IN-VIVO MR-IMAGING AND SPECTROSCOPY USING HYPERPOLARIZED XE-129

Hyperpolarized Xe-129 has been used to obtain gas phase images of mous e lung in vivo, showing distinct ventilation variation as a function o f the breathing cycle. Spectra of Xe-129 in the thorax show complex st ructure in both the gas phase (-4 to 3 ppm) and tissue-dissolved (190- 205 ppm) regions. The alveolar gas peak shows correlated intensity and frequency oscillations, both attributable to changes in lung volume d uring breathing. The two major dissolved peaks near 195-200 ppm are at tributed to lung parenchyma and to blood; they reach maximum intensity in 5-10 s and decay with an apparent T-1 of 30 s. Another peak at 190 ppm takes 20-30 s to reach maximum; this must represent other well-va scularized tissue (e.g., heart and other muscles) in the thorax. The m aximum integrated area of the tissue components reaches 30-80% of the maximum alveolar gas area, indicating that imaging at tissue frequenci es can be achieved.