Estimation of brain iron concentration in vivo using a linear relationship between regional iron and apparent transverse relaxation rate of the tissue water at 4.7T
✍ Scribed by Fumiyuki Mitsumori; Hidehiro Watanabe; Nobuhiro Takaya
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- English
- Weight
- 870 KB
- Volume
- 62
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
Maps of the apparent transverse relaxation time (T~2~^†^) were collected on a transaxial plane across the basal ganglia in 54 healthy subjects at 4.7T using a multiecho adiabatic spin‐echo (MASE) imaging sequence. We attempted to quantify the nonhemin iron concentration ([Fe]) in various brain regions in vivo based on the linear relationship between the apparent relaxation rate constant (R~2~^†^ = 1/T~2~^†^) and regional [Fe], as demonstrated previously in 12 subjects. The calculated [Fe] in five gray matter (GM) regions agreed well with the previously reported regional iron distribution as well as reproduced its age‐dependent change. In particular, a decrease of iron in the thalamus region in subjects over 30 years of age was demonstrated while an upward trend was shown in other regions. Furthermore, the average R~2~^†^ in each GM region in subjects over 30 years of age showed a deviation from the regression line with [Fe] in an identical manner to that obtained in the previous 12 subjects. This strongly suggests that there is a systematic regional factor affecting R~2~^†^, in addition to iron. Interregional difference in the macromolecular mass fraction (f~M~) explained this systematic deviation well. When accounting for f~M~ in the analysis, the apparent transverse relaxation rate seems to give a significantly better estimation of regional [Fe]. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.