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Diffusion-weighted imaging differentiates ischemic tissue from traumatized tissue
C C Hanstock1, A I Faden, M R Bendall
1Department of Molecular Sciences, James Cook University, Townsville, Queensland, Australia.
Background And Purpose:
Diffusion-weighted magnetic resonance imaging (MRI) has been shown to be particularly effective in detecting early (0 to 4 hours) pathophysiological changes in localized brain regions after cerebral ischemia. The present study sought to establish whether diffusion-weighted MRI would be similarly effective in predicting outcome after traumatic brain injury.
Methods:
Diffusion-weighted MRI images and T2-weighted MRI images were obtained over 4 hours after either moderate fluid percussion-induced traumatic brain injury or unilateral carotid ligation in rats.
Results:
Diffusion-weighted MRI images of traumatic brain injury demonstrated focal regions of image hypointensity as early as 1 hour after trauma. The relative diffusion coefficient in these hypointense regions was significantly increased (P < .005) by 4 hours after trauma compared with the noninjured hemisphere, but only in the transverse plane in the x direction. In contrast, induction of diffuse, nonfocal ischemia by unilateral carotid ligation resulted in scattered regions of hyperintensity with a significant (P < .001) decrease in relative diffusion coefficient as early as 1 hour after ligation compared with the noninjured hemisphere. This decrease exhibited no directionality.
Conclusions:
We conclude that traumatic brain injury results in an increased water diffusion distance with the directionality indicative of bulk flow of extracellular fluid toward the lateral ventricles (vasogenic edema). In contrast, the decreased water diffusion distance with no apparent directionality observed in ischemia is most likely indicative of cytotoxic edema. Diffusion-weighted MRI therefore has the potential to differentiate cases of traumatic brain injury with no focal ischemia from those instances of traumatic brain injury in which focal ischemia is a complication.
Insights
Diffusion-weighted MRI can detect early changes in traumatic brain injury (TBI) and differentiate it from ischemic stroke by identifying increased water diffusion indicative of vasogenic edema in TBI.
Area of Science:
- Neuroimaging
- Biomedical Engineering
- Radiology
Background:
- Diffusion-weighted MRI (DW-MRI) effectively detects early pathophysiological changes in localized brain regions after cerebral ischemia.
- The efficacy of DW-MRI in predicting outcomes after traumatic brain injury (TBI) requires further investigation.
Purpose of the Study:
- To determine if DW-MRI can predict outcomes following traumatic brain injury.
- To compare DW-MRI findings in TBI with those in ischemic stroke.
Main Methods:
- Diffusion-weighted MRI and T2-weighted MRI images were acquired in rats after inducing traumatic brain injury or unilateral carotid ligation.
- Imaging was performed within 4 hours post-injury.
Main Results:
- Traumatic brain injury showed focal hypointensity on DW-MRI as early as 1 hour post-trauma.
- Increased relative diffusion coefficient in the transverse plane (x-direction) was observed in TBI by 4 hours.
- Ischemic stroke showed scattered hyperintensity and decreased relative diffusion coefficient without directionality.
Conclusions:
- Traumatic brain injury leads to increased water diffusion distance, suggesting vasogenic edema.
- Ischemia results in decreased water diffusion distance, indicative of cytotoxic edema.
- DW-MRI can differentiate TBI from focal ischemia, aiding in complication identification.