In vivo Xe-129 NMR in rat brain during intra-arterial injection of hyperpolarized Xe-129 dissolved in a lipid emulsion

Hyperpolarized Xe-129 was dissolved in a lipid emulsion and administered to anaesthetized rats by manual injections into the carotid (approximately 1- 1.5 mt in a maximum time of 30 s). During injection, Xe-129 NMR brain spect ra at 2.35 T were recorded over 51 s, with a repetition time of 253 ms. Two peaks assigned to dissolved Xe-129 were observed (the larger at 194 +/- 1 ppm assigned to intravascular xenon and the smaller at 199 +/- 1 ppm to xen on dissolved in the brain tissue). Their kinetics revealed a rapid intensit y increase, followed by a plateau (approximately 15 s duration) and then a decrease over 5 s, This behaviour was attributed to combined influences of the T-1 relaxation of the tracer, of radiofrequency sampling, and of the tr acer perfusion rate in rat brain. Similar kinetics were observed in experim ents carried out on a simple microvessel phantom. An identical experimental set-up was used to acquire a series of 2D projection Xe-129 images on the phantom and the rat brain. (C) 2000 Academie des sciences/Editions scientif iques et medicales Elsevier SAS.