A forward-subtraction procedure for removing hyperfine artifacts in electron paramagnetic resonance imaging.

The potential for using electron paramagnetic resonance (EPR) imaging in biological applications has been limited by the lack of ideal single-line imaging probes. The commonly used nitroxides exhibit multiple lines, causing either hyperfine-based limitations in the maximum obtainable image resolution or hyperfine-based artifacts in the reconstructed image. The application of a numerical method, based on forward-subtraction principles for removing hyperfine artifacts in the measured projections is reported. It is demonstrated by using computer simulations, imaging of phantoms, and imaging of rat hearts, that marked enhancement in image quality and resolution can be obtained by removing the hyperfine-imposed limit on the gradient magnitude and performing postacquisition corrections for removing hyperfine artifacts in the image.