Delivery efficiency and susceptibility to setup uncertainties of flattening filter free lung SBRT: influence of isocentre geometry and treatment modality.

This study used a cohort of ten patients to investigate the sensitivity of OAG SBRT lung plans to offsets in the isocentre position and compared it to those where the isocentre is placed at the centre of the target volume, i.e. central axis geometry (CAG). Comparisons were made for SBRT treatment plans using 3D conformal radiotherapy (3DCRT) and volumetric modulated arc therapy (VMAT). No statistically significant difference was found between OAG and CAG for SBRT treatments delivered with either 3DCRT or VMAT techniques in terms of plan quality metrics. Planned monitor units for 3DCRT plans were significantly less (p<0.001) using CAG compared to OAG for this patient cohort, suggesting more efficient treatment delivery. These significant differences in delivery efficiency based on isocentre geometry were not observed in the VMAT plans. The susceptibility of 3DCRT and VMAT plans to systematic setup uncertainties of 1 mm and 2 mm was not significantly influenced by choice of isocentre geometry. OAG and CAG based treatments are equally robust to systematic uncertainties in isocentre positioning. PMID: 30255854 [PubMed - as supplied by publisher]
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research