title: Fully automated quality assurance and localization of volumetric MEG for single-subject mapping.
abstract: Robust and reproducible source mapping with magnetoencephalography is particularly challenging at the individual level. We evaluated a receiver-operating characteristic reliability (ROC-r) method for automated production of volumetric MEG maps in single-subjects. ROC-r provides quality assurance comparable to that offered by goodness-of-fit (GoF) and confidence volume (CV) for equivalent current dipole (ECD) modeling.
  
  
  
  ROC-r utilizes within-session reproducibility for quality assurance, latency identification, and thresholding of volumetric source maps. We tested ROC-r on simulated and real MEG with a strongly focal source, using somatosensory evoked fields (SEFs) elicited by bilateral median nerve stimulation (MNS). For quality assurance, the ROC-r reliable fraction (FR) was compared to the ECD GoF and CV. Peak beamformer locations and latencies identified by ROC-r were compared to the ECD for co-localization accuracy.
  
  
  
  The predominant component of the SEF response occurred around 35ms, contralateral to the MNS.
  
  
  
  FR and 1/CV were more strongly correlated (mean Pearson's correlation: 0.76; 95% CI 0.60-0.87) than FR and GoF (0.65; 95% CI 0.32-0.85). There was no difference in the latency of the peak GoF (35.0+/-0.6ms), CV (34.8+/-0.7ms) and FR (35.5+/-0.8ms). The ECD fits and ROC-r peaks co-localized to within a mean (median) distance of 8.3+/-5.9mm (6.2mm).
  
  
  
  ROC-r volumetric mapping co-localized closely with the standard ECD approach. This analysis can be added to any whole-brain MEG source imaging protocol, and is especially useful for single-subject mapping. Additionally, the development of FR as an analogue to GoF or CV for volumetric mapping is a critical improvement for clinical applications.
authors.affiliation: Dalhousie University, Canada.
authors.forename: Tynan
authors.initials: T
authors.lastname: Stevens
authors.affiliation: Dalhousie University, Canada; IWK Health Centre, Canada. Electronic address: tim.bardouille@dal.ca.
authors.forename: Tim
authors.initials: T
authors.lastname: Bardouille
authors.affiliation: Dalhousie University, Canada.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Stroink
authors.affiliation: Dalhousie University, Canada.
authors.forename: Shaun
authors.initials: S
authors.lastname: Boe
authors.affiliation: Dalhousie University, Canada.
authors.forename: Steve
authors.initials: S
authors.lastname: Patterson
authors.affiliation: Dalhousie University, Canada; IWK Health Centre, Canada.
authors.forename: Steven
authors.initials: S
authors.lastname: Beyea
mesh_terms: D000328:Adult; D019540:Area Under Curve; D001921:Brain / Q000502:physiology; D001931:Brain Mapping / Q000379:methods*; D003198:Computer Simulation; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory; D005260:Female; D007839:Functional Laterality; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D008297:Male; D008475:Median Nerve / Q000502:physiology; D010363:Pattern Recognition, Automated / Q000379:methods*; D011785:Quality Assurance, Health Care / Q000379:methods*; D012372:ROC Curve; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Automated thresholds; Functional mapping; Magnetoencephalography; Quality assurance; Source localization