Transverse relaxation of selectively excited metabolites in stroke at 21.1 T

Abstract

Purpose: This study seeks to evaluate in vivo T2 relaxation times of selectively excited stroke-relevant metabolites via 1H relaxation-enhanced magnetic resonance spectroscopy (RE-MRS) at 21.1 T (900 MHz). Methods: A quadrature surface coil was designed and optimized for investigations of rodents at 21.1 T. With voxel localization, a RE-MRS pulse sequence incorporating the excitation of selected metabolites was modified to include a variable echo delay for T2 measurements. A middle cerebral artery occlusion (MCAO) animal model for stroke was examined with spectra taken 24 h post occlusion. Fourteen echo times were acquired, with each measurement completed in less than 2 min. Results: The RE-MRS approach produced high-quality spectra of the selectively excited metabolites in the stroked and contralateral regions. T2 measurements reveal differential results between these regions, with significance achieved for lactic acid. Conclusion: Using the RE-MRS technique at ultra-high magnetic field and an optimized quadrature surface coil design, full metabolic T2 quantifications in a localized voxel is now possible in less than 27 min. Magn Reson Med 77:520–528, 2017. © 2016 International Society for Magnetic Resonance in Medicine.