Characterization of T(2)* heterogeneity in human brain white matter.
Recent in vivo MRI studies at 7.0 T have demonstrated extensive heterogeneity of T(2)* relaxation in white matter of the human brain. In order to study the origin of this heterogeneity, we performed T(2)* measurements at 1.5, 3.0, and 7.0 T in normal volunteers. Formalin-fixed brain tissue specimens were also studied using T(2)*-weighted MRI, histologic staining, chemical analysis, and electron microscopy. We found that T(2)* relaxation rate (R(2)* = 1/T(2)*) in white matter in living human brain is linearly dependent on the main magnetic field strength, and the T(2)* heterogeneity in white matter observed at 7.0 T can also be detected, albeit more weakly, at 1.5 and 3.0 T. The T(2)* heterogeneity exists also in white matter of the formalin-fixed brain tissue specimens, with prominent differences between the major fiber bundles such as the cingulum (CG) and the superior corona radiata. The white matter specimen with substantial difference in T(2)* has no significant difference in the total iron content, as determined by chemical analysis. On the other hand, evidence from histologic staining and electron microscopy demonstrates these tissue specimens have apparent difference in myelin content and microstructure.
Li
Tie-Qiang
TQ
Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disease and Stroke, National Institutes of Health, Bethesda, Maryland, USA. tieqiang.li@karolinska.se
Yao
Bing
B
van Gelderen
Peter
P
Merkle
Hellmut
H
Dodd
Stephen
S
Talagala
Lalith
L
Koretsky
Alan P
AP
Duyn
Jeff
J
D000328:Adult; D000465:Algorithms; D001921:Brain / Q000033:anatomy & histology* / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008954:Models, Biological; D009413:Nerve Fibers, Myelinated / Q000502:physiology* / Q000648:ultrastructure*