Hyperpolarized xenon relaxation times in perfluorocarbon emulsion and plasma mixtures

Hyperpolarized xenon (Hyp-/sup 129/Xe) has great potential in perfusion, blood flow and functional investigations of organs beyond the lungs. Injection of xenon in a dissolved carrier would be the best delivery method for this purpose. The blood substitute perfluorooctyl bromide (PFOB) emulsion is the leading candidate as a carrier. To assess the suitability of PFOB emulsion as a Hyp-/sup 129/Xe carrier, spectra of Hyp-/sup 129/Xe in plasma, PFOB, and plasma-PFOB mixtures have been recorded. Longitudinal relaxation (T/sub 1/) measurements have been made. The T/sub 1/ was found to be about 6 s in plasma, 108/spl plusmn/5 s in PFOB emulsion and 18/spl plusmn/4 s in a mixture of 60% PFOB and 40% plasma. The relaxation time in the PFOB-plasma mixture is enhanced compared to plasma alone however there is a significant reduction in T/sub 1/.