The influencing factors and precision improvement of IMRT head and neck tumor setup errors guided by CBCT imaging

This study aimed to analyze the factors that affect and improve the accuracy in the setup errors of intensity-modulated radiotherapy (IMRT) for head and neck tumor using CBCT imaging. A retrospective analysis was performed using the Elekta synergy linear accelerator airborne imaging system. CBCT scanning was performed during the pre-treatment (pr), post-correction (pc), and post-treatment (pt) periods, respectively. CBCT image-guided setup error data and the affecting factors were analyzed, and the standardized process for enhancing IMRT precision was put forward accordingly. The setup errors in the X, Y, and Z directions during the pr period were (0.63±0.77), (0.93±1.01), and (0.72±0.92) mm, during the pc period they were (0.06±0.54), (0.07±0.59), and (0.02±0.32) mm, and during the pt period they were (0.07±0.90), (0.16±0.71), and (0.05±0.87) mm, respectively. The pr and pc showed significant differences in the setup errors in the X, Y, and Z directions (Fx=9.66, Fy=6.29, Fz=38.49), (P<0.05), and during the pr period the frequencies of the setup of ≥3 mm were 8, 20, and 8 in the X, Y, and Z directions, accounting for 4.6%, 11.6%, and 4.6%, respectively. The setup errors gained their maximum value in the Y direction. The setup errors for IMRT in head and neck tumors remained low and matched the contribution to reduce the setup error. There are multiple factors affecting the setup errors of head and neck tumors. The pre-intervention parts should emphasize the positioning of the plastic mask and the preparation of the radiotherapy planning and quality control should be strictly performed to standardize the treatment-processes and monitor the equipment.