Abstract：Objective To study a new quantitative method—arc-beam modulation complexity score (AMCS) to evaluate the plan complexity of volumetric-modulated arc therapy (VMAT), and the effect of the six metrics on VMAT dosimetric verification. Methods The six metrics, which contain the average of beam area (ABA), the average of leaf travel (ALT), the average of beam width (ABW), the modulation complexity score (MCS), the leaf travel and modulation complexity score (LTMCS) and AMCS, was calculated to quantify the plan complexity of VMAT for 127 selected patients. Delta4 system was used for verifying the VMAT plans and the γ pass rate was calculated. The relativity between the six metrics and the pass rates or between the 6 parameters were analyzed with Pearson method. Results The average of ABA, ALT, ABW, MCS, LTMCS and AMCS were (73.5±24.1) cm2, (69.6±9.8) cm, (3.63±1.03) cm, 0.33±0.05, 0.14±0.04 and 0.16±0.05, respectively. A negative correlation was observed for ALT and the pass rate, and the other metrics had a positive correlation with it (P=0.000).The correlation between AMCS and the pass rate was the strongest with Pearson’s (r=0.637) in the six metrics. The percentage of arcs with a pass rate lower the 95% was 60.7 when AMCS is lower than the average, while it was 9.9% when AMCS is higher than the average. Both ABA and ABW had no significant correlation with ALT (P=0.720, 0.073), and the other metrics had significant correlations (P=0.000-0.003). Conclusions AMCS is a suitable quantitative metric to evaluate the plan complexity of VMAT, and could be used to forecast the result of dosimetric verification of VMAT plans. It could be also use to compare the multiple VMAT plans complexity and help us to choose the best plan.
Li Guangjun,Li Yanlong,Wang Xuetao et al. The quantitative method to evaluate the plan complexity of volumetric-modulated arc therapy[J]. Chinese Journal of Radiation Oncology, 2015, 24(6): 684-687.
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