Analysis of asymmetries in ictal and inter-ictal SPECT images for the localization of epileptic foci

In patients suffering from focal epilepsy, the region of seizure onset is characterized by hyperperfusion during the seizure (ictal state), and hypoperfusion in normal (inter-ictal) state. For diagnosis and surgery planning in epilepsy patients, ictal and inter-ictal SPECT images play a major role. However, comparison of this kind of data is a difficult clinical problem due to varying physiological uptake in brain regions. For this reason, different analysis methods such as standard reading by a clinical expert, comparison to a normal database, subtraction ictal SPECT co-registered to MRI (SISCOM) or asymmetry analysis are applied, for a comprehensive analysis of the data. The latter is usually hampered by functional and anatomical asymmetries which aggravate analysis. For this reason, a novel approach for asymmetry analysis is presented in this work, which overcomes the aforementioned limitations. The approach was successfully applied to SPECT datasets of 10 epilepsy patients.