肝局灶性病变的MR-DWI:不同b值和测量区域的诊断价值

Differential diagnosis of focal with diffusion-weighted MR imaging with different b values and measurement position hepatic lesions

目的探讨扩散加权成像(diffusion-weighted imaging,DWI)不同b值和病灶不同区域的表观扩散系数(apparent diffusion coefficient,ADC)值、指数化表观扩散系数(eADC)值、灌注ADC值、灌注eADC值和灶肝比值在肝脏占位性病变中的诊断价值。方法对51例肝脏占位病变行扩散加权成像扫描,其中恶性病变31例(原发性肝癌11例,肝转移瘤20例),良性病变20例(肝血管瘤12例,肝囊肿8例),测量低b值(50、150 s/mm2)、中b值(400、500 s/mm2)、高b值(750、1 000 s/mm2)肝占位病变的ADC值、eADC值,并根据低b值和高b值的ADC值和eADC差值计算灌注ADC值、灌注eADC值。根据不同b值测量的整体ADC值计算肝癌和肝转移瘤的病灶ADC值和周围肝实质ADC值比值,即灶肝比值。分析肝占位病变在不同b值、不同区域各个测量参数之间以及肝癌与肝转移瘤的ADC灶肝比值和eADC灶肝比值的差异。结果低b值时,肝脏各种占位病变的ADC值与eADC值差异均无统计学意义(P>0.05);中b值时,肝脏良、恶性病变的整体、中心ADC值与eADC值差异有统计学意义(P=0.01);高b值时,肝脏良、恶性病变的边缘、中心及整体ADC值与eADC值差异有统计学意义(P<0.05);肝脏良、恶性病变的边缘、中心及整体灌注ADC值与eADC差异有统计学意义(P<0.05);高b值时,肝癌与肝转移瘤的整体ADC灶肝比值、eADC灶肝比值差异有统计学意义(P<0.05)。结论应用高b值DWI检查是鉴别肝脏良恶性占位病变比较有效的方法。整体ADC灶肝比值、eADC灶肝比值能作为肝癌与肝转移瘤鉴别诊断依据。

Objective To evaluate the utility of the apparent diffusion coefficient（ADC） value,exponential apparent diffusion coefficient（eADC） value,perfusion ADC（ADCper） and perfusion eADC（eADCper） values,lesion-to-liver ratio of diffusion-weighted imaging（DWI） in differentiating liver focal lesions with different b values and measurement positions.Methods Fifty-one patients with liver focal lesions underwent DW-MRI at 1.5 Tesla.The ADC value and eADC value were measured for low（50,150 s/mm2）,moderate（400,500 s/mm2） and high（750,1000 s/mm2） b values on the entire lesions,margins and center regions.ADCper and eADCper values of focal liver lesions were calculated with the difference in ADC and eADC values between low and high b value.The ratios of ADC value and eADC value of entire HCC and liver metastasis to adjacent hapatic parenchyma were measured with different b values.The differences of all measured parameters with different b values between liver focal lesions were compared between lesion margins and center regions.ADCper and eADCper values of HCC and liver metastasis were compared with different b values.Results No difference in ADC or eADC value with low b value was found in liver focal lesions（P0.05）,whereas the difference in both ADC and eADC values of the entire lesion and center regions with moderate b value was found（P0.05）.The differences in both ADC and eADC values with high b value between benign and malignant leisions of the entire lesion and margins and center regions was statistically significant（P0.05）.The difference of both ADCper and eADCper of entire leisions,margins and center regions with high b value between benign and malignant lesions had statistical significance（P0.05）.in addition,The difference of both ADCl-to-l ratio and eADC l-to-l with high b value between entire HCC and liver metastasis was found（P0.05）,while there was no significant difference in low and moderate b values（P0.05）.Conclusion DWI is a effective method for differentiating liver benign and malignant lesions with high b value.Besides,entire ADCl-to-l ratio and eADC l-to-l is helpful to differentiating HCC and liver metastasis..