Ultrasound Elastography and MR Elastography for Assessing Liver Fibrosis: Part 1, Principles and Techniques.
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ABSTRACT: Objective
The purpose of this article is to provide an overview of ultrasound and MR elastography, including a glossary of relevant terminology, a classification of elastography techniques, and a discussion of their respective strengths and limitations.Conclusion
Elastography is an emerging technique for the noninvasive assessment of mechanical tissue properties. These techniques report metrics related to tissue stiffness, such as shear-wave speed, magnitude of the complex shear modulus, and the Young modulus.
SUBMITTER: Tang A
PROVIDER: S-EPMC4819982 | biostudies-literature | 2015 Jul
REPOSITORIES: biostudies-literature
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Ultrasound Elastography and MR Elastography for Assessing Liver Fibrosis: Part 1, Principles and Techniques.
Tang An A Cloutier Guy G Szeverenyi Nikolaus M NM Sirlin Claude B CB
AJR. American journal of roentgenology 20150423 1
<h4>Objective</h4>The purpose of this article is to provide an overview of ultrasound and MR elastography, including a glossary of relevant terminology, a classification of elastography techniques, and a discussion of their respective strengths and limitations.<h4>Conclusion</h4>Elastography is an emerging technique for the noninvasive assessment of mechanical tissue properties. These techniques report metrics related to tissue stiffness, such as shear-wave speed, magnitude of the complex shear ...[more]
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Project description:PurposeTo evaluate the diagnostic accuracy of magnetic resonance (MR) elastography as a method to help diagnose clinically substantial fibrosis in patients with nonalcoholic fatty liver disease (NAFLD) and, by using MR elastography as a reference standard, to compare various laboratory marker panels in the identification of patients with NAFLD and advanced fibrosis.Materials and methodsThis retrospective study was institutional review board approved and HIPAA complaint. Informed consent was waived. This study was conducted in patients with NAFLD, who were identified by imaging characteristics consistent with steatosis in a prospective database that tracks all MR elastographic examinations. Six laboratory-based models of fibrosis were compared with MR elastographic results as well as fibrosis stage from liver biopsy results. The area under the receiver operating characteristic curve (AUROC), sensitivity, specificity, positive predictive value, and negative predictive value of each data set were compared.ResultsAmong 325 patients with NAFLD with MR elastographic data, there were 142 patients who underwent liver biopsy within 1 year of MR elastography. When comparing MR elastography results with liver biopsy results, the best cutoff for advanced fibrosis (stage F3-F4, 46 [32.4%] of 142) was 4.15 kPa (AUROC = 0.954, sensitivity = 0.85, specificity = 0.929). This cutoff value identified 104 patients with advanced fibrosis (32.0% of 325 patients). The FIB-4 score (AUROC = 0.827) and NAFLD fibrosis score (AUROC = 0.821) had the best diagnostic accuracy for advanced fibrosis, with high negative predictive values (NAFLD fibrosis score = 0.90 and FIB-4 score = 0.899).ConclusionMR elastography is a useful diagnostic tool for detecting advanced fibrosis in NAFLD. Of the laboratory-based methods, the NAFLD fibrosis and FIB-4 scores can most reliably detect advanced fibrosis.
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Project description:Purpose To investigate the utility of magnetic resonance (MR) elastography-derived mechanical properties in the discrimination of hepatic inflammation and fibrosis in the early stages of chronic liver diseases. Materials and Methods All studies were approved by the institutional animal care and use committee. A total of 187 animals were studied, including 182 mice and five pigs. These animals represented five different liver diseases with a varying combination and extent of hepatic inflammation, fibrosis, congestion, and portal hypertension. Multifrequency three-dimensional MR elastography was performed, and shear stiffness, storage modulus, shear loss modulus, and damping ratio were calculated for all animals. Necroinflammation, fibrosis, and portal pressure were either histologically scored or biochemically and physically quantified in all animals. Two-sided Welch t tests were used to evaluate mean differences between disease and control groups. Spearman correlation analyses were used to evaluate the relationships between mechanical parameters and quantitative fibrosis extent (hydroxyproline concentration) and portal pressure. Results Liver stiffness and storage modulus increased with progressively developed fibrosis and portal hypertension (mean stiffness at 80 Hz and 48-week feeding, 0.51 kPa ± 0.12 in the steatohepatitis group vs 0.29 kPa ± 0.01 in the control group; P = .02). Damping ratio and shear loss modulus can be used to distinguish inflammation from fibrosis at early stages of disease, even before the development of histologically detectable necroinflammation and fibrosis (mean damping ratio at 80 Hz and 20-week feeding, 0.044 ± 0.012 in the steatohepatitis group vs 0.014 ± 0.008 in the control group; P < .001). Damping ratio and liver stiffness vary differently with respect to cause of portal hypertension (ie, congestion- or cirrhosis-induced hypertension). These differentiation abilities have frequency-dependent variations. Conclusion Liver stiffness and damping ratio measurements can extend hepatic MR elastography to potentially enable assessment of necroinflammatory, congestive, and fibrotic processes of chronic liver diseases. © RSNA, 2017 Online supplemental material is available for this article.
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