Rombouts S A, Barkhof F, Hoogenraad F G, Sprenger M, Scheltens P
Department of Clinical Physics and Engineering, University Hospital, Vrije Universiteit, Amsterdam, The Netherlands.
Magn Reson Imaging. 1998;16(2):105-13. doi: 10.1016/s0730-725x(97)00253-1.
Within-subject reproducibility of visual brain activation using multislice echo planar functional magnetic resonance imaging (fMRI) was tested. Ten healthy subjects underwent fMRI with visual stimulation on three occasions: two studies in one scanning session (without repositioning); and a third study 1 h to 2 weeks later. Following a three-dimensional matching procedure, activation was measured and compared between sessions on a voxel-by-voxel basis. Data were filtered to full-width-at-half-maximum of 4.0 x 4.0 x 5.0 mm and a conservative Bonferroni-corrected significance threshold was applied to correlation maps. For reproducibility, change in centre of mass of the activated volume, a ratio of the number of pixels and a ratio of the number of overlapping pixels was calculated. Further, reproducibility was tested varying significance thresholds and at different filter widths. Average changes in centre of mass of the activated volume were 2.63 and 3.96 mm between Studies 1 and 2 and 1 and 3, respectively. The reproducibility of the number 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 increasing the filter widths increased reproducibility. It is concluded that fMRI 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 contribution of motion, repositioning errors, and true physiological changes.
采用多层回波平面功能磁共振成像（fMRI）测试了视觉脑激活的受试者内重复性。10名健康受试者接受了3次带有视觉刺激的fMRI检查：在一次扫描过程中进行两项研究（无需重新定位）；在1小时至2周后进行第三项研究。经过三维匹配程序后，逐体素测量并比较各次扫描之间的激活情况。数据被滤波至半高全宽为4.0×4.0×5.0毫米，并对相关图应用保守的Bonferroni校正显著性阈值。为了评估重复性，计算了激活体积的质心变化、像素数量比和重叠像素数量比。此外，还在不同的显著性阈值和不同的滤波宽度下测试了重复性。在研究1和研究2之间以及研究1和研究3之间，激活体积质心的平均变化分别为2.63毫米和3.96毫米。激活体素数量的重复性在研究1和研究2之间为90%，在研究1和研究3之间为88%。研究1和研究2之间重叠像素的比例为74%，研究1和研究3之间为64%。改变显著性阈值表明，在一定范围内，重叠达到最大值，增加滤波宽度可提高重复性。结论是，在配备回波平面成像的常规临床系统上，带有视觉刺激的fMRI可用于测量脑活动，且具有相当好的重复性。在区分运动、重新定位误差和真正生理变化的影响方面仍存在困难。
