Role of DWI MRI in Evaluation of Hypervascular Focal Lesions of Cirrhotic Liver

Abstract

Hepatic focal lesions may be benign or malignant and some of the hyper vascular focal lesions may be benign. Therapy requires an accurate diagnosis, which in turn relies primarily on appropriate imaging and image-guided biopsy. Triphasic CT was believed to be the standard in evaluating the hepatic focal lesions and together with alpha-feto protein, the lesions were decided either non conclusive and needing biopsy or conclusive. According to number and distribution of the lesions (if proved malignant); surgery, radiofrequency ablation, alcohol injection or chemo-embolization was decided. Unfortunately, not all cases with HCC having high alpha fetoprotein and not all cases having typical imaging criteria of HCC and also, not all lesions detected by US are seen in the dynamic CT study. MRI provides better soft-tissue contrast and identification of different tissue properties by their signal appearance on different MR phases. Moreover, a wide variety of contrast agents are currently available for use in MR imaging. MRI having many sequences, markedly helps in the detection of small lesions and in reaching the diagnosis easily sometimes without contrast as in cysts and hemangiomas and sometimes with contrast injection. For hepatic focal lesions detection and characterization, conventional MRI relies on T1-weighted, T2-weighted, and dynamic gadolinium-enhanced T1-weighted imaging. DW MRI in the liver is a relative new and increasingly used imaging technique. It has the advantage that it can be obtained during a single breath-hold; it provides unique information that reflects tissue cellularity and organization. The ADC maps can also provide quantitative measurements of tissue water diffusibility, which can be used not only for disease assessment, but also for the evaluation of disease response to treatment. MRI with intravenous contrast injection is a safe and well tolerated technique that is easily performed and is sensitive for early detection of malignant neoplastic hepatic lesions, and for differentiation between the premalignant and the malignant lesions. This technique is complementary to other imaging modalities and laboratory studies for full assessment of the hepatocellular nodules in cirrhotic livers.