广州医科大学学报

目的：探讨乳腺托架、乳腺托架+发泡胶、面颈肩架+发泡胶对乳腺癌放射治疗摆位精度的影响。方法：回顾性分析本院2024年6月至12月61例乳腺癌患者数据，根据体位固定方式分为三组：A组（乳腺托架，n=18）、B组（乳腺托架+发泡胶，n=22）、C组（面颈肩架+发泡胶，n=21）。所有患者接受锥形束CT扫描（首周3次，后每周1次），记录六维摆位误差。采用Pearson相关分析评估托架倾角与误差关系，采用多元线性回归与随机森林模型分析多因素影响，并使用van Herk公式计算PTV外扩边界。结果：C组在六维方向上的摆位误差均最小（X:0.2±0.1 cm,Y:0.3±0.1 cm,Z:0.3±0.2 cm;Pitch:1.0±0.4°，Roll:0.9±0.4°，Yaw:0.9±0.4°），显著优于A组（P<0.01）；乳腺托架倾角与Y误差呈强正相关，倾角每增加1°误差增加0.02 cm；随机森林模型显示固定技术权重最高（0.38）,BMI≥24且年龄≥55岁患者摆位误差风险增加3.2倍（95%CI:1.7～5.9）；基于误差计算的PTV外扩边界在C组最小（X/Y/Z:0.6/0.8/0.9 cm）；Ⅲ期患者Roll误差较Ⅰ～Ⅱ期患者高0.3°（P=0.047）。结论：面颈肩架+发泡胶可显著提升摆位精度，缩小PTV外扩边界，适用于基层医疗机构。

Objective:To investigate the effects of breast board,breast board + foam cushion,and head-neck-shoulder(HNS)frame + foam cushion on positioning accuracy in breast cancer radiotherapy.Methods:A retrospective analysis was conducted on data from 61 breast cancer patients treated between June and December 2024. Patients were divided into three groups based on immobilization techniques:Group A(breast board,n=18),Group B(breast board +foam cushion,n=22),and Group C(HNS frame + foam cushion,n=21). All patients underwent cone-beam CT(CBCT)scans(three times in the first week,then weekly),with six-dimensional positioning errors recorded. Pearson correlation was used to assess the relationship between board tilt angle and errors,while multiple linear regression and random forest models were employed to analyze multifactorial influences. The van Herk formula was applied to calculate PTV margins.Results:Group C demonstrated the smallest positioning errors across all six dimensions(X:0.2±0.1 cm,Y:0.3±0.1 cm,Z:0.3±0.2 cm;Pitch:1.0±0.4°,Roll:0.9±0.4°,Yaw:0.9±0.4°),significantly superior to Group A(P<0.01). Breast board tilt angle showed a strong positive correlation with Y-axis errors,with each 1° increase in tilt angle elevating errors by 0.02 cm. Random forest analysis identified immobilization technique as the most influential factor(weight=0.38). Patients with BMI≥24 and age≥55 had a 3.2-fold higher risk of positioning errors(95%CI 1.7-5.9).The calculated PTV margins were smallest in Group C(X/Y/Z:0.6/0.8/0.9 cm). Stage Ⅲ patients exhibited 0.3°greater Roll errors than Stage Ⅰ-Ⅱ patients(P=0.047).Conclusion:The HNS frame + foam cushion significantly improves positioning accuracy and effectively reduces PTV margins,making it suitable for various healthcare institutions.