Contrast agent with a preferential intracellular distribution.
Intracellular agents (such as manganese derivatives and ultrasmall superparamagnetic iron oxide), exhibit a flow- and metabolism-dependent uptake. These properties may allow delayed imaging, similar to isotopic methods.
Phospholipid liposomes are rapidly sequestered by the cells in the reticuloendothelial system (RES), primarily in the liver. For imaging of the liver, liposomes may be labeled with MR contrast medium, both positive (T1-shortening) paramagnetic media, and negative (T2-shortening) superparamagnetic media.
Several other nonliposome MR contrast media are also taken up by the RES, e.g.:
Other MR contrast agents accumulate selectively in the hepatocytes, e.g.: