Molecular Imaging is a new diagnostic discipline to visualize biological processes.
Molecular magnetic resonance imaging (mMRI) offers the potential to image tissues at the cellular and subcellular level. Targeted MR contrast agents enhance the diagnostic specificity and range of molecular magnetic resonance imaging.
Other modalities that can be used for noninvasive molecular imaging:

See also Nanoparticle, Monocrystalline Iron Oxide Nanoparticle, Polycrystalline Iron Oxide Nanoparticles, Liposomes, Monoclonal Antibodies, Bimodal Imaging, Tumor Specific Agents, and Intracellular Contrast Agents.

The company changed its name from Advanced Magnetics, Inc. to AMAG Pharmaceuticals, Inc. in July 2007.
AMAG Pharmaceuticals, Inc., a biopharmaceutical company, developed and manufactured organ-specific diagnostic contrast agents that provide clearer images during magnetic resonance imaging (MRI) tests used to detect tumors and other abnormalities.
The company had two MRI related products on the market: Feridex I.V. (for the diagnosis of liver lesions) and GastroMARK (used for bowel and abdominal MR imaging). In November 2008, AMAG Pharmaceuticals, Inc. decided to discontinue the manufacturing of Feridex. The development of Combidex as a contrast agent for lymph disease has also been stopped.
The Company has now two commercial products: Feraheme® and GastroMARK®. Feraheme® is the trade name of Ferumoxytol (formerly Code 7228) and is indicated for the treatment of iron deficiency anemia. Feraheme® is also being developed as a diagnostic agent for vascular-enhanced magnetic resonance imaging (MRI) to assess peripheral arterial disease.

MRI Contrast Agents:

Contrast enhanced MRI is a commonly used procedure in magnetic resonance imaging. The need to more accurately characterize different types of lesions and to detect all malignant lesions is the main reason for the use of intravenous contrast agents.
Some methods are available to improve the contrast of different tissues. The focus of dynamic contrast enhanced MRI (DCE-MRI) is on contrast kinetics with demands for spatial resolution dependent on the application. DCE-MR imaging is used for diagnosis of cancer (see also liver imaging, abdominal imaging, breast MRI, dynamic scanning) as well as for diagnosis of cardiac infarction (see perfusion imaging, cardiac MRI). Quantitative DCE-MRI requires special data acquisition techniques and analysis software.
Contrast enhanced magnetic resonance angiography (CE-MRA) allows the visualization of vessels and the temporal resolution provides a separation of arteries and veins. These methods share the need for acquisition methods with high temporal and spatial resolution.
Double contrast administration (combined contrast enhanced (CCE) MRI) uses two contrast agents with complementary mechanisms e.g., superparamagnetic iron oxide to darken the background liver and gadolinium to brighten the vessels. A variety of different categories of contrast agents are currently available for clinical use.
Reasons for the use of contrast agents in MRI scans are:
Common Indications:
Brain MRI : Preoperative/pretreatment evaluation and postoperative evaluation of brain tumor therapy, CNS infections, noninfectious inflammatory disease and meningeal disease.
Spine MRI : Infection/inflammatory disease, primary tumors, drop metastases, initial evaluation of syrinx, postoperative evaluation of the lumbar spine: disk vs. scar.
Breast MRI : Detection of breast cancer in case of dense breasts, implants, malignant lymph nodes, or scarring after treatment for breast cancer, diagnosis of a suspicious breast lesion in order to avoid biopsy.

For Ultrasound Imaging (USI) see Contrast Enhanced Ultrasound at Medical-Ultrasound-Imaging.com. See also Blood Pool Agents, Myocardial Late Enhancement, Cardiovascular Imaging, Contrast Enhanced MR Venography, Contrast Resolution, Dynamic Scanning, Lung Imaging, Hepatobiliary Contrast Agents, Contrast Medium and MRI Guided Biopsy.

(McAb) Monoclonal antibodies are used for tumor detection and localization in nuclear medicine. In MRI, monoclonal antibodies labeled with paramagnetic or superparamagnetic particles are being studied for targeting tumors, for example contrast agent containing gadolinium attached to a targeting antibody. The antibody would bind to a specific target (e.g., a metastatic melanoma cell) while the gadolinium would increase the MRI signal. Further developments are MRI contrast agents that specifically target glucose receptors on tumor cells; coupled with the high spatial resolution of high field MRI devices, these agents have potentials to detect small tumor foci.
The monoclonal antibody manufacturers produce a wide variety of ligands, which can be directed against a multiplicity of pathologic molecular targets. MRI enhanced with targeted contrast agents can be used for molecular imaging.

(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..