Highlights
- •An ‘end-to-end’ IMRT audit was carried out in Portugal.
- •A customized anthropomorphic phantom SHANE was used to mimic a typical H&N patient.
- •A small volume ionization chamber and film were used for dosimetric verification.
- •Globally the results were within the defined tolerances in all centres.
- •Factors contributing to poorer results were identified and recommendations given.
Abstract
Purpose
The IAEA newly developed “end-to-end” audit methodology for on-site verification of
IMRT dose delivery has been carried out in Portugal in 2018. The main goal was to
evaluate the physical aspects of the head and neck (H&N) cancer IMRT treatments. This
paper presents the national results.
Methods
All institutions performing IMRT treatments in Portugal, 20 out of 24, have voluntarily
participated in this audit. Following the adopted methodology, a Shoulder, Head and
Neck End-to-End phantom (SHANE) – that mimics an H&N region, underwent all steps of
an IMRT treatment, according to the local practices. The measurements using an ionization
chamber placed inside the SHANE phantom at four reference locations (three in PTVs
and one in the spinal cord) and an EBT3 film positioned in a coronal plane were compared
with calculated doses. FilmQA Pro software was used for film analysis.
Results
For ionization chamber measurements, the percent difference was within the specified
tolerances of ±5% for PTVs and ±7% for the spinal cord in all participating institutions.
Considering film analysis, gamma passing rates were on average 96.9%±2.9% for a criterion
of 3%/3 mm, 20% threshold, all above the acceptance limit of 90%.
Conclusions
The national results of the H&N IMRT audit showed a compliance between the planned
and the delivered doses within the specified tolerances, confirming no major reasons
for concern. At the same time the audit identified factors that contributed to increased
uncertainties in the IMRT dose delivery in some institutions resulting in recommendations
for quality improvement.
Keywords
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Article info
Publication history
Published online: August 23, 2019
Accepted:
August 15,
2019
Received in revised form:
July 25,
2019
Received:
March 22,
2019
Identification
Copyright
© 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
