T2† measurement during acute cerebral ischemia by Carr‐Purcell MRI at 4T

Abstract

Metabolic and structural changes occur in brain tissue within minutes of ischemia. The adiabatic multi‐echo (Carr‐Purcell) localization pulse sequence LASER has shown promise in detecting tissue contrast changes within the first hour of ischemia. The purpose of this initial study was to combine the LASER localization sequence with fast 3D echo‐planar imaging (EPI) to quantify the regional apparent transverse relaxation (T₂^†) in a rabbit model of acute embolic ischemia at 4 Tesla. Carr‐Purcell T₂^†‐weighted images were acquired at 7 different echo‐times and used to estimate T₂^† in both cortex and striatum. In ischemic tissue identified by 2,3,5 ‐ triphenyltetrazolium chloride (TTC) staining, the T₂^† increased by approximately 31% after 1 hour of ischemia and remained elevated until study completion at 4 h of ischemia. Lesion volume, defined as the number of pixels with T₂^† greater than 90 ms, increased by 40% between 1 and 4 h after induction of ischemia. Carr‐Purcell LASER‐EPI T₂^†‐weighted images show promise in detecting early tissue changes in focal cerebral ischemia. Magn Reson Med, 2005.