Electron spin resonance imaging of tissues with lipid-rich areas

Electron spin resonance imaging and spectroscopy of lipid-rich samples were studied at 9 Ghz. Using both lipid- and aqueous-soluble nitroxides good delineation of fat- and muscle-rich regions of tissue was obtained. Several different principles can be used to differentiate between these types of tissues and potentially between different types of lipids. These principles include lipophilicity of nitroxides, viscosity (which is higher in lipids), oxygen solubility (oxygen is four times more soluble in lipids), and the distribution of paramagnetic metal ions. These techniques have potential applicability for directly studying metabolism and oxygen concentration in tissues by ESR techniques and for investigating potential contrast agents for in vivo NMR techniques.