<i>In vivo</i> measurement of <i>T</i>₂ distributions and water contents in normal human brain

TLDR

Using a 32‑echo imaging pulse sequence, T₂ relaxation decay curves were acquired from five white‑ and six gray‑matter brain structures in 12 normal volunteers. Water content was 0.71 g/ml in white matter and 0.83 g/ml in gray matter, with white‑matter structures showing higher myelin‑water percentages and broader T₂ distributions, indicating distinct water environments that may serve as reliable markers for normal myelin.

Abstract

Abstract Using a 32‐echo imaging pulse sequence, T 2 relaxation decay curves were acquired from five white‐ and six gray‐matter brain structures outlined in 12 normal volunteers. The water contents of white and gray matter were 0.71 (0.01) and 0.83 (0.03) g/ml, respectively. All white‐matter structures had significantly higher myelin water percentages (signal percentage with T 2 between 10 and 50 ms) than all gray‐matter structures. The range in geometric mean T 2 of the main peak for both white and gray matter was from 70 to 86 ms. T 2 distributions from the posterior internal capsules and splenium of the corpus callosum were significantly wider (width is related to water environment inhomogeneity) than those from any other white‐ or gray‐matter structures. Thus, quantitative measurement and analysis of T 2 relaxation reveals differences in brain tissue water environments not discernible on conventional MR images. These differences may make short T 2 components reliable markers for normal myelin.