Development and optimization of three-dimensional spatial EPR imaging for biological organs and tissues.

The development and optimization procedures for obtaining high-quality three-dimensional spatial electron-paramagnetic-resonance images of large lossy samples at L band are described. Strategies for selecting optimized parameters for projection acquisition, instrumentation, and algorithms for correcting drifts in microwave frequency and inaccuracies in the static and gradient magnetic fields are described. Image reconstruction was performed using a two-stage filtered back-projection method with spectral deconvolution. With this instrumentation, correction algorithms, and image reconstruction method, spatially accurate 3D images of radical distribution were observed in complex phantoms using 0.5 mM nitroxide labels. The results indicate that high-quality images of lossy samples, including biological organs and tissues of up to 25 mm in size, could be obtained in a reasonable time with submillimeter resolution.