Traumatic brain injury (TBI) is associated with various neurocognitive deficits, and rapid assessment of the damage is potentially important for the prevention and treatment of these deficits. Imaging assessment of mild or moderate damage outside the primary lesion area after TBI, however, remains challenging. Magnetization transfer (MT) has clearly been underutilized in imaging the damage caused by TBI. Here, we applied the MT ratio (MTR) using sweep imaging with Fourier transformation (SWIFT) to study microstructural tissue damage in the thalamocortical pathway outside the primary lesion in a lateral fluid percussion injury rat model of TBI, 5 months after injury. MTR was decreased in layers VIb-IV of the barrel cortex and related subcortical areas, mainly indicating demyelination, which was verified by histology. The largest MTR change in the cortex was in layer VIb (−8.2%, pFDR = 0.01), and the largest MTR change in the subcortical areas was in the caudal-most portion of the internal capsule (−11.0%, pFDR < 0.005). These areas exhibited the greatest demyelination and substantial cellularity attributed to gliosis. Correlation analysis of group-averaged results from the subcortical areas revealed an excellent correlation of MTR with myelin (r2 = 0.94, p < 0.001), but no correlation with increased cellularity as detected by Nissl staining. Thus, MTR using SWIFT can be a valuable tool for the assessment of subtle changes after TBI in both cortical and subcortical areas.
Bibliographical noteFunding Information:
We are grateful for the financial support of the Emil Aaltonen Foundation, Academy of Finland, and UEF-Brain Strategic Funding from the University of Eastern Finland. Research leading to these results received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n?602102 (EPITARGET). We also thank Mrs Maarit Pulkkinen for her work on histology and Mr Jarmo Hartikainen for technical assistance and animal handling.
Copyright © 2016 John Wiley & Sons, Ltd.
- magnetization transfer
- sweep imaging with Fourier transformation
- traumatic brain injury