Reproducibility of BOLD-based functional MRI obtained at 4 T

The reproducibility of activation patterns in the whole brain obtained by f unctional magnetic resonance imaging (fMRI) experiments at 4 Tesla was stud ied with a simple finger-opposition task. Six subjects performed three runs in one session, and each run was analyzed separately with the t-test as a univariate method and Fisher's linear discriminant analysis as a multivaria te method. Detrending with a first- and third-order polynomial as well as l ogarithmic transformation as preprocessing steps for the t-test were tested for their impact on reproducibility. Reproducibility across the whole brai n was studied by using scatter plots of statistical values and calculating the correlation coefficient between pairs of activation maps. In order to c ompare reproducibility of "activated" voxels across runs, subjects and mode ls, 2% of all voxels in the brain with the highest statistical values were classified as activated. The analysis of reproducible activated voxels was performed for the whole brain and within regions of interest. We found cons iderable variability in reproducibility across subjects, regions of interes t, and analysis methods. The t-test on the linear detrended data yielded be tter reproducibility than Fisher's linear discriminant analysis, and theref ore seems to be a robust although conservative method. Preliminary data ind icate that these modeling results may be reversed by preprocessing to reduc e respiratory and cardiac physiological noise effects. The reproducibility of both the position and number of activated voxels in the sensorimotor cor tex was highest, while that of the supplementary motor area was much lower, with reproducibility of the cerebellum falling in between the other two ar eas. Hum. Brain Mapping 7:267-283, 1999. (C) 1999 Wiley-Liss, Inc.