Design and implementation of a film dosimetry audit tool for comparison of planned and delivered dose distributions in high dose rate (HDR) brachytherapy

A novel phantom is presented for 'full system' dosimetric audit comparing planned and delivered dose distributions in HDR gynaecological brachytherapy, using clinical treatment applicators. The brachytherapy applicator dosimetry test object consists of a near full-scatter water tank with a...

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Bibliographic Details
Published in:Physics in medicine & biology 2013-10, Vol.58 (19), p.6623-6640
Main Authors: Palmer, Antony L, Lee, Chris, Ratcliffe, Ailsa J, Bradley, David, Nisbet, Andrew
Format: Article
Language:English
Subjects:
audit
brachytherapy
Brachytherapy - standards
Clinical Audit - methods
EBT3
Film Dosimetry - instrumentation
Film Dosimetry - standards
Gafchromic
high dose rate (HDR)
Humans
Phantoms, Imaging
Pilot Projects
quality control (QC)
Radiation Dosage
radiochromic
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
Reproducibility of Results
Uncertainty
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Summary:A novel phantom is presented for 'full system' dosimetric audit comparing planned and delivered dose distributions in HDR gynaecological brachytherapy, using clinical treatment applicators. The brachytherapy applicator dosimetry test object consists of a near full-scatter water tank with applicator and film supports constructed of Solid Water, accommodating any typical cervix applicator. Film dosimeters are precisely held in four orthogonal planes bisecting the intrauterine tube, sampling dose distributions in the high risk clinical target volume, points A and B, bladder, rectum and sigmoid. The applicator position is fixed prior to CT scanning and through treatment planning and irradiation. The CT data is acquired with the applicator in a near clinical orientation to include applicator reconstruction in the system test. Gamma analysis is used to compare treatment planning system exported RTDose grid with measured multi-channel film dose maps. Results from two pilot audits are presented, using Ir-192 and Co-60 HDR sources, with a mean gamma passing rate of 98.6% using criteria of 3% local normalization and 3 mm distance to agreement (DTA). The mean DTA between prescribed dose and measured film dose at point A was 1.2 mm. The phantom was funded by IPEM and will be used for a UK national brachytherapy dosimetry audit.
ISSN:0031-9155
1361-6560
DOI:10.1088/0031-9155/58/19/6623