title: Volumetric localization of epileptic activities in tuberous sclerosis using synthetic aperture magnetometry.
abstract: BACKGROUND
  Magnetoencephalography (MEG) is a novel noninvasive technique for localizing epileptic zones. Tuberous sclerosis complex (TSC) is often associated with medically refractory epilepsy with multiple epileptic zones. Surgical treatment of TSC requires accurate localization of epileptogenic tubers.
  
  
  OBJECTIVE
  The objective of this study was to introduce a new MEG technique, synthetic aperture magnetometry (SAM), to volumetrically localize irritable zones and clarify the correlations between SAM, dipole modeling and anatomical tubers.
  
  
  METHODS
  Eight pediatric patients with TSC confirmed by clinical and neuroimaging findings were retrospectively studied. MEG data were recorded using a whole-cortex CTF OMEGA system. Sleep deprivation was employed to provoke epileptiform activity. Irritable zones were localized using both dipole modeling and SAM.
  
  
  RESULTS
  MRI detected 42 tubers in the eight patients. Dipole modeling localized 28 irritable zones, and 19 out of the 28 zones were near tubers (19/42, 45%). SAM found 51 irritable zones, and 31 out of the 51 zones were near tubers (31/42, 74%). Among the 51 irritable zones determined by SAM, thirty-five zones were in 1-35 Hz, nine zones were in 35-60 Hz, and seven zones were in 60-120 Hz.
  
  
  CONCLUSIONS
  The new method, SAM, yielded very plausible equivalent sources for patients who showed anatomical tubers on MRI. Compared to conventional dipole modeling, SAM appeared to offer increased detection of irritable zones and beneficial volumetric and frequency descriptions.
authors.affiliation: Department of Diagnostic Imaging, Brain and Behavior Program, Research Institute, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Xiao
authors.forename: Jing
authors.initials: J
authors.lastname: Xiang
authors.forename: Stephanie
authors.initials: S
authors.lastname: Holowka
authors.forename: Amrita
authors.initials: A
authors.lastname: Hunjan
authors.forename: Rohit
authors.initials: R
authors.lastname: Sharma
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Otsubo
authors.forename: Sylvester
authors.initials: S
authors.lastname: Chuang
mesh_terms: D001931:Brain Mapping / Q000379:methods; D002648:Child; D002675:Child, Preschool; D004827:Epilepsy / Q000150:complications / Q000473:pathology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007223:Infant; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D012189:Retrospective Studies; D014402:Tuberous Sclerosis / Q000150:complications / Q000473:pathology*