Quantitative assessment of liver fat with magnetic resonance imaging and spectroscopy

Abstract

Hepatic steatosis is characterized by abnormal and excessive accumulation of lipids within hepatocytes. It is an important feature of diffuse liver disease, and the histological hallmark of nonalcoholic fatty liver disease (NAFLD). Other conditions associated with steatosis include alcoholic liver disease, viral hepatitis, human immunodeficiency virus (HIV) and genetic lipodystrophies, cystic fibrosis liver disease, and hepatotoxicity from various therapeutic agents. Liver biopsy, the current clinical gold standard for assessment of liver fat, is invasive and has sampling errors, and is not optimal for screening, monitoring, clinical decision‐making, or well suited for many types of research studies. Noninvasive methods that accurately and objectively quantify liver fat are needed. Ultrasound (US) and computed tomography (CT) can be used to assess liver fat but have limited accuracy as well as other limitations. Magnetic resonance (MR) techniques can decompose the liver signal into its fat and water signal components and therefore assess liver fat more directly than CT or US. Most MR techniques measure the signal fat‐fraction (the fraction of the liver MR signal attributable to liver fat), which may be confounded by numerous technical and biological factors and may not reliably reflect fat content. By addressing the factors that confound the signal fat‐fraction, advanced MR techniques measure the proton density fat‐fraction (the fraction of the liver proton density attributable to liver fat), which is a fundamental tissue property and a direct measure of liver fat content. These advanced techniques show promise for accurate fat quantification and are likely to be commercially available soon. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.

Effects of Insulin Glargine and Liraglutide Therapy on Liver Fat as Measured by Magnetic Resonance in Patients With Type 2 Diabetes: A Randomized Trial

“…A triglyceride model of human liver fat spectra, described by Hamilton et al (22), was used to incorporate spectral correction of multifrequency interference effects of the protons in the fat. The PDFF in each pixel then was calculated as the ratio of the fat proton density to the total (fat and water) proton density (15).…”

“…The MRI-proton density fat fraction (PDFF) is a promising noninvasive biomarker for quantification of hepatic steatosis (15,16).…”

947 Shared Genetic Effects Between Hepatic Steatosis and Fibrosis: A Prospective Twin Study

“…MRI-PDFF has been previously shown to be a highly precise, accurate, and reproducible noninvasive biomarker to quantify hepatic fat content. (25,26), correlates well with MR spectroscopy (r 2 =0.99, p<0.001) (22,23), and is superior to noninvasive imaging techniques such as ultrasound and computed tomography for measuring hepatic fat content (27) even in iron-overloaded livers that may coexist with NAFLD livers. (28) MRI-PDFF has also been shown to correlate well with histology from contemporaneous liver biopsies.…”

Comparison of ultrasonography and dual echo magnetic resonance imaging in the diagnosis of fatty liver disease

“…Bu şekilde karaciğerin en çok yağlanan ya da yağlanmadan korunan bölgeleri hızlı ve güvenilir bir şekilde belirlenebilir. Dual eko görüntüleme bu özelliği ile karaciğer biyopsisi için doğru yeri belirlemede veya tercihen noninvazif kantitatif doku yağ oranı ölçümü için MRS örneklem alanını belirlemek için kullanılabilir [27]. İç faz ve dış faz dual eko görüntüler, multieko görüntüleme ile elde olunan proton yoğunluklu yağ oranı (PDFF: proton density fat fraction) tespitine ve MRS'ye göre daha yaygın kullanım alanı bulduğundan YKH'nın tanı, derecelendirme ve takibinde pratik ve güvenilir bir yöntem olarak kullanılmaya devam etmektedir.…”