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Diffusion tensor MR imaging in diffuse axonal injury
Konstantinos Arfanakis1, Victor M Haughton, John D Carew
1Department of Medical Physics, University of Wisconsin, Madison 53706-1532, USA.
Background And Purpose:
Disruption of the cytoskeletal network and axonal membranes characterizes diffuse axonal injury (DAI) in the first few hours after traumatic brain injury. Histologic abnormalities seen in DAI hypothetically decrease the diffusion along axons and increase the diffusion in directions perpendicular to them. DAI therefore is hypothetically associated in the short term with decreased diffusion anisotropy. We tested this hypothesis by measuring the diffusion characteristics of traumatized brain tissue with use of diffusion tensor MR imaging.
Methods:
Five patients with mild traumatic brain injuries and 10 control subjects were studied with CT, conventional MR imaging, and diffusion tensor imaging. All patients were examined within 24 hours of injury. In each participant, diffusion tensor indices from homologous normal-appearing white matter regions of both hemispheres were compared. These indices were also compared between homologous regions of each patient and the control group. In two patients, diffusion tensor images from the immediate post-trauma period were compared with those at 1 month follow-up.
Results:
Patients displayed significant reduction of diffusion anisotropy in several regions compared with the homologous ones in the contralateral hemisphere. Such differences were not observed in the control subjects. Significant reduction of diffusion anisotropy was also detected when diffusion tensor results from the patients were compared with those of the controls. This reduction was often less evident 1 month after injury.
Conclusion:
White matter regions with reduced anisotropy are detected in the first 24 hours after traumatic brain injury. Therefore, diffusion tensor imaging may be a powerful technique for in vivo detection of DAI.
Insights
Diffusion tensor imaging detects reduced diffusion anisotropy in traumatic brain injury patients within 24 hours. This finding aids in the in vivo detection of diffuse axonal injury (DAI).
Area of Science:
- Neuroimaging
- Traumatic Brain Injury Research
- Biomedical Engineering
Background:
- Diffuse axonal injury (DAI) involves cytoskeletal and axonal membrane disruption post-traumatic brain injury (TBI).
- DAI hypothetically reduces axonal diffusion and increases perpendicular diffusion, leading to decreased diffusion anisotropy.
- Diffusion tensor imaging (DTI) measures diffusion characteristics to assess white matter integrity.
Purpose of the Study:
- To test the hypothesis that DAI is associated with decreased diffusion anisotropy in the short term.
- To evaluate the utility of DTI for detecting DAI in vivo.
Main Methods:
- Studied 5 mild TBI patients and 10 controls using CT, conventional MRI, and DTI within 24 hours of injury.
- Compared diffusion tensor indices between homologous white matter regions within patients and between patients and controls.
- Assessed changes in DTI metrics at 1-month follow-up in two patients.
Main Results:
- Patients showed significantly reduced diffusion anisotropy in multiple white matter regions compared to contralateral homologous areas.
- Reduced diffusion anisotropy was also observed when comparing TBI patients to control subjects.
- This reduction in anisotropy was less pronounced at the 1-month follow-up.
Conclusions:
- Reduced white matter anisotropy is detectable within 24 hours after TBI.
- DTI is a powerful tool for the in vivo detection of diffuse axonal injury.
- DTI findings may normalize over time, suggesting potential for monitoring recovery.