全身MR扩散加权成像在非小细胞肺癌淋巴结转移诊断与鉴别诊断中的价值

Identification of lymph node metastases by use of whole.body diffusion-weighted imaging in non- small cell lung cancer patients

目的比较全身MR—DWI（WB—DWI）、常规MRI和（或）CT（MRI—CT）及二者联合应用（WB—DWI＋MRI—CT）对非小细胞肺癌（NSCLC）淋巴结转移的检出能力。方法对56例病理确诊的NSCLC患者行WB—DWI、胸部CT扫描，并于扫描后1周内对可疑淋巴结转移部位行常规MR扫描，必要时增强扫描。应用ROC曲线比较WB—DWI、MRI—CT及二者联合应用在NSCLC淋巴结转移中的诊断价值。应用X2检验比较全身WB．DWI、MRI—CT及二者联合应用对不同大小淋巴结的检出能力，应用方差分析比较ADC值在良恶性淋巴结鉴别诊断中的价值。结果（1）WB—DWI、MRI—CT及二者联合应用3种方法对长径〈2cm淋巴结（共123枚，三者分别检出109、98、117枚）的检出率差异具有统计学意义（x2=13．819，P〈0．01），二者联合应用优于单独应用MRI—CT（x2=13．324，P〈0．01），而对其余2组（长径2～3cm淋巴结共46枚，三者分别检出43、40、45枚；长径〉3cm淋巴结共27枚，三者均全部检出），差异无统计学意义（x2=3．816，P〉0．05）。（2）MRI—CT诊断效果优于单独应用WB．DWI，WB—DWI＋MRI—CT诊断NSCLC淋巴结转移的ROC曲线下面积（x2=0．978）、敏感度、特异度、准确性（分别为97．4％、88．9％、86．3％）均高于MRI—CT或WB—DWI。（3）NSCLC淋巴结转移组ADC值明显低于良性淋巴结组[（0．79±0．15）×10^-3和（1．59±0．15）×10^-3mm2／s，F=332．813，P〈0．01]。结论WB—DWI是常规MRI-CT的有益补充，可以用于疑似NSCLC淋巴结转移患者的早期筛查，结合常规MRI—CT图像及ADC值测定，在NSCLC淋巴结转移诊断与鉴别诊断方面具有一定价值。

Objective To prospectively and directly compare the capability of whole-body DWI, MRI and/or CT （MRI-CT）, and whole-body DWI with MRI-CT for assessment of lymphatic metastases in non-small cell lung cancer （NSCLC） patients. Methods The institutional review board approved this study; informed consent was obtained from patients. A total of 56 NSCLC patients underwent whole-body DWI and thoracic CT scan prospectively. Conventional MRI was performed in suspicious lymphatic metastases parts within one week after inspection. Final diagnosis of the lymphatic metastases in each patient was determined on the basis of results of all radiologic and follow-up examinations. Two chest radiologists independently assessed all examination results and used a five-point visual scoring system to evaluate the probability of metastases. Final diagnosis based on each of the methods was made by consensus of two readers. Receiver operating characteristic （ROC） analysis was used to compare the capability for lymphatic metastases assessment among whole-body DWI, MRI-CT and whole-body DWI with MRI-CT. The detection abilities of lymph nodes with different size were compared with X2 test. Value of apparent diffusion coefficient （ ADC ） in the differential diagnosis of benign and malignant lymph nodes was compared with the variance analysis. Results （ 1 ） Lymph nodes metastases were divided into 3 groups according to the length diameter （ 〈 2,2--3, 〉 3 cm ）. A statistically significant difference （ X2 = 13. 819, P 〈 0. 01 ） was found in detection of lymph nodes （ 〈 2 cm） among whole-body DWI,MRI-CT and whole-body DWI with MRI-CT（within the 123 lymph nodes, 109,98 and 117 were detected respectively） ,whole-body DWI with MRI-CT was superior to conventional MRI-CT（ X2 = 13. 324, P 〈0. 01 ）. There were no statistically significant difference between the other 2 groups （in the length diameter 2-3 cm group, 43,40 and 45 of all 46 lymph nodes were detected respectively by whole-body DWI, MRI-CT and whole-body DWI with MRI-CT, X2 = 3.816, P 〉 0. 05, while in the length diameter 〉 3 cm group, all of the 27 lymph nodes were detected by each of them. （2） Conventional MRI-CT was superior to whole-body DWI in the diagnosis of lymph node metastasis in NSCLC. The area under ROC curve value of whole-body DWI with MRI-CT （ Az = 0. 978 ）, the sensitivity, specificity, accuracy （ 97.4 % , 88.9 % , 86. 3 % respectively） were significantly higher than conventional MRI-CT or whole-body DWI. （3）The ADC value of malignant lymph nodes were significantly lower than those of benign [ （ 0. 79± 0. 15 ） ×10^-mm2/s vs （ 1.59 ± 0. 15 ） ×10^-3 mm2/s, F = 332. 813, P 〈 0.01 ].The sensitivity, specificity, accuracy were 100% with the cut-off value of 1.06×10^-3mm2/s. Conclusions Whole-body DWI is the beneficial supplements of MRI-CT and can be used as a earlier clinical technique in patients with suspected NSCLC lymph node metastasis. Combined with ADC value, it can be used for assessment and differential diagnosis of lymphatic metastases in NSCLC patients.