ABSTRACT
Purpose
Recently, the Varian multichannel vaginal cylinder (MCVC) set for high-dose-rate 192Ir brachytherapy was commercially released. This MCVC was distinct from our existing
MCVC in its peripheral channel layout and tip design. This investigation sought to
assess the dosimetric impact of these changes.
Methods and Materials
The dimensions of the virtual model for each applicator were compared against both
physical and radiographic measurements. Volumetric dose distributions were generated
in silico using a model-based dose calculation algorithm (MBDCA). To characterize the effects
of the new peripheral channel layout on dose to adjacent areas (“dose-spill”), point
doses were compared using two sets of applicator-based reference points: at surface
or 5 mm radially from surface. To evaluate the dose-shaping capabilities, a dose distribution
was generated for the new applicator and assessed against a representative dose distribution
for a patient previously treated with existing equipment.
Results
Based on both physical and radiographic measurements, virtual models were representative
of each applicator within ±1 mm. Commissioning of the MBDCA was benchmarked based
on AAPM Working Group on Dose Calculation Algorithms in Brachytherapy. The layout
of the new applicator reduced dose-spill to other reference points significantly,
as much as a factor of 16.3, compared with the existing equipment. The rounded tip
shape and curve of the peripheral channels in the new applicator produced more conformity
to its HR-CTV than existing equipment.
Conclusions
Compared with our existing equipment, the design changes in the new Varian MCVC set
offered improved control of dose spill and better conformality to HR-CTV.
Keywords
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Article info
Publication history
Published online: January 04, 2022
Accepted:
November 8,
2021
Received in revised form:
November 5,
2021
Received:
July 8,
2021
Footnotes
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Disclosures: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The authors report no proprietary or commercial interest in any product mentioned or concept discussed in this article.
Identification
Copyright
© 2021 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.
