NMR of hyperpolarized Xe-129 in the canine chest: spectral dynamics duringa breath-hold

One of the major goals of hyperpolarized-gas MR imaging has been to obtain Xe-129 dissolved-phase images in humans. Since the dissolved-phase signal i s much weaker than the gas-phase signal, highly optimized MR pulse sequence s are required to obtain adequate images during a single breath-hold. In pa rticular, a solid understanding of the temporal dynamics of xenon as it pas ses from the lung gas spaces into the parenchyma, the blood and other downs tream compartments is absolutely essential. Spectroscopy experiments were p erformed in the canine chest to elucidate the behavior of xenon exchange in the lung. The experiments covered a time range from 1 ms to 9 s and theref ore considerably extend the data currently available in the literature. It was found that the integrals of the dissolved-phase resonances approached p lateau values within approximately 200 ms, and then increased again after a pproximately 1 s. This behavior suggests an early saturation of the parench yma before xenon reaches downstream compartments. Mono-exponential recovery curves with time constants on the order of 100 ms were fit to the data. Th ese results potentially provide information on several underlying physiolog ical parameters of the lung, including the parenchymal and blood volumes as well as the diffusion properties of lung tissue. Copyright (C) 2000 John W iley & Sons, Ltd.