In vivo measurement of transverse relaxation time in the mouse brain at 17.6 T

Purpose: To establish regional T₁ and T₂ values of the healthy mouse brain at ultra‐high magnetic field strength of 17.6 T and to follow regional brain T₁ and T₂ changes with age. Methods: In vivo T₁ and T₂ values in the C57BL/6J mouse brain were followed with age using multislice‐multiecho sequence and multiple spin echo saturation recovery with variable repetition time sequence, respectively, at 9.4 and 17.6 T. Gadolinium‐tetra‐azacyclo‐dodecane‐tetra‐acetic acid phantoms were used to validate in vivo T₂ measurements. Student's t‐test was used to compare mean relaxation values. Results: A field‐dependent decrease in T₂ is shown and validated with phantom measurements. T₂ values at 17.6 T typically increased with age in multiple brain regions except in the hypothalamus and the caudate‐putamen, where a slight decrease was observed. Furthermore, T₁ values in various brain regions of young and old mice are presented at 17.6 T. A large gain in signal‐to‐noise ratio was observed at 17.6 T. Conclusions: This study establishes for the first time the normative T₁ and T₂ values at 17.6 T over different mouse brain regions with age. The estimates of in vivo T₁ and T₂ will be useful to optimize pulse sequences for optimal image contrast at 17.6 T and will serve as baseline values against which disease‐related relaxation changes can be assessed in mice. Magn Reson Med, 70:985–993, 2013. © 2012 Wiley Periodicals, Inc.