Highlights
- •Dosimetric performances of forward and inverse optimization methods were compared.
- •Two inverse optimization methods achieved the best dose homogeneity to the target.
- •One of the two was also most effective in reducing hot spots to the vaginal mucosa.
Abstract
Purpose
A direct planning approach with multi-channel vaginal cylinders (MVCs) used for HDR
brachytherapy of vaginal cancers is particularly challenging. Purpose of this study
was to compare the dosimetric performances of different forward and inverse methods
used for the optimization of MVC-based vaginal treatments for endometrial cancer,
with a particular attention to the definition of strategies useful to limit the high
doses to the vaginal mucosa.
Methods
Twelve postoperative vaginal HDR brachytherapy treatments performed with MVCs were
considered. Plans were retrospectively optimized with three different methods: Dose
Point Optimization followed by Graphical Optimization (DPO + GrO), Inverse Planning
Simulated Annealing with two different class solutions as starting conditions (surflPSA
and homogIPSA) and Hybrid Inverse Planning Optimization (HIPO). Several dosimetric
parameters related to target coverage, hot spot extensions and sparing of organs at
risk were analyzed to evaluate the quality of the achieved treatment plans. Dose homogeneity
index (DHI), conformal index (COIN) and a further parameter quantifying the proportion
of the central catheter loading with respect to the overall loading (i.e., the central
catheter loading index: CCLI) were also quantified.
Results
The achieved PTV coverage parameters were highly correlated with each other but uncorrelated
with the hot spot quantifiers. HomogIPSA and HIPO achieved higher DHIs and CCLIs and
lower volumes of high doses than DPO + GrO and surflPSA.
Conclusions
Within the investigated optimization methods, HIPO and homoglPSA showed the highest
dose homogeneity to the target. In particular, homogIPSA resulted also the most effective
in reducing hot spots to the vaginal mucosa.
Keywords
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Article info
Publication history
Accepted:
November 9,
2017
Received in revised form:
October 20,
2017
Received:
August 17,
2017
Identification
Copyright
© 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
