基于四维CT扫描分析金属夹和血清肿确定部分乳腺外照射内大体肿瘤体积及计划靶体积间差异

Comparison of the volume and localization of internal gross target volume and planning target volume delineated by clips and seroma based on 4D-CT scan for external-beam partial breast irradiation after breast conserving surgery

目的 基于四维CT（4D-CT）扫描,探讨保乳术后乳腺癌患者基于金属夹和血清肿确定术腔内大体肿瘤体积（IGTV）及计划靶体积（PTV）间体积和位置差异.方法 在4D-CT 10个时相图像上,基于术腔各边界金属夹勾画大体肿瘤靶体积（GTV）并定义为GTVc,基于术腔血清肿勾画GTV并定义为GTVs,两者结合勾画GTV并定义为GTVc＋s,10个时相图像融合分别得到IGTVc、IGTVs和IGTVc＋s,边界外扩15 mm,分别得到PTVc、PTVs和PTVc ＋s.结果 IGTVc＋s的体积为（35.73±19.77） cm3,与IGTVc[（28.35±17.54）cm3]和IGTVs[（24.19±21.53）cm3]比较,差异均有统计学意义（均P＜0.05）;IGTVc与IGTVs比较,差异无统计学意义（P =0.210）.PTVc＋s的体积为（191.59±69.74）cm3,大于PTVc[（161.53±61.07）cm3]和PTVs[（148.98±62.22）cm3],差异均有统计学意义（均P＜0.05）;PTVc与PTVs比较,差异无统计学意义（P =0.171）.IGTVc对IGTVc＋s、IGTVs对IGTVc＋s、PTVc对PTVc＋s和PTVs对PTVc ＋s的相互包含度（DI）均优于IGTVc＋s对IGTVc、IGTVc＋s对IGTVs、PTVc＋s对PTVc及PTVc ＋s对PTVs的DI（均P＜0.05）.IGTVc/IGTVc＋s、IGTVs/IGTVc＋s间的适形指数（CI）分别为0.63±0.14和0.54±0.17,均高于IGTVc/IGTVs间CI（0.40±0.14,均P＜0.05）.PTVc/PTVs、PTVc/PTVc＋s和PTVs/PTVc＋s的CI分别为0.73±0.12、0.78±0.13和0.75±0.17,差异无统计学意义（P＞0.05）.基于不同参照物确定的IGTV间和PTV间的DI和CI均与对应靶区中心间距呈负相关（均P＜0.05）.结论 不同参照物确定的术腔靶区间存在体积和空间位置差异,将基于4D-CT获取的10个时相靶区融合,并外扩得到PTV显著缩小了体积和位置差异,提高了靶区间的重合度.金属夹结合血清肿确定靶区,并进行外扩得到PTV是实施部分乳腺外照射较为理想的靶区.

Objective To explore the differences in volume and localization of the internal gross target volume and planning target volume delineated by clips and/or seroma based on four-dimensional computed tomography （4D-CT） during free-breathing in breast cancer patients after breast conserving surgery.Methods Fifteen breast cancer patients after breast-conserving surgery （BCS） were recruited for external-beam partial breast irradiation （EB-PBI）.On the ten sets CT images,the gross tumor volumes （GTV） formed by the clips,the seroma,and both the clips and seroma were delineated and defined as GTVc,GTVs and GTVc ＋ s,respectively.Ten GTVc,GTVs and GTVc ＋ s on the ten sets CT images produced the IGTVc,IGTVs,IGTVc ＋ s.The PTVc,PTVs,PTVc ＋ s were created by adding 15 mm to the IGTVc,IGTVs,IGTVc ＋ s,respectively.The IGTV and PTV volume and distance between the centers of IGTVc,IGTVs,IGTVc ＋ s and PTVc,PTVs,PTVc ＋ s were all recorded.Conformity index （CI） and degree of inclusion （DI） were calculated for IGTV/IGTV and PTV/PTV,respectively.Results The volume of IGTVc ＋ s[（35.73 ± 19.77） cm3] was significantly larger than the IGTVc [（28.35 ± 17.54）cm3] and IGTVs [（24.19 ± 21.53） cm3] （P ＜ 0.05）,and the volume of PTVc ＋ s [（191.59 ± 69.74）cm3] was significantly larger than that of the PTVc [（161.53 ± 61.07） cm3] and PTVs [（148.98 ±62.22） cm3] （P ＜ 0.05）.There were significant differences between the DIs of IGTVc in IGTVc ＋ s and IGTVc ＋ s in IGTVc,the DIs of IGTVs in IGTVc ＋ s and IGTVc ＋ s in IGTVs,the DIs of PTVc in PTVc ＋s and PTVc ＋ s in PTVc,and the DIs of PTVs vs.PTVc ＋ s and PTVc ＋ s in PTVs （P ＜ 0.05 for all）.The CI of IGTVc/IGTVc ＋ s （0.63 ± 0.14） and the CI of IGTVs/IGTVc ＋ s （0.54 ± 0.17） were significant larger than that of the CI of IGTVc/IGTVs （0.40 ± 0.14） （P ＜ 0.05）.There were non-significant differences among the CI of PTVc/PTVs,PTVc/PTVc ＋ s and PTVs/PTVc ＋ s （0.73 ± 0.12,0.78 ± 0.13 vs.0.75 ± 0.17）.The DIs and CIs of IGTV/IGTV and PTV/PTV were negatively correlated with their centroid distance （P ＜ 0.05）.Conclusions There are volume difference and spatial mismatch between the target volumes delineated on the basis of surgical clips and seroma.The DI and CI between the PTVs are larger than that between the IGTV.External-beam partial breast irradiation should be implemented based on the PTV that is defined based on both seroma and surgical clips.