Performance evaluation of gated volumetric modulated arc therapy

Abstract

Background: Aim of this study is to evaluate the accuracy of the gated volumetric modulated arc therapy (VMAT/RapidArc) using 2D planar dosimetry, DynaLog files and COMPASS 3D dosimetry system. Materials and Methods: Pre-treatment quality assurance of 10 gated VMAT plans was verified using 2D array and COMPASS 3D dosimetry system. Advantage of COMPASS over 2D planar is that it provides the clinical consequence of error in treatment delivery. Measurements were performed for non-gated and different phase ga.ng window level (80%, 50%, 30% & 20%) to know the impact of ga.ng in VMAT dose delivery. Results: In 2D planar dosimetry, gamma agreement index (GAI) for all measurements were more than 95%. DynaLog file analysis shows the average devia.ons between actual and expected posi.ons of monitor units, gantry and mul.-leaf collimator. The STDVs MU and gantry posi.on were less than 0.10 MU and 0.33° respec.vely. Root mean square (RMS) of the devia.ons of all leaves were less than 0.58 mm. The results from COMPASS show that 3D dose volume parameters for ten pa.ents measured for different phase ga.ng window level were within the tolerance level of ±5%. Average 3D gamma of PTV and OAR's for different window level was less than 0.6. Conclusion: The results from this study show that gated VMAT delivery provided dose distribu.ons equivalent to non-gated delivery to within clinically acceptable limits and COMPASS along with Matrix Evolu.on can be effec.vely used for pretreatment verifica.on of gated VMAT plans.

Dosimetric evaluation of respiratory gated volumetric modulated arc therapy for lung stereotactic body radiation therapy using 3D printing technology

“…Respiratory gated volumetric modulated arc therapy (VMAT) has been reported to sustain tumor dose conformity and normal organ sparing despite the significant target motion induced by the patient’s respiration during beam delivery [1–3]. Recently, gating technology in VMAT has become clinically available to improve the dosimetric efficacy of stereotactic body radiotherapy (SBRT) to respiratory moving targets.…”

“…Recently, several studies on gated VMAT for SBRT have reported using a homogeneous dynamic phantom under both static and gating conditions [1,3,13,15]. However, no study has shown the dosimetric results of gated VMAT while considering the heterogeneity and realistic target motion in lung SBRT.…”

“…However, the patient-specific implementation of actual organ tissues has been morphologically limited with such phantoms. In addition, the realistic respiratory motions have generally not been considered [1,3,4].…”