Characterization of hyperpolarized xenon-129 dissolved in perfluorooctyl bromide emulsions as a novel magnetic resonance contrast agent

Current imaging methods used for cancer detection are limited in terms of sensitivity, specificity and spatial resolution. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) methods with Gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) are promising, but limited by the fact that contrast is obtained indirectly from the magnetic resonance (MR) signal of the water protons. Hyperpolarized 129Xe (H-Xe) dissolved in perfluorooctyl bromide (PFOB) emulsions stabilized with egg-yolk phospholipid (EYP) has been suggested as a possible in vivo MR contrast agent. Xenon is biocompatible, diffusible and soluble in biological media. These properties and the high MR signal of the H-Xe gas represent the rationale of this thesis.;Flow rate measurements using the linewidths of dynamically acquired MR spectra of H-Xe dissolved in PFOB emulsions injected into a flowing water stream are presented. The advantages and limitations of this method for possible in vivo blood perfusion measurements for cancer detection, as well as their implications on future work are discussed.;A theoretical radial diffusive exchange model based on the generalized Bloch equations is developed in order to investigate the MR spectra of H-Xe dissolved in PFOB emulsions. In the slow exchange regime, a relationship between the linewidth of the MR peaks and the average residence times of the spins in the two compartments is validated. By fitting the theoretical spectra to experimental spectra, EYP membrane permeability and porosity are estimated. Spectra of H-Xe dissolved in mixtures of PFOB emulsions and blood are presented and the slow exchange relationship is confirmed.