3.0T高分辨MRI诊断直肠癌直肠系膜淋巴结转移的应用价值

Diagnostic accuracy of 3.0T high-resolution MRI for assessment mesorectal lymph node metastases in patients with rectal cancer

目的探讨3.0T高分辨MRI对直肠癌直肠系膜淋巴结转移的诊断价值。方法采用描述性病例系列研究方法，回顾性收集中山大学附属第一医院2015年11月至2016年11月期间经病理证实为原发直肠癌且术前行3.0T直肠2D高分辨MRI检查患者的影像学和术后病理资料，纳入患者的手术时间需距术前MRI检查不超过2周，排除术前接受放疗、化疗或同期放化疗者以及MRI检查后未行手术者。MRI扫描序列包括高分辨矢状位、冠状位、正交轴位T2加权像（T2WI），重复时间为3000-4000 ms，回波时间为77-87 ms，层厚均为3 mm，无间隔扫描，视野为18-22 cm。两名腹部MRI诊断医师分别测量淋巴结最短径（各测量3次取平均值），观察淋巴结形态、边缘及信号特征。高分辨MRI T2WI评价淋巴结转移标准为形态不规则、边缘模糊和（或）信号混杂。将术前MRI诊断淋巴结有无转移的结果与术后病理结果进行对照，计算高分辨MRI评价直肠系膜淋巴结及不同短径淋巴结转移的灵敏度、特异度、准确性、阳性预测值（PPV）、阴性预测值（NPV），并采用Kappa检验评价高分辨MRI与病理结果的一致性。Kappa值为0-0.20为一致性极低，0.21-0.40为一致性一般，0.41-0.60为一致性中等，0.61-0.80为高度一致性，0.81-1.00为几乎完全一致。结果共81例患者纳入本研究，其中男50例、女31例，年龄为（59.3±11.1）岁。病理诊断为高分化腺癌1例、中分化腺癌63例、中-低分化腺癌9例、低分化腺癌2例、黏液腺癌3例、绒毛管状腺癌3例；T1期2例、T2期20例、T3期45例、T4期14例；N0期34例、N1期40例、N2期7例；M0期76例、M1期5例。MRI与病理相匹配淋巴结共377枚，168枚（44.6%）为转移淋巴结，58.0%（47/81）的患者淋巴结转移阳性。转移淋巴结短径的中位数为5.4（2.4-18.6）mm，长于未转移淋巴结的短径[中位数3.8（2.0-8.7）mm，Z=10.586，P = 0.000]。高分辨MRI评价淋巴结是否转移的灵敏度为74.4%（125/168）、特异度为94.7%（198/209）、准确性为85.7%（323/377）、PPV为91.9%（125/136）、NPV为82.2%（198/241）。术前高分辨MRI评价淋巴结是否转移和患者是否有转移淋巴结的结果与术后病理结果一致性的Kappa值分别为0.71和0.70，为高度一致。短径〉10 mm的14枚淋巴结均有转移，高分辨MRI诊断的灵敏度、准确性及PPV均为100.0%，与病理结果完全一致。124枚短径5-10 mm的淋巴结中，95枚（76.6%）有转移，高分辨MRI诊断的灵敏度为78.9%（75/95）、特异度为86.2%（25/29）、准确性为80.6%（100/124）、PPV为94.9%（75/79）、NPV为55.6%（25/45），与病理结果的一致性中等（Kappa值为0.55）。239枚短径≤5mm淋巴结，59枚（24.7%）有转移，高分辨MRI诊断的灵敏度为61.0%（36/59）、特异度为96.1%（173/180）、准确性为87.4%（209/239）、PPV为83.7%（36/43）、NPV为88.3%（173/196），与病理结果高度一致（Kappa值为0.63）。结论直肠高分辨MRI能清楚观察直肠系膜淋巴结形态、边缘及信号特征，对直肠系膜淋巴结转移有较高的诊断价值。

