Abstract
The aim of this paper is to evaluate clinically relevant quality assurance (QA) tests
for RapidArc prostate patients. 26 plans were verified by the COMPASS system that
provides an independent angle response and a reconstruction of dose distribution in
patient CT model. Plan data were imported from treatment planning system via DICOM.
The fluencies, measured by a 2D detector, were used by COMPASS to forward calculate
dose in CT patients and reconstruct dose-volume-histogram (DVH). The gamma analysis
was performed, using both the criteria 3%-3-mm and 2%-2 mm, for the whole grid patient
and the per-structure volume. A DVH-based analysis was accomplished for target and
organs-at-risk (OAR). The correlation between gamma passing rates and DVH discrepancies
was performed using Pearson's test. Sensitivity, specificity and accuracy of whole
and per-structure gamma method were calculated.
No significant DVH deviation was observed for target and OAR. Weak correlation between
gamma passing rates and dosimetric deviations was observed, all significant r-values were negative. The whole gamma method shows lack of sensitivity to detect
dosimetric deviations >5%. Instead, a better balance between sensitivity and specificity
was obtained employing per structure gamma both with 3%-3 mm and 2%-2 mm criteria.
Because of the poor correlation between DVH goals and gamma passing rates, we encourage
the DVH-based gamma passing rates, when it is possible. At least, a gamma method specific
for structure was strongly suggested.
Keywords
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Article info
Publication history
Published online: January 31, 2014
Accepted:
January 11,
2014
Received in revised form:
January 10,
2014
Received:
August 19,
2013
Identification
Copyright
© 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Inc. All rights reserved.
