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

Abstract

Purpose: To establish regional T(1) and T(2) values of the healthy mouse brain at ultra-high magnetic field strength of 17.6 T and to follow regional brain T(1) and T(2) changes with age. Methods: In vivo T(1) and T(2) 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 T(2) measurements. Student's t-test was used to compare mean relaxation values. Results: A field-dependent decrease in T(2) is shown and validated with phantom measurements. T(2) 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, T(1) 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 T(1) and T(2) values at 17.6 T over different mouse brain regions with age. The estimates of in vivo T(1) and T(2) 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, 2012. © 2012 Wiley Periodicals, Inc.