error was observed with a kernel regression as 0.27 ± 0.04 mm for protons, and with a Gaussian process as 0.18 ± 0.02 mm for carbon ions, which shows feasibility of range verification for proton and carbon therapy based on charged secondary particles using the digital tracking calorimeter.