Electron Paramagnetic Resonance (EPR) provides a sensitive means of detecting and quantitating free radical species. Conventional continuous wave (CW) EPR has provided insight into the basic chemistry of free radical reactions and has most recently been increasingly used to probe the intricacies of biological free radical intermediates. Although EPR is vastly more sensitive than NMR, presently its use to study biological tissue has been limited by the frequency used, routinely greater l GHz where penetration of the radiation is minimal. Because radiation induces a cascade of electrons and ultimately results in formation of free radical species, the RBB has been developing both a pulsed Fourier Transform (FT) EPR system for spectroscopy and Imaging. Since excited electrons relax in microseconds and less, the use of nanosecond FT-EPR with heretofore unachievable rapid signal sampling and averaging is required for detection of transient, short-lived free radical signals. Likewise, the previous technologic limitations imposed by CW-EPR microwave frequencies may be overcome when EPR at radiofrequencies with pulsing techniques with efficient data sampling/averaging are employed. The goals of this project are to create a prototypical FT-EPR instrument for in vitro biologic studies and to establish the foundation of FT-EPR in vivo imaging. The feasibility of this experiment at radio frequencies and one and two dimension images of electrons has been demonstrated. An efficient sampler/averager has been designed and tested which demonstrates that the signal intensity of the free radical species can be enhanced to significant extent by acquiring the signal and averaging in short time intervals (
