Stéatose hépatique et séquence phase- opposition de phase : aspects théoriques et applications pratiques à 3T

Liver steatosis may evolve into steatohepatitis then cirrhosis with related complications. It may also contribute to hepatocellular failure, sometimes fatal after major hepatectomy, especially in the setting of liver transplantation with living donor. Imaging must allow non-invasive detection and accurate quantification. In and out of phase MR imaging routinely performed in clinical practice is a simple and robust means of achieving these goals. In this article, we will review the histological, pathophysiologic, and clinical features of liver steatosis and the key points of in and out of phase pulse sequences and underlying physical principles. The T2* relaxation, cause of a loss of signal between both echo times must be taken into account. Echo times must be known for image interpretation, and optimized, especially at 3T. Finally, the T1 of lipids and water is different and causes T1 effects that may lead to quantification errors while being advantageous for image interpretation. The combination of these factors allows detection and quantification of liver steatosis in routine clinical practice.