title: Texture analysis on the edge-enhanced fluence of VMAT.
abstract: BACKGROUND
  Textural features of edge-enhanced fluence were analysed to quantify modulation degree of volumetric modulated arc therapy (VMAT) plans.
  
  
  METHODS
  Twenty prostate and twenty head and neck VMAT plans were retrospectively selected. Fluences of VMAT plans were generated by integration of monitor units shaped by multi-leaf collimators (MLCs) at each control point. When generating fluences, the values of pixels representing MLC tips were doubled to prevent smearing out of small or irregular fields (edge-enhancement). Six kinds of textural features, including angular second moment, inverse difference moment, contrast, variance, correlation and entropy, were calculated with particular displacement distances (d) of 1, 5 and 10. Plan delivery accuracy was evaluated by gamma-index method, mechanical parameter differences between plan and delivery and differences in dose-volumetric parameters between plan and delivery. Spearman's correlation coefficients (r s ) were calculated between the values of textural features and VMAT delivery accuracy.
  
  
  RESULTS
  The r s values of contrast (d = 1) with edge-enhancement to global gamma passing rates with 2%/2 mm, 1%/2 mm and 2%/1 mm were 0.546 (p < 0.001), 0.744 (p < 0.001) and 0.487 (p = 0.001), respectively. Those with local 2%/2 mm, 1%/2 mm and 2%/1 mm were 0.588, 0.640 and 0.644, respectively (all with p < 0.001). The r s values of contrast (d = 1) to MLC and gantry angle errors were -0.853 and 0.655, respectively (all with p < 0.001). The contrast (d = 1) showed statistically significant r s values in 11 dose-volumetric parameter differences from a total of 35 cases, and generally showed better correlations to plan delivery accuracy than did previously suggested textural features with non-edge-enhanced fluences, as well as conventional modulation indices.
  
  
  CONCLUSIONS
  Contrast (d = 1) with edge-enhanced fluences could be used as modulation index for VMAT.
authors.affiliation: Interdiciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Republic of Korea. vsoyounv@gmail.com.|Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea. vsoyounv@gmail.com.|Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea. vsoyounv@gmail.com.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea. vsoyounv@gmail.com.
authors.forename: So-Yeon
authors.initials: SY
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea. leodavinci@naver.com.|Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea. leodavinci@naver.com.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea. leodavinci@naver.com.|Center for Convergence Research on Robotics, Advanced Institutes of Convergence Technology, Suwon, Republic of Korea. leodavinci@naver.com.
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Park
authors.affiliation: Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, Republic of Korea. s1moremore@gmail.com.
authors.forename: Wonmo
authors.initials: W
authors.lastname: Sung
authors.affiliation: Interdiciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Republic of Korea. ihkim@snu.ac.kr.|Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea. ihkim@snu.ac.kr.|Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea. ihkim@snu.ac.kr.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea. ihkim@snu.ac.kr.|Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Republic of Korea. ihkim@snu.ac.kr.
authors.forename: Il Han
authors.initials: IH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea. sye@snu.ac.kr.|Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea. sye@snu.ac.kr.|Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea. sye@snu.ac.kr.|Department of Transdisciplinary Studies, Program in Biomedical Radiation Sciences, Seoul National University Graduate School of Convergence Science and Technology, Seoul, Republic of Korea. sye@snu.ac.kr.
authors.forename: Sung-Joon
authors.initials: SJ
authors.lastname: Ye
mesh_terms: D000465:Algorithms; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D010315:Particle Accelerators; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy*; D011786:Quality Control; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies