Water proton MR properties of human blood at 1.5 Tesla: Magnetic susceptibility, T-1, T-2, T-2* and non-Lorentzian signal behavior

Accurate knowledge of the magnetic properties of human blood is required fo r the precise modeling of functional and vascular flow-related MRI, Herein are reported determinations of the relaxation parameters of blood, employin g in vitro samples that are well representative of human blood in situ. The envelope of the blood (H2O)-H-1 free-induction decay signal magnitude duri ng the first 100 msec following a spin echo at time TE is well-described em pirically by an expression of the form, S(t) = S-o. exp{-R-2*. (t - TE) - A R* (t - TE)(2)}. The relaxation parameters AR* and R-2* increase as a funct ion of the square of the susceptibility difference between red blood cell a nd plasma and depend on the spin-echo time. The Gaussian component, AR*, sh ould be recognized in accurate modeling of MRI phenomena that depend upon t he magnetic state of blood. The magnetic susceptibility difference between fully deoxygenated and fully oxygenated red blood cells at 37 degreesC is 0 .27 ppm, as determined independently by MR and superconducting quantum inte rference device (SQUID) measurements. This value agrees well with the 1936 report of Pauling and Coryell (Proc Natl Acad Sci USA 1936;22:210-216), but is substantially larger than that frequently used in MRI literature. Magn Reson Med 45:533-542, 2001, (C) 2001 Wiley-Liss, Inc.