Dynamic spectroscopy of hyperpolarized Xe-129 in rat lung

Xenon is a promising candidate for an exogenous MRI tracer because of its affinity for lipids and possible polarization. The estimation of net detectability of dissolved phase xenon in vivo is important for a development of diagnostic applications. The purposes of this study were to develop a hyperpolarized ¹²⁹Xe experiment system on 3-T and to measure dissolved phase signal in a rat lung. The ¹²⁹Xe gas was polarized using the optical pumping technique, was manually insufflated to male Sprague–Dawley rat under spontaneous respiration anesthetized by intraperitoneal injection of urethane (1 mg/g), and was measured in a rat lung by frequency selective spectroscopy. A full fractional optimum experiment of two-factor (flip angle, TR) and three-level (30°, 60°, 90°, 600, 1000, 1400 ms) was designed for SNR. A flip angle (∼60°) with 1 s TR made maximum signal in dissolved phase dynamic spectroscopy. Two dominant peaks of 212 for RBC and 201 ppm for tissue were observed, and their average signal ratio to that of gas was 5.6% and 4.4%, respectively. We have developed a hyperpolarized ¹²⁹Xe experiment system, which could yield enough amount and polarization for dynamic analysis in a rat lung using the 3-T MRI system.