Three-dimensional in vivo ESR imaging in rats.

The first experiment of tridimensional in vivo ESR imaging at 1.2 GHz is described in this paper. The tails of rats weighing 300-350 grams were visualized using 1 cc of a 50 * 10(-3) M solution of nitroxide free radical injected in the caudal vein. In an even distribution of spin label is assumed this would correspond to a final concentration of about 10(-4) M. A reconstruction from projections was used to obtain the images. The apparatus utilizes stationary field gradients. Projections were obtained by sweeping the main field. For 3D reconstructions, the projections were collected along 32 * 8 field gradient orientations. The whole procedure takes approximately 18 minutes.