Radiological–pathological correlation of diffusion tensor and magnetization transfer imaging in a closed head traumatic brain injury model

Abstract

Objective Metrics of diffusion tensor imaging (DTI) and magnetization transfer imaging (MTI) can detect diffuse axonal injury in traumatic brain injury (TBI). The relationship between the changes of these imaging measures and the underlying pathologies is still relatively unknown. This study investigated the radiological-pathological correlation between these imaging techniques and immunohistochemistry using a closed head rat model of TBI. Methods TBI was performed on female rats followed longitudinally by MRI out to 30 days post-injury, with a subset of animals selected for histopathological analyses. A MRI-based finite element analysis was generated to characterize the pattern of the mechanical insult and estimate the extent of brain injury to direct the pathological correlation with imaging findings. Results DTI axial diffusivity and fractional anisotropy (FA) were sensitive to axonal integrity, while radial diffusivity showed significant correlation to the myelin compactness. FA was correlated to astrogliosis in the gray matter while mean diffusivity was correlated to increased cellularity. Secondary inflammatory responses also partly affected the changes of these DTI metrics. The magnetization transfer ratio (MTR) at 3.5 ppm demonstrated a strong correlation with both axon and myelin integrity. Decrease in MTR at 20 ppm correlated with the extent of astrogliosis in both gray and white matter. Interpretation While conventional T2-weighted MRI did not detect abnormalities following TBI, DTI and MTI afforded complementary insight into the underlying pathologies reflecting varying injury states over time, thus may substitute for histology to reveal DAI pathologies in vivo. This correlation of MRI and histology furthers understanding of the microscopic pathology underlying DTI and MTI changes in TBI.

Repetitive Model of Mild Traumatic Brain Injury Produces Cortical Abnormalities Detectable by Magnetic Resonance Diffusion Imaging, Histopathology, and Behavior

“…Closed head impact in rats resulted in reduced FA in the corpus callosum, which corresponded with axonal injury. 52 CCI in rats produces a cortical contusion lesion along with pathology in a widespread distribution of white matter tracts and corresponds with bidirectional changes in FA. 14 In this report, FA was reduced in the corpus callosum, but was increased in subcortical white matter as well as in some white matter tracts.…”

Fractal Analysis of Brain Blood Oxygenation Level Dependent (BOLD) Signals from Children with Mild Traumatic Brain Injury (mTBI)

“…A recent diffusion tensor imaging (DTI) study of mTBI patients showed decreased fractional anisotropy (FA) in the vermis compared to normal controls [33]. Lower FA has been implicated in reduction of myelin integrity, which for mTBI likely would be due to shearing forces causing micro tears in the axons.…”

“…Lower FA has been implicated in reduction of myelin integrity, which for mTBI likely would be due to shearing forces causing micro tears in the axons. [33]. They suggested that damage on these cerebellar regions could be associated with a dysfunction in primitive fear conditioning circuits [34].…”

Measuring the progression of upper motor neuron disease using diffusion MRI and its correlation with Clinical phenotype

“…There have been studies that have investigated the correlation between the DTI appearances and the underlying pathology (Tu, Williams et al 2016). Alteration of diffusivity occurs as a result of changes in microstructural tissue and fiber organization.…”

“…Alteration of diffusivity occurs as a result of changes in microstructural tissue and fiber organization. Microstructural architecture and increased cellularity were postulated to correlate with gliosis in fractional anisotropy (FA) and mean diffusivity (MD) (Tu, Williams et al 2016). Quantitative FA measures are believed to reflect changes in the myelination, fiber density and packing (Mädler, Drabycz et al 2008).…”