Overview of MR Diffusion Tensor Imaging and Spatially Normalized FDG-PET for Diffuse Axonal Injury Patients with Cognitive Impairments

Abstract

We detected and compared brain dysfunction areas using both magnetic resonance (MR) diffusion tensor imaging (DTI) and spatially normalized ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET; statistical FDG-PET) for the patients with memory and cognitive impairments due to traumatic brain injury. A total of 70 diffuse axonal injury patients with memory and cognitive impairments (DAI patients) and 69 age-matched normal subjects were studied with DTI and statistical FDG-PET. All subjects underwent examinations with a 1.5-T Signa MRI system. We used a single-shot spin-echo echoplanar sequence for diffusion-tensor analysis. Tractographic results were analyzed with diffusion tensor visualization (dTV) software. The group analysis for fractional anisotropy (FA) was performed with the SPM99 software package. FDG-PET was performed on all patients. After PET imaging, statistical analysis using the easy Z-score imaging system (eZIS) was undertaken with processing steps that included smoothing, normalization, and Z transformation with respect to a normal database. The Z-score map was superimposed on a three-dimensional MRI brain scan. Group analysis was performed using statistical parametric mapping analysis. A decline of FA was observed around the corpus callosum in the DAI patients compared with that of normal subjects, and reduced glucose metabolism was seen in the cingulate association. These results suggest that the reduced metabolism in the cingulate cortex indicated deprived neuronal activation caused by the impaired neuronal connectivity that was revealed with DTI. Furthermore, the metabolic abnormalities in the cingulate cortex may be responsible for memory and cognitive impairments. Age-related cerebral metabolic and blood flow decline was observed in the anterior cingulate association. The clinical combination of DTI and statistical PET has a role in neuroimage interpretation for patients with memory and cognition impairments because its three-dimensional visualization allows more objective and systematic investigation.