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Dosimetric accuracy of dynamic couch rotation during volumetric modulated arc therapy (DCR-VMAT) for primary brain tumours

Smyth, Gregory, Evans, Philip M., Bamber, Jeffrey C, Mandeville, Henry C, Rollo Moore, A, Welsh, Liam C, Saran, Frank H and Bedford, James L (2019) Dosimetric accuracy of dynamic couch rotation during volumetric modulated arc therapy (DCR-VMAT) for primary brain tumours Physics in Medicine & Biology, 64 (8), 08NT01.

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Radiotherapy treatment plans using dynamic couch rotation during volumetric modulated arc therapy (DCR-VMAT) reduce the dose to organs at risk (OARs) compared to coplanar VMAT, while maintaining the dose to the planning target volume (PTV). This paper seeks to validate this finding with measurements. DCR-VMAT treatment plans were produced for five patients with primary brain tumours and delivered using a commercial linear accelerator (linac). Dosimetric accuracy was assessed using point dose and radiochromic film measurements. Linac-recorded mechanical errors were assessed by extracting deviations from log files for multi-leaf collimator (MLC), couch, and gantry positions every 20 ms. Dose distributions, reconstructed from every fifth log file sample, were calculated and used to determine deviations from the treatment plans. Median (range) treatment delivery times were 125 s (123–133 s) for DCR-VMAT, compared to 78 s (64–130 s) for coplanar VMAT. Absolute point doses were 0.8% (0.6%–1.7%) higher than prediction. For coronal and sagittal films, respectively, 99.2% (96.7%–100%) and 98.1% (92.9%–99.0%) of pixels above a 20% low dose threshold reported gamma  <1 for 3% and 3 mm criteria. Log file analysis showed similar gantry rotation root-mean-square error (RMSE) for VMAT and DCR-VMAT. Couch rotation RMSE for DCR-VMAT was 0.091° (0.086–0.102°). For delivered dose reconstructions, 100% of pixels above a 5% low dose threshold reported gamma  <1 for 2% and 2 mm criteria in all cases. DCR-VMAT, for the primary brain tumour cases studied, can be delivered accurately using a commercial linac.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Electronic Engineering
Authors :
Smyth, Gregory
Evans, Philip
Bamber, Jeffrey C
Mandeville, Henry C
Rollo Moore, A
Welsh, Liam C
Saran, Frank H
Bedford, James L
Date : 26 February 2019
Funders : Cancer Research UK
DOI : 10.1088/1361-6560/ab0a8e
Grant Title : Cancer Research UK
Copyright Disclaimer : Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Additional Information : Embargo OK Metadata OK No Further Action
Depositing User : James Marshall
Date Deposited : 24 Aug 2020 14:39
Last Modified : 24 Aug 2020 14:39

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