WITHIN-SUBJECT REPRODUCIBILITY OF VISUAL ACTIVATION PATTERNS WITH FUNCTIONAL MAGNETIC-RESONANCE-IMAGING USING MULTISLICE ECHO-PLANAR IMAGING

Within-subject reproducibility of visual brain activation using multis lice echo planar functional magnetic resonance imaging (fMRI) was test ed, Ten healthy subjects underwent fMRI with visual stimulation on thr ee occasions: two studies in one scanning session (without repositioni ng); and a third study 1 h to 2 weeks later, Following a three-dimensi onal matching procedure, activation was measured and compared between sessions on a voxel-by-voxel basis, Data were filtered to full-width-a t-half-maximum of 4.0 x 4.0 x 5.0 mm and a conservative Bonferroni-cor rected significance threshold was applied to correlation maps, For rep roducibility, change in centre of mass of the activated volume, a rati o of the number of pixels and a ratio of the number of overlapping pix els was calculated, Further, reproducibility was tested varying signif icance thresholds and at different filter widths, Average changes in c entre of mass of the activated volume were 2.63 and 3.96 mm between St udies 1 and 2 and 1 and 3, respectively, The reproducibility of the nu mber of activated voxels was 90% and 88% (Studies 1 and 2 and 1 and 3) , The ratio of overlapping pixels was 74% between Studies 1 and 2 and 64% between Studies 1 and 3, Varying the significance threshold showed that at a certain range, the overlap reached a maximum, and increasin g the filter widths increased reproducibility, It is concluded that fM RI with visual stimulation can be used to measure brain activity with reasonably good reproducibility on a routine clinical system equipped with echo planar imaging, Difficulties remain in separating the contri bution of motion, repositioning errors, and true physiological changes . (C) 1998 Elsevier Science Inc.