WATER-SOLUBLE FREE-RADICALS AS BIOLOGICALLY RESPONSIVE AGENTS IN ELECTRON-PARAMAGNETIC-RESONANCE IMAGING

Electron paramagnetic resonance imaging (EPRI) is currently being deve loped at frequencies between 200 MHz and 2 GHz. EPRI can map the in vi vo distribution of paramagnetic species, such as water soluble free ra dicals; nitroxide free radicals are commonly used. EPR images reflect the complexity of metabolic actions on the exogenous delivered nitroxi des. Their reduction rate in vivo is affected by parameters such as ox ygen concentration, pH and biodistribution. This paper illustrates the main features of low frequency EPRI and reconstruction techniques. Ex amples of EPR imaging, such as two-dimensional (2D) spatial mapping of the distribution of a nitroxide free radical in phantoms and in whole rat, are given.