Patient selection and simulation
Of 81 patients previously treated with VMAT CSI at our institution during 2012-2022, only five patients had PTV length less than 50 cm in the cranio-caudal direction (current RefleXion X1 Treatment Planning System (TPS) limitation). These five patients were included in the planning feasibility study. Patients were simulated using Siemens CT scanner (slice thickness 2 mm) in the head-first-supine (HFS) position with arms by side, immobilized in 5-point head and neck mask and AccuForm cushion (CIVCO) in the neutral neck position. All patients were treated under anesthesia.