Imaging Evaluation for Steatotic Liver Disease

Abstract

Metabolic dysfunction-associated steatotic liver disease (MASLD), previously known as nonalcoholic fatty liver disease, is the fastest-growing cause of chronic liver disease worldwide, affecting approximately 30% of the global population. Imaging is vital for detecting, quantifying, and monitoring hepatic steatosis-the defining abnormality of MASLD-and subsequent fibrosis-the key determinant of liver-related outcomes. This review summarizes the principles, clinical usage, efficacy, and advancements in various imaging modalities for the noninvasive assessment of hepatic steatosis and fibrosis, with an emphasis on ultrasound, CT, and MRI. Additionally, this review explores the evolving landscape of MASLD diagnostic approaches, including machine-learning techniques, opportunistic screening, standardized imaging guidelines, and therapies, emphasizing the pivotal role that radiologists can play in shaping these developments.

Keywords: CSE-MRI; Chemical-shift-encoded; MASLD; MR elastography; Metabolic dysfunction-associated steatotic liver disease; PDFF; Proton density fat fraction; Quantitative ultrasound.

Fig. 1. MASLD prevalence worldwide. The global prevalence of MASLD is estimated to be approximately 30%, with ranges from 25% to 44%. Adapted from Younossi et al., Hepatology 2023;77:1335-1347 [1], under a CC BY-NC-ND license. Map created with www.mapchart.net. MASLD = metabolic dysfunction-associated steatotic liver disease

Fig. 2. At-risk MASH is a subset of MASH, which in turn is a subset of MASLD. MASH = metabolic-associated steatohepatitis, MASLD = metabolic dysfunction-associated steatotic liver disease

Fig. 3. Three different pediatric patients with varying severity of steatotic liver disease by conventional ultrasound. Note the increasing liver parenchymal echogenicity, blurring of vessels, and increased beam attenuation with increased severity of steatosis.

Fig. 4. Steatotic liver disease on qualitative ultrasound. Qualitative ultrasound examination of a 52-year-old woman with biopsy-proven steatotic liver disease demonstrates an elevated AC of 1.15 dB/cm-MHz and a BSC of 0.0042 1/cm-sr. The image was reconstructed using the radiofrequency data acquired from an ultrasound system (Siemens ACUSON S3000; Siemens Healthineers) with a 4C1 (1–4 MHz nominal) transducer. AC = attenuation coefficient, BSC = backscatter coefficient

Fig. 5. Steatotic liver disease on non-contrast CT. A, B: Axial non-contrast CT images of a 28-year-old woman with alcohol-associated liver disease before (A) and after (B) 3 months of abstinence. Note that the attenuation of the liver is <40 HU in image (A) while it is >40 HU in image (B). HU = Hounsfield units

Fig. 6. Steatotic liver disease on MRI-PDFF. Axial non-contrast MRI of a 48-year-old woman with biopsy-proven steatotic liver disease. Multi-echo MRI is utilized to decompose the liver signal into fat and water signal components, which are utilized to compute the PDFF. ^*At echo times suitable for chemical-shift-based fat-water signal separation. PDFF = proton density fat fraction, IP = in-phase, OP = out-of-phase

Fig. 7. Artificial intelligence-derived PDFF measurement from conventional IP and OP MR images. PDFF = proton density fat fraction, IP = in-phase, OP = out-of-phase, CNN = convolutional neural network

Fig. 8. Hepatic fibrosis on ultrasound elastography. Ultrasound elastography examination in two patients with varying degrees of hepatic fibrosis. A: A 67-year-old man with a history of alcohol-associated cirrhosis with a SWS value of 1.93 m/s (4.5 MHz frequency, C1-6 probe, GE LOGIQ E10 system). B: A 57-year-old woman with a history of decompensated cirrhosis with a SWS value of 2.8m/s (4.5 MHz frequency, C1-6 probe, GE LOGIQ E10 system). SWS = shear wave stress

Fig. 9. Hepatic fibrosis on MRE. MRE examination in two patients with varying degrees of hepatic fibrosis. A: A 65-year-old woman with a liver biopsy-negative for fibrosis with a stiffness value of 1.54 kPa. B: A 49-year-old man with biopsy-proven hepatic fibrosis (stage F2) with a stiffness value of 4.04 kPa. MRE = MR elastography