The feasibility of breath control management guided stereotactic ablation body radiotherapy of liver tumors by volumetric modulated arc therapy

Objective: To investigate the feasibility and plan quality of the image-guided volumetric modulated arc therapy (VMAT) based voluntary deep exhale breath-holding technique in the stereotactic ablative body radiotherapy (SABR) for liver tumors. Methods: Fifteen patients with liver tumors were involved in this study. All patients were immobilized with voluntary deep exhale breath hold (vDEBH) combined with real-time position management (RPM) respiratory gating system. Treatment was planned using VMAT with 2 modified partial arc and re-planned using intensity modulated radiation therapy (IMRT) technique for comparison. Dosimetric parameters were calculated for plan quality assessment. Quality assurance studies included absolute dose and multiple planar dose verifications, total monitor units and delivery time analysis. Daily cone beam computed tomography imaging was used to verify the motions. Results: There were no significant dosimetric differences between VMAT and conventional IMRT plans(P > 0.05). Both techniques were able to minimize doses to organs at risk including normal liver, kidneys, spinal cord, and stomach. However, the average monitor units with VMAT were significantly lower 28.1% than those with IMRT(t = 3.064, P < 0.05). The average beam-on time in VMAT plans was 31.6% shorter than that in IMRT plans(t = 2.278, P < 0.05). Conclusions: The utilization of VMAT in the treatment planning of SABR for liver tumors under breath control mode has better dosimetrics. In comparison to conventional IMRT plans, VMAT plans have higher efficiency and feasibility. (authors)