The Use of MRI Apparent Diffusion Coefficient Value (ADC Value) to Assess Liver Cirrhosis

Introduction Hepatitis is known to induce severe liver diseases such as liver cirrhosis and liver cancer which are serious threats to public health. The evaluation of the severity of liver cirrhosis is very important for the selection of appropriate treatment plan and the monitoring of patient response to treatment [1].

Noninvasive Child-Pugh classification is a common method to assess liver function, treatment outcome and prognosis in patients with chronic liver cirrhosis [2].

Accurate staging of liver fibrosis (commonly determined by liver biopsy) is critical because it determines the indication of antiviral treatment and prognosis of patients with chronic viral hepatitis. For example, patients with cirrhosis are at higher risk of end-stage liver disease, portal hypertension, and hepatocellular carcinoma and are less likely to respond to antiviral therapy [8-9].

However, liver biopsy is relatively invasive, limited by sample size, and difficult to repeat. Thus, noninvasive tools to assess the degree of fibrosis of the whole liver are urgently needed. Several noninvasive MRI techniques have been investigated for the diagnosis of liver fibrosis and cirrhosis, including diffusion weighted imaging (DWI) [20-24], MR Elastography [25], and perfusion-weighted imaging [26-27].

DWI is a particularly appealing method for the diagnosis of liver fibrosis because it is easy to implement and process, without the need for contrast agents. Apparent diffusion coefficient (ADC) has been shown to be a promising marker of fibrosis and cirrhosis by several independent investigators [20-24].

Recently magnetic resonance Diffusion Weighted Imaging (DWI) has become another noninvasive approach to assess liver cirrhosis by analyzing the changes of water diffusion based on the apparent diffusion coefficient (ADC) [3].

Several studies showed that ADC values of cirrhotic liver were correlated with the results of Child-Pugh classification for the evaluation of the severity of liver cirrhosis [4-7].

However, whether ADC values of cirrhotic liver are correlated with the results of Child-Pugh classification, it remains unclear. The DWI is a specific MRI technique that evaluates the motion of, mainly, water protons in the tissue. The apparent diffusion coefficient (ADC) is the most frequently used DWI measure and provides useful information about inflammation, perfusion and local cell breakdown. The ADC map is calculated based on exponential fitting of DWI over multiple b-values and is used to measure diffusion quantitatively. Prior studies have shown that in liver fibrosis water diffusion may be diminished by extracellular collagen fibers and proteoglycans, thus, reduced ADC values have been reported for liver fibrosis. [10,11,12,13,14,15,16,17,18,20].

These findings suggest DWI could be a useful imaging technique to evaluate fibrosis. In more recent studies, researchers examined the relationship between the stages of hepatic fibrosis and ADC values [14,15,16,19,20].