New Directions in Magnetic Resonance in Acute Cerebral Ischemia

1993 ◽  
Vol 4 (1) ◽  
pp. 3-11 ◽  
Author(s):  
Marc Hommel ◽  
Sylvie Grand ◽  
Philippe Devoulon ◽  
Jean-François Le Bas
Keyword(s):  
Cerebral Ischemia ◽  
Magnetic Resonance ◽  
Acute Cerebral Ischemia ◽  
New Directions

scholarly journals Quantitative T1ρ and Magnetization Transfer Magnetic Resonance Imaging of Acute Cerebral Ischemia in the Rat

2002 ◽  
Vol 22 (5) ◽  
pp. 547-558 ◽  
Author(s):  
Heidi I. Mäkelä ◽  
Mikko I. Kettunen ◽  
Olli H. J. Gröhn ◽  
Risto A. Kauppinen
Keyword(s):  
Magnetic Resonance Imaging ◽  
Cerebral Ischemia ◽  
Magnetic Resonance ◽  
Neuronal Damage ◽  
Magnetization Transfer ◽  
Dependent Manner ◽  
Resonance Imaging ◽  
Prognostic Information ◽  
Acute Cerebral Ischemia ◽  
Ischemic Brain Tissue

It has been previously shown that T1 in the rotating frame (T1ρ) is a very sensitive and early marker of cerebral ischemia and that, interestingly, it can provide prognostic information about the degree of subsequent neuronal damage. In the present study the authors have quantified T1ρ together with the rate and other variables of magnetization transfer (MT) associated with spin interactions between the bulk and semisolid macromolecular pools by means of Z spectroscopy, to examine the possible overlap of mechanisms affecting these magnetic resonance imaging contrasts. Substantial prolongation of cerebral T1ρ was observed minutes after induction of ischemia, this change progressing in a time-dependent manner. Difference Z spectra (contralateral nonischemic minus ischemic brain tissue) showed a significant positive reminder in the time points from 0.5 to 3 hours after induction of ischemia, the polarity of this change reversing by 24 hours. Detailed analysis of the MT variables showed that the initial Z spectral changes were due to concerted increase in the maximal MT (+3%) and amount of MT (+4%). Interestingly, the MT rates derived either from the entire frequency range of Z spectra or the time constant for the first-order forward exchange (ksat) were unchanged at this time, these variables reducing only one day after induction of ischemia. The authors conclude that T1ρ changes in the acute phase of ischemia coincide with both elevated maximal MT and amount of MT. These changes occur independent of the overall MT rate and in the absence of net water gain to the tissue, whereas in the consolidating infarction the decrease in the rate and amount of MT, as well as the extensive prolongation of T1ρ, are associated with water accumulation.

Validation of Transcranial Doppler with Magnetic Resonance Angiography in Acute Cerebral Ischemia

2011 ◽  
Vol 21 (2) ◽  
pp. e34-e40 ◽  
Author(s):  
Demudu Babu Boddu ◽  
Vijay K. Sharma ◽  
V.C.S.S. Bandaru ◽  
Y. Jyotsna ◽  
D. Padmaja ◽  
...  
Keyword(s):  
Cerebral Ischemia ◽  
Magnetic Resonance ◽  
Magnetic Resonance Angiography ◽  
Transcranial Doppler ◽  
Acute Cerebral Ischemia

In vivo diffusion–perfusion magnetic resonance imaging of acute cerebral ischemia

1991 ◽  
Vol 69 (11) ◽  
pp. 1719-1725 ◽  
Author(s):  
John Kucharczyk ◽  
Jan Mintorovitch ◽  
Haleh Asgari ◽  
Mitsuharu Tsuura ◽  
Michael Moseley
Keyword(s):  
Cerebral Ischemia ◽  
Magnetic Resonance ◽  
Resonance Imaging ◽  
Mr Images ◽  
Ischemic Brain ◽  
Diffusion Weighted ◽  
Acute Cerebral Ischemia ◽  
Planar Images ◽  
Echo Planar

We compared the anatomic extent and severity of ischemic brain injury shown on diffusion-weighted magnetic resonance (MR) images, with cerebral tissue perfusion deficits demonstrated by a nonionic intravascular T2*-shortening magnetic susceptibility contrast agent used in conjunction with standard T2-weighted spin-echo and gradient-echo echo-planar images. Diffusion-weighted images displayed increased signal intensity in the vascular territory of the middle cerebral artery 25–40 min after permanent occlusion, whereas T2-weighted images without contrast were negative or equivocal for at least 2–3 h after stroke was induced. Contrast-enhanced T2-weighted and echo-planar images revealed perfusion deficits that were spatially closely related to the anatomic regions of ischemic tissue injury. These data indicate that diffusion-weighted MR images are very sensitive to early onset pathophysiologic changes induced by acute cerebral ischemia. Combined sequential diffusion–perfusion imaging enables noninvasive in vivo examination of the relationship between hypoperfusion and evolving ischemic brain injury.Key words: in vivo, diffusion, perfusion, acute cerebral ischemia, magnetic resonance imaging.

