Modulation indices for volumetric modulated arc therapy.
The aim of this study is to present a modulation index (MI) for volumetric modulated arc therapy (VMAT) based on the speed and acceleration analysis of modulating-parameters such as multi-leaf collimator (MLC) movements, gantry rotation and dose-rate, comprehensively. The performance of the presented MI (MIt) was evaluated with correlation analyses to the pre-treatment quality assurance (QA) results, differences in modulating-parameters between VMAT plans versus dynamic log files, and differences in dose-volumetric parameters between VMAT plans versus reconstructed plans using dynamic log files. For comparison, the same correlation analyses were performed for the previously suggested modulation complexity score (MCS(v)), leaf travel modulation complexity score (LTMCS) and MI by Li and Xing (MI Li&Xing). In the two-tailed unpaired parameter condition, p values were acquired. The Spearman's rho (r(s)) values of MIt, MCSv, LTMCS and MI Li&Xing to the local gamma passing rate with 2%/2 mm criterion were -0.658 (p < 0.001), 0.186 (p = 0.251), 0.312 (p = 0.05) and -0.455 (p = 0.003), respectively. The values of rs to the modulating-parameter (MLC positions) differences were 0.917, -0.635, -0.857 and 0.795, respectively (p < 0.001). For dose-volumetric parameters, MIt showed higher statistically significant correlations than the conventional MIs. The MIt showed good performance for the evaluation of the modulation-degree of VMAT plans.
Department of Radiation Oncology, Seoul National University Hospital, Seoul, 110-744, Republic of Korea. Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, 110-744, Republic of Korea. Biomedical Research Institute, Seoul National University College of Medicine, Seoul, 110-744, Republic of Korea. Center for Convergence Research on Robotics, Advanced Institutes of Convergence Technology, Suwon, 443-270, Republic of Korea.
Jong Min
JM
Park
So-Yeon
SY
Park
Hyoungnyoun
H
Kim
Jin Ho
JH
Kim
Joel
J
Carlson
Sung-Joon
SJ
Ye
D006801:Humans; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*