Acoustic radiation force impulse imaging as noninvasive marker of hepatic fibrosis

Abstract

Background: Acoustic Radiation Force impulse Imaging (ARFI) is a novel non-invasive technique studying the localized mechanical properties of tissue by utilizing short, high intensity acoustic pulses (shear wave pulses) to assess the mechanical response(tissue displacement), providing a measure of tissue elasticity. Aims: To investigate the feasibility of ARFI imaging as a noninvasive method for assessing liver fibrosis compared to liver biopsy scores in patients with suspected chronic liver disease. Method: A prospective comparison study of ARFI elastography (Virtual Touch imaging, ACUSON S2000 ultrasound unit, Siemens) in a consecutive series of patients who underwent liver biopsy for assessment of liver stiffness was measured in meters per second. Mean ARFI velocities were compared with Modified Ishak scores and Brunt score for fibrosis in liver biopsy findings. Results: Study included 40 patients of suspected chronic liver disease who underwent liver biopsy and ARFI Elastography from the same segment of liver between the age group of 38.7 ± 14.4 years with predominant male gender (80%) over a period of 1 year. Cryptogenic cause for chronic hepatitis (32.5%) was the leading cause followed by NASH (22.5%) and then contributed equally by viral etiology of HCV and HBV (20%) each. The median ARFI value is 1.55mt/sec and there is an increasing trend of ARFI values as Childs score increases. ARFI proved to be a better predictor of advanced fibrosis (F3 or F4). The spearman rho correlation coefficients between median values of ARFI measurements and the histological fibrosis stage of the Metavir score and Brunt score were both highly significant (P< 0.01) with rho of 0.523 and 0.69 respectively. Conclusion: Our study showed that ARFI sonoelastography stands out on account of its very good correlation with liver biopsy (gold standard for evaluating liver fibrosis).