Log file-based patient dose calculations of double-arc VMAT for head-and-neck radiotherapy

Abstract Purpose The logfile-based method cannot display dosimetric changes due to linac component miscalibration because of the insensitivity of logfiles to linac component miscalibration. The purpose of this study was to supply dosimetric changes in logfile-based patient dose calculations for double-arc volumetric-modulated arc therapy (VMAT) in head-and-neck cases. Methodsand materials Fifteen head-and-neck cases participated in this study. For each case, treatment planning system (TPS) doses were produced by double-arc and single-arc VMAT. Miscalibration-simulated logfiles were generated by inducing a leaf miscalibration of ±0.5 mm into the logfiles that were acquired during VMAT irradiation. Subsequently, patient doses were estimated using the miscalibration-simulated logfiles. Results For double-arc VMAT, regarding planning target volume (PTV), the change from TPS dose to miscalibration-simulated logfile dose in D mean was 0.9 Gy and that for tumor control probability was 1.4%. As for organ-at-risks (OARs), the change in D mean was mean and radiobiologicalmetrics ( P Conclusions Using the logfile-based method for PTV and OARs, the logfile-based method estimate of patient dose using the double-arc VMAT has accuracy comparable to that obtained using the single-arc VMAT.