A reliable and time-saving semiautomatic spike-template-based analysis of interictal EEG-fMRI.
OBJECTIVE
A prerequisite for the implementation of interictal electroencephalography-correlated functional magnetic resonance imaging (EEG-fMRI) in the presurgical work-up for epilepsy surgery is straightforward processing. We propose a new semi-automatic method as alternative for the challenging and time-consuming visual spike identification.


METHODS
Our method starts from a patient-specific spike-template, built by averaging spikes recorded on the EEG outside the scanner. Spatiotemporal cross-correlations between the template and the EEG measured during fMRI were calculated. To minimize false-positive detections, this time course of cross-correlations was binarized by means of a spike-template-specific threshold determined in healthy controls. To inform our model for statistical parametric mapping, this binarized regressor was convolved with the canonical hemodynamic response function. We validated our "template-based" method in 21 adult patients with refractory focal epilepsy with a well-defined epileptogenic zone and interictal spikes during EEG-fMRI. Sensitivity and specificity for detecting the epileptogenic zone were calculated and represented in receiver operating characteristic (ROC) curves. Our approach was compared with a previously proposed semiautomatic "topography-based" method that used the topographic amplitude distribution of spikes as a starting point for correlation-based fitting.


RESULTS
Good diagnostic performance could be reached with our template-based method. The optimal area under the ROC curve was 0.77. Diagnostic performance of the topography-based method was overall low.


CONCLUSIONS
Our new template-based method is more standardized and time-saving than visual spike identification on intra-scanner EEG recordings, and preserves good diagnostic performance for detecting the epileptogenic zone.
Laboratory for Epilepsy Research, UZ Leuven & KU Leuven, Leuven, Belgium; Medical Imaging Research Center, UZ Leuven & KU Leuven, Leuven, Belgium.
Simon
S
Tousseyn
Patrick
P
Dupont
David
D
Robben
Karolien
K
Goffin
Stefan
S
Sunaert
Wim
W
Van Paesschen
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000098:blood supply* / Q000503:physiopathology*; D001931:Brain Mapping; D004569:Electroencephalography; D004827:Epilepsy / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D012372:ROC Curve; D012680:Sensitivity and Specificity; D017603:Signal Detection, Psychological; D055815:Young Adult
D010100:Oxygen
EEG-fMRI; Epilepsy; Focus localization; Presurgical evaluation; Semiautomatic; Spike detection