Fast measurement of relaxation times by steady-state free precession of 129Xe in carrier agents for hyperpolarized noble gases.

Hyperpolarized gases ((129)Xe and (3)He) are being used increasingly in both MRI and NMR spectroscopy studies. However, it has been shown that carrier agents are required to preserve the long relaxation times of gases in biological fluids. Optimized gas transport can be achieved through controlled T(1) and T(2) measurements of (129)Xe gas at equilibrium, using the steady-state free precession method (SSFP). The accuracy of the method was proven with the use of CuSO(4)-doped water samples and xenon dissolved in chloroform. The following T(1) and T(2) values were measured for xenon dissolved in a 30% intralipid emulsion: T(1) = 29 +/- 3 s; T(2) = 1.0 +/- 0.1 s. The values obtained in the intralipid emulsion contrast significantly with those obtained in conventional gas NMR experiments, in which it is commonly assumed that T(1) = T(2). This highlights the importance of obtaining accurate relaxation time measurements for medical applications of hyperpolarized gases. Copyright 2003 Wiley-Liss, Inc.