Abstract
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Objectives Accurate localisation of epileptogenic focus is crucial in epilepsy surgery. Subtraction Ictal SPECT Co-registered to MRI (SISCOM) method is most often used, but lacks of specificity, in particular in frontal epilepsia.This study assessed whether multifractal analysis helps identifying the foci.
Methods A multifractal analysis has been developed as follows: a Hölder exponent, calculated for each voxel, on interictal and ictal SPECT series, was correlated to grey level intensity in a supervised classification method (Support Vector Machines).This method was applied to 13 patients with refractory temporal lobe epilepsy. Interictal and ictal cerebral perfusion images of Tc-99m HMPAO-SPECT were acquired on a dedicated brain camera (Tomomatic 564 ; Medimatic Inc.). The results were compared to those from SISCOM and with an expert interpretation.
Results Hyperperfusion areas were well identified in 12 of 13 cases. The foci were more accurately located and defined than those obtained by SISCOM. Interestingly, this tool was less operator-dependent, since it requires no threshold.
Conclusions The multifractal analysis enables identifying the area highly likely to be the epileptogenic focus (previous study using fractal analysis only targeted an interface point). Given these encouraging results, we plan to investigate the robustness of the method using synthetic data and to extend the application to more difficult cases (i.e. frontal epilepsy).
- © 2009 by Society of Nuclear Medicine