The mole is the basic unit of substance.
Definition: The amount of substance that contains as many elementary units as there are atoms in 0.012 kg of carbon-12.

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.

Structure formed of atoms of various elements.

(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.

Short name: MION, central moiety: Fe3+/Fe2+, relaxivity: r1=3.7, r2=6.5, B0=0.47T
MIONs are under development (preclin.) as contrast agents (taken up by the RES) for MR angiography, MR lymphography, tumor detection and detection of infarctioned tissue. Also called monodisperse iron oxide nanoparticles or nanocompounds.