Temporal brain imaging by a rapid scan ESR-CT system in rats receiving intraperitoneal injection of a methyl ester nitroxide radical.

We performed in vivo ESR-CT (electron spin resonance-computed tomography) on rats' heads, in which the blood-brain barrier-permeable nitroxide radical, 3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCAM) was injected intraperitoneally, using a rapid scan ESR-CT system operating at 700 MHz. In a spatiotemporal study we found that different regions of the brain showed differences in the rate of decay of the radical. Repeated injection of PCAM gave clear ESR-CT images of the brain. We think that the present method is useful for evaluating the capacity to eliminate exogenous free radicals in some parts of the brain.