锥形束CT引导下乳腺癌保乳术后调强放疗摆位误差及配准方式分析

摘要

目的 探讨机载锥形束CT(CBCT)引导下乳腺癌保乳术后调强放疗(IMRT)不同乳腺厚度时摆位误差及配准方式的差异.方法 2016年3-10月,选择温州医科大学附属第一医院放化疗科接受IMRT的乳腺癌保乳术后患者85例,在医科达Synergy加速器上的机载CBCT引导下,对IMRT治疗前摆位进行验证.把CBCT重建图像和计划图像进行匹配.计算六维方向上的摆位误差,并在线自动校准上述误差.线下分别测量每例患者乳腺厚度(乳腺组织最大径,即乳腺组织最凸点至最近胸壁肌外缘的距离)并分组,对比分析自动骨性配准下和自动灰度配准下X轴(左右)、Y轴(上下)、Z轴(前后)及矢轴位(GX)、冠状位(GY)、横状位(GZ)的摆位误差.结果 自动骨性配准下和自动灰度配准下,85例患者X轴和GY的摆位误差间差异有统计学意义(P<0.05).自动骨性配准下A组(乳腺厚度≤30 mm)、B组(乳腺厚度>30~45 mm)、C组(乳腺厚度>45 mm)患者各个方向的摆位误差间差异均无统计学意义(P>0.05);自动灰度配准下3组患者各个方向的摆位误差间差异均无统计学意义(P>0.05).结论 乳腺癌保乳术后IMRT不同乳腺厚度患者摆位误差间无明显差异,两种配准方式建议首先使用灰度配准.放疗前进行CBCT引导下摆位误差校准,可以提高乳腺癌放疗的精度,从而实现精确放疗.%Objective To investigate the setup errors and registration algorithm under different breast thickness of intensity modulated radiation therapy(IMRT) after breast-conserving surgery of breast cancer based on cone-beam CT(CBCT).Methods Eighty five patients who received IMRT after breast conserving surgery in Department of Radiotherapy of the First Affiliated Hospital of Wenzhou Medical University from March to October 2016 were selected.Based on the onboard CBCT of Elekta Synergy accelerator,setup verification was made before IMRT treatment.Match the CBCT reconstructed image with the scheduled CT image.The setup error in the six-dimensional direction was calculated,and the above error on-line was automatically calibrated.The thickness of the breast of each patient(the largest diameter of the breast tissue,that is,the most salient point of the breast tissue to the nearest margin of the chest wall) was measured,and based on the bone-based registration and grey-based registration,the setup error of horizontal movement in X(left and right),Y(upper and lower),Z(front and rear) axes and the sagittal position(GX),coronal position(GY) and transverse position(GZ) were comparatively analyzed.Results There was significant difference in the setup error between the X axis and the GY of the 85 patients based on the bone-based registration and grey-based registration(P<0.05).In the automatic bone-based registration,there was no significant difference in the setup error among A group(thickness of breast ≤30 mm),B group(30< thickness of breast ≤45 mm) and C group(thickness of breast >45 mm)(P>0.05).In the automatic grey-based registration,there was no significant difference in the setup error of each direction among the three groups(P>0.05).Conclusion There are no significant differences in setup errors under different breast thickness of IMRT after breast-conserving surgery of breast cancer.The grey-based registration is recommended first in the two registration methods.The error calibration before radiotherapy can significantly improve the accuracy of breast cancer treatment,and thus realize the precise radiotherapy.