Echo-based Single Point Imaging: A Novel Pulsed EPR Imaging Modality for High Spatial & Spectral Resolution for In Vivo Quantitative Oximetry

Sankaran Subramanian¹, Nallathamby Devasahayam¹, Shingo Matsumoto¹, Murali C. Krishna¹

Two main approaches are currently in vogue for time-domain spectroscopic EPR imaging. The first one is Single Point Imaging involving global phase encoding which gives high resolution images, where the oximetry, however, is a T2* based approach relying on apparent line widths. The second approach for EPR oximetric imaging utilizes the conventional 90-τ-180 Spin-Echo pulse and filtered back-projection. The image is T2-weighted but the resolution is subject to susceptibility broadening. A novel time-domain spectroscopic EPR imaging approach, that is a unique combination of the above-mentioned techniques, is presented here. It provides quantitative T2 based oximetry combined with line-width-independent high resolution.