APPLICATION OF HIGH-FIELD SPECTROSCOPIC IMAGING IN THE EVALUATION OF TEMPORAL-LOBE EPILEPSY

Previous spectroscopic imaging studies of temporal lobe epilepsy have used comparisons of metabolite content or ratios to lateralize the sei zure focus. Although highly successful, these studies have shown signi ficant variations within each of the groups of healthy subjects and pa tients. This variation may arise from the natural differences seen in metabolite concentration in gray and white matter, the complex anatomy seen about the hippocampus, and the large voxels typically employed a t 1.5 T. Using a 4.1T whole body system, we have acquired spectroscopi c images with 0.5 cc nominal voxels (1 cc after filtering) to evaluate the regional variation in metabolite content of the hippocampus, temp oral gray and white matter, midbrain, and cerebellar vermis. Using a t hreshold value of 0.90 for CR/NAA, a value 90% of all normal hippocamp al voxels lay below, we have correctly identified the presence of epil eptogenic tissue in patients with unilateral as well as bilateral seiz ures. By using comparisons to healthy values of the CR/NAA ratio, this method enables the visualization of bilateral disease and provides in formation on the extent of gray matter involvement.