Laser-polarized 129 Xe dissolved in a foam preparation of fresh in blood found 4.5 { 1 s in red blood cells and 9 { 2 s in human blood was investigated. The NMR signal of 129 Xe dissolved plasma (18). This experiment used thermally polarized 129 Xe in blood was enhanced by creating a foam in which the dissolved and therefore required many hours of signal averaging. Po-129 Xe exchanged with a large reservoir of gaseous laser-polarized tential systematic problems with such long measurement 129 Xe. The dissolved 129 Xe T 1 in this system was found to be signifitimes include sedimentation and degradation of the blood. cantly shorter in oxygenated blood than in deoxygenated blood.
In their recent demonstration of an injectable polarized
The T 1 of 129 Xe dissolved in oxygenated blood foam was found to 129 Xe agent, Bifone et al. (19) found a 5 s 129 Xe T 1 in blood be approximately 21 ({5) s, and in deoxygenated blood foam to using an open-air sample tube, which may have affected the be greater than 40 s. To understand the oxygenation trend, T 1 value obtained. In the reported in vivo rodent investigations measurements were also made on plasma and hemoglobin foam of polarized 129 Xe dissolved in blood and other tissues preparations. The measurement technique using a foam gas-liquid exchange interface may also be useful for studying foam coars- (12, 13, 15), only effective polarization lifetimes were deening and other liquid physical properties. α§ 1997 Academic Press termined because of the 129 Xe exchange with the lung gas space and other tissues. In contrast, the measurement reported here exploits the 129 Xe gas-blood phase exchange in a closed in vitro system. The surface area for exchange was