Hemosiderosis is the accumulation of iron in the reticuloendothelial system, namely, the liver and spleen. This is in contrast to hemochromatosis, which generally spares the spleen. It can be seen in patients who undergo repeated blood transfusions, or have rapid RBC turnover (sickle cell anemia, thallasemia).
For those without good explanation for hemosiderosis, LFT should be followed serially, and liver biopsy can be obtained to quantify iron if LFT become persistantly abnormal. With normal LFT and a normal transferrin saturation, therapy is not indicated.
In the MRI above, note the dark appearance of both the liver and spleen. This represents abnormally low signal, and will be so in both T1 and T2 sequences.