MR平扫及动态增强扫描对进展期胃癌术前TNM分期的临床应用研究

Dynamic contrast enhanced MR study on preoperative TNM staging of advanced gastric carcinoma

目的探讨MR平扫及动态增强扫描对进展期胃癌术前TNM分期的临床应用价值。方法通过采用低张、水充盈技术,对10例健康成人志愿者和35例临床经胃镜活检确诊为胃癌患者行MR平扫及动态增强扫描,结果采用双盲法阅片,并与手术病理结果进行对照,对所有MRI分期与病理分期进行Kappa一致性检验。结果10例正常者胃壁各部位的厚度均小于6mm,T1WI、T2WI均表现为均匀的等信号,其中T1WI反相位上胃壁外围可见宽度恒定的低信号带;35例胃癌患者中29例病变T1WI呈稍低信号改变(82.9%),6例病变呈等信号(17.1%),所有病变T2WI均呈等或低信号改变;动态增强扫描30例病灶均呈明显强化,其中20例呈不规则强化,10例呈分层强化。MRI对T2、T3、T4期胃癌分期的敏感性分别达75.0%、85.7%、100%,特异性分别为84.2%、81.0%、100%;若将T3和T4合为一组,则判断浆膜浸润的敏感性为88.9%,特异性为76.5%,准确性为82.9%;对T分期诊断总准确性为80.0%。MRI对淋巴结转移的检出率仅为47.8%,对周围脏器转移灶的检出率为55.6%。结论MR平扫结合动态增强扫描对进展期胃癌术前TNM分期具有一定优势,特别是T分期和M分期,但对N分期的判断准确性较低。

Objective To evaluate the diagnostic value of MRI on preoperative TNM staging in advanced gastric carcinoma. Methods With hypotonia and water filling, the stomach of 10 normal volunteers and 35 cases of gastric carcinoma diagnosed by biopsy underwent pre-contrast and dynamic contrast enhanced MR scans. The imaging findings and tumor staging were blindly and independently assessed by two radiologists, and the imaging findings were correlated with the pathologic results. Results The thickness of normal gastric wall was less than 6 mm, and the wall showed homogeneous isointensity on both T1WI and T2WI. A low signal band was always revealed along the outer gastric wall on out-of-phase T1WI. The gastric carcinoma showed thickened wall and slight hypointensity （n=29, 82.9%） or isointensity （n=6, 17.1%） on TIWI. All the lesions showed iso-or hypointensity on T2WI. On dynamic scan, marked enhancement was detected in all 30 cases, with irregular enhancement in 20 cases and layered enhancement in 10 cases. The sensitivity of MRI for the staging of T2, T3, and T4 was 75.0%, 85.7%, and 100%, respectively, and the specificity was 84.2%, 81.0%, and 100%, respectively. The sensitivity, specificity, and accuracy on serosal invasion were 88.9%, 76.5%, and 82.9%, respectively, when T3 and T4 were combined. The accuracy on total T-staging was 80.0%. The detection rate of MRI on N-staging was only 47.8%. The detection rate on M-staging was 55.6%. Conclusion Combined conventional and dynamic contrast enhanced, MRI is superior in T-staging and M-staging. However, MRI has limitations in the evaluation of N-staging.