Assessment of Brain SPECT in Epilepsy with a New Subtraction and 3D Display Program
Ictal SPECT has an established role in the localisation of seizures for the pre-surgical evaluation of patients. A new subtraction program was used to re-assess SPECT studies obtained in 9 patients with temporal lobe epilepsy who presented to the comprehensive epilepsy program at the Queen Elizabeth Hospital between 2000 and 2007 for video-telemetry monitoring. Two Ictal and 7 Postictal studies were obtained. The original reports from visual interpretation without subtraction were re-assessed after subtraction using an enhanced 3D image display. Subtraction was performed after coregistration of the Ictal to the Inter-Ictal scan and count normalization. The Ictal and Inter-ictal scans and their positive and negative difference images were displayed together in 4 linked panels with mouse-driven browsing of their transverse, sagittal and coronal sections. After a brief training period, two nuclear medicine physicians were asked to generate new reports, given the same patient history as for the original report. When all new reports were completed, they were compared with the original reports. The multi-panel 3D display was well accepted by the physicians. In each postictal and one ictal study, lateralising or localising changes and/or evidence of spread to the contra-lateral temporal lobe was seen that was not detected on the visually interpreted studies. The other Ictal subtraction study agreed with the visually interpreted SPECT. SPECT difference imaging performed by a locally written computer program appears to aid in SPECT interpretation in the pre-surgical evaluation of a small group of patients with temporal lobe epilepsy.