scholarly journals Diffusion-Weighted Magnetic Resonance Imaging of Acute Focal Cerebral Ischemia: Comparison of Signal Intensity with Changes in Brain Water and Na+,K+ -ATPase Activity

1994 ◽  
Vol 14 (2) ◽  
pp. 332-336 ◽  
Author(s):  
Jan Mintorovitch ◽  
G. Y. Yang ◽  
Hiroaki Shimizu ◽  
John Kucharczyk ◽  
Pak H. Chan ◽  
...  
Keyword(s):  
Cerebral Ischemia ◽  
Magnetic Resonance ◽  
Atpase Activity ◽  
Water Content ◽  
Signal Intensity ◽  
Focal Cerebral Ischemia ◽  
Mr Images ◽  
Diffusion Weighted ◽  
Acute Cerebral Ischemia ◽  
Brain Water

Diffusion-weighted magnetic resonance (MR) images from rats during acute cerebral ischemia induced by middle cerebral artery occlusion were analyzed for correspondence with changes in brain water, cation concentrations, and Na+,K+-ATPase activity measured in vitro after 30 or 60 min of ischemia. In the ischemic hemisphere, signal intensity was increased at 30 min (p < 0.05 vs contralateral hemisphere) and further increased at 60 min. Na+,K+-ATPase activity was 34% lower in ischemic cortex and 40% lower in ischemic basal ganglia after 30 min (p < 0.05), but water content and Na+ and K+ concentrations were not significantly different between hemispheres. After 60 min, water content and Na+ concentration were increased, and both Na+,K+-ATPase activity and K+ concentration were decreased in the ischemic hemisphere (p < 0.05). These findings are consistent with the hypothesis that the early onset of signal hyperintensity in diffusion-weighted MR images may reflect cellular edema associated with impaired membrane pump function. Early in vivo detection and localization of potentially reversible ischemic cerebral edema may have important research and clinical applications.

scholarly journals Early Detection of Irreversible Cerebral Ischemia in the Rat Using Dispersion of the Magnetic Resonance Imaging Relaxation Time, T1ρ

2000 ◽  
Vol 20 (10) ◽  
pp. 1457-1466 ◽  
Author(s):  
Olli H J. Gröhn ◽  
Mikko I. Kettunen ◽  
Heidi I. Mäkelä ◽  
Markku Penttonen ◽  
Asla Pitkänen ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Relaxation Time ◽  
Cerebral Ischemia ◽  
Magnetic Resonance ◽  
Neuronal Damage ◽  
Therapeutic Window ◽  
Resonance Imaging ◽  
Mca Occlusion ◽  
Acute Cerebral Ischemia ◽  
The Impact

The impact of brain imaging on the assessment of tissue status is likely to increase with the advent of treatment methods for acute cerebral ischemia. Multimodal magnetic resonance imaging (MRI) demonstrates potential for selecting stroke therapy patients by identifying the presence of acute ischemia, delineating the perfusion defect, and excluding hemorrhage. Yet, the identification of tissue subject to reversible or irreversible ischemia has proven to be difficult. Here, the authors show that T1 relaxation time in the rotating frame, so-called T1ρ, serves as a sensitive MRI indicator of cerebral ischemia in the rat. The T1ρ prolongs within minutes after a drop in the CBF of less than 22 mL 100 g−1 min−1. Dependence of T1ρ on spin-lock amplitude, termed as T1ρ dispersion, increases by approximately 20% on middle cerebral artery (MCA) occlusion, comparable with the magnitude of diffusion reduction. The T1ρ dispersion change dynamically increases to be 38% ± 10% by the first 60 minutes of ischemia in the brain region destined to develop infarction. Following reperfusion after 45 minutes of MCA occlusion, the tissue with elevated T1ρ dispersion (yet normal diffusion) develops severe histologically verified neuronal damage; thus, the former parameter unveils an irreversible condition earlier than currently available MRI methods. The T1ρ dispersion as a novel MRI index of cerebral ischemia may be useful in determination of the therapeutic window for acute ischemic stroke.

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