Quantification of blood oxygen saturation on the basis of a measurement of its magnetic susceptibility demands knowledge of the difference in volume susceptibility between fully oxygenated and fully deoxygenated blood (Δχ(do) ). However, two very different values of Δχ(do) are currently in use. In this work we measured Δχ(do) as well as the susceptibility of oxygenated blood relative to water, Δχ(oxy) , by MR susceptometry in samples of freshly drawn human blood oxygenated to various levels, from 6 to 98% as determined by blood gas analysis. Regression analysis yielded 0.273 ± 0.006 and -0.008 ± 0.003 ppm (cgs) respectively, for Δχ(do) and Δχ(oxy) , in excellent agreement with previous work by Spees et al. (Magn Reson Med 2001;45:533-542).
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