Oxygen-induced leakage of spin polarization in Overhauser-enhanced magnetic resonance imaging: Application for oximetry in tumors.

Overhauser-enhanced Magnetic Resonance Imaging (OMRI) is a double resonance technique applied for oxygen imaging in aqueous samples and biological tissues. In this report, we present an improved OMRI approach of oxygen measurement using the single line "Finland" trityl spin probe. Compared to a traditional approach, we introduced an additional mechanism of leakage of spin polarization due to an interaction of a spin system with oxygen. The experimental comparison of the new approach with an oxygen-dependent leakage factor to a traditional approach performed in phantom samples in vitro, and mouse tumor model in vivo, shows improved accuracy of determination of oxygen and contrast agent concentrations.