Transverse Relaxation of Tissue Water in Human Brain: Relative Contributions of Iron and Macromolecules

Fumiyuki Mitsumori¹, Hidehiro Watanabe¹, Nobuhiro Takaya¹, Michael Garwood², Edward Auerbach²

Apparent transverse relaxation rate (R₂) of the tissue water was measured in various regions of healthy human brain at four different fields of 1.9, 3, 4.7, and 7T using a multi-echo adiabatic spin echo (MASE) sequence. The R₂ increased with field strength (B₀). Distribution of R₂ in various regions is well explained by contributions from regional non-hemin iron concentration ([Fe]) and macromolecular mass fraction defined by 1 water fraction. Assuming an equation of R₂ = α[Fe] + βf_M + γ, the coefficient α increased linearly with B₀, as previously observed in ferritin solution.