Magnetic Resonance Imaging in Focal Liver Lesions with Diffusion Weighted Imaging (DWI) and Pathological Correlation

ABSTRACT

Background: Magnetic resonance signal intensity of focal liver lesions is affected by numerous pathologic factors. Lesion histologic features, such as cellularity, vascularity, stromal component, and intratumoral necrosis or hemorrhage, strongly affect T1 and T2 relaxation times. Aim and objectives: To assess the lesion characterization potential of MRI by evaluating unenhanced and dynamic gadolinium enhanced sequences, Histopathological correlation of the lesions to explain the major MRI findings and Assessment of the lesions by diffusion weighted imaging and investigating the role of b value in differentiating malignant and benign lesions Materials and methods: The study was done on 42 patients where contrast was given in 38 members. Focal liver lesions were analyzed based on clinical findings, laboratory investigations and MR imaging. Sonographically detected focal lesions were included in the study. Tissue diagnosis (FNAC/ Biopsy), surgery were done in feasible cases. In other cases, where surgery/ tissue diagnosis is not possible, follow up was done (range 3 months - 12 months, average 7.2 months). Results: MRI features of forty two patients with focal liver lesions were studied and morphological features and signal intensities of the masses were described. Contrast study was done in 39 cases. Of the 42 cases, 24 lesions were benign and 18 lesions were malignant. The mean age group ranged from 18 to 74 years with majority between 40 to 60 years. 61% of the lesions were located in right lobe of the liver. Contrast enhancement was done in 39 cases. Contrast enhancement was able to better delineate the cases. Specific pattern of contrast enhancement was typical of certain lesions as Karuna V, R Vikash Babu. Magnetic Resonance Imaging in Focal Liver Lesions with Diffusion Weighted Imaging (DWI) and Pathological Correlation. IAIM, 2019; 6(11) 81-93. Page 82 homogenous early arterial phase enhancement for hepatocellular carcinoma and ring enhancement in arterial phase for metastases. Delayed enhancement was specific for cholangiocarcinoma. Hemangiomas showed peripheral puddling and delayed central enhancement. Diffusion weighted imaging can be used as an additional tool in differentiating benign and malignant focal liver lesions. ADC value using a cut-off of 1.43 X 10 – 3 sec/ mm2 was a useful adjunct for determining benign cystic lesions and hemangiomas from malignant lesions. Conclusion: MRI was able to predict diagnosis in 38 of the 42 tumors. It could suggest the nature of all lesions in benign cysts, hemangiomas, focal nodular hyperplasia and metastases. But it was not possible to achieve a specific diagnosis in two early abscesses, one multifocal hepatocellular carcinoma and one case of regenerative nodules. This accounted for a detection rate of 90%. Thus MR imaging is a powerful tool for the evaluation of focal liver lesions. Pre contrast T1 weighted gradient echo images, T2 weighted images, in phase and out phase imaging, EPI – DWI and gadolinium enhanced T1 weighted images provide accurate characterization of the lesions.