Application Study Of Diffusion Weighted MR Imaging In Focal Liver Lesions

Objective: To evaluate the value of diffusion weighted magnetic resonance imaging in diagnosis and differentiation of focal liver masses.Materials and method: 20 healthy persons and 60 patients were recruited, all the subjects underwent first routine T1-weighted and T2-weighted imaging of the whole liver and then diffusion-weighted MR imaging by using 4 different b factors under breath-hold. signal intensity were measured and ADC,SNR and CNR were calculated.Result: 16 of 80 cases were excluded for poor images. So there were, in fact, 64 cases,among whom were12 healthy people and 46 patients with 70 local hepatic lesions (12 hepatic cysts, 6 hepatic hemangiomas, 28 metastatic liver tumors, 20 hepatocellular carcinomas, 3 cholangiocellular carcinomas, 1 focal nodular hyperplasia ) and 10 hepatic cirrhosis (4 with hepatocellular carcinomas).The mean ADCs (mm2/s)were 1.75×10-3±0.57 in liver,1.45×10-3±0.46 in spleen,1.98×10-3±0.43 in the pancreas, 2.52×10-3±0.50in the kidney, 3.11×10-3±0.31 in the gallbladder, 1.73×10-3±0.40 in the erector spinal muscles. The mean ADCs of cirrhotic liver were 1.80×10-3±0.61,which were slightly higher than those of normal liver, but the difference were not statistically significant(p>0.05). The mean ADCs were 2.89×10-3±0.60mm2/s in hepatic cyst,2.77×10-3±0.99mm2/s in the hepatic hemangioma,1.86×10-3±0.53mm2/s in the metastatic liver tumor,1.62×10-3mm2/s ±0.51 in the hepatocellular carcinoma. The mean ADCs of benign tumors (hepatic cyst and hemangioma) were higher than those of malignant tumors (hepatocellular carcinomas and metastatic liver tumors), and both was statistically significant (P<0.001). And the value 2.50×10-3mm/s2 of ADCs can distinguish benign tumors from malignant ones. The differences of ADCs of hepatocellular carcinomas and metastatic liver tumors were not statistically significant (P>0.05). The ratio of ADCs of hepatic solid tumors (hepatocellular carcinomas and metastatic liver tumors) to that of liver parenchyma was statistically significant (P<0.001). When gradient factor (b) is 300s/mm2~600 s/mm2, the SNR and CNR of liver were the most suitable.Conclusion:Diffusion-weighted imaging can be used as a non-invasive method for diagnosis and differential diagnosis in focal liver lesions; The gradient factor(b)between 300s/mm2 and 600 s/mm2 was the most suitable in diffusion weighted imaging; Diffusion-weighted images and the ADCs can refect the blood supply to the foci;The ADCs of cirrhotic hepatic tissue may not be less than that of normal liver;The ratio of ADCs of hepatic solid tumors to that of liver parenchyma is valuable in differential diagnosis of hepatocellular carcinomas and metastatic liver tumors;Some issues in EPI-DWI need discussing.