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NEUROLOGY 1994;44:1484
© 1994 American Academy of Neurology

MRI diffusion mapping of reversible and irreversible ischemic injury in focal brain ischemia

Y. Hasegawa, MD, M. Fisher, MD, L. L. Latour, BS, B. J. Dardzinski, ME and C. H. Sotak, PhD

Department of Neurology (Drs. Hasegawa and Fisher), The Medical Center of Central Massachusetts-Memorial; the Department of Biomedical Engineering (Dr. Sotak and L. Latour and B. Dardzinski), Worcester Polytechnic Institute; and the Departments of Neurology (Dr. Fisher) and Radiology (Drs. Fisher and Sotak), University of Massachusetts Medical School, Worcester, MA.

The reduction of the apparent diffusion coefficient (ADC) of water shortly after a focal ischemic insult is thought to reflect intracellular water accumulation (cytotoxic edema) related to high-energy metabolism failure and loss of ion homeostasis. We attempted to clarify whether varying ranges of ADC measurements in ischemic brain tissue can be used to differentiate between reversible and irreversible ischemic lesions before reperfusion in a temporary ischemia model. We induced 45 minutes of temporary ischemia in 12 rats using the middle cerebral artery suture occlusion method. Regional changes of ADC values were serially measured in seven regions of interest in each hemisphere and evaluated by {Delta}ADC, defined as the difference between ADC value in an ischemic region and that in a contralateral homologous region. We acquired dynamic contrast-enhanced perfusion images 2 minutes before and after reperfusion to document reduced perfusion and its restoration. We confirmed the infarct area by 2,3,5-triphenyltetrazolium chloride staining 24 hours after occlusion and correlated this with the MRI studies. Recovery of initially reduced ADC values occurred only in ischemic regions where {Delta}ADC values were not below –0.25 x 10–5 cm2/sec. Although the extent of infarction at postmortem examination varied in regions with moderately decreased prereperfusion ADC values, more than 70% of regions of interest with slight declines of prereperfusion ADC values exhibited no infarction. ADC values progressively decreased after reperfusion in regions that initially had severely decreased prereperfusion ADC values, and postmortem examination always demonstrated infarction in such regions. These results suggest that measurement of {Delta}ADC can provide information that will enable the clinician to discriminate between irreversible and potentially reversible ischemic regions before reperfusion is performed.

Address correspondence and reprint requests to Dr. Yasuhiro Hasegawa, Department of Neurology, The Medical Center of Central Massachusetts-Memorial, 119 Belmont Street, Worcester, MA 01605.

Supported in part by the Harrington Neurological Research Fund.

Received November 29, 1993. Accepted in final form February 8, 1994.






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