The Resolution of Oxygen in EPR Images

¹National Cancer Institute, National Institutes of Health, Bethesda, MD, USA; ²NINDS, National Institutes of Health, Bethesda, MD, USA

Tissue oxygenation maps identifying normoxic and hypoxic areas are useful to understand tumor biology. Recent advances in EPR imaging have realized mapping of the tissue oxygenation in three dimensions. Co-registration of oxygen maps with images from other modalities facilitates examination of oxygen levels in sub-volumes or specific organs. However, understanding the contrasts of oxygen levels in different parts of the body requires knowledge of its resolution both in space and magnitude. The intrinsic resolution of pO2 is governed by the fundamentals of the imaging technique such as the gradient magnitude, relaxation times and oxygen sensitivity. Instrumental parameters including S/N ratio and field homogeneity and image reconstruction artifacts may also add to loss of resolution. Therefore it is necessary to define parameters to specify the resolution of oxygen levels, and present their estimates with digitally enhanced higher resolution images. The definition and determination of these resolution parameters of pO2 images are discussed