SEOP apparatus. (a) laser diode bar; (b) beam-splitter cube (1/3 feedback along cavity axis, 2/3 transmission along cell axis); (c) holographic grating; (d) λ/4-wave plate; (e) ceramic oven for housing cell (lid removed); (f) B 0 coils.
(a) Experimental 129Xe polarization vs. cell temperature at gas flow rates of 300 and 500 sccm. HP 129Xe (samples obtained without cryogenic accumulation) signals were measured in the 1.5 T system. NB: blue and red lines are guides for the eye. (b) Modeled polarization vs. cell temperature.
129Xe polarization vs. gas flow rate through the cell. The red line represents the modeled polarization for different gas flow rates (residency times), where a theoretical spin-exchange rate, , of 0.0033 Hz was used along with a theoretical equilibrium polarization (infinite residency time) of 86%. The blue line shows a fit (using Eq. (5) ) to the experimental polarization data. From the fit, an empirical value for the spin-exchange rate, , was extrapolated to be 0.022 Hz, giving an empirical spin-exchange time of = 45 s. Black dotted line indicates the flow rate of 650 sccm for which the residency time, t res, of the gas in the cell is equal to the empirical spin-exchange time.
(a) Freeze-out cryogenic glassware within holding magnetic field of ∼ 0.3 T. (b) T 1 of frozen Xe held within the freeze-out glassware. A T 1 of 87 ± 2 min was estimated by performing an exponential fit (blue line) to the FID signal decrease as a function of storage time.
Normalized 1.5 T signal vs. freeze-out accumulation time. The blue line represents the theoretical polarization decay with accumulation time (Eq. (10) ).
In vivo gas-phase human lung images from a healthy volunteer at 3 T. (a) and (b) are 2D images of HP 129Xe acquired from isotopically enriched gas mixtures (86% 129Xe) flowed through the cell at volumetric flow rates (Q) of 300 and 600 sccm; (c) and (d) are 3D images of HP 129Xe, both produced at a flow rate of 300 sccm for different accumulation times, t a. Respective SNR values calculated for lungs in images (a), (b), (c), and (d) are 56, 52, 49, and 102.
Upper half: calculated number densities of atoms in the cell and binary spin-destruction cross sections, . Lower half: vdW and binary spin-destruction and spin-exchange rates. All cross sections and rates correspond to a SEOP cell at a temperature 373 K, pressure of 2 bars (temperature and pressure of the cell when filling it with the gas mixture, total gas number density of 1.44 amg) and a gas composition of 3% Xe, 10% N2, and 87% He.
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