MRI扩散加权成像鉴别兔良恶性淋巴结实验研究

Differentiation of benign from malignant lymph nodes using diffusion weighted imaging in rabbit models

目的探讨DWI鉴别良恶性淋巴结的价值。方法32只健康新西兰大白兔,随机分为两组(每组16只),分别建立良性(16个淋巴结)和恶性淋巴结(16个淋巴结)模型。对所有实验兔均行MRI检查。在淋巴结最大层面上选取感兴趣区,获得淋巴结表观扩散系数(ADClymphnode);同时测量同层肌肉的ADC值(ADCmuscle),计算相对ADC(rADC=ADClymphnode/ADCmuscle)。采用两独立样本t检验分别比较良、恶性淋巴结ADC值与rADC值的差异;采用受试者工作特征曲线(ROC曲线),分析ADC及rADC定性诊断淋巴结的效能。结果良、恶性淋巴结在DWI均表现为相对高信号。良、恶性淋巴结ADC值分别为(0.92±0.13)×10^-3mm^2/s^-1和(0.76±0.08)×10^-3mm^2/s^-1;良、恶性淋巴结rADC值分别为0.71±0.05和0.63±0.05,良、恶性组淋巴结的ADC值及rADC值差异均有统计学意义(P均<0.05)。利用ADC值鉴别良、恶性淋巴结的ROC曲线下面积为0.83(最佳阈值为0.84×10^-3mm^2/s^-1),利用rADC值进行鉴别的ROC曲线下面积为0.88(最佳阈值为0.66),二者比较无统计学意义(P>0.05)。结论DWI对定性淋巴结病变有一定的价值,且rADC未能改善淋巴结的定性诊断。

Objective To explore the value of diffusion weighted imaging (DWI) in differentiating benign and malignant lymph nodes. Methods Thirty-two healthy new zealand rabbits were randomly divided into benign and malignant groups (16 rabbits peRgroup). The benign (16 lymph nodes) and metastatic lymph node model (malignant group, a total of 16 lymph nodes) were established, respectively. All rabbits underwent the MRI examination. The apparent diffusion coefficients of lymph node (ADClymph node) and of ipsilateral muscle at the same plane (ADCmuscle) were measured. Results ADC (rADC) were obtained as following: rADC=ADC lymph node /ADCmuscle. The ADC and rADC values of benign and malignant lymph nodes were compared by using independent sample t test, and the efficacy of ADC and rADC in qualitative diagnosis of lymph nodes was analyzed by ROC curve. Results both benign and malignant lymph nodes showed the relatively high signal on DWI. The ADC and rADC values between the benign and malignant lymph nodes were statistically significant 〔(0.92 ± 0.13)×10 ^-3 mm/s vs (0.76±0.08)×10 ^-3 mm/s;0.71±0.05 vs 0.63±0.05, respectively, and all P <0.05〕. When ADC and rADC were used to differentiate benign and malignant nodes, the area undeRthe receiveR operating characteristic curve was 0.82 foRADC (the threshold of 0.84×10 ^-3 mm/s) and 0.88 foRrADC (the threshold of 0.66), and no significant difference was found between the two methods ( P =0.53). Conclusion DWI enables the differentiation of benign from malignant lymph nodes. And rADC do not improve the capacity of ADC foR differentiating of benign from malignant lymph nodes.