Premium
Reduced xenon diffusion for quantitative lung study—the role of SF 6
Author(s) -
Mair Ross W.,
Hoffmann Dominik,
Sheth Sameer A.,
Wong Glenn P.,
Butler James P.,
Patz Samuel,
Topulos George P.,
Walsworth Ronald L.
Publication year - 2000
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/1099-1492(200006)13:4<229::aid-nbm637>3.0.co;2-s
Subject(s) - xenon , sulfur hexafluoride , diffusion , bar (unit) , chemistry , inert gas , analytical chemistry (journal) , relaxation (psychology) , gaseous diffusion , nuclear magnetic resonance , thermodynamics , chromatography , physics , organic chemistry , meteorology , psychology , social psychology , electrode
The large diffusion coefficients of gases result in significant spin motion during the application of gradient pulses that typically last a few milliseconds in most NMR experiments. In restricted environments, such as the lung, this rapid gas diffusion can lead to violations of the narrow pulse approximation, a basic assumption of the standard Stejskal–Tanner NMR method of diffusion measurement. We therefore investigated the effect of a common, biologically inert buffer gas, sulfur hexafluoride (SF 6 ), on 129 Xe NMR and diffusion. We found that the contribution of SF 6 to 129 Xe T 1 relaxation in a 1:1 xenon/oxygen mixture is negligible up to 2 bar of SF 6 at standard temperature. We also measured the contribution of SF 6 gas to 129 Xe T 2 relaxation, and found it to scale inversely with pressure, with this contribution approximately equal to 1 s for 1 bar SF 6 pressure and standard temperature. Finally, we found the coefficient of 129 Xe diffusion through SF 6 to be approximately 4.6 × 10 −6 m 2 s −1 for 1 bar pressure of SF 6 and standard temperature, which is only 1.2 times smaller than the 129 Xe self diffusion coefficient for 1 bar 129 Xe pressure and standard temperature. From these measurements we conclude that SF 6 will not sufficiently reduce 129 Xe diffusion to allow accurate surface‐area/volume ratio measurements in human alveoli using time‐dependent gas diffusion NMR.