(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.

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Cytogen Corporation of Princeton, NJ is a product-driven, oncology-focused biopharmaceutical company. Cytogen markets several products through its in- house oncology sales force: ProstaScint® (a monoclonal antibody-based imaging agent used to image the extent and spread of prostate cancer); BrachySeed™ I-125 and BrachySeed™ Pd-103 (two uniquely designed, next generation radioactive seed implants for the treatment of localized prostate cancer), and NMP22® BladderChek™ (a highly accurate and convenient antibody-based point-of-care staging test for bladder cancer detection). Cytogen has also developed Quadramet®, a skeletal targeting therapeutic radiopharmaceutical for the relief of bone pain in prostate and other types of cancer. Cytogen's pipeline comprises product candidates at various stages of clinical development, including fully human monoclonal antibodies and cancer vaccines based on PSMA (prostate specific membrane antigen) technology, which was exclusively licensed from Memorial Sloan-Kettering Cancer Center.
A license and marketing agreement with AMAG Pharmaceuticals Inc' (formerly Advanced Magnetics), to market the functional molecular imaging agent Combidex®, was terminated in 2007.

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.

Tumor specific MRI contrast agents are in development to provide better delineation and progression information for various tumors. Clinical oncology has a need for contrast agents that can identify tumors and metastases at a size of 100,000 cells rather than 1,000,000,000 cells. This level of sensitivity requires excellent tumor targeting of imaging agents and a high MRI signal.
Tumor specific agents accumulate at pathological tissues by passive or active targeting mechanisms. Passive targeting agents use e.g., the natural defense mechanisms in which phagocytic cells remove foreign particles from the body. Active targeting is based on a ligand-directed, site-specific accumulation of contrast agents. The availability of macromolecular contrast agents such as feruglose and ultrasmall superparamagnetic iron oxide (USPIO), which permit the assessment of tissue permeability, may also improve the detection of tumor grade, tumor type, and response to drugs that target angiogenesis.

See also Monoclonal Antibodies, Metalloporphyrins, Nitroxides and Ferrioxamine.