Abstract
Purpose
The lunar design of a Venezia ovoid makes commissioning of the applicator very challenging
with traditional autoradiography. In this study, we propose a novel solution to ovoid
commissioning and a quality assurance (QA) workflow to effectively assess the entire
source path.
Methods and materials
A two-step commissioning process, using electron radiation and radiochromic films,
was developed to verify the most distal source position. The ovoid was first attached
to a film and was irradiated with a 12 MeV linac beam. This process was repeated on
a separate, unexposed film, followed by irradiating it with a HDR source at the most
distal position. Two lengths, including the ovoid thickness and the distance between
the irradiated spot and the ovoid's outer surface, were obtained from the films’ intensity
maps. The offset value was calculated from the subtraction of the two measured lengths.
Besides acquiring the offset, a source positional simulator (SPS) and a series of
planar x-rays from two orthogonal orientations were used to characterize source movement
within the ovoid.
Results
Compared to x-ray-based autoradiography, the electron exposure significantly improved
the ovoid's visibility on film. Our approach did not use surrogate, which further
improved measurement outcomes by decreasing inherent uncertainties. The SPS results
suggested the source movement was complex within the cervicovaginal area, but it was
predictable with the proposed QA workflow.
Conclusion
We introduced a novel, surrogate-free method to commission the Venezia ovoid, which
facilitated a manual applicator reconstruction. Additionally, we recommended QA multiple
source positions to safely use the ovoid in clinical settings.
Keywords
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Article info
Publication history
Published online: October 18, 2022
Accepted:
August 29,
2022
Received in revised form:
July 22,
2022
Received:
April 30,
2022
Footnotes
Disclosures: The authors declare no conflict of interest.
Identification
Copyright
© 2022 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.
