基于不同体位定位CT探讨不同勾画者勾画保乳术后部分乳腺外照射靶区差异

目的比较基于不同体位定位CT下不同勾画者勾画保乳术后部分乳腺外照射(EB-PBI)靶区差异。方法2016-2017年间27例保乳术后拟行EB-PBI的患者在自由呼吸状态下序贯完成俯卧位及仰卧位模拟定位3DCT扫描。5位勾画者分别在两种不同体位CT图像上基于术腔金属夹完成瘤床(TB)靶区勾画和临床靶区(CTV)的构建。比较两种体位不同勾画者间的靶体积、变异系数(COV)、匹配指数(MD)差异。结果无论仰卧位还是俯卧位时,不同勾画者所勾画TB、CTV均不同(P<0.001、P=0.001、P<0.001、P=0.001)。俯卧位时不同勾画者CTV交集比仰卧位大5.79cm3(P=0.011)。仰卧位时5位勾画者的COVCTV显著大于俯卧位(P=0.014)。仰卧位时5位勾画者的MDTBTB及MDTBCTV均显著劣于俯卧位(P<0.001、P=0.001)。结论与仰卧位相比,基于俯卧位构建EB-PBI靶区可显著减少不同勾画者间差异,提高勾画者间的一致性。因此,在自由呼吸状态下基于俯卧位施行EB-PBI更为合理。

Interobserver variability in the delineation of the target volume based on supine and prone simulation 3DCT for external-beam partial breast irradiation after breast-conserving surgery

Objective To explore the interobserver variabilities in the delineation of the target volume using simulation three-dimensional computed tomography (3DCT) between the supine and prone positions for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS). Methods Twenty-seven breast cancer patients who were scheduled to receive EB-PBI after BCS from July 2016 to April 2017 were enrolled in this study. All patients underwent axial 3DCT simulation scanning in the supine and prone positions during free breathing. Based on two different simulation 3DCT acquired, the gross target volume (TB) formed by using surgical clips and the clinical target volume (CTV) were delineated by five radiologists using specific guidelines. The following parameters including the target volume, coefficient of variations (COV) and matching degree (MD) were calculated to analyze the interobserver variability. Twenty-seven breast cancer patients who were scheduled to receive EB-PBI after BCS from July 2016 to April 2017 were enrolled in this study. Results Whether in the supine or prone position, the interobserver variabilities for TB and CTV were statistically significant (P<0.001,P=0.001,P<0.001,P=0.001). And the intersection of CTV in the prone position was 5.79 cm³ greater than that in the supine position (P=0.011). The interobserver variability of COVCTV in the prone positionwas significantly lower than that in the supine position (P=0.014). And the interobserver variabilities of MDTBTB and MDTBCTV in the prone positionwere statistically greater than those in the supine position, respectively (P<0.001,P= 0.001). Conclusions When delineating the target volume of EB-PBI in the prone position, the interobsever variability can be reduced compared with that in the supine position. Hence, it is more reasonable to carry out EB-PBI in the prone position in free breathing.