Toward understanding transverse relaxation in human brain through its field dependence

Fumiyuki Mitsumori, Hidehiro Watanabe, Nobuhiro Takaya, Michael Garwood, Edward J. Auerbach, Shalom Michaeli, Silvia Mangia

Research output: Contribution to journalArticle

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Abstract

Apparent transverse-relaxation rate constants (R 2 = 1/T 2) were measured in various regions of the healthy human brain using a multiecho adiabatic spin-echo sequence at five different magnetic fields, 1.5, 1.9, 3, 4.7, and 7 T. The R 2 values showed a clear dependence on magnetic field strength (B 0). The regional distribution of the R 2 was well explained by the sum of three components: (1) regional nonhemin iron concentration ([Fe]), (2) regional macromolecular mass fraction (fM), and (3) a region-independent factor. Accordingly, R 2 = α[Fe] + βfM + γ, where coefficients α, β, and γ were experimentally determined at each magnetic field by a least square fitting method using multiple regression analysis. Although the coefficient α linearly increased with B0, β showed a quadratic dependence on top of a field-independent component. The coefficient γ also increased slightly with B0 on top of a field-independent component. The linear dependence of α on B0 was consistent with that observed for the transverse-relaxation rate of water protons in ferritin solutions as found previously by others. The quadratic dependence of β on B0 was accounted for by isochronous and anisochronous exchange mechanisms using intrinsic-relaxation parameters obtained from the literature.

Original languageEnglish (US)
Pages (from-to)947-953
Number of pages7
JournalMagnetic resonance in medicine
Volume68
Issue number3
DOIs
StatePublished - Sep 1 2012

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Keywords

  • field dependence
  • human brain
  • iron
  • macromolecule
  • transverse relaxation

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