A brand name for ferumoxide (same as Feridex®)
Endoremâ„¢ is a black to reddish-brown aqueous colloid of superparamagnetic iron oxide associated with dextran for intravenous administration as a MRI contrast medium for the detection of liver lesions that are associated with an alteration in the RES.
Endoremâ„¢ is taken up by macrophages, found only in healthy liver cells but not in most tumors. Tissues such as metastases, primary liver cancer, cysts and various benign tumors, adenomas and hyperplasia retain their native signal intensity, so the contrast between normal and abnormal tissue is increased.

See also Ferumoxide.

A brand name for ferumoxide (same as Endorem™)
Feridex® is a sterile aqueous colloid of superparamagnetic iron oxide associated with dextran for intravenous administration as a MRI contrast medium for the detection of liver lesions that are associated with an alteration in the RES.
Feridex® is taken up by macrophages, found only in healthy liver cells but not in most tumors. Tissues such as metastases, primary liver cancer, cysts and various benign tumors, adenomas and hyperplasia retain their native signal intensity, so the contrast between normal and abnormal tissue is increased. Feridex® is a black to reddish-brown aqueous colloid.
See also Ferumoxide.

In November 2008, AMAG Pharmaceuticals, Inc. decided to discontinue the manufacturing of Feridex.

The France-based Guerbet Group is highly specialized in contrast media for medical imaging. Its strategic goal is to be a key player in this market. Products include Dotarem (Magnetic Resonance Imaging) and Xenetix (X-ray Imaging).

MRI Contrast Agents:

The characteristics of a hepatobiliary contrast agent are specific liver uptake and excretion via the biliary system. The paramagnetic substance (e.g. manganese, gadolinium) is taken up by normal hepatocytes. Diseased liver tissue did not include hepatocytes or their function is disturbed. Therefore, the signal of healthy liver tissue increases on T1 weighted sequences, but not in the liver lesions.
Another type of liver imaging contrast agent is superparamagnetic iron oxide. These particles accumulate in the reticuloendothelial system (RES) of the liver, and darken the healthy liver tissue in T2 weighted images. RES cells (including Kupffer cells) are existing in healthy liver tissue, in altered tissue with reduced RES activity or without RES cells the contrast agent concentration is also low or not existing, which improves the liver to lesion contrast.
Benefits of hepatobiliary contrast agents:
Differences of a hepatobiliary contrast agent compared with a targeted contrast agent for Kupffer cells:
See also Superparamagnetic Contrast Agents, Hepatobiliary Chelates, Liver Imaging, Endoremâ„¢, Primovistâ„¢, and Classifications, Characteristics, etc.

See also the related poll result: 'The development of contrast agents in MRI is'

(SPIO) Relatively new types of MRI contrast agents are superparamagnetic iron oxide-based colloids (median diameter greater than 50nm). These compounds consist of nonstoichiometric microcrystalline magnetite cores, which are coated with dextrans (in ferumoxide) or siloxanes (in ferumoxsil). After injection they accumulate in the reticuloendothelial system (RES) of the liver (Kupffer cells) and the spleen. At low doses circulating iron decreases the T1 time of blood, at higher doses predominates the T2* effect.
SPIO agents are much more effective in MR relaxation than paramagnetic agents. Since hepatic tumors either do not contain RES cells or their activity is reduced, the contrast between liver and lesion is improved. Superparamagnetic iron oxides cause noticeable shorter T2 relaxation times with signal loss in the targeted tissue (e.g., liver and spleen) with all standard pulse sequences. Magnetite, a mixture of FeO and Fe2O3, is one of the used iron oxides. FeO can be replaced by Fe3O4.
Use of these colloids as tissue specific contrast agents is now a well-established area of pharmaceutical development. Feridex®, Endorem™, GastroMARK®, Lumirem®, Sinerem®, Resovist® and more patents pending tell us that the last word in this area is not said.
Some remarkable points using SPIO:

See also Superparamagnetism, Superparamagnetic Contrast Agents and Classifications, Characteristics, etc..