E1534. How to Read MRI Liver Elastography: A Step-By-Step Approach
Loma Linda University
Loma Linda University
In the last few years, noninvasive and reliable methods aim to replace liver biopsy for the evaluation of liver fibrosis. Liver biopsy is the gold standard for the assessment of liver fibrosis but there are several limitations, such as invasive nature with morbidity and small mortality risk, suboptimal sample sizes, sampling error, and subjective/semi-quantitative pathologic staging. There are four techniques of liver elastography: transient elastography, point shear wave elastography (ARFI), supersonic shear wave imaging, and MR elastography. MR elastography is the most accurate noninvasive technique of staging of fibrosis.
Educational Goals / Teaching Points
In this exhibit, we will review the basic principles, techniques, and limitations of liver MR elastography. We will present a step-by-step approach to help the radiologists know how to read and interpret a liver MR elastography exam.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Different levels of fibrosis exist that in practice are assessed using a histological score. The most widely used is the METAVIR score, which incorporates five stages of fibrosis: F0 (no fibrosis), F1 (portal fibrosis without septa: minimal fibrosis), F2 (portal fibrosis with a few septa: moderate fibrosis or clinically significant fibrosis), F3 (septal fibrosis with many septa but no cirrhosis: severe fibrosis), and F4 (cirrhosis). The shear wave velocity in the tissue is directly related to the stiffness of the tissue. Velocity of shear waves is faster in stiff or hard tissues and slower in soft tissues. The quality of liver MR elastography images depends on using appropriate sequences, breathing technique, and adequate section positioning.
Liver MR elastography is the best and most accurate noninvasive modality in detection and staging of hepatic fibrosis. Liver MR elastography can be used for determination of eligibility for antiviral drugs with hepatitis C and evaluation of response to antiviral treatments. Reporting reliable liver stiffness values requires direct supervision of radiologist for quality control of images and proper interpretation.