A to Z of Imaging Modalities for the Diagnosis and Quantification of Hepatic Steatosis

Steatotic liver disease (SLD), marked by triglyceride accumulation in over 5% of hepatocytes, affects around a quarter of the global population. A key subtype, Metabolic dysfunction-associated steatotic liver disease (MASLD), is closely associated with obesity, type 2 diabetes, and metabolic syndrome, with rising prevalence worldwide. MASLD can lead to severe hepatic complications such as cirrhosis, liver failure, and hepatocellular carcinoma if left untreated. While liver biopsy remains the diagnostic gold standard for assessing hepatic steatosis, its invasive nature and sampling variability underscore the need for reliable non-invasive alternatives. Advances in imaging have enabled the development of modalities such as ultrasonography (US), computed tomography, and magnetic resonance imaging (MRI) for non-invasive steatosis assessment. Conventional US, though widely used, is limited by observer dependency and poor sensitivity for detecting mild steatosis. Quantitative US techniques, particularly attenuation coefficient-based algorithms, have shown improved diagnostic accuracy. The controlled attenuation parameter, often used with transient elastography, offers quick and cost-effective assessment, albeit with reduced sensitivity in obese individuals and limited grading accuracy. CT enables steatosis evaluation via liver attenuation values and liver-spleen attenuation ratios. Dual-energy CT enhances tissue differentiation and correlates moderately well with magnetic resonance imaging proton density fat fraction (MRI-PDFF) and histopathology but is constrained by radiation exposure and limited sensitivity for mild steatosis. MRI techniques—especially PDFF-based imaging—provide superior accuracy and reproducibility in liver fat quantification. PDFF allows for non-invasive, radiation-free mea-surement across the full steatosis spectrum, with established diagnostic thresholds. Additionally, MR spectroscopy offers the most precise quantification but remains primarily research-based due to logistical constraints. In summary, non-invasive imaging modalities, particularly MRI-PDFF, are increasingly favored for diagnosing and monitoring hepatic steatosis. Future research should focus on optimizing and standardizing these techniques to enhance clinical integration and management of SLD.

Keywords: Steatosis, Liver, Ultrasonography, Computed tomography, Magnetic resonance imaging