Measurement of alveolar oxygen partial pressure in the rat lung using Carr‐Purcell‐Meiboom‐Gill spin–spin relaxation times of hyperpolarized 3 He and 129 Xe at 74 mT

Regional measurement of alveolar oxygen partial pressure can be obtained from the relaxation rates of hyperpolarized noble gases, 3 He and 129 Xe, 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 3 He 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 3 He and 129 Xe 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 3 He and 129 Xe were determined to be (5.2 ± 0.6) ×10 −6 Pa −1 sec −1 and (7.3 ± 0.4) ×10 −6 Pa −1 s −1 compared with spin‐lattice relaxivity constants of (4.0 ± 0.4) ×10 −6 Pa −1 s −1 and (4.3 ± 1.3) × 10 −6 Pa −1 s −1 , respectively. In vivo experimental measurements of alveolar oxygen partial pressure using 3 He in whole rat lung show good agreement ( r 2 = 0.973) with predictions based on lung volumes and ventilation parameters. For 129 Xe, multicomponent relaxation was observed with one component exhibiting an increase in R 2 with decreasing alveolar oxygen partial pressure. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.