Objective To evaluate the diagnostic value of 3.0T high-resolution MRI in mesorectal lymph node metastasis of rectal cancer. Methods The images and postoperative pathological data of patients with pathologically diagnosed rectal cancer who underwent prospective 3.0T two dimensional high-resolution MRI rectal examinations and surgery within two weeks after MRI examination at the First Affiliated Hospital, Sun Yat-sen University from November 2015 to November 2016 were retrospectively collected. Patients who received preoperative neoadjuvant therapy and those who did not undergo operation after MRI examination were excluded. The MRI sequences included high- resolution sagittal, coronal and oblique axial T2 weighted image （T2WI） （repetition time/echo time, 3000-4000 ms/77-87 ms; slice thickness/gap, 3 ram/0 mm; field of view, 18-22 cm）. Two abdominal MRI radiologists independently assessed the morphology, margin, signal of all visible mesorectal nodes, measured their minor axes （three times for each radiologist） and gave estimation of the malignancy. The criteria of metastatic nodes on high-resolution MRI T2WI were nodes with irregular shape, ill-defined border and/or heterogeneous signal. The results of MRI diagnosis were compared with postoperative pathology. The sensitivity, specificity, accuracy, positive predictive value （PPV） and negative predictive value （NPV） of mesorectal nodes and nodes with different short-axis diameter ranges were calculated to evaluate the diagnostic efficiency of high-resolution MRI. Kappa statistics was used to evaluate the agreement for per node and for per patient between high-resolution MRI and pathological results. A Kappa value of 0-0.20 indicated poor agreement; 0.21-0.40 fair agreement; 0.41-0.60 moderate agreement; 0.61-0.80 good agreement; and 0.81-1.00 excellent agreement. Results A total of 81 patients were enrolled in the retrospective cohort study, including 50 males and 31 females with age of （59.3 ±11.1） years. Histopathology showed 1 case of well differentiated adenocarcinoma, 63 of moderately differentiated adenoearcinoma, 9 of moderately to poorly differentiated adenocareinoma, 2 of poorly differentiated adenocarcinoma, 3 of mucinous adenocarcinoma and 3 of tubulovillous adenocarcinoma. Histopathological staging showed 2 cases in T1 stage, 20 in T2 stage, 45 in T3 stage and 14 in T4 stage; 34 in NO stage, 40 in N1 stage and 7 in N2 stage; 76 in M0 stage and 5 in M1 stage. A total of 377 nodes were included in the node-by-node evaluation, of which 168 （44.6%） nodes were metastatic from 58.0% （47/81 ） patients. The median short-axis diameter was 5.4 （2.4-18.6） mm in metastatic nodes, which was significantly larger than 3.8 （2.0-8.7） mm in non-metastatic nodes [Z=10.586, P=0.000]. The sensitivity, specificity, accuracy, PPV and NPV were 74.4% （125/168）, 94.7% （198/209）, 85.7% （323/377）, 91.9% （125/136） and 82.2% （198/241）, respectively. The Kappa values between high-resolution MRI and histopathologieal diagnosis for node-by-node and patient-by-patient were 0.71 and 0.70 respectively, indicating good agreements. Fourteen nodes 〉10 mm were all metastatic. The results of high-resolution MRI for nodal status were consistent with the results of histopathological diagnosis, and the sensitivity, accuracy and PPV were all 100.0%. Among 124 nodes with short-axis diameter of 5-10 mm, 95 （76.6%） were metastatic, and the sensitivity, specificity, accuracy, PPV and NPV were 78.9% （75/95）, 86.2% （25/29）, 80.6% （100/124）, 94.9% （75/79） and 55.6% （25/45）, respectively. The agreement was fair （Kappa value 0.55） between high-resolution MRI and histopathological diagnosis. Among 239 nodes with short-axis diameter ≤5 mm, 59 （24.7%） were metastatic, and the sensitivity, specificity, accuracy, PPV and NPV were 61.0% （36/59）, 96.1% （173/180）, 87.4% （209/239）, 83.7% （36/43） and 88.3% （173/196）, respectively. The agreement was good （Kappa value 0.63） between high-resolution MRI and histopathological diagnosis. Conclusion Rectal high-resolution MRI has good diagnostic value for estimating metastatic mesorectal nodes by evaluating the morphology, margin and signal of nodes.