R. Edward Hogan

DEPARTMENT OF Neurology
Keywords: epilepsy, seizures, MRI, SPECT

For MRI analysis, we employ computational anatomy, general pattern theory, and other mathematical principles to provide an analytic framework and tools for studying structures, such as the hippocampus, using large-deformation high-dimensional mapping (HDM-LD). HDM-LD is a semi-automated technique that can generate highly reproducible results in patients with epilepsy, and enables surface rendering of structures at a greater resolution than the initially acquired images. We have documented that HDM-LD shows accentuated areas of change in the hippocampal regions most affected in mesial temporal sclerosis, a cause of refractory epileptic seizures. Future areas of research will involve application of HDM-LD to other brain structures in patients with epilepsy. Important potential clinical applications for HDM-LD include measurements of neuroanatomical brain changes to assist in diagnosis of different types of epilepsy, and to more precisely document disease progression in patients with chronic epilepsy.

Single photon emission computed tomography (SPECT) allows measurement of brain cerebral blood flow perfusion, which correlates well with the electrographic pattern of epileptic seizures. For SPECT scanning, we apply computer-aided methods of post-image acquisition processing of ictal and interictal SPECT images, including subtraction ictal SPECT and subtraction ictal SPECT coregistered to MRI (SISCOM) to improve the clinical usefulness of SPECT. Such techniques “normalize” pixel values between ictal and interictal SPECT images and enable quantization of differences between images. We have also developed the technique of composite SISCOM, which uses non-linear coregistration of groups of subtraction SPECT images to form a single, composite image. This technique allows investigation of ictal perfusion changes common to larger numbers of patients with MTLE, which has important implications in interpretation of SPECT studies for clinical use in localizing the region of seizure onset, and defining neuronal networks involved in epileptic seizures.