title: Single-subject voxel-based relaxometry for clinical assessment of temporal lobe epilepsy.
abstract: OBJECTIVE
  T2 relaxometry, quantitative assessment of T2 relaxation time in magnetic resonance (MR) data, typically uses manually drawn regions of interest (ROIs). This approach is limited by its subjectivity and its restricted scope of investigation. A recently developed approach called voxel-based relaxometry (VBR) provides an unbiased statistical analysis of the whole brain. Our objective was to assess the clinical utility of single-subject VBR for patients with temporal lobe epilepsy (TLE).
  
  
  METHODS
  Forty-five patients with TLE confirmed by history, EEG, and structural MRI and 25 control subjects were scanned at 3T using a modified Carr-Purcell-Meiboom-Gill MR sequence. ROIs were drawn for each patient and control subject, and measurements were made on unregistered T2 maps. VBR was performed on a single-subject basis at a significance level of alpha=0.05. Patients were grouped according to seizure focus (left mesial, right mesial, other), and whether structural MR imaging was normal or abnormal.
  
  
  RESULTS
  Up to 85% of patients in the temporal lobe groups demonstrated T2 abnormalities. VBR detected abnormalities either in equal numbers or in more patients (up to 23% more) than ROI analysis for each group. The number of detected abnormalities per patient was higher using VBR (3.38 versus 2.04, p<0.05). VBR also identified abnormalities that were missed by ROI analysis. The rate of VBR detection of abnormalities was higher for patients than controls (76% versus 36%).
  
  
  CONCLUSIONS
  VBR can be performed on single subjects with TLE and it detects considerably more abnormalities than ROI analysis. VBR may be a clinically useful tool for the detection of T2 abnormalities at the seizure focus and sites remote from it.
authors.affiliation: Department of Electrical and Computer Engineering, University of Calgary, Alberta, Canada.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Kosior
authors.forename: M Louis
authors.initials: ML
authors.lastname: Lauzon
authors.forename: Richard
authors.initials: R
authors.lastname: Frayne
authors.forename: Paolo
authors.initials: P
authors.lastname: Federico
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001931:Brain Mapping; D004569:Electroencephalography / Q000379:methods; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012063:Relaxation / Q000502:physiology*; D013702:Temporal Lobe / Q000473:pathology* / Q000503:physiopathology; D013997:Time Factors; D055815:Young Adult