Future uses of MR imaging agents.

Existing paramagnetic agents and novel superparamagnetic pharmaceuticals under development promise to advance substantially the frontiers of MR imaging. Used in conjunction with ultrafast MR techniques, such as echoplanar imaging and turboFLASH (fast low-angle shot), relaxivity agents (e.g., dysprosium, gadolinium), which alter T1 characteristics of tissue protons they act on, can be used to generate quantitative maps of dynamic blood-brain barrier permeability as well as regional hemodynamic profiles of diseased heart and other organs. In addition, the magnetic susceptibility (T2*)-altering effects of gadolinium can be exploited to map regional cerebral blood volume during task-activated and pathologic brain states. Magnetic susceptibility agents, such as monocrystalline iron oxide nanoparticles (MIONs), allow the advantages of scintigraphy to be joined with the high spatial resolution of MR imaging. Not only can these magnetopharmaceutical preparations serve as hemodynamic markers, they have already enabled function-specific imaging at the cellular level under diverse pathologic conditions.