Preliminary study of effect of multiple factors of intensity-modulated radiation therapy on dose verification

Objective: To analyze the relationship between planning factors of intensity-modulated radiation therapy (IMRT) and gamma index and investigate the effect of each parameter upon the γ passing rate of IMRT. Methods: Gamma analysis was performed using 3%/3 mm acceptance criteria for 457 IMRT beams with different planning factors. During multi-factor ANOVA analysis of planning factors and gamma passing rate, the control variables primarily included the minimum segment area, minimum number of monitor unit (MU), number of segment, segment conversation, and the spatial resolution in the measured dose distribution. Results: The percentage of pixels with passing γ significantly differed under different minimum segment area, segment conversation and the spatial resolution in the measured dose distribution (all P < 0.05). No significant correlation was observed between the passing rate and the minimum number of MU and the number of segment (P > 0.05). Conclusions: According to the actual situation of the equipment, the minimum segment area should be determined during IMRT planning. Direct machine parameter optimization should be performed. Appropriate resolution of the plane dose images can be chosen according to the minimum detector interval of dose matrix device. (authors)