Dosimetry of Pacemaker in VMAT for Lung SBRT

Abstract

This study investigated the possibility to include the pacemaker in volumetric modulated arc therapy (VMAT) plan optimization for lung stereotactic body radiotherapy (SBRT) to reduce the pacemaker dose. Moreover, dose distributions of the planning target volume (PTV) and organs-atrisk (OARs) with and without lowering the pacemaker dose in VMAT plans were compared with the PTV close to and far away from the pacemaker. Patients with PTVs in their left and right lung were selected in their lung SBRT. VMAT plans with pacemaker regarded as an OAR or not in the plan optimization were created. Dose-volume histograms (DVHs) of PTVs and OARs were determined and compared. Our results showed that it is possible to achieve an acceptable PTV coverage by lowering the pacemaker dose in the VMAT plan, though larger dose-volume deviation of PTV can be found when it is closer to the pacemaker. In addition, DVH deviations for OARs were not significant when the pacemaker was regarded as an OAR in the plan. We also found that the dosimetric change is sensitive to the OARs namely, trachea, bronchus, esophagus and cord when the pacemaker was included in the plan optimization. We concluded that it is possible to reduce the pacemaker dose by regarding the pacemaker as an OAR in the VMAT plan for lung SBRT. This is especially important for patient depending seriously on the pacemaker, as the VMAT beam for SBRT is directly on the device with a very high dose per fraction.