Abstract
BackgroundComprehensively textural feature performance test from volumetric modulated arc therapy (VMAT) fluences to predict plan delivery accuracy.MethodsA total of 240 VMAT plans for various treatment sites were analyzed, with Trilogy and TrueBeam STx systems. Fluence maps superposed fluences at each control point per plan. The textural features were the angular second moment (ASM), inverse difference moment (IDM), contrast, variance, correlation, and entropy, calculated from fluence maps using three displacement distances. Correlation analysis of textural feature performance as predictors of VMAT delivery accuracy used global gamma passing rates with MapCHECK2 and ArcCHECK dosimeters, and mechanical delivery errors calculated from machine log files.ResultsSpearman’s rank correlation coefficients (r) of the ASM (d = 10) to the gamma passing rates with 1%/2 mm using the MapCHECK2 were 0.358 and 0.519, respectively (p < 0.001). For the ArcCHECK, they were 0.273 (p = 0.001) and 0.259 (p = 0.009), respectively. The r-values of the ASM (d = 10) to the Trilogy and TrueBeam STx MLC errors were − 0.843 and − 0.859, respectively (p < 0.001), and those to the MU delivery errors were − 0.482 and − 0.589, respectively (p < 0.001). The ASM (d = 10) showed better performance in predicting VMAT delivery accuracy.ConclusionsThe ASM (d = 10) calculated from VMAT plan fluence maps were strongly correlated with global gamma passing rates and MLC delivery errors, and can predict VMAT delivery accuracy.
Highlights
Textural feature performance test from volumetric modulated arc therapy (VMAT) fluences to predict plan delivery accuracy
As a modulation index for VMAT, we proposed textural features calculated from the fluence maps of VMAT plans in a previous study [23]
We demonstrated that two textural features showed superior performance to modulation complexity score for VMAT (MCSv) and modulation index to support station-parameteroptimized radiation therapy (MISPORT) in assessing the VMAT modulation
Summary
Textural feature performance test from volumetric modulated arc therapy (VMAT) fluences to predict plan delivery accuracy. For VMAT, the global gamma-index approach with a gamma criterion of 2%/2 mm and 90% passing rate has been recommended by several previous studies [14, 15]. It is convenient and practical, recent studies have taken issue with the clinical irrelevance of gamma passing rates [12, 16, 17]. Independent verification of VMAT delivery accuracy cannot be performed with this method because the machine log file is acquired from the linac control system. Several studies have suggested calculating the modulation degree of VMAT plans for predicting VMAT delivery accuracy [11, 19,20,21,22]
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