Compensation for target motion in ion beam therapy

Active beam scanning results in serious distortion of ion-beam irradiation field in the presence of target motion and causes damage to healthy tissues around tumor target compared to passive beam shaping techniques. Therefore, it is necessary to establish suitable conformal irradiation methods for moving targets caused by the factor such as respiration in active ion beam scanning system. In this paper, motion detection, 4D-CT and three main ion beam specific mitigation techniques, namely rescanning, gating and beam tracking, are introduced. In addition, three motion mitigation techniques are compared comprehensively in terms of target conformation, robustness and implementation complexity, respectively. For target conformation, the beam tracking is superior to gating, and gating is better than beam rescanning; the robustness decreases in the order rescanning-gating-beam tracking; for implementation complexity, beam rescanning is the most simple technology, followed by gating, while beam tracking is the most complex technique. (authors)