Abstract
Patient-specific quality assurance (QA) data must be migrated from outdated QA systems
to new ones to produce objective results that can be understood by oncologists. We
aimed to evaluate a method for obtaining a high correlation of dose distributions
according to various gamma passing rates among two types of 2D detectors for the migration
of patient-specific QA data of volumetric modulated arc therapy (VMAT). The patient-specific
QA of 20 patients undergoing VMAT was measured in two different modes: standard single
measurement (SM) mode and multiple merged measurements (MM) techniques using ArcCHECK
(AC) and OCTAVIUS (OT). The correlation of the measured and calculated dose distributions
was evaluated according to varying gamma passing rates (3%/3 mm, 2%/3 mm, 2%/2 mm,
and 1%/1 mm). The gamma passing rates were analyzed using the Anderson–Darling normality
test. Treatment plan dose distributions were calculated by intentionally shifting
the calculation isocenter position (x,y,z ± 0.5, ± 1.0, ± 1.5, and ± 2.0 mm). The
highest correlation between the SM and MM was observed with a gamma passing rate of
1%/1 mm with AC (r = 0.866) and 3%/2 mm with OT (r = 0.916). However, SM and MM did
not follow a normal distribution with a rate of 3%/2 mm in OT. The second-highest
correlation was obtained with a rate of 2%/2 mm (r = 0.900). Among the two 2D detectors,
the highest correlation between the calculated and measured dose distributions was
obtained for a gamma passing rate of 1%/1 mm using SM in AC and 2%/2 mm using MM in
OT (r = 0.716). Adjusting the gamma passing rate and measurement mode of AC and OT
resulted in higher correlations between measured and calculated dose distributions.
The high correlation between different 2D detectors objectively indicated a potential
migration method. This enabled the sharing of more accurate patient-specific QA data
from 2D detectors with different phantoms. A high correlation was observed between
the two types of detectors in this study (r = 0.716); therefore, the proposed method
should be useful for oncologists to share information regarding patient-specific QA
for VMAT.
Keywords
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Article info
Publication history
Published online: July 15, 2022
Accepted:
June 16,
2022
Received in revised form:
May 6,
2022
Received:
January 19,
2022
Identification
Copyright
© 2022 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.
