Independent verification of gantry angle for pre-treatment VMAT QA using EPID.

Journal Article (Journal Article)

We propose a method to incorporate independent verification of gantry angle for electronic portal imaging device (EPID)-based pre-treatment quality assurance (QA) of clinical volumetric modulated arc therapy (VMAT) plans. Gantry angle is measured using projections in the EPID of a custom phantom placed on the couch and the treatment plan is modified so as to be incident on the phantom with a portion of the beam that is collimated in the clinical plan. For our implementation, collimator and couch angles were set to zero and the inferior jaw and two most inferior multi-leaf collimator pairs were opened for the entire QA delivery. A phantom containing five gold coils was used to measure the gantry rotation through which each portal image was acquired. We performed the EPID QA for ten clinical plans and evaluated accuracy of gantry angle measurement, scatter incident on the imager due to the phantom, inter-image pixel linearity and inter- and intra-image noise. The gantry angle could be measured to within 0.0 ± 0.3° for static gantry and 0.2 ± 0.2° for arc acquisitions. Scatter due to the presence of the phantom was negligible. The procedure was shown to be feasible and adds gantry angle to the treatment planning parameters that can be verified by EPID-based pre-treatment VMAT QA.

Full Text

Duke Authors

Cited Authors

  • Adamson, J; Wu, Q

Published Date

  • October 21, 2012

Published In

Volume / Issue

  • 57 / 20

Start / End Page

  • 6587 - 6600

PubMed ID

  • 23010739

Electronic International Standard Serial Number (EISSN)

  • 1361-6560

Digital Object Identifier (DOI)

  • 10.1088/0031-9155/57/20/6587


  • eng

Conference Location

  • England