title: Textural feature calculated from segmental fluences as a modulation index for VMAT.
abstract: OBJECTIVE
  Textural features calculated from various segmental fluences of volumetric modulated arc therapy (VMAT) plans were optimized to enhance its performance to predict plan delivery accuracy.
  
  
  METHODS
  Twenty prostate and twenty head and neck VMAT plans were selected retrospectively. Fluences were generated for each VMAT plan by summations of segments at sequential groups of control points. The numbers of summed segments were 5, 10, 20, 45, 90, 178 and 356. For each fluence, we investigated 6 textural features: angular second moment, inverse difference moment, contrast, variance, correlation and entropy (particular displacement distances, d = 1, 5 and 10). Spearman's rank correlation coefficients (rs) were calculated between each textural feature and several different measures of VMAT delivery accuracy.
  
  
  RESULTS
  The values of rs of contrast (d = 10) with 10 segments to both global and local gamma passing rates with 2%/2 mm were 0.666 (p <0.001) and 0.573 (p <0.001), respectively. It showed rs values of -0.895 (p <0.001) and 0.727 (p <0.001) to multi-leaf collimator positional errors and gantry angle errors during delivery, respectively. The number of statistically significant rs values (p <0.05) to the changes in dose-volumetric parameters during delivery was 14 among a total of 35 tested parameters.
  
  
  CONCLUSIONS
  Contrast (d = 10) with 10 segments showed higher correlations to the VMAT delivery accuracy than did the conventional modulation indices.
authors.affiliation: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea; Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: So-Yeon
authors.initials: SY
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea; Center for Convergence Research on Robotics, Advance Institutes of Convergence Technology, Suwon, Republic of Korea. Electronic address: leodavinci@naver.com.
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea; Center for Convergence Research on Robotics, Advance Institutes of Convergence Technology, Suwon, Republic of Korea.
authors.forename: Jung-In
authors.initials: JI
authors.lastname: Kim
authors.affiliation: Graduate School of Information, Yonsei University, Seoul, Republic of Korea.
authors.forename: Hyoungnyoun
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea; Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Republic of Korea; Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Republic of Korea.
authors.forename: Il Han
authors.initials: IH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Seoul National University Hospital, Seoul, Republic of Korea; Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Republic of Korea; Biomedical Research Institute, Seoul National University College of Medicine, Seoul, Republic of Korea; Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Seoul National University Graduate School of Convergence Science and Technology, Seoul, Republic of Korea.
authors.forename: Sung-Joon
authors.initials: SJ
authors.lastname: Ye
mesh_terms: D006258:Head and Neck Neoplasms / Q000532:radiotherapy; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D012189:Retrospective Studies
keywords: Degree of modulation; Fluence; Texture analysis; Volumetric modulated arc therapy