ABSTRACT
The aim of magnetic resonance (MR) molecular imaging is to noninvasively map the cellular expression of important biomarkers associated with normal physiology or disease. Standard MR imaging methods lack the resolution and sensitivity required for direct detection of these cellular biomarkers due to their very low concentrations in vivo. To overcome this obstacle, MR molecular imaging often relies on specically engineered nanoparticles that can (1) bind to the biomarker of interest, (2) accumulate at the target site, and (3) generate sufcient image contrast. Nanoparticle constructs allow for the incorporation of multiple binding ligands, which can improve the targeting ability, and multiple relaxation agents, which amplify the MR signal enhancement. MR molecular imaging contrast agents generally utilize either paramagnetic gadolinium chelates or superparamagnetic iron oxide to generate image contrast. Most iron oxide contrast agents consist of rigid structures that are outside the scope of this chapter, but have been extensively described in the literature [1-5]. Gadolinium agents have been grafted onto a wide range of nanoparticle constructs, including liposomes, micelles, dendrimers, polymers, viral particles, and liquid per-uorocarbon particles.
