Refined method for calculation of compensation parameters

Irradiations of intra-fractionally moving organs with a scanned ion beam need to be performed with a dedicated motion mitigation technique to avoid cold-spots in the delivered dose distribution due to interplay [1]. One possible way to achieve this is beam tracking [2]. Beam tracking compensates organ motion by adjusting the position of the pencil beam in real-time during treatment delivery. This approach requires 4D treatment plan optimization, i.e. lateral and a longitudinal compensation parameters for each combination of beam position and motion phase [3]. This report presents a novel approach for compensation parameter optimization that takes the scanpath and the dose distribution of an individual beam position into account. We aim at less performance demands for the energy compensation system (energy change in between beam positions, i.e. within 10 ms).