title: False-positive analysis of functional MRI during simulated deep brain stimulation: a phantom study.
abstract: OBJECTIVE
  To investigate the false-positive activations/deactivations in functional MRI (fMRI) of deep brain stimulation (DBS) using a phantom.
  
  
  METHODS
  fMRI experiments were performed on a 1.5T scanner using a single-shot gradient-echo echo-planar imaging (GE-EPI) sequence (TR/TE/FA = 6000 msec/60 msec/90 degrees ) on an agar-gel phantom inserted with DBS electrodes. During the experimental blocks, two-second stimuli were delivered during the interscan waiting time (ISWT), which was adjusted by changing the number of slices acquired within the TR (3500 msec with 30 slices and 5160 msec with 10 slices). Data were analyzed using SPM2 software, and the false-positive voxels were detected with five different P-value thresholds.
  
  
  RESULTS
  The number of false-positive voxels in experimental conditions had no significant differences from those in control conditions with either long or short ISWT, which increased with the P-value threshold from zero at P < 0.0001 to approximately 40 at P < 0.05. The pattern of increasing number of false-positive reactions along with P-value was similar between all conditions.
  
  
  CONCLUSIONS
  False-positive findings from fMRI with similar experimental design can be well controlled with a statistical threshold of P < 0.001 or tighter. The short ISWT of 3500 msec did not increase false-positive reactions compared to the long ISWT of 5160 msec.
authors.affiliation: Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Ho-Ling
authors.initials: HL
authors.lastname: Liu
authors.forename: Hsin-Mei
authors.initials: HM
authors.lastname: Chen
authors.forename: Yu-Chien
authors.initials: YC
authors.lastname: Wu
authors.forename: Siew-Na
authors.initials: SN
authors.lastname: Lim
authors.forename: Chih-Mao
authors.initials: CM
authors.lastname: Huang
authors.forename: Yuan-Yu
authors.initials: YY
authors.lastname: Hsu
authors.forename: Yau-Yau
authors.initials: YY
authors.lastname: Wai
authors.forename: Tony
authors.initials: T
authors.lastname: Wu
mesh_terms: D016477:Artifacts; D046690:Deep Brain Stimulation; D017352:Echo-Planar Imaging / Q000379:methods*; D005189:False Positive Reactions; D007091:Image Processing, Computer-Assisted / Q000379:methods; D019047:Phantoms, Imaging; D012685:Sepharose; D013997:Time Factors
chemical_list: D012685:Sepharose