Prediction of Hepatocellular Carcinoma Incidence Risk by Ultrasound Elastography

In patients with chronic hepatitis and continuous inflammation of the liver, fibrosis develops during the course of wound healing, and with recurrent accumulation of scar tissue and regenerative nodular formation, chronic hepatitis progresses to cirrhosis. In untreated patients with chronic hepatitis C infection, which is a leading cause of hepatocellular carcinoma (HCC), the Metavir liver fibrosis stage (F0, no fibrosis; F4, cirrhosis)[1] increases at an annual rate of F0.1 [2], with a concurrent increase in the incidence of HCC [3]. Therefore, it is extremely important to evaluate the liver fibrosis stage during follow up of chronic hepatitis C so as to understand the HCC risk. However, liver biopsy, the gold standard for diagnosing liver fibrosis, is susceptible to sampling variability [4] and diagnostic variability among pathologists. In addition, repeat biopsy is not recommended because of its invasiveness, the associated pain and risk of hemorrhage. Although serum fibrosis marker and hematologybased prediction algorithms have been widely reported for evaluating liver fibrosis, the results obtained with these methods may be affected by fibrotic conditions in other organs. Ultrasound elastography emerged as an imaging modality around 2010 and has been found in many studies to be diagnostically useful for liver fibrosis. The word “elastography” (“elasticity” + “graphy”), a collective term for the graphical display of tissue elasticity, was first used in 1991 to describe the technique of strain elastography proposed by Dr. Ophir at the University of Texas. Another term, “tissue elasticity imaging,” is used to define the graphic technology used to capture tissue elasticity over a wider area. However, the terms “elastography” and “tissue elasticity imaging” are now often used interchangeably and are even applied to non-graphic quantitative measurement methods such as that employed by FibroScan. Ultrasound elastography is classified into two major types based on the measurement principles adopted: strain elastography, which displays differences in tissue strain and is used in real-time tissue elastography (RTE), which is the first commercially available machine in the world launched in 2003 and shear wave elastography, which measures the speed of propagating waves and is used in FibroScan and Virtual Touch tissue quantification (VTQ) [5](table 1). While strain elastography enables the measurement (display) of liver fibrosis, © 2014 S. Karger AG, Basel 2235-1795/14/0031-0001$39.50/0 www.karger.com/lic Liver Cancer 2014;3:1–5