Dynamic dephasing changes in developing ischemic cerebral infarction in rats studied by Carr–Purcell T2 magnetic resonance imaging

Carr–Purcell (CP) T2 MRI with adiabatic pulses, acquired with varying interecho interval (τCP), was used to study the time course of T2 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-T2 relaxation times. This was not associated with signal change in the relative dynamic-dephasing images, as computed by subtracting short τCP CP-T2 images from long τCP images and normalizing for long τCP images. A day after MCAo strong CP-T2 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 T2 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 T2 images. Magn Reson Med 53:960–964, 2005. © 2005 Wiley-Liss, Inc.