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Field dependent transverse relaxation rate increase may be a specific measure of tissue iron stores
Author(s) -
Bartzokis George,
Aravagiri Manickam,
Oldendorf William H.,
Mintz Jim,
Marder Stephen R.
Publication year - 1993
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910290406
Subject(s) - ferritin , relaxometry , nuclear magnetic resonance , relaxation (psychology) , in vivo , diffusion mri , globus pallidus , transferrin , chemistry , white matter , magnetic resonance imaging , nuclear medicine , biomedical engineering , physics , medicine , biology , neuroscience , spin echo , radiology , biochemistry , microbiology and biotechnology , basal ganglia , central nervous system
The degree to which MRI magnet field strength affects measured transverse relaxation rates ( R 2 ) defines a measure termed the field dependent R 2 increase (FDRI). We report here the results of in vivo and in vitro experiments that were conducted to evaluate whether FDRI is a potentially useful measure of tissue iron stores. T 2 relaxation times were obtained using two clinical MRI instruments operating at 0.5 and 1.5 Tesla, and relaxation rates ( R 2 ) were calculated as the reciprocal of T 2 . The in vivo experiment measured R 2 in human brain frontal white matter, caudate nucleus, putamen, and globus pallidus. The FDRI was very highly correlated with published brain iron levels for the four regions examined. The in vitro experiment measured R 2 in agarose gel‐based phantoms containing physiologic forms and amounts proteins involved in iron storage and transport (ferritin, apoferritin, transferrin, and apotransferrin). Significant field dependence was observed only for the ferritin phantoms. The differences in the R 2 values obtained at the two field strengths were striking, and were proportional to the ferritin levels of the phantoms. These studies suggest that FDRI may be a specific measure of tissue ferritin. The quantitative significance of the results to imaging and possible applications to the clinical investigation of pathologic states are discussed.