High permeability material used to shape the uniformity of the useful volume of a magnet, especially a permanent magnet. Also called Pole Tip.

Magnetic shielding through the use of high permeability material in the walls (plus floor and ceiling) of the magnet room. Room shielding can be complete (e.g., six sides of a box, Faraday cage), or partial if the fringe field is to be reduced only in certain areas (see also Magnetic Shielding).

Magnetic shielding by attaching a high permeability yoke to the magnet (passive shielding) or by incorporating additional magnetic field-generating coils designed to reduce the external field (active shielding).

See also Magnetic shielding, Active Shielding and Passive Shielding.

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.

High permeability structure used to concentrate the magnetic flux inside itself and thus decrease the magnetic fringe field and increase the field strength in the useful volume of a magnet.