Clinical application value of surface-guided automatic positioning in pelvic tumor radiotherapy

Background and purpose: Radiotherapy is an important means to treat pelvic tumors. It is important to improve the accuracy of radiotherapy and enhance the effectiveness. This study aimed to compare and analyze the influence of positioning errors during the radiotherapy of patients using surface guided radiotherapy (SGRT) automatic positioning versus traditional surface marking positioning. Methods: We performed a retrospective analysis of 50 patients with pelvic tumors who received radiotherapy and had simple positioning fixation methods at the Fudan University Shanghai Cancer Center from April 2023 to April 2024. A total of 25 patients were treated using SGRT (observation group), and 25 patients were treated using traditional surface marking (control group). After positioning according to the two positioning techniques, cone beam computed tomography (CBCT) images were collected. These data were compared with the initial reference computed tomography (CT) images within 6 dimensions. The correction error values of the six dimensions were recorded. We calculated the averages, standard deviations, and the number of cases and probabilities in different interval distributions. SPSS 27.0 was used to perform statistical analysis of the data from the two groups of patients. We also analyzed the correlation of patients in the observation group within the 6 dimensions. Results: The non-parametric test showed significant differences in only the LNG and PITCH directions (P<0.05). The number of cases (probability) in the observation group with errors less than 3 mm and less than 1 were 108 (86.4%), 93 (74.4%), 108 (86.4%), and 96 (76.8%), 111 (88.8%), 107 (85.6%), respectively. In the control group, the numbers were 113 (90.4%), 107 (85.6%), 118 (94.4%), and 71 (56.8%), 95 (76.0%), 110 (88.0%), respectively. The Spearman correlation analysis showed that in the observation group, the left-right direction had a negative correlation with pitch, roll and yaw, while all other directions were positively correlated. Statistically significant positive correlations (P<0.05) were found between the superior-inferior and pitch directions, left-right and roll directions, as well as pitch and roll directions, with positive correlation coefficients (r = 0.270, r = 0.301, and r = 0.247). Conclusion: The application of SGRT automatic positioning can achieve the effect of regular surface marking line positioning, has advantages in rotation direction adjustment, and can replace surface marking line positioning where conditions permit.