MRI for fatty liver cells/steatosis
Liver steatosis is a reversible storage of fat droplets (mainly triglycerides) in the liver cells. A distinction is made etiologically between the much more common alcohol-induced fatty liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD). An important subtype of NAFLD is non-alcohol-induced steato-hepatitis (NASH), which is characterized by diffuse fatty degeneration of the liver and an additional inflammatory reaction (1).
Magnetic resonance imaging is the best method for determining liver fat content. In addition to the visual, qualitative assessment, MRI also enables a quantitative assessment of fatty liver. The quantification of fat in MRI is made possible by measuring the signal intensity ratio of the fat signal to the absolute signal in terms of a fat signal fraction (FSF). Using this technique, MRI can reliably distinguish between healthy and steatotic livers and identify patients at risk of liver surgery.
MRI for hemochromatosis
Haemochromatosis is a hereditary disease with increased iron absorption in the upper small intestine. This leads to iron deposition, particularly in the liver, pancreas, lymph nodes, heart and skin. Secondary haemochromatosis or haemosiderosis must be distinguished from primary haemochromatosis, which is an acquired iron overload of the liver. Due to an increased iron intake/release, e.g. in the context of blood transfusions or chronic hemolysis, iron deposits primarily occur in the liver and spleen.
In addition to liver fat determination, magnetic resonance imaging is also the best non-invasive method for determining the liver iron content in the context of hemochromatosis. In addition to the visual assessment, a quantitative assessment of iron overload is also possible with MRI. Based on the iron load determined in the MRI, either the diagnosis can be made, treatment can be initiated if necessary or treatment that has already been started can be monitored.
Magnetic resonance elastography for liver fibrosis/cirrhosis
Fibrosis is generally understood to be a proliferation of connective tissue in the liver tissue as a reaction to cell damage, usually in the context of liver inflammation(hepatitis). The increase in the extracellular matrix leads to a loss of liver function and, secondarily, to portal hypertension with complications such as esophageal varices, ascites or even liver failure. The development of liver fibrosis is related to the duration and intensity of exposure to the noxious agent and is reversible in the early stages. The final stage of diffuse liver fibrosis is liver cirrhosis.
The measurement of liver stiffness using ultrasound and magnetic resonance elastography has proven to be a promising indicator of the degree of fibrosis. In magnetic resonance elastography, pressure waves are generated via an external vibration device on the upper abdomen, which cyclically compress the adjacent liver. Using a special sequence, it is possible to visualize the progression of the waves or their wavelength and thus draw conclusions about liver stiffness or the individual stages of fibrosis.