High-dose hypofractionated pencil beam scanning carbon ion radiotherapy for lung tumors: Dosimetric impact of different spot sizes and robustness to interfractional uncertainties

PurposeThe robustness against setup and motion uncertainties of gated four-dimensional restricted robust optimization (4DRRO) was investigated for hypofractionated carbon ion radiotherapy (CIRT) of lung tumors.MethodsCIRT plans of 9 patients were optimized using 4DRRO strategy with 3 mm setup errors, 3% density errors and 3 breathing phases related to the gate window. The prescription was 60 Gy(RBE) in 4 fractions. Standard spots (SS) were...