The spin polarization lifetime of xenon in blood

We measured the spin polarization lifetime (T₁) of laser-polarized ¹²⁹Xe dissolved in fresh human blood in vitro, an important factor in determining the polarization delivered to target tissues for in vivo NMR. A blood-foam preparation was used to enhance the dissolved ¹²⁹Xe NMR signal. We found that the ¹²⁹Xe T₁ is significantly shorter in oxygenated blood than in deoxygenated blood, implying a T₁ of 5-10 seconds in arterial blood and 15-25 seconds in venous blood. The measurement technique using a laser-polarized ¹²⁹Xe gas-liquid exchange interface in a foam may also be generally useful in studying foam coarsening, gas diffusion through films, and other liquid physical properties.

Figure 2. Observed decay of NMR peak integrals for laser-polarized ¹²⁹Xe dissolved in (A) oxygenated blood foam, (B) deoxygenated blood foam, and (C) oxygenated and (D) deoxygenated plasma foam. Decay of the accompanying ¹²⁹Xe gas component (open dot) is shown above the blood and plasma signals (filled dot). All ¹²⁹Xe integrals were normalized to the first point in the time series. In all cases, the gas phase ¹²⁹Xe magnetization was much greater than the dissolved plases ¹²⁹Xe magnetization (G >> B). The gas signals were fitted to monoexponentials, and the blood and pasma signals were fitted to biexponential functions (solid lines) with one exponential rate given by the observed gas signal decay rate.

Figure 2. Observed decay of NMR peak integrals for laser-polarized ¹²⁹Xe dissolved in (A) oxygenated blood foam, (B) deoxygenated blood foam, and (C) oxygenated and (D) deoxygenated hemoglobin foam. Decay of the accompanying ¹²⁹Xe gas component (open dot) is shown above the blood and plasma signals (filled dot). The gas phase ¹²⁹Xe magnetization was greatly reduced by RF pulses prior to acquisition (G ~ B). The gas signals were fitted to biexponential functions (solid lines). All ¹²⁹Xe integrals were normalized to the first point in the time series.

Note: These investigations were performed in close collaboration with scientists at the MR Division of the Brigham and Women's Hospital.

Reference:

NMR of laser polarized ¹²⁹Xe in blood foam.

See also our related biomedical research:

Polarized xenon in rat lungs and body tissues

Xenon uptake calculations for humans

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