Evaluation of the plan delivery accuracy of intensity-modulated radiation therapy by texture analysis using fluence maps.

Affiliation

Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 03080, Republic of Korea; Biomedical Research Institute, Seoul National University Hospital, Seoul 03080, Republic of Korea; Department of Radiation Oncology, Seoul National University Hospital, Seoul 03080, Republic of Korea; Institute for Smart System, Robotics Research Laboratory for Extreme Environments, Advanced Institutes of Convergence Technology, Suwon 16229, Republic of Korea. Electronic address: [Email]

Abstract

OBJECTIVE : The aim of this study is to evaluate the plan delivery accuracy of intensity-modulated radiation therapy (IMRT) by using textural features calculated from fluence maps.
METHODS : In total, 202 IMRT plans were generated with the Trilogy (C-series linac) and TrueBeam STx systems. Fluence maps were obtained for each IMRT plan. With the fluence map, six textural features were calculated, namely angular second moment (ASM), inverse difference moment (IDM), contrast, variance, correlation, and entropy (particular displacement distances, d = 1, 5, and 10). To evaluate performances of textural features in predicting IMRT delivery accuracy, Spearman's rank correlation coefficients (rs) were calculated between textural feature values and measures of conventional methods.
RESULTS : For Trilogy, correlation (d = 1) showed rs values of -0.764 (p < 0.001) with gamma passing rates of 2%/1 mm and 0.863 (p < 0.001) with multi-leaf collimator (MLC) errors. For TrueBeam STx, variance (d = 10) showed rs values of 0.691 (p < 0.001) with gamma passing rates of 1%/2 mm and -0.585 (p < 0.001) with MLC errors.
CONCLUSIONS : Correlation (d = 1) for Trilogy and variance (d = 10) for TrueBeam STx demonstrated the potential in predicting IMRT delivery accuracy with high correlations to conventional IMRT delivery accuracy measures.

Keywords

Fluence,Intensity-modulated radiation therapy,Modulation index,Texture analysis,