Highlights
- •A new method based on intraoperative imaging was employed for breast IOERT setup verification.
- •Treatment delivery verification of breast IOERT performed using film dosimetry.
- •Surface dose and distal end dose were measured by the EBT2 film.
- •Image-based setup verification and in-vivo dosimetry are quite mandatory for breast IOERT QA.
Abstract
Introduction
Single fraction nature of intraoperative radiotherapy highly demands a quality assurance
procedure to qualify both beam setup and treatment delivery. The aim of this study
is to evaluate the treatment setup during breast intraoperative electron radiotherapy
(IOERT) and in-vivo dose delivery verification.
Materials and methods
Twenty-five breast cancer patients were enrolled and setup verification for each case
was performed using C-arm imaging. The received dose by surface and distal end of
target was measured by EBT2 film. The significance level of difference between obtained
dosimetry results and predicted ones was evaluated by the T statistical test.
Results
Acquired C-arm images in two different oblique views revealed any misalignment between
the applicator and shielding disk. The mean difference between the measured surface
dose and expected one was 1.8% ± 1.2 (p = 0.983) while a great disagreement, 11.1% ± 1.5
(p < 0.001), was observed between the measured distal end dose and expected one. This
discrepancy is mainly correlated to the backscattering effect from the shielding disk.
Target depth nonuniformities can also contribute to this remarkable difference.
Conclusion
Employing the intraoperative imaging for IOERT setup verification can considerably
improve the treatment quality. Therefore, it is suggested to implement this imaging
procedure as a part of treatment quality assurance. Favorable agreement between the
predicted and measured surface doses demonstrates the applicability of EBT2 film for
dose delivery verification. The results of in-vivo dosimetry showed that the electron
backscattering from employed shielding disk can affect the received dose by the distal
end of tumor bed.
Keywords
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Article info
Publication history
Published online: March 24, 2019
Accepted:
March 19,
2019
Received in revised form:
February 25,
2019
Received:
October 15,
2018
Identification
Copyright
© 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
