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Published on: December 28, 2014
Dynamic dephasing changes in developing ischemic cerebral infarction in rats studied by Carr-Purcell T2 magnetic
Martin Kavec1, Olli H J Gröhn, Heidi I Gröhn
1Department of Biomedical NMR and National Bio-NMR Facility, A. I.Virtanen Institute, University of Kuopio, Kuopio, Finland.
Abstract:
Carr-Purcell (CP) T(2) MRI with adiabatic pulses, acquired with varying interecho interval (tau(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 tau(CP) CP-T(2) images from long tau(CP) images and normalizing for long tau(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.
Insights
Middle cerebral artery occlusion (MCAo) in rats caused irreversible increases in T(2) MRI relaxation times. Dynamic-dephasing contrast showed novel behavior in post-stroke brain tissue, aiding in infarction age assessment.
Area of Science:
- Neuroimaging
- Biophysics
- Medical Physics
Background:
- Magnetic Resonance Imaging (MRI) is crucial for studying brain tissue.
- T(2) relaxation times are sensitive to tissue changes.
- Dynamic-dephasing contrast offers insights into tissue microdynamics.
Purpose of the Study:
- To investigate the time course of T(2) and dynamic-dephasing contrast in the rat brain after middle cerebral artery occlusion (MCAo).
- To assess the utility of these MRI parameters in characterizing post-stroke brain tissue and determining infarction age.
Main Methods:
- Carr-Purcell (CP) T(2) MRI with adiabatic pulses and varying interecho intervals (tau(CP)) were employed.
- MCAo was induced in rats for 30 minutes.
- Analysis involved absolute CP-T(2) relaxation times and relative dynamic-dephasing contrast derived from image subtraction.
Main Results:
- MCAo led to an irreversible increase in absolute CP-T(2) relaxation times.
- Relative dynamic-dephasing contrast did not initially change but declined later post-MCAo.
- Striatal T(2) hyperintensity and low apparent diffusion coefficient were observed one day after MCAo, with diminished dynamic-dephasing contrast.
Conclusions:
- Dynamic-dephasing contrast exhibits unique behavior in post-stroke brain tissue.
- This novel behavior provides valuable data for assessing the age of infarction in conjunction with T(2) images.
- CP T(2) MRI with dynamic-dephasing contrast is a promising technique for stroke evaluation.
