title: MEG Frequency Analysis Depicts the Impaired Neurophysiological Condition of Ischemic Brain.
abstract: OBJECTIVE
  Quantitative imaging of neuromagnetic fields based on automated region of interest (ROI) setting was analyzed to determine the characteristics of cerebral neural activity in ischemic areas.
  
  
  METHODS
  Magnetoencephalography (MEG) was used to evaluate spontaneous neuromagnetic fields in the ischemic areas of 37 patients with unilateral internal carotid artery (ICA) occlusive disease. Voxel-based time-averaged intensity of slow waves was obtained in two frequency bands (0.3-4 Hz and 4-8 Hz) using standardized low-resolution brain electromagnetic tomography (sLORETA) modified for a quantifiable method (sLORETA-qm). ROIs were automatically applied to the anterior cerebral artery (ACA), anterior middle cerebral artery (MCAa), posterior middle cerebral artery (MCAp), and posterior cerebral artery (PCA) using statistical parametric mapping (SPM). Positron emission tomography with 15O-gas inhalation (15O-PET) was also performed to evaluate cerebral blood flow (CBF) and oxygen extraction fraction (OEF). Statistical analyses were performed using laterality index of MEG and 15O-PET in each ROI with respect to distribution and intensity.
  
  
  RESULTS
  MEG revealed statistically significant laterality in affected MCA regions, including 4-8 Hz waves in MCAa, and 0.3-4 Hz and 4-8 Hz waves in MCAp (95% confidence interval: 0.020-0.190, 0.030-0.207, and 0.034-0.213), respectively. We found that 0.3-4 Hz waves in MCAp were highly correlated with CBF in MCAa and MCAp (r = 0.74, r = 0.68, respectively), whereas 4-8 Hz waves were moderately correlated with CBF in both the MCAa and MCAp (r = 0.60, r = 0.63, respectively). We also found that 4-8 Hz waves in MCAp were statistically significant for misery perfusion identified on 15O-PET (p<0.05).
  
  
  CONCLUSIONS
  Quantitatively imaged spontaneous neuromagnetic fields using the automated ROI setting enabled clear depiction of cerebral ischemic areas. Frequency analysis may reveal unique neural activity that is distributed in the impaired vascular metabolic territory, in which the cerebral infarction has not yet been completed.
authors.affiliation: Department of Diagnostic and Interventional Radiology, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Shinichi
authors.identifier: http://orcid.org/0000-0003-4671-0342
authors.initials: S
authors.lastname: Sakamoto
authors.affiliation: Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Ikeda
authors.affiliation: Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Naohiro
authors.initials: N
authors.lastname: Tsuyuguchi
authors.affiliation: Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Takehiro
authors.initials: T
authors.lastname: Uda
authors.affiliation: Medical Imaging Business Department, Ricoh Company, Ltd., Kanazawa, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Okumura
authors.affiliation: Medical Imaging Business Department, Ricoh Company, Ltd., Kanazawa, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Asakawa
authors.affiliation: Applied Electronics Laboratory, Kanazawa Institute of Technology, Kanazawa, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Haruta
authors.affiliation: Nihon Medi-Physics Corporation, Tokyo, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Nishiyama
authors.affiliation: Department of Clinical Laboratory, Hokuto Hospital, Obihiro, Japan.
authors.forename: Toyoji
authors.initials: T
authors.lastname: Okada
authors.affiliation: Department of Neurosurgery, Hokuto Hospital, Obihiro, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Kamada
authors.affiliation: Department of Neurosurgery, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Ohata
authors.affiliation: Department of Diagnostic and Interventional Radiology, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Yukio
authors.initials: Y
authors.lastname: Miki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002545:Brain Ischemia / Q000175:diagnosis*; D001931:Brain Mapping; D002340:Carotid Artery Diseases / Q000175:diagnosis*; D002343:Carotid Artery, Internal / Q000000981:diagnostic imaging*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography