False-positive analysis of functional MRI during simulated deep brain stimulation: a phantom study.
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.
Liu
Ho-Ling
HL
Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan.
Chen
Hsin-Mei
HM
Wu
Yu-Chien
YC
Lim
Siew-Na
SN
Huang
Chih-Mao
CM
Hsu
Yuan-Yu
YY
Wai
Yau-Yau
YY
Wu
Tony
T
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
D012685:Sepharose