Comparison of the efficiency of rescanning with and without respiratory gating technique in pencil beam scanning proton therapy for organ motion management

Pencil beam scanning (PBS) proton therapy has the capability of delivering a conformal dose to the target with relatively low dose to normal tissues. Several studies showed the advantages of PBS for lung cancer treatment. However, respiratory motion causes the interplay effect between organ motion and dynamic beam delivery. Many mitigation techniques have been introduced to reduce the interplay effect, including gating and rescanning. Rescanning is categorized into layered and volumetric rescanning. Recently, breath-sampled (BS) layered rescanning has been developed, giving superior dosimetric results than conventional rescanning for target motion of less than 10 mm but the treatment time was increased. In this work, BS layered scanning for a larger target motion was investigated in combination with gating. The efficiency, in terms of doimetric parameters and treatment time, of the following treatment techniques was compared: (1) gating alone, (ii) BS layered rescanning alone and (iii) BS layered rescanning combined with the gating technique. The four-dimensional computed tomography (4DCT) dataset of a lung cancer patient with a target motion of 11.6 mm was used in this study. The treatment plans were created in an open-source treatment planning system, namely matRad.