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目的:分析不同b值下病变的弥散加权成像技术(diffusion-weighted imaging,DWI)信号特点及其表面扩张系数(apparent diffusion coefficient,ADC),探讨其在肺部肿瘤MRI中的应用价值。方法 :收集37例CT发现并经病理或临床随访证实肺部肿块,行肺部常规MRI序列以及不同b值(500、800、1 000 s/mm2)DWI。在病灶最大径层面上,分别测量各b值下病变的DWI信号强度、ADC值;通过受试者操作特征曲线(receiver operating characteristic curve,ROC),分析最佳b值及ADC值对肺部肿块的鉴别诊断作用;分析病灶DWI信号大小、ADC值与病理类型的关系。结果:(1)肺部良性肿块DWI呈等低信号或低信号,大多数恶性肿块DWI呈现等信号或高信号。(2)良性肿块在b值为500、800、1 000 s/mm2时,ADC值分别为(2.142±0.560)×10~(-3)、(1.746±0.499)×10~(-3)、(1.457±0.374)×10~(-3)mm2/s;恶性肿块在b值为500、800、1 000 s/mm2时,ADC值分别为(1.499±0.298)×10~(-3)、(1.274±0.230)×10~(-3)、(1.179±0.176)×10~(-3)mm2/s。(3)3种b值对良恶性肿块的ADC值差异均有统计学意义(t=4.637,P<0.001;t=3.695,P<0.001;t=3.097,P<0.004)。(4)3组b值ROC曲线下面积(AUC)分别为0.869、0.794和0.765,AUC>0.5,可以作为良恶性肿块鉴别诊断的有效指标,其中以500 s/mm2时所测ADC值的曲线下面积最大,ADC值良恶性鉴别阈值取1.475×10~(-3)mm2/s时,诊断作用最高,敏感性为0.833、特异性为0.773、约登指数0.606。结论:DWI信号强度及ADC值大小对肺部肿块鉴别诊断有较高价值,肺良性和恶性病变组ADC值均随b值增加而逐渐变小。
OBJECTIVE: To analyze the characteristics of diffusion-weighted imaging (DWI) signals and their apparent diffusion coefficients (ADCs) at different b-values, and to explore their value in the MRI of lung tumors. Methods: Thirty-seven CT findings of lung masses were confirmed by pathology or clinical follow-up. Conventional lung MRI sequences and different b values (500, 800 and 1000 s / mm2) DWI were performed. DWI signal intensity and ADC value of lesion at each b value were measured at the maximal diameter of lesion, and the best b value and ADC value were analyzed by the receiver operating characteristic curve (ROC) The differential diagnosis of DWI signal size, ADC value and pathological type of relationship. Results: (1) DWI of benign lungs showed low signal or low signal, and most of DWI showed equal signal or high signal. (2) The ADC values were (2.142 ± 0.560) × 10 ~ (-3), (1.746 ± 0.499) × 10 ~ (-3), respectively, when the b value was 500,800 and 1 000 s / (1.457 ± 0.374) × 10 ~ (-3) mm2 / s, ADC values were (1.499 ± 0.298) × 10 ~ (-3) at b values of 500, 800 and 1 000 s / (1.274 ± 0.230) × 10 ~ (-3), (1.179 ± 0.176) × 10 ~ (-3) mm2 / s. (3) There were significant differences in the ADC value between the three b values for benign and malignant masses (t = 4.637, P <0.001; t = 3.695, P <0.001; t = 3.097, P <0.004). (4) The area under the curve of ROC of three groups of b values were 0.869, 0.794 and 0.765, respectively. The AUC> 0.5 could be used as the effective index for the differential diagnosis of benign and malignant masses. The curve of ADC value measured at 500 s / mm2 The largest area under the ADC value of 1.475 × 10 ~ (-3) mm2 / s threshold for the diagnosis of the highest sensitivity of 0.833, specificity of 0.773, Youden index of 0.606. Conclusion: The DWI signal intensity and ADC value have high value in the differential diagnosis of lung mass. The ADC value of benign and malignant lung lesions group decreases with the increase of b value.