Robustness evaluation of carbon ion radiotherapy for ventricular tachycardia

Favorable clinical outcomes of carbon-ion radiotherapy (CIRT) for ventricular arrhythmia have been reported, and optimal treatment strategies are being explored. We assessed the robustness of CIRT plans against cardiac motion in ventricular tachycardia. Electrocardiographic (ECG)-gated computed tomography (CT) images at end-diastole and end-systole were used for planning, and dose distributions were recalculated on the opposite phase to evaluate dosimetric changes. Cardiac motion reduced target coverage by about 13.8-19.0%, whereas a 5-mm margin or robust optimization reduced the decrease approximately to 5%. An optimization approach that accounts for cardiac motion using ECG-gated CT provided a favorable balance for clinical application.