β Scribed by Frank Q. Ye; Peter S. Allen
No coin nor oath required. For personal study only.
The enhancement of the water proton transverse relaxation, ΞR~2~, brought about by a difference between intra and extracellular paramagnetic susceptibilities in a suspension of red blood cells (RBC) has been evaluated both experimentally and theoretically in terms of (i) the refocusing interval, Ξ~180~, of a CPMG pulse sequence, (ii) the difference in paramagnetic susceptibility, and (iii) the shape of the cell surface. At a hematocrit of 45, the increase in the relaxation enhancement, ΞR~2~, with increasing Ξ~180~, was a factor of two greater for the naturally biconcave RBC, than for the quasiβspherical RBC in hypotonic suspensions. This difference could be modeled in terms of a transmembrane correlation time, Ο = 5.5 ms, across an RBC surface characterized by a demagnetizing factor which differs by 0.13 from that of a sphere. The increase in ΞR~2~ with increasing magentization difference between the RBC and its surroundings was found to be marginally less than quadratic, both experimentally and from the model.
π SIMILAR VOLUMES
The magnetic field dependence of the water proton T, is calculated for aqueous solutions of nitroxides based on a detailed analysis of early T, measurements on nitroxide solutions made as a function of magnetic field. The results parallel those for TI closely and, unlike metal systems, the implicati