扩散加权成像eADC值诊断前列腺良恶性结节价值探讨

eADC value of magnetic resonance diffusion-weighted imaging in diagnosis of benign and malignant prostatic nodules

目的探讨MRI扩散加权成像(DWI)的指数化表观扩散系数(e ADC)评价前列腺良恶性结节的可行性。方法选择2013年1月至2017年12月在南京医科大学附属南京医院行MRI DWI检查的可疑前列腺癌患者66例,年龄41~88岁,平均年龄60.00岁。行MRI检测,并与病理检测结果对照。MRI扫描序列包括T_1加权成像(T_1WI)、T_2加权成像(T_2WI)、脂肪抑制序列和DWI序列(b=0 s/mm^2、1 000 s/mm^2);并测量表观扩散系数(ADC)值、e ADC值。前列腺良恶性结节之间的ADC或e ADC值差异比较采用独立样本t检验。绘制所测数值的受试者工作特征曲线(ROC),比较曲线下面积,根据约登指数(灵敏度+特异度-1)最大值,计算ADC和e ADC值的诊断阈值,比较两者的灵敏度和特异度。结果共发现96个病灶,其中良性病灶(前列腺增生组)44个,恶性病灶(前列腺癌组)52个。前列腺增生组ADC值为(0.98±0.15)×10^(-3)mm^2/s,前列腺癌组ADC值为(0.63±0.15)×10^(-3 )mm^2/s;两组间差异有显著统计学意义(t=-11.62,P<0.01);以0.78×10^(-3)mm^2/s为最佳阈值,ADC诊断前列腺癌的灵敏度和特异度分别为93.20%、88.50%。前列腺增生组平均e ADC值为(0.20±0.17)×10^(-3 )mm^2/s,前列腺癌组e ADC值为(0.34±0.10)×10^(-3 )mm^2/s;两组间差异有显著统计学意义(t=5.30,P<0.01);以0.22×10^(-3 )mm^2/s为最佳阈值,e ADC诊断前列腺癌的灵敏度和特异度分别为94.20%、84.10%。ADC的ROC曲线下面积为0.953,e ADC的ROC曲线下面积为0.924,两者的诊断效能相近,差异无统计学意义。结论e ADC图消除了T_2投射效应,改进了组织对比度,是评估前列腺癌的一个有价值的参考指标。

Objective To investigate the feasibility of exponential apparent diffusion coefficient（eADC）of MRI diffusion weighted imaging（DWI）in evaluating the prostate benign and malignant nodules.Methods From January 2013 to December2017,a total of 66 suspected prostate cancer patients underwent MRI DWI were enrolled,aged 41-88 years old with mean age of 60.00 years old.All of them performed MRI examination and compared with pathological results.The MRI scanning sequences included conventional T1weighted imaging（T1WI）,T2weighted imaging（T2WI）,fat suppression imaging and DWI（b=0 s/mm^2,1 000 s/mm^2）.The apparent diffusion coefficient（ADC）value and e ADC value were measured.The differences of ADC or e ADC values between prostate benign and malignant nodules were compared with independent sample t test.The receiver operating characteristic curve（ROC）of measured values was drawn,and area under the curve were compared.Based on Youden index（sensitivity＋specificity-1）maximum value,the diagnostic threshold of ADC and e ADC values was calculated and the sensitivity and specificity were compared.ResultsA total of 96 lesions were detected,which included 44 benign lesions（prostate hyperplasia group）and 52 malignant lesions（prostate cancer group）.The ADC value of prostate hyperplasia group was（0.98±0.15）×10^-3mm^2/s and prostate cancer group was（0.63±0.15）×10^-3mm^2/s,there was statistically significant difference between 2 groups（t=-11.62,P〈0.01）.With 0.78×10^-3mm^2/s as the best threshold,the sensitivity and specificity of e ADC in diagnosis prostate cancer were 93.20%and 88.50%,respectively.The mean e ADC value of prostate hyperplasia group was（0.20±0.17）×10^-3mm^2/s and prostate cancer group was（0.34±0.10）×10^-3mm^2/s,there was significant difference between 2 groups（t=5.30,P〈0.01）.With 0.22×10^-3mm^2/s as the best threshold,the sensitivity and specificity of e ADC in diagnosis prostate cancer were 94.20%and 84.10%,respectively.The area under ROC curve of ADC was 0.953and area under ROC curve of e ADC was 0.924,the diagnostic efficiency of 2 curves were similar,which was no significant differences.Conclusion The e ADC eliminate the T2projection effect and improve tissue contrast,which is a valuable reference for assessment of prostate cancer.