Noninvasive imaging assessment of non-alcoholic fatty liver disease: focus on liver scintigraphy.

Noninvasive diagnoses of nonalcoholic fatty-liver disease (NAFLD) involve the use of serologic markers and imaging methods, such as conventional ultrasonography (US), computed tomography, and magnetic resonance imaging. Although these methods are reliable for the noninvasive detection of moderate to severe fatty changes in the liver, they are not reliable for detecting nonalcoholic steatohepatitis (NASH) and fibrosis. New imaging technologies, such as US-based transient elastography, acoustic radiation force impulse and magnetic resonance-based elastography, can reportedly be used to determine the severity of liver fibrosis associated with NASH. In this context, the field of nuclear medicine through liver scintigraphy has recently been proposed, and is being explored for use in the diagnosis of NASH. More importantly, nuclear medicine may contribute to the distinction between simple steatosis and NASH. For example, the enhanced release of cytokines and the decrease in the phagocytic activity of Kupffer cells play important roles in the pathogenesis of NASH. Removal of technetium-99m colloid from circulation by Kupffer cell phagocytosis therefore provides a valuable imaging technique. Thus, nuclear medicine is poised to provide useful tools for the evaluation of patients with NAFLD. However, the evidence is still scarce, and more studies with larger samples are needed to identify their role before they are used in clinical practice.