Tissue oxymetry using magnetic resonance spectroscopy

Abstract

A noninvasive method for in vivo measurement of tissue oxygen concentration has been developed. Several techniques currently used suffer limitations that prevent their practical clinical use. Our method is to use the paramagnetism of molecular oxygen to build a method for noninvasive tissue oxymetry. By using paramagnetism of molecular oxygen, magnetic resonance spectroscopy (MRS) can be used to measure tissue oxygenation. Chemical shifts of brain metabolites and water have a downfield shift with increased amounts of oxygen. Chemical shifts were linearly dependent on the fraction of inspired oxygen (FI02) and the slope is approximately 0.0003 ppm per percent change of oxygen. The slope was not significantly different between brain metabolites or water. Furthermore, the slope agreed with simple theoretical predictions using Henry's law and the magnetic susceptibility of molecular oxygen. Changes in brain oxygenation in the same animals was confirmed using gradient echo BOLD measurements of changes in R2* as a function of F10₂ in the same animals. The results demonstrated the promising potential of this technique. The implementation of this method in stroke and tumor models is discussed. Thesis Supervisor: Bruce Jenkins