双能CT碘图评估甲状腺微小乳头状癌颈淋巴结转移潜能的价值

Dual-energy CT iodine image for evaluation of cervical lymph node metastatic potential in papillary thyroid microcarcinoma

目的探讨甲状腺微小乳头状癌(PTMC)双能CT碘图形态及功能定量参数评估颈部淋巴结转移(LNM)潜能的可行性。方法回顾性分析2014年7月至2016年12月95例行颈部双能CT扫描,且术后病理初次诊断为PTMC患者的临床和影像资料。根据患者是否发生颈部LNM分为LNM组(59例)和无LNM组(36例)。患者双能CT扫描结果经双能量软件后处理得到碘图,分析CT碘图各形态特征(肿瘤大小、数目、纵横比、形态、结节强化环是否完整、结节是否突破甲状腺包膜、微钙化及强化程度)及其诊断效能。测量动脉期和静脉期PTMC实质成分和同层面颈内动脉的碘浓度(IC)和CT值,计算动静脉期病灶的标准化碘浓度(NIC)和标准化CT值。LNM组和无LNM组间动静脉期IC、NIC、CT值、标准化CT值比较采用两独立样本t检验。并绘制ROC曲线,分析2期NIC和标准化CT值的诊断效能。结果颈部LNM组和无LNM组的PTMC多发病灶、结节最大径>5.0 mm、纵横比>1、形态不规则、结节强化环不完整及结节突破甲状腺包膜的概率差异具有统计学意义(χ^2分别为14.965,8.724、11.494、8.097、6.324、23.272,P均<0.05),且与转移潜能呈正相关(r分别为0.397、0.303、0.348、0.309、0.258、0.495,P均<0.05),且以结节突破甲状腺包膜诊断颈部LNM效能最高(灵敏度77.9%、特异度72.2%、准确度75.8%)。动脉期无LNM组NICROI和标准化CT值分别为0.29±0.10、0.33±0.11,小于LNM组的0.45±0.15、0.44±0.13,差异有统计学意义(t值分别为-4.891、-3.462,P均<0.001)。静脉期LNM组NIC和标准化CT值均高于无LNM组(t值分别为-3.381、-2.18,P均<0.05)。各项定量参数中,动脉期NIC诊断颈部LNM效能最高,ROC曲线下面积(AUC)最大,为0.814,敏感度为73.5%,特异度为79.2%,此时诊断阈值为0.208。结论双能CT碘图的形态征象和功能学定量参数对术前评估PTMC的颈部LNM潜能具有较大临床价值。

Objective To investigate the feasibility of morphology and quantitative parameters for evaluation of lymph node metastatic (LNM) potential in papillary thyroid microcarcinoma (PTMC) with dual-energy CT iodine image.Methods The ninety-five PTMC patients (59 patients with LNM,36 patients without LNM in the neck) whom underwent dual-energy contrast scanning and confirmed by first postoperative pathology results were enrolled in this retrospective study from July 2014 to December 2016.Dual-energy iodine images were obtained by the dual-energy post-processing software.The iodine image morphology of each patient was analyzed,including size,number,aspect ratio,shape,uncompleted enhanced ring sign,nodule which breaks through the thyroid capsule,microcalcification,and enhanced-degree,and diagnostic efficiency of each imaging feature was calculated.The iodine concentration (IC) and CT value of PTMC solid parts were measured in arterial phase and venous phase images respectively,as well as theNICnod (normalized iodine concentration) and normalized CT value.The independent sample t test was performed to compare quantitative parameters between the LNM group and non-LNM group.ROC curves with quantitative parameters of two phases were used to analyze the diagnostic efficiencies of NIC and normalized CT value.Results Statistically,in the iodine image,the imaging features of LNM group,including multiple lesions,maximum diameter of nodules,aspect ratio,irregular shape,uncompleted enhanced ring sign,and nodule which breaks through the thyroid capsule,had significant differences compared with those of non-LNM group in the neck (χ^2 were 14.965,8.724,11.494,8.097,6.324,23.272;P all<0.05),and there were positive correlations with LNM potential (r were 0.397,0.303,0.348,0.309,0.258,0.495;P all<0.05),the diagnostic efficiency of nodule which breaks through the thyroid capsule was the highest among the imaging features for diagnosis of cervical LNM (sensitivity 77.9%,specificity 72.2%,accuracy 75.8%).During the artery phase,mean NICROI and normalized CT value of non-LNM group were respectively 0.29±0.10,0.33±0.11,and these of LNM group were respectively 0.45±0.15,0.44±0.13.NICROI and normalized CT value of non-LNM group were less than LNM group′s (t=-4.891,-3.462;P all<0.001).During the venous phase,NICROI and normalized CT value of LNM group were higher than non-LNM group′s (t=-3.381,-2.18;P all<0.05).Among all quantitative parameters,the NIC of arterial phase has the highest diagnostic efficacy for the diagnosis of cervical LNM.The area under the ROC curve (AUC) was the largest,0.814,the sensitivity was 73.5%,the specificity was 79.2%,and the diagnostic threshold was 0.208.Conclusion Dual-energy CT iodine image morphology and quantitative parameters have important clinical value for evaluation of cervical lymph node metastatic potential in PTMC.