ABSTRACT
ObjectiveThe objective is to investigate the possibility of isocenter dual-guided resetting of surface guided radiation therapy （SGRT） combined with image guided radiation therapy （IGRT） in postoperative radiotherapy for breast cancer. To assess the setup error accuracy between the new resetting mode and the traditional resetting mode. MethodsRetrospective analysis was performed on breast cancer patients who underwent ELEKTA infinity accelerator radiotherapy in sun yat-sen university cancer center from July 13， 2021 to October 15， 2022. According to different reset methods， the patients were divided into a simulation group （41 cases） and a dual-guided group （40 cases）. The simulation group was reset using a simulator， CBCT scans were performed and setup errors were recorded during the first treatment； The dual-guided group was guided by AlignRT and combined with CBCT for isocenter dual-guided resetting， and the setup error obtained by CBCT registration was recorded. The global setup errors of chest region of interest （CROI） ， the local residual errors of supraclavicular region of interest （SROI） and the resetting time of the two reset methods were calculated and compared respectively. The advantages of the CBCT error distribution in the dual-guided resetting of SGRT combined with IGRT were analyzed. ResultsThe median of the global setup errors （X/cm， Y/cm， Z/cm， Rx°， Ry°， Rz°） of the simulation group and the median of the dual-guided group in the CROI were statistically significant （P<0.05） except the Rz and Ry directions. The local residual errors of the two groups of the SROI were calculated. The median of the errors of X/cm， Y/cm， Z/cm， Rx°， Ry°， Rz° were statistically significant （P<0.05） except the X and Y axis. The resetting time of the simulation group was significantly longer than that of the dual-guided group （238.64±28.56） s， t=-24.555， P=0.000， and the difference was statistically significant （P<0.05）. The CBCT error distribution of the dual-guide group was analyzed， and it was found that the absolute values of translation errors of X， Y and Z axis were all within 0.4 cm， while the proportions of ≤ 0.3 cm were 95%， 93% and 93%， respectively. The proportions of rotation errors of Rx， Ry and Rz ≤ 1.5 ° were 90%， 93% and 90%， respectively. ConclusionIn postoperative radiotherapy of breast cancer， SGRT combined with IGRT for isocenter dual-guided resetting can effectively correct the rotational setup errors and residual errors， and improve the accuracy of radiotherapy with less resetting time and high feasibility， which compared with the traditional simulator resetting mode. This precise， unmarked resetting method can be widely used in clinical practice.