title: Signal fluctuations induced by non-T1-related confounds in variable TR fMRI experiments.
abstract: OBJECTIVE
  To assess and model signal fluctuations induced by non-T(1)-related confounds in variable repetition time (TR) functional magnetic resonance imaging (fMRI) and to develop a compensation procedure to correct for the non-T(1)-related artifacts.
  
  
  METHODS
  Radiofrequency disabled volume gradient sequences were effected at variable offsets between actual image acquisitions, enabling perturbation of the measurement system without perturbing longitudinal magnetization, allowing the study of non-T(1)-related confounds that may arise in variable TR experiments. Three imaging sessions utilizing a daily quality assurance (DQA) phantom were conducted to assess the signal fluctuations, which were then modeled as a second-order system. A modified projection procedure was implemented to correct for signal fluctuations arising from non-T(1)-related confounds, and statistical analysis was performed to assess the significance of the artifacts with and without compensation.
  
  
  RESULTS
  Assessment using phantom data reveals that the signal fluctuations induced by non-T(1)-related confounds was consistent in shape across the phantom and well-modeled by a second-order system. The phantom exhibited significant spurious detections (at P < 0.01) almost uniformly across the central slices of the phantom.
  
  
  CONCLUSIONS
  Second-order system modeling and compensation of non-T(1)-related confounds achieves significant reduction of spurious detection of fMRI activity in a phantom.
authors.affiliation: School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana, USA. hu@ecn.purdue.edu
authors.forename: Shuowen
authors.initials: S
authors.lastname: Hu
authors.forename: Olumide
authors.initials: O
authors.lastname: Olulade
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Tamer
authors.forename: Wen-Ming
authors.initials: WM
authors.lastname: Luh
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Talavage
mesh_terms: D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008954:Models, Biological; D015233:Models, Statistical; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity