On the origin of paramagnetic inhomogeneity effects in blood.
Hydrogen, sodium, and fluorine (added F-) NMR spectra of venous and oxygenated blood were measured. The fluorine resonance was seen as a single peak in both samples, and all three resonances exhibited the same deoxy-oxy shift. Because F- exchanges slowly across the red cell membrane, and because sodium is 95% extracellular, these results suggest that the intra-extracellular field difference delta B is less than 0.1 ppm. A small value of delta B tends to rule out transmembrane exchange as an important contributor to relaxation in MRI of blood and hematomas. However, the broadening of the resonances with deoxygenation, by 0.3-0.4 ppm, indicates that both intra- and extracellular gradients are of comparable and sufficient magnitude to produce the T2-weighted hypointensity seen in clinical magnetic resonance images of hematomas at high fields.
Brooks
R A
RA
Neuroimaging Section, NINCDS, National Institutes of Health, Bethesda, Maryland 20892.
Brunetti
A
A
Alger
J R
JR
Di Chiro
G
G
D001769:Blood; D004910:Erythrocyte Membrane / Q000378:metabolism; D005461:Fluorine; D006406:Hematoma / Q000097:blood / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D006859:Hydrogen; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D010100:Oxygen; D012964:Sodium
D005461:Fluorine; D006859:Hydrogen; D012964:Sodium; D010100:Oxygen