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Implementation and evaluation of a transit dosimetry system for treatment verification

Ricketts, K; Navarro, C; Lane, K; Moran, M; Blowfield, C; Kaur, U; Cotten, G; ... Adeyemi, A; + view all (2016) Implementation and evaluation of a transit dosimetry system for treatment verification. Physica Medica , 32 (5) pp. 671-680. 10.1016/j.ejmp.2016.04.010. Green open access

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Abstract

PURPOSE: To evaluate a formalism for transit dosimetry using a phantom study and prospectively evaluate the protocol on a patient population undergoing 3D conformal radiotherapy. METHODS: Amorphous silicon EPIDs were calibrated for dose and used to acquire images of delivered fields. The measured EPID dose map was back-projected using the planning CT images to calculate dose at pre-specified points within the patient using commercially available software, EPIgray (DOSIsoft, France). This software compared computed back-projected dose with treatment planning system dose. A series of tests were performed on solid water phantoms (linearity, field size effects, off-axis effects). 37 patients were enrolled in the prospective study. RESULTS: The EPID dose response was stable and linear with dose. For all tested field sizes the agreement was good between EPID-derived and treatment planning system dose in the central axis, with performance stability up to a measured depth of 18cm (agreement within -0.5% at 10cm depth on the central axis and within -1.4% at 2cm off-axis). 126 transit images were analysed of 37 3D-conformal patients. Patient results demonstrated the potential of EPIgray with 91% of all delivered fields achieved the initial set tolerance level of ΔD of 0±5-cGy or %ΔD of 0±5%. CONCLUSIONS: The in vivo dose verification method was simple to implement, with very few commissioning measurements needed. The system required no extra dose to the patient, and importantly was able to detect patient position errors that impacted on dose delivery in two of cases.

Type: Article
Title: Implementation and evaluation of a transit dosimetry system for treatment verification
Location: Italy
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.ejmp.2016.04.010
Publisher version: http://doi.org/10.1016/j.ejmp.2016.04.010
Language: English
Additional information: Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
Keywords: EPIDs, Radiotherapy, Transit dosimetry, Treatment verification, Portal Imaging Devices, Imrt Verification, Cancer
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Surgery and Interventional Sci
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Surgery and Interventional Sci > Department of Targeted Intervention
URI: https://discovery.ucl.ac.uk/id/eprint/1487705
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