Three-dimensional whole body imaging of spin probes in mice by time-domainradiofrequency electron paramagnetic resonance

Imaging of stable paramagnetic spin probes in phantom objects and in vivo w as evaluated using a RF time domain EPR spectrometer/imager operating at 30 0 MHz. Projections were collected using static magnetic field gradients and images were reconstructed using filtered back-projection techniques. Resul ts from phantom objects containing approximately 10(17) spins of stable par amagnetic probes with single narrow EPR spectra provide three-dimensional s patial images with resolution better than 2 mm, When the spin probe was adm inistered to mice, the spin probe accumulation was temporally observed in t he thoracic, abdominal, and pelvic regions. A three-dimensional image (from 144 projections) from a live mouse was collected in 5 min. Using fiducial markers, the spin probe accumulation in organs such as liver, kidney, and b ladder could be observed. Differences in the oxygen status between liver an d kidney were observed from the EPR images from mice administered with spin probe, by treating the time-domain responses with convolution difference a pproach, prior to image reconstruction. The results from these studies sugg est that, with the use of stable paramagnetic spin probes and time-domain R F EPR, it is possible to perform in vivo imaging on animals and also obtain important spatially resolved physiologic information. Published 2000 Wiley -Liss, Inc.(dagger).