保乳术后放疗四维CT呼气末术腔勾画影响因素分析

Analysis of influential factors for variability in delineation of lumpectomy cavity based on 4DCT in end-exhalation phase

目的基于四维CT（4DCT）探讨CT层厚、术腔可见度评分（CVS）及金属夹个数对保乳术后术腔（LC）勾画的影响。方法术腔放置金属夹数目≥5个的35例保乳术后患者入组行4DCT扫描，全部患者均于T50时相图像上勾画LC。分别依据CT层厚、CVS及金属夹个数对患者进行分组，评价不同组间勾画者间及勾画者自身LC差异（△inter和Aintra）及LC间相似度（DSC）。结果不同勾画因素对勾画者自身影响均相似（P=0．628、0．842、0．080）。4DCT层厚为2、3、5mm者间△inter、DSCinter均相似差异（P=0．211、0．727），且与层厚无关（P=0．414、0．594）。LC体积与△inter呈负相关（P=0．024），且体积大于平均体积者DSC。较高（P=0．025）、△inter较小（P=0．009）。CVS3～5分者的DSCinter明显优于1～2分的（P=0．004），且CVS与DSCinter存在正相关（P=0．007）。△inter和DSCinter在金属夹数7～9与5～6个间均相似（P=0．159、0．825）。结论对放置5个以上金属夹标记术腔边界的乳腺癌保乳术后患者术腔体积和CVS仍是造成术腔勾画差异的主要影响因素，且金属夹数目在5—6个基础上再增加对术腔确定并无临床优势。

Objective To investigate the effects of computed tomography （CT） slice thickness, lumpectomy cavity （ LC ） volume, cavity visualization score （ CVS ）, and number of metal clips on the interobserver and intraobserver variability in the delineation of LC after breast-conserving surgery based on four-dimensional （4D） CT. Methods Thirty-five patients who had underwent breast-conserving surgery and had at least 5 metal clips placed in the LCs underwent 4DCT scans. For each patient, LC was delineated on the CT images in the T50 （end-exhalation） phase. The patients were stratified according to LC volume, CVS, CT slice thickness, and number of metal clips. Among different patient groups, interobserver and intraobserver variability in LC （ Ainter and Aintra ） and the dice similarity coefficients （DSCs） between LCs （DSCimer and DSCtriner） were evaluated and compared. Results LC volume, CVS, number of metal clips, and 4DCT slice thickness were not significantly correlated with Atriner and DSCintra （P=0. 628, 0. 842, 0. 080）. There were no significant differences in Ainter and DSCinter between the patient groups with 4DCT slice thickness of 2, 3, and 5 mm （P = 0. 211 and 0. 727）, and there was no correlation between 4DCT slice thickness and Ainter and DSCi.ter （P=0. 414,0. 594 ）. LC volume was negatively correlated with △inter （P = 0. 024） ; compared with those with LC volumes smaller than the mean value, the patients with LC volumes not smaller than the mean value had a significantly higher DSCinterr （P = 0. 025 ） and a significantly lower Aimor（P=0. 009）. The patient group with a CVS of 3 -5 had a significantly higher DSCinter than that with a CVS of 1 -2（P =0. 004） , and CVS was positively correlated with DSCinter（P =0. 007）. There were no significant differences in Ainter and DSCi between the patient groups with 7 -9 and 5 -6 metal clips （P = 0. 159,0. 825）. Conclusions For the breast cancer patients who have at least 5 metal clips placed at the boundary of LC after breast-conserving surgery, LC volume and CVS are still the main influential factors for variability in LC delineation. More metal clips in addition to 5 -6 ones are not helpful for LC delineation.