基于磁共振扩散加权成像直肠癌ADC值与其分化程度及神经脉管侵犯相关性研究

目的探讨磁共振弥散加权成像中表观扩散系数(apparent diffusion coefficient,ADC)、指数化表观扩散系数(exponential apparent diffusion coefficient,e ADC)与直肠癌分化程度及神经脉管侵犯的相关性。材料与方法 32例直肠癌患者进行术前常规序列及b值为50、500、1000 s/mm~2的MR扩散加权序列检查,测定不同b值下瘤体、正常肠壁的ADC、e ADC值并比较其差异。同时比较同一分化程度肿瘤不同b值间ADC、e ADC值的差异以及同一b值不同分化程度、神经脉管侵犯是否阳性的肿瘤间ADC、e ADC值的差异及相关性。结果直肠癌在不同b值的弥散加权成像(diffusion weighted imaging,DWI)图像上,均表现为稍高或高信号,b值为50、500、1000 s/mm~2的瘤体平均ADC值分别为(2.732±0.805)×10~(-3) mm~2/s、(1.226±0.195)×10~(-3) mm~2/s、(1.042±0.228)×10~(-3) mm~2/s,瘤体e ADC值分别为(0.097±0.058)mm~2/s、(0.304±0.055)mm~2/s、(0.363±0.070)mm~2/s,随着b值升高,组织ADC值降低,e ADC值则升高。不同b值条件下,瘤体ADC值随着肿瘤分化程度增高而增高,e ADC值则相反,b值为500、1000 s/mm~2的序列中,差异有统计学意义(b=500 s/mm~2时,P=0.03,F=4.123;b=1000 s/mm~2时,P=0.001,F=10.797);除b=1000 s/mm~2中神经侵犯阳性组平均ADC值较阴性平均ADC值高外,其余组神经脉管侵犯阳性结果组平均ADC值均较阴性组ADC值低。进行不同b值下瘤区ADC值与其分化程度Spear_son相关性分析,当b值为1000 s/mm~2时,病变ADC值与分化程度呈正相关(r_s=0.742,P0.05),而与e ADC值呈负相关(r_s=-0.630,P0.05);b值为1000 s/mm~2的病灶的ADC值诊断直肠腺癌效能较佳。结论磁共振弥散加权成像ADC值及e ADC值在一定程度上能够反映肿瘤的分化程度及脉管癌栓受侵情况,ADC值可作为早期检测、直肠癌放化疗疗效及预后评价的重要影像学指标。

Correlation research of the ADC value of MR diffusion weighted imaging in differential differentiation of rectal tumor,perineural invasion and peritumor-intravascular cancer emboli

Objective:To observe the correlation of the apparent diffusion coefifcient (ADC) value, exponential apparent diffusion coefifcient (eADC) value of MR diffusion weighted imaging (DWI) in differential differentiation of rectal tumor with different b values, and the correlation of ADC value and perineural invasion, peritumor-intravascular cancer emboli in tumor.Materials and Methods:Thirty-two patients with operable rectal cancer underwent preoperative MR imaging with single-shot echo plannar imaging (EPI) diffusion-weighted sequences (b=50, 500, 1000 s/mm2). Measure and compare the apparent diffusion coefifcient(ADC) value and exponential apparent diffusion coefifcient (eADC) value of MR diffusion weighted imaging (DWI) in rectal wall and differential differentiation of rectal tumor, and the correlation of ADC value and perineural invasion, peritumor-intravascular cancer emboli in tumor. All of them were compared with pathologicstaging.Results:The rectal carcinomas were slightly high signal or high signal on DWI. When b value is 50, 500, 1000 s/mm2 , the mean ADC value of tumor is (2.732±0.805)×10-3 mm2/s, (1.226±0.195)×10-3 mm2/s, (1.042±0.228)× 10-3 mm2/s, the mean eADC value of tumor is (0.097±0.058) mm2/s, (0.304±0.055) mm2/s, (0.363±0.070) mm2/s, respectively. With each b value, the mean ADC value of tumor increases following the ascending of differentiated degree of rectal carcinoma, and the mean eADC value decreases. When b value is 500, 1000 s/mm2, the difference is statistically signiifcant (b=500 s/mm2,P= 0.03, F= 4.123; b=1000 s/mm2,P=0.001,F=10.797). In most of group, the mean ADC value of peritumor-intravascular cancer emboli and perineural invasion are lower than the negative, and the difference is statistically signiifcant in b=500 s/mm2 of MR diffusion weighted imaging. And analyze thespearson correlation coefficient of differential differentiation of rectal tumor in different b values.The ADC value of tumor and differentiation have positive correlation (rs=0.742,P<0.05), and have negative correlation with eADC values (rs=-0.630,P<0.05) with b value of 1000 s/mm2. ADC values have the better diagnostic efifciency for diagnosis of rectal adenocarcinoma with b value of 1000 s/mm2.Conclusion:The diffusion-weighted imaging is a rapid and feasible method in detecting rectal cancer. The correlation can be pointed out between ADC and pathological classiifcation of each tumor, and the relationship of the ADC value and perineural invasion, peritumor-intravascular cancer emboli in tumor. Therefore, the ADC value can respresent an important imaging biomarker for assessing the response to radiochemotherapy and the prognose of the tumor.