Pulmonary Perfusion and Xenon Gas Exchange in Rats: MR Imaging with Intravenous Injection of Hyperpolarized 129Xe

Abstract

Purpose To develop and demonstrate a method for regional evaluation of pulmonary perfusion and gas exchange based on intravenous injection of hyperpolarized xenon 129 (¹²⁹Xe) and subsequent magnetic resonance (MR) imaging of the gas-phase ¹²⁹Xe emerging in the alveolar airspaces. Materials and Methods Five Fischer 344 rats that weighed 200—425 g were prepared for imaging according to an institutional animal care and use committee—approved protocol. Rats were ventilated, and a 3-F catheter was placed in the jugular (n = 1) or a 24-gauge catheter in the tail (n = 4) vein. Imaging and spectroscopy of gas-phase ¹²⁹Xe were performed after injecting 5 mL of half-normal saline saturated with ¹²⁹Xe hyperpolarized to 12%. Corresponding ventilation images were obtained during conventional inhalation delivery of hyperpolarized ¹²⁹Xe. Results Injections of ¹²⁹Xe-saturated saline were well tolerated and produced a strong gas-phase ¹²⁹Xe signal in the airspaces that resulted from ¹²⁹Xe transport through the pulmonary circulation and diffusion across the blood-gas barrier. After a single injection, the emerging ¹²⁹Xe gas could be detected separately from ¹²⁹Xe remaining in the blood and was imaged with an in-plane resolution of 1 × 1 mm and a signal-to-noise ratio of 25. Images in one rat revealed a matched ventilation-perfusion deficit, while images in another rat showed that xenon gas exchange was temporarily impaired after saline overload, with recovery of function 1 hour later. Conclusion MR imaging of gas-phase ¹²⁹Xe emerging in the pulmonary airspaces after intravenous injection has the potential to become a sensitive and minimally invasive new tool for regional evaluation of pulmonary perfusion and gas exchange. Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/2522081550/DC1 © RSNA, 2009