Abstract：Objective To explore setup errors of clinical target volume to planning target volume (CTV-PTV) margin in pelvic tumor
based on Halcyon accelerator’s fully guided mode with 100% image guidance. Methods A total of 19 patients with pelvic tumors
who underwent intensity modulated radiation therapy on the Halcyon accelerator from January to May 2023 were selected as the
study subjects. A total of 900 cone beam CT images were collected, including 300 sets of inter-fractional, post-correction and intrafractional
images for each patient. These images were registered and fused with the planned CT to obtain the three-dimensional vector
error, represented by X (left-right), Y (head-foot), and Z (anterior-posterior) directions. Then, the setup errors and their distribution
trends were calculated, and the margin of CTV-PTV based on the corrected and intra-fractional setup errors were determined.
Results In the X direction, the absolute setup errors between inter-fractional, corrected and intra-fractional were (2.07±1.82),
(0.19±0.19), (0.30±0.28) mm respectively. In the Y direction, the absolute setup errors were (3.87±2.67), (0.23±0.31),
(0.27±0.23) mm respectively. In the Z direction, the absolute setup errors were (0.72±0.83), (0.20±0.22), (0.30±0.27) mm
respectively. All differences were statistically significant (P<0.05). There were 97% and 96.33% of corrected and intra-fractional setup
errors in the X, Y, Z directions within 1 mm. CTV-PTV margin had been reduced from 6.36 mm to 1.06 mm. Conclusion From
the perspective of setup errors, for pelvic tumor treatment based on Halcyon accelerator (100% image guided mode), the CTV-PTV
margin is calculated as 1.1 mm based on the corrected and intra-fractional setup errors. Treatment of pelvic tumor patients using the
Halcyon accelerator can reduce setup errors, improve the safety and accuracy of targeting the tumor region and organs at risk, reduce
the CTV-PTV margin, and minimize the volume of normal tissues involved.
董晓庆，胡杰，林清. 基于Halcyon加速器百分百图像引导模式
下盆腔肿瘤CTV-PTV边界外放的研究[J]. 中国医疗设备, 2024, 39(4): 60-65.
DONG Xiaoqing, HU Jie, LIN Qing. Research on CTV-PTV Margin for Pelvic Tumor Based on the Halcyon Accelerator’s Guided
Mode with 100% Image Guidance. China Medical Devices, 2024, 39(4): 60-65.
