DESIGN, CONSTRUCTION AND USE OF A LARGE-SAMPLE FIELD-CYCLED PEDRI IMAGER

The design, construction and use of a large-scale field-cycled proton- electron double-resonance imaging (FC-PEDRI) imager is described. The imager is based on a whole-body sized, vertical field, 59 mT permanent magnet. Field cycling is accomplished by the held compensation method , and uses a secondary, resistive magnet with an internal diameter of 52 cm. The magnetic field can be switched from zero to 59 mT or vice v ersa in 40 ms. It is used with a double-resonance coil assembly (NMR/E PR) comprising a solenoidal NMR transmit/receive coil and a coaxial, e xternal birdcage resonator for EPR irradiation. Experiments to image t he distribution of an exogenous nitroxide free radical in anaesthetize d rabbits are described.