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MR microscopy at 7.0 T: Effects of brain iron
Author(s) -
Malisch Timothy W.,
Hedlund Laurence W.,
Suddarth Steve A.,
Johnson G. Allan
Publication year - 1991
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.1880010308
Subject(s) - substantia nigra , myelin , chemistry , nuclear magnetic resonance , brain tissue , pathology , biophysics , anatomy , biology , neuroscience , medicine , parkinson's disease , physics , central nervous system , disease
Abstract The T2 of brain tissue is known to be field dependent, decreasing as B 0 increases. Previous studies have attributed reduced T2 in the structures of the extrapyramidal motor system (EPMS) to high iron concentrations. The present study was designed to manipulate physiologic iron concentrations and study the effects on T2 and on the field dependence of T2 at 7.0 T in whole formalin‐fixed brains. A rat model was devised in which iron concentrations in the structures of interest were altered by diet manipulation. Cerebral structures with different iron content were imaged and T2 measured with MR microscopy at both 2.0 and 7.0 T. T2 of all tissues was shorter by 40%–60% at 7.0 T. Although some dependence of T2 on iron concentration was evident, it was less than expected. The strongest correlation was in the substantia nigra. The highest‐resolution studies, at 30 × 30 × 50 μm, show the myelin bundles in many of the EPMS structures but not in the substantia nigra. From these data, it appears that T2 at greater field strengths depends more on susceptibility‐induced spin dephasing imposed by diffusion through the tissue micro‐structure than on the presence of iron.