Short name: SHU 555 A, generic name: Ferucarbotran
A RES-directed MRI contrast agent (SPIO) made-up of a colloidal sol of iron oxide nanoparticles coated with carboxydextran (Resovist®, Cliavist™).
It is used for the detection and characterization of especially small focal liver lesions and offers the opportunity to make a reliable diagnosis at a very early stage of patients with suspected liver tumors.
Bayer Schering Pharma AG announced that it has received marketing approval for the liver-specific contrast agent Resovist® in Japan. See Contrast Agents and Superparamagnetic Contrast Agents.

GastroMARK® belongs to the negative oral contrast agents (same as Lumirem®, another brand name for ferumoxsil). GastroMARK® is used to distinguish the loops of the bowel from other abdominal structures and physiology. When GastroMARK® is ingested, it flows through and darkens the stomach and the small intestine in 30 to 45 minutes. By more clearly identifying the intestinal loops, GastroMARK® improves visualization of adjacent abdominal tissues such as the pancreas.

Paramagnetic substances, for example Gd-DTPA solutions, are used as MRI oral contrast agents in gastrointestinal imaging to depict the lumen of the digestive organs. Different Gd-DTPA solutions or zeolites containing gadolinium can be used e.g., for diagnosis of delayed gastric emptying, diagnosis of Crohn's disease etc.
Low concentrations of gastrointestinal paramagnetic contrast agents cause a reduction in T1 relaxation time; consequently, these agents act on T1 weighted images by increasing the signal intensity of the bowel lumen. High concentrations cause T2 shortening by decreasing the signal, similar to superparamagnetic iron oxide. Gd-DTPA chelates are unstable at the low pH in the stomach, therefore buffering is necessary for oral use.

See also Gadopentetate Gastrointestinal, Gadolinium Zeolite, Negative Oral Contrast Agents, Gastrointestinal Superparamagnetic Contrast Agents, and Ferric ammonium citrate.

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'

Categories of negative oral contrast agents:
Negative oral contrast media are usually based on superparamagnetic particles and act by inducing local field inhomogeneities, which results in shortening of both T1 and T2 relaxation times. Superparamagnetic contrast agents have predominant T2 weighted effects. Biphasic contrast media are agents that have different signal intensities on different sequences, depending on the concentration at which they are used.
Suitable materials for oral contrast agents should have little or no absorption by the stomach or intestines, complete excretion, no motion or susceptibility artifacts, affordability, and uniform marking of the gastrointestinal tract. Benefits of negative oral contrast agents are the reduction of ghosting artifacts caused by the lack of signal. Superparamagnetic iron oxides produce also in low concentrations a noticeable signal loss; but can generate susceptibility artifacts especially in gradient echo sequences. Perfluorochemicals do not dilute in the bowel because they are not miscible with water.
High cost, poor availability, and limited evaluations of side effects are possible disadvantages.
Negative oral contrast agents are used e.g., in MRCP, where the ingestion of 600-900 ml of SPIO cancels out the signal intensity of the lumen (in addition after the injection of a gadolinium-based contrast medium, the enhancement of the inflammatory tissues is clearer seen), and in MR abdominal imaging of Crohn's disease in combination with mannitol.

Blueberry or pineapple juices are useable for examinations of the pancreas (MRCP, upper abdominal imaging) as cheep contrast agents, because of the content of magnetic substances (e.g. manganese).

See also Ferristene, Ferumoxsil, Oral Magnetic Particles, Gastrointestinal Imaging.