Impact of high dose volumetric CT on PTV margin reduction in VMAT prostate radiotherapy.

Impact of high dose volumetric CT on PTV margin reduction in VMAT prostate radiotherapy. Phys Med Biol. 2019 Feb 07;: Authors: Cho YB, Alasti H, Kong V, Catton C, Berlin A, Chung P, Bayley A, Jaffray DA Abstract The aim of the study is to determine PTV margin for inter-observer variability in the volumetric modulated arc therapy (VMAT) prostate radiotherapy with high-dose volumetric CT (HDVCT) and conventional helical CT (CCT) for planning. Secondly to investigate the impact of geometric (PTV expansion) and dosimetric (conformity) imperfection of planning process on the PTV margin analysis. Prostate gland of ten patients were scanned with CCT and HDVCT techniques consecutively on a 320 slice volumetric CT scanner with wide field detector of 16 cm. Five radiation oncologists delineated CTV of the prostate. VMAT plans were developed with PTV margin of 4mm and 6mm (totaling 200 plans) and target coverage of each plan was evaluated on the target volume in agreement determined by shared voxels with three or more from 5 observers. Dosimetry on 200 VMAT plans showed that PTV margin for inter-observer variability were 6mm and 4mm for CCT and HDVCT techniques, respectively. It is about 3mm smaller than our estimation from the previous study (8.8mm and 7.3mm) based on the inter-observer variability. This difference is mainly due to the accuracy of PTV volume expansion and limited dose conformity to guarantee target coverage. PTVs were measured...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research