3.0T MRI扩散加权成像及灌注加权成像在肾脏良恶性肿瘤鉴别诊断中的价值

Diffusion weighted imaging and perfusion weighted imaging in the differential diagnosis of benign and malignant renal masses on 3.0 T MRI

目的 评价3.0 T MRI扩散加权成像（DWI）和灌注加权成像（PWI）在肾脏肿瘤良恶性及不同病理组织学类型之间鉴别诊断的价值.方法 选取2012年6月至2013年12月,在同济大学附属同济医院放射科15名健康志愿者及46例经病理证实的肾脏肿瘤患者（其中肾透明细胞癌18例,乳头状肾细胞癌8例,肾嫌色细胞癌7例,肾血管平滑肌脂肪瘤13例）均行3.0 T MRI扩散加权成像（DWI）及灌注加权成像（PWI）扫描.采用单因素方差分析方法比较PWI所得血管通透性常数（Ktrans）、血液回流常数（Kep）、细胞外血管外间隙容量（Ve）,以及DWI所得表观扩散系数（ADC）值在不同病理类型肾脏肿瘤之间的差异.应用ROC曲线分析比较DWI及PWI两种成像方法对于鉴别肾脏肿瘤良恶性的诊断价值.结果 正常肾实质ADC值最高,为（2.10±0.24） ×10-3 mm2/s,与肾脏良、恶性肿瘤之间差异均有统计学意义（均P ＜0.05）;良性肿瘤的ADC值高于各组恶性肿瘤,差异均有统计学意义（均P ＜0.05）;恶性肿瘤中,肾透明细胞癌的ADC值最高,与乳头状细胞癌及嫌色细胞癌之间差异均有统计学意义（均P ＜0.05）,而乳头状细胞癌与嫌色细胞癌之间ADC值差异无统计学意义.正常肾实质与各病理类型肾脏肿瘤之间Ktrans、Kep及Ve值差异均有统计学意义（均P＜0.05）.肾脏各组恶性肿瘤的Ktrans值及Ve值均高于良性肿瘤,差异均有统计学意义（均P ＜0.05）,恶性肿瘤中,仅肾透明细胞癌的Kep值高于良性肿瘤,差异有统计学意义（P＜0.05）,其他肾脏恶性肿瘤病理类型与良性肿瘤的Kep值差异无统计学意义.肾脏恶性肿瘤中,肾透明细胞癌、肾乳头状细胞癌及肾嫌色细胞癌的Ktrans值分别为（0.85 ±0.27）、（0.51±0.04）、（0.39 ±0.05）/min,三者逐渐减低,各组间差异均有统计学意义（均P ＜0.05）.肾透明细胞癌的Ve值（0.42±0.08）高于肾乳头状细胞癌Ve值（0.29 ±0.14）,差异有统计学意义（P＜0.05）;而恶性肿瘤各组间Kep值差异均无统计学意义（均P＞0.05）.运用ROC曲线比较DWI及PWI两种检查方法鉴别肾脏肿瘤良恶性的诊断价值,其中,Ktrans所得曲线下面积最大（AUC=0.937）,灵敏度和特异度分别为87.9％和85.7％,并以0.38/min作为鉴别肾脏良恶性肿瘤的临界值;ADC所得曲线下面积为0.823（AUC=0.823）,灵敏度和特异度分别为72.7％和92.9％,所得鉴别良恶性肿瘤的ADC临界值为1.40×10-3mm2/s;Ve所得曲线下面积为0.803（AUC=0.803）,灵敏度和特异度分别为78.8％和71.4％,所得临界值为0.29/min;Kep则表现出较低的鉴别诊断价值.结论 3.0 T MRI DWI及PWI能有效鉴别肾脏肿瘤良恶性及不同病理组织学类型.PWI在鉴别肾脏肿瘤良恶性方面优于DWI,其中Ktrans值的诊断价值最高,但ADC值所提供的相关细胞结构特征及对水分子扩散运动的影响信息也是不可替代的.

Objective To explore the value of diffusion weighted imaging （DWI） and perfusion weighted imaging （PWI） in identifying benign and malignant renal masses and differentiating the histological types of renal masses.Methods Fifteen healthy volunteers and 46 patients with renal masses proven by pathology,including clear cell carcinomas （n =18）,papillary carcinomas （n =8）,chromophobe carcinomas （n =7） and angiomyolipomas （n =13）,were examined with DWI and PWI scan at 3.0 T MRI.ANOVA was employed to compare the values of transfer constant （Ktrans）,rate constant of backflux （Kep） and extra-vascular extra-cellular space fractional volume （Ve） proceeded by PWI and the value of ADC resulted from DWI between normal kidney and different histological types of renal masses.Receiver operating characteristics （ROC） curve was used to analyze and compare the diagnostic value of the methods of PWI and DWI in differentiating benign and malignant renal masses.Results The ADC value of normal renal parenchyma was （2.10 ± 0.24） × 10-3 mm2/s,which was statistically higher than benign and malignant renal masses （P ＜ 0.05）.The ADC value of benign masses was statistically higher than that of all histological types of malignant masses （P ＜ 0.05）.Among three histological types of malignancies,clear cell carcinoma showed the statistically highest ADC value （P ＜ 0.05）.But the difference between papillary carcinoma and chromophobe carcinoma had no statistical significance （P ＞ 0.05）.Values of K,Kep and Ve between normal renal parenchyma and different histological types of renal masses had statistical differences.Values of Ktrans and Ve in three histological types of malignant renal masses were statistically higher than those of benign renal masses.Kep value of clear cell carcinoma was significantly higher than that of benign renal masses （P ＜ 0.05）.However,other histological types of malignant masses had no significant difference with benign masses.For three malignant masses,Ktrans of clear cell carcinoma,papillary carcinoma and chromophobe carcinoma were （0.85 ± 0.27）,（0.51 ± 0.04） and （0.39 ± 0.05）/min respectively.All values gradually reduced.And the differences were statistically significant （P ＜ 0.05）.The Ve value of renal clear cell carcinoma was statistically higher than that of papillary carcinoma （P ＜ 0.05）.ROC curve was used to analyze and compare the diagnostic value of PWI versus DWI in differentiating benign and malignant renal masses.The K of benign and malignant renal masses had the largest AUC （AUC =0.937） at a threshold of 0.38/min.And there were a sensitivity of 87.9％ and a specificity of 85.7％.The AUC of ADC was 0.823,sensitivity 72.7％ and specificity 92.9％.The ADC threshold for differentiating benign from malignant masses was 1.40 × 10-3mm2/s; AUC of Ve 0.803,sensitivity 78.8％ and specificity 71.4％,a threshold of 0.29/min; Kep showed lower diagnostic value.Conclusion 3.0T MRI DWI and PWI can effectively differentiate benign and different histological types of malignant renal masses.And PWI is superior to DWI in differentiating benign and malignant renal masses.Ktrans with the largest AUC showed the highest diagnostic value.And ADC is also irreplaceable in providing the information of cellular structural features and the movement of water diffusion.