Relaxation enhancement of the transverse magnetization of water protons in paramagnetic suspensions of red blood cells.
The enhancement of the water proton transverse relaxation, delta R2, 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, delta 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, delta R2, with increasing delta 180, was a factor of two greater for the naturally biconcave RBC, than for the quasi-spherical RBC in hypotonic suspensions. This difference could be modeled in terms of a transmembrane correlation time, tau = 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 delta R2 with increasing magnetization difference between the RBC and its surroundings was found to be marginally less than quadratic, both experimentally and from the model.
Ye
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FQ
Department of Biomedical Engineering, University of Alberta, Edmonton, Canada.
Allen
P S
PS
D000818:Animals; D003198:Computer Simulation; D004285:Dogs; D004912:Erythrocytes; D006400:Hematocrit; D008280:Magnetics; D014867:Water
D014867:Water