Dynamic dephasing changes in developing ischemic cerebral infarction in rats studied by Carr–Purcell T 2 magnetic resonance imaging

Carr–Purcell (CP) T 2 MRI with adiabatic pulses, acquired with varying interecho interval (τ CP ), was used to study the time course of T 2 and relative dynamic‐dephasing contrast in the rat brain. Exposure to 30 min of middle cerebral artery occlusion (MCAo) resulted in an irreversible increase in absolute CP‐ T 2 relaxation times. This was not associated with signal change in the relative dynamic‐dephasing images, as computed by subtracting short τ CP CP‐ T 2 images from long τ CP images and normalizing for long τ CP images. A day after MCAo strong CP‐ T 2 hyperintensity and low apparent diffusion coefficient were evident in the striatum with a decline in relative dynamic‐dephasing contrast. Low dynamic dephasing contrast prevailed in striatum until day 5 post‐MCAo, returning to control levels with similar time course to normalizing T 2 and diffusion. The present results show a novel behavior of dynamic‐dephasing contrast in poststroke brain tissue, providing data to assess the age of infarction in association to T 2 images. Magn Reson Med 53:960–964, 2005. © 2005 Wiley‐Liss, Inc.