Echo-based Single Point Imaging (ESPI): A novel pulsed EPR imaging modality for high spatial resolution and quantitative oximetry

► Narrow-line non-toxic spin probes are used for in vivo EPR imaging. ► FT-EPR oximetric Imaging depends on line broadening by in vivo pO2. ► Spin-Echo back-projection leads to T2 based pO2 mapping but T2∗ dependent resolution. ► SPI leads to high resolution images with T2∗ based pO2 requires pre-calibration. ► Echo-based SPI gives both high resolution images and quantitative T2-based pO2.