Measurement of Alveolar Oxygen Partial Pressure in the Rat Lung Using Carr-Purcell-Meiboom-Gill Spin-Spin Relaxation Times of Hyperpolarized 3He and 129Xe at 74 mT

Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, He-3 and Xe-129, in the lungs. Recently, it has been demonstrated that measurements of alveolar oxygen partial pressure can be obtained using the spin-spin relaxation rate (R-2) of He-3 at low magnetic field strengths (<0.1 T) in vivo. R-2 measurements can be achieved efficiently using the Carr-Purcell-Meiboom-Gill pulse sequence. In this work, alveolar oxygen partial pressure measurements based on Carr-Purcell-Meiboom-Gill R-2 values of hyperpolarized He-3 and Xe-129 in vitro and in vivo in the rat lung at low magnetic field strength (74 mT) are presented. In vitro spin-spin relaxivity constants for He-3 and Xe-129 were determined to be (5.2 +/- 0.6) x 10(-6) Pa-1 sec(-1) and (7.3 +/- 0.4) x 10(-6) Pa-1 s(-1) compared with spin-lattice relaxivity constants of (4.0 +/- 0.4) x 10(-6) Pa-1 s(-1) and (4.3 +/- 1.3) x 10(-6) Pa-1 s(-1), respectively. In vivo experimental measurements of alveolar oxygen partial pressure using He-3 in whole rat lung show good agreement (r(2) = 0.973) with predictions based on lung volumes and ventilation parameters. For Xe-129, multicomponent relaxation was observed with one component exhibiting an increase in R2 with decreasing alveolar oxygen partial pressure. Magn Reson Med 64:1484-1490, 2010. (C) 2010 Wiley-Liss, Inc.