Mesures de la perfusion cérébrale chez le rat à l’aide de la RMN du 129Xe hyperpolarisé : étude de fluides biologiques vecteurs du 129Xe

The high xenon solubility in blood and tissues makes hyperpolarized ¹²⁹Xe a potential MR tracer for tissue perfusion studies. Two biocompatible fluids were studied with a view to be used as delivery media for hyperpolarized xenon injection: the carrier agents were ¹²⁹Xe micro-bubbles in Echovist (2–3 μm in diameter), and Intralipid ¹²⁹Xe suspension. Xenon chemical shifts and longitudinal relaxation time T₁ were measured at 2.35 T in both fluids. Xenon chemical shift of the dissolved phase in Echovist was 204.1 ± 0.5 ppm from the micro-bubbles gas phase resonance data (0 ppm). Xenon T₁ was 20.0 s in micro-bubbles in Echovist and 19.0 s for the dissolved phase. Xenon chemical shift in Intralipid was 194.6 ± 0.5 ppm. T₁ was 15.2 ± 4.9 s (n = 5) in Intralipid 20 % and 20.9 ± 2.9 s (n = 4) in Intralipid 30 %. Using an intra-carotid injection of a small volume (0.15 mL) of hyperpolarized xenon dissolved in Intralipid 30 %, cerebral blood flow was measured in rats (160 ± 30 mL·(100 g)^–1·min^–1, n = 10). Rat brain xenon images were performed with 2-D projection–reconstruction pulse sequence, enabling regional blood flow measurements.