NEW EXPERIMENTAL PROCEDURES FOR IN-VIVO L-BAND AND RADIO-FREQUENCY EPR SPECTROSCOPY IMAGING

Electron paramagnetic resonance spectroscopy/imaging experiments are c urrently being performed on small animals and isolated organs. The exo genous paramagnetic probes commonly used are nitroxide (aminoxyl) free radicals. Nitroxide reduction and clearance were evaluated to underst and in vivo distribution and metabolism. Pharmacokinetics data were co llected with the same nitroxide at three different frequencies in an e xternal rat blood circuit, in a mouse head and in a whole rat body. A 280 MHz spectrometer made it possible to obtain images of a whole rat body after nitroxide intravenous injection. At L-band (1500 MHz), a sy nchronization technique was used to obtain images of a dynamic phantom utilized to mimic the model of the isolated perfused rat heart. Diffe rent experimental procedures are discussed and the problems which affe ct sensitivity and resolution are evaluated.