Highlights
- •Passing rate of two dimensional quality assurance for intensity-modulated radiotherapy depends on coronal plane chosen.
- •Passing is generally correlated to gradients of the radiation fluence within the plan.
- •This correlation cannot be easily determined and used for choosing the plane in which to perform quality assurance.
Abstract
Intensity modulated radiation therapy (IMRT) delivery involves a complex series of
beam angles and multileaf collimator (MLC) arrangements, requiring quality assurance
to be performed to validate delivery before treatment. The purpose of this work is
to investigate the effect of dose gradient on quality assurance (QA) passing rate.
Many (n = 40) IMRT plans were delivered and measured using a 2D planar array of ion
chambers; additionally, eleven plans were measured at several coronal planes. For
each measurement, dose gradient was assessed using a number of metrics and passing
rate assessed at both 3%/3 mm and 3%/2 mm criteria. The passing rates of the various
IMRT plans were shown to be generally correlated to gradient, with an average distance
correlation of 0.54 ± 0.04 for the lateral dose gradient. The passing rate for an
individual plan was shown to vary with coronal slice, though the correlation to dose
gradient was not predictable. Even though the passing rate was strongly related to
dose gradient for many of the plans, the signs of the correlations were not always
negative, as hypothesized. The coronal plane at which QA is performed affects passing
rate, though dose gradient may not easily be used to predict slices at which passing
rate is higher.
Keywords
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Article info
Publication history
Published online: April 26, 2023
Accepted:
April 17,
2023
Received in revised form:
April 10,
2023
Received:
March 11,
2023
Identification
Copyright
© 2023 Associazione Italiana di Fisica Medica e Sanitaria. Published by Elsevier Ltd. All rights reserved.
