Quantitative Elastography Methods in Liver Diseases Kennedy Et Al
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This copy is for personal use only. To order printed copies, contact [email protected] Quantitative Elastography Methods in Liver Disease: Current STATE OF THE ART STATE 1 n Evidence and Future Directions Y r Paul Kennedy, PhD Chronic liver diseases often result in the development of Mathilde Wagner, MD, PhD liver fibrosis and ultimately, cirrhosis. Treatment strat- Laurent Castéra, MD egies and prognosis differ greatly depending on the sever- REVIEWS AND COMMENTA Cheng William Hong, MD ity of liver fibrosis, thus liver fibrosis staging is clinically Curtis L. Johnson, PhD relevant. Traditionally, liver biopsy has been the method Claude B. Sirlin, MD of choice for fibrosis evaluation. Because of liver biopsy Bachir Taouli, MD limitations, noninvasive methods have become a key re- search interest in the field. Elastography enables the non- invasive measurement of tissue mechanical properties Online SA-CME through observation of shear-wave propagation in the See www.rsna.org/education/search/ry tissue of interest. Increasing fibrosis stage is associated Learning Objectives: with increased liver stiffness, providing a discriminatory After reading the article and taking the test, the reader will be feature that can be exploited by elastographic methods. able to: Ultrasonographic (US) and magnetic resonance (MR) im- n Describe the basic principles of elastography methods aging elastographic methods are commercially available, n Describe the current performance of elastography in liver each with their respective strengths and limitations. Here, disease the authors review the technical basis, acquisition tech- n Identify pitfalls and confounders of liver stiffness niques, and results and limitations of US- and MR-based measurements using US and MR imaging elastography techniques. Diagnostic performance in the Accreditation and Designation Statement most common etiologies of chronic liver disease will be The RSNA is accredited by the Accreditation Council for Continuing presented. Reliability, reproducibility, failure rate, and Medical Education (ACCME) to provide continuing medical education emerging advances will be discussed. for physicians. The RSNA designates this journal-based SA-CME activity for a maximum of 1.0 AMA PRA Category 1 Credit™. Physicians should claim only the credit commensurate with the q RSNA, 2018 extent of their participation in the activity. Disclosure Statement Online supplemental material is available for this article. The ACCME requires that the RSNA, as an accredited provider of CME, obtain signed disclosure statements from the authors, ed- itors, and reviewers for this activity. For this journal-based CME activity, author disclosures are listed at the end of this article. 1 From the Translational and Molecular Imaging Institute (P.K., B.T.) and Department of Radiology (B.T.), Icahn School of Medicine at Mount Sinai, 1470 Madison Ave, New York, NY 10029; Department of Radiology, Sorbonne Universités, UPMC, Hôpital Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France (M.W.); Department of Hepatology, University Paris-VII, Hôpital Beaujon, Clichy, France (L.C.); Liver Imaging Group, Department of Radiology, University of California–San Diego, San Diego, Calif (C.W.H., C.B.S.); Department of Biomedical Engineering, University of Delaware, Newark, Del (C.L.J.). Received March 29, 2017; revision requested May 3; final revision received July 20; accepted August 2; final version accepted September 7. Address correspondence to B.T. (e-mail: [email protected]). C.W.H. and C.B.S. supported by National Institute of Biomedical Imaging and Bioengineering (T32EB005970) and National Institute of Diabetes and Digestive and Kidney Diseases (R01DK087877, R01DK088925, R01DK106419). P.K. and B.T. supported by National Cancer Institute (U01 CA172320) and National Institute of Diabetes and Digestive and Kidney Diseases (R01DK087877). q RSNA, 2018 738 radiology.rsna.org n Radiology: Volume 286: Number 3—March 2018 STATE OF THE ART: Quantitative Elastography Methods in Liver Diseases Kennedy et al hronic liver diseases are a major fibrosis may be beneficial in monitoring composite scores, such as FibroTest/Fi- cause of morbidity and mortality treatment efficacy, disease progression, broSure (BioPredictive, Paris, France) Cin the United States and world- and in establishing prognosis. (21), the enhanced liver fibrosis, or wide. The most prevalent etiologies of Until recently, liver fibrosis was pri- ELF (Siemens Healthineers, Erlangen, chronic liver diseases include chronic marily assessed with liver biopsy, which Germany), test (22), and FibroMeter hepatitis B virus (HBV) infection, is the reference standard for staging of (Echosens, Paris, France) (23). Though chronic hepatitis C virus (HCV) infec- liver fibrosis and grading of necroin- simple to perform, these tests have tion, nonalcoholic fatty liver disease flammatory changes, by using various limited accuracy in intermediate levels (NAFLD), and alcohol abuse (1). In the semiquantitative scoring systems (8– of fibrosis (24), and they are generally United States, chronic liver diseases 15). The most commonly used scoring considered less accurate than elasto- affect approximately 360 per 100 000 systems include the METAVIR score in graphic methods (25). persons and are the 12th leading cause chronic HBV or HCV infections and the of death, with an estimated mortality Brunt score in nonalcoholic steatohepa- of 12 deaths per 100 000 persons (2,3) titis (NASH) (8,9). All scoring systems Principles of Elastography and a projected financial burden ex- (except the Ishak score) range from F0 Elastography, first coined by Ophir et al ceeding $100 billion annually, mostly to F4, where F0 indicates no fibrosis; (26), describes the noninvasive assess- from NAFLD and chronic HCV infection F1, mild fibrosis; F2, moderate fibrosis; ment of tissue mechanical properties (4,5). Chronic liver diseases can lead F3, advanced fibrosis, and F4, cirrho- such as elasticity, which describes the to liver fibrosis, which is the result of sis. Despite its strengths, liver biopsy resistance to deformation of a tissue to chronic liver injury (6). The end-stage has several drawbacks: liver biopsy is an applied stress. In quantitative elas- of liver fibrosis is cirrhosis, which has relatively invasive and associated with tography methods, the stress is applied potential complications including portal a low rate of complications (approxi- via shear-wave propagation, generated hypertension, liver failure, and hepato- mately 3%) such as pain and bleeding, transiently, for example, via single me- cellular carcinoma (HCC). There is ev- which reduce patient acceptance and chanical impulse, or dynamically, for idence that when the underlying cause limit its suitability for repeated mea- example, via continuous application of is removed, liver fibrosis may regress or surements and disease monitoring. acoustic waves. US and MR elastograph- stabilize (7). Accurate staging of liver Also, biopsy enables the analysis of ic methods are available clinically and only a small portion of the liver, about are summarized in Figure 1 and Table 1. 1/50 000th of the total parenchyma, A more comprehensive overview of the Essentials introducing sampling variability and elastographic methods to be reviewed is nn Elastographic methods are accu- possible diagnostic errors (16,17). In- included in the Appendix E1 (online). rate tools for diagnosing liver ter- and intraobserver variability have Quantitative US elastography fibrosis and cirrhosis in a wide also been suggested as limitations to methods include transient elastogra- range of etiologies. biopsy, which may be linked to the in- phy (TE) and acoustic radiation force nn US-based transient elastography consistency in the definition of some impulse (ARFI) techniques such as is the most validated elasto- pathologic features (8,16,18). Finally, graphic technique. liver biopsy lacks dynamic information nn Acoustic radiation force impulse about the speed of disease progression. https://doi.org/10.1148/radiol.2018170601 All of these limitations make liver bi- elastographic methods are inte- Content codes: grated into clinical US systems opsy an imperfect reference standard. Radiology 2018; 286:738–763 allowing elastography to be per- An important ramification of these limitations is the difficulty in validating formed in routine clinical Abbreviations: examinations. noninvasive tests with use of biopsy as ARFI = acoustic radiation force impulse the reference standard, as the inherent AUC = area under the receiver operating characteristic n n MR elastography offers excellent flaws of biopsy can cause misinterpreta- curve diagnostic accuracy, although it is tion of results. GRE = gradient recalled echo less well validated and less avail- Alternative, noninvasive methods HBV = hepatitis B virus HCC = hepatocellular carcinoma able than US elastographic of evaluating liver health are being de- methods. HCV = hepatitis C virus veloped, such as serum markers and ICC = intraclass correlation coefficient nn Liver stiffness measurement can ultrasonographically (US) and mag- NAFLD = nonalcoholic fatty liver disease be affected by a variety of con- netic resonance (MR) imaging–based NASH = nonalcoholic steatohepatitis founding factors, such as hepatic elastography. Serum markers include pSWE = point SWE inflammation, congestion, chole- simple markers—such as platelet SWE = shear-wave elastography stasis (for all elastographic count, aspartate aminotransferase-to-