| Mild traumatic brain injury (MTBI) is a major public health concern in the United States for which conventional magnetic resonance imaging (MRI) and computerized tomography are unable to detect any evidence of neuronal tissue damage capable of explaining long-term or permanently disabling cognitive impairment in patients. The purpose of this dissertation was to apply three quantitative MRI techniques to study the thalamus and white matter in MTBI patients, which included diffusion tensor imaging (DTI) and diffusional kurtosis imaging (DKI), two previously developed structural approaches, and segmented true-fast imaging with steady-state precession (True-FISP) arterial spin-labeling (ASL), a newly developed functional approach, and determine whether they can be used complimentarily for the detection of brain injury and early prediction of cognitive outcome. Three studies were conducted, one investigation to determine if segmented True-FISP ASL can be used to measure perfusion in the thalamus and a second cross-sectional investigation and a third longitudinal investigation to determine if in MTBI patients DTI, DKI, and ASL can be used to detect the presence, if any, and extent of disease related differences compared to controls in the thalamus and white matter and associations with tests for neuropsychological performance. It was found that segmented True-FISP ASL provided estimates for average absolute perfusion in the thalamus which are in agreement with accepted mean baselines and that in MTBI patients DTI, DKI, and ASL measures showed significant cross-sectional and longitudinal differences compared to controls in the thalamus and various white matter regions while cognitive impairment was significantly associated with DKI measures in the thalamus. In conclusion, these results suggest that segmented True-FISP ASL is a practical and quantitative technique suitable for measurement of perfusion in the thalamus and that the combined use of DTI, DKI, and ASL provides complementary information about the thalamus and white matter in MTBI patients which might be useful for investigating dynamical changes over a short follow-up period and early prediction of long-term or permanent brain damage and cognitive outcome. |
