Contrastive Analysis the Positioning Errors of Two Fixed Methods in Postoperative Radiotherapy for Cervical Cancer Based on CBCTand Six-dimensional Bed/XIAO Chunhui， QIU Meiying，LI Jingwen，LU Xinxin，LIWenyu.//Medical InnovationofChina，2025，22（16）：067-072

[Abstract] Objective： To compare and analyze the positioning errors and the impact on the margin expansionof theclinical target volume （CTV）oftwo bodyfixationmodalities （thermoplastic filmfixationandnegative pressure vacuum pad fixation）based on cone beam computed tomography （CBCT） and six-dimensional bed in postoperative radiotherapy of cervicalcancer，inorder tooptimize body fixation protocols and improve the precision of radiotherapy.Method：A totalof 1O2 patients who received postoperative radiotherapy for cervical cancer inthe Oncology Department of Ganzhou Women and Childen's Health Care Hospital between January 2O22 and December 2024 were selected and randomly divided into the experimental group （5O cases，using thermoplastic film fixation） and the control group （52 cases，using negative pressure vacuum pad fixation）.All patients were scanned using CBCT to obtain positional information during radiotherapyand combined with a six-dimensional bed for positional error correction.The patients'positioning errors in the three translational directions of X（anteroposterior），Y（left and right）， Z （head and foot）and the three rotational directions of RX （pitchangle），RY （rollangle），RZ （yaw angle） wererecordedatthest，6th，1th，6th，andstiotherapyssions，espctively，andeangesino beforeand after correction were compared.Meanwhile，the impact of thetwo fixation methods onmargin expansionof the CTV wasassessed.Result： Before correction，the initial positioning errors of the experimental group inthe three translational directionsof X，Y，and Z were significantlysmaller than thoseofthe control group，with statistically significant differences （ P lt;0.05），while the errors in the three rotational directions of RX，RY，and RZ were smaller than those of the control group，but the differences were not statistically significant （ Pγ gt;0.05）.After correction， the positioning errorsof theexperimental groupinthethree translational directionsofX，Y，andZwerestillsignificantly smaller than those of the control group，with statistically significant differences （ P lt;0.05），and the magnitude of correctionwas better than that of the control group，with statistically significant differences （ P lt;0.05）. In the rotational directions，the differences in the corrected errors between the two groups were not statistically significant （ P gt;0.05）， butthe magnitude of correction in the experimental group was still smaller than that in thecontrol group，butthe difference was not statistically significant （ P gt;0.05）. The reduction amplitudes of positioning errors in the X， Y and Z directions of the experimental group were significantly higher than those of the control group （ P lt;0.05）. In terms of thetranslation direction，the margin expansion of the CTVof patients in the experimental group were significantly smaller than those in the control group，the differences were statistically significant （ P lt;0.05）. The reduction of the margin expansion of the CTV（inthe X，Y，and Z directions）weresignificantly positively correlated with the reduction of the V4O of the rectum and the mean dose of the bladder （Plt;0.05 ）.Conclusion：Thermoplastic film fixation combined with CBCTand six-dimensional bedcan more efectively reduce positioning errors and reduce the CTV margin expansion in postoperative radiotherapy for cervical cancer， thereby improving the precision of radiotherapy.

[Key words] Cervical cancer Postoperative radiotherapy Positioning errorCBCT Six-dimensional bedThermoplastic film fixation Negative pressure vacuum pad fixation

First-author's address：Department of Oncology，Ganzhou Women and Childen's Health Care ospital，Ganzhou3410o0，China doi： 10.3969/j.issn.1674-4985.2025.16.017

子宫颈癌作为一种高发的女性恶性肿瘤，其发病率在全球女性恶性肿瘤中排名第二，尤其在发展中国家，其发病与致死情况相较于发达国家更为严峻[。针对ⅡIB期及更晚期的子宫颈癌患者，放射治疗构成了主要的治疗策略之一[。随着医学影像学和计算机技术的不断发展，锥形束CT（conebeamcomputedtomography，CBCT）和六维床在放疗中的应用日益广泛。CBCT作为一种先进的影像引导技术，能够在治疗前对患者的体位进行精确验证和调整[3。六维床则提供了六个自由度的调整能力，包括三个平移方向和三个旋转方向，能够更精准地纠正患者的体位偏差[4。这种组合技术在肿瘤体积较小或器官运动幅度较大的病例中具有显著优势。近年来，多项研究对CBCT和六维床在放疗中的应用进行了探讨。例如，有研究通过对比分析CBCT与三维治疗床的配准误差，发现六维床在摆位误差的校正上更具优势[5。此外，CBCT联合六维床的应用不仅提高了摆位精度，还减少了靶区外放边界，从而降低了正常组织的受照剂量。在子宫颈癌术后放疗中，体位固定方式的选择尤为重要。传统的热塑膜固定和负压真空垫固定虽然能够提供一定的体位稳定性，但在摆位误差的控制上仍存在局限性。而CBCT联合六维床的校正方式则通过实时影像引导和多自由度调整，显著提高了放疗的精准度。本研究旨在通过对比分析基于CBCT和六维床技术，对仰卧位负压真空垫与俯卧位热塑体膜两种固定方式在子宫颈癌术后放疗中的摆位误差进行比较分析，为优化体位固定、提高放疗精准度提供科学依据。……