Diffusion Tensor Imaging Fiber Tractography Research Articles

Diffusion tensor imaging fiber tractography for evaluating diffuse axonal injury

Patients with Diffuse axonal injury (DAI) frequently exhibit cognitive disorders chronically. Radiologic recognition of DAI can help understand the clinical syndrome and to make treatment decisions. However, CT and conventional MRI are often normal or demonstrate lesions that are poorly related to the cognitive disorders. Recently, diffusion tensor imaging (DTI) fiber tractography has been shown to be useful in detecting various types of white matter damage. The aim of this study was to evaluate the feasibility of using DTI fiber tractography to detect lesions in DAI patients, and to correlate the DAI lesions with the cognitive disorders. We investigated two patients with chronic DAI. Both had impaired intelligence, as well as attention and memory disorders that restricted their activities of daily living. In both patients, DTI fiber tractography revealed interruption of the white matter fibers in the corpus collosum and the fornix, while no lesions were found on conventional MRI. The interruption of the fornix which involves the circuit of Papez potentially correlates with the memory disorder. Therefore, DTI fiber tractography may be a useful technique for the evaluation of DAI patients with cognitive disorders.

Diffusion Tensor Imaging in the Corpus Callosum in Children after Moderate to Severe Traumatic Brain Injury

Diffusion tensor imaging (DTI) is a recent imaging technique that assesses the microstructure of the cerebral white matter (WM) based on anisotropic diffusion (i.e., water molecules move faster in parallel to nerve fibers than perpendicular to them). Fractional anisotropy (FA), which ranges from 0 to 1.0, increases with myelination of WM tracts and is sensitive to diffuse axonal injury (DAI) in adults with traumatic brain injury (TBI). However, previous DTI studies of pediatric TBI were case reports without detailed outcome measures. Using mean FA derived from DTI fiber tractography, we compared DTI findings of the corpus callosum for 16 children who were at least 1 year (mean 3.1 years) post-severe TBI and individually matched, uninjured children. Interexaminer and intraexaminer reliability in measuring FA was satisfactory. FA was significantly lower in the patients for the genu, body, and splenium of the corpus callosum. Higher FA was related to increased cognitive processing speed and faster interference resolution on an inhibition task. In the TBI patients, higher FA was related to better functional outcome as measured by the dichotomized Glasgow Outcome Scale (GOS). FA also increased as a function of the area of specific regions of the corpus callosum such as the genu and splenium, and FA in the splenium was reduced with greater volume of lesions in this region. DTI may be useful in identifying biomarkers related to DAI and outcome of TBI in children.

Diffusion Tensor Imaging with Three-dimensional Fiber Tractography of Traumatic Axonal Shearing Injury: An Imaging Correlate for the Posterior Callosal "Disconnection" Syndrome: Case Report.

Abstract OBJECTIVE: To demonstrate that magnetic resonance diffusion tensor imaging (DTI) with three-dimensional (3-D) fiber tractography can visualize traumatic axonal shearing injury that results in posterior callosal disconnection syndrome. METHODS: A 22-year-old man underwent serial magnetic resonance imaging 3 days and 12 weeks after blunt head injury. The magnetic resonance images included whole-brain DTI acquired with a single-shot spin echo echoplanar sequence. 3-D DTI fiber tractography of the splenium of the corpus callosum was performed. Quantitative DTI parameters, including apparent diffusion coefficient and fractional anisotropy, from the site of splenial injury were compared with those of a normal adult male volunteer. RESULTS: Conventional magnetic resonance images revealed findings of diffuse axonal injury, including a lesion at the midline of the splenium of the corpus callosum. DTI performed 3 days posttrauma revealed that the splenial lesion had reduced apparent diffusion coefficient and fractional anisotropy, reflecting a large decrease in the magnitude of diffusion parallel to the white matter fibers, which had partially recovered as revealed by follow-up DTI 12 weeks postinjury. 3-D tractography revealed an interruption of the white matter fibers in the posteroinferior aspect of the splenium that correlated with the patient's left hemialexia, a functional deficit caused by disconnection of the right visual cortex from the language centers of the dominant left hemisphere. CONCLUSION: DTI with 3-D fiber tractography can visualize acute axonal shearing injury, which may have prognostic value for the cognitive and neurological sequelae of traumatic brain injury.