Reproducibility of BOLD-based functional MRI obtained at 4 T

Abstract

The reproducibility of activation patterns in the whole brain obtained by functional magnetic resonance imaging (fMRI) experiments at 4 Tesla was studied 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 multivariate method. Detrending with a first- and third-order polynomial as well as logarithmic transformation as preprocessing steps for the t-test were tested for their impact on reproducibility. Reproducibility across the whole brain was studied by using scatter plots of statistical values and calculating the correlation coefficient between pairs of activation maps. In order to compare reproducibility of "activated" voxels across runs, subjects and models, 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 considerable variability in reproducibility across subjects, regions of interest, and analysis methods. The t-test on the linear detrended data yielded better reproducibility than Fisher's linear discriminant analysis, and therefore seems to be a robust although conservative method. Preliminary data indicate that these modeling results may be reversed by preprocessing to reduce respiratory and cardiac physiological noise effects. The reproducibility of both the position and number of activated voxels in the sensorimotor cortex was highest, while that of the supplementary motor area was much lower, with reproducibility of the cerebellum falling in between the other two areas.

Combining fMRI and DTI: A framework for exploring the limits of fMRI-guided DTI fiber tracking and for verifying DTI-based fiber tractography results

“…The individual extensions of the activated regions during specific tasks differed not only between subjects but also on an intrasubject basis when measurements were repeated, as also shown in (Liu et al, 2004;Tegeler et al, 1999;van Gelderen et al, 2005). Thus, the spherical seed region approach accounts for the individual functional neuroanatomy while providing comparable and reproducible start conditions between subjects.…”

Reproducibility of BOLD, perfusion, and CMRO2 measurements with calibrated-BOLD fMRI

“…The majority of BOLD reproducibility studies either examined: 1) the spatial reproducibility of the volume of activation (Rombouts et al 1998;Tegeler et al 1999) or 2) the stability of the dynamics of the hemodynamic response function (HRF) in the context of an event-related study (Aguirre et al 1998;Handwerker et al 2004). Our study differs from these previous studies in that it evaluates the utility of fMRI in generating robust functional response data that have direct physiological significance (%CBF, %CMRO 2 , M, n) rather than evaluating the robustness of fMRI in the context of brain mapping.…”

Motion or activity: their role in intra- and inter-subject variation in fMRI

“…Unfortunately reduction of variability by smoothing comes at the cost of reduced spatial resolution. Physiological noise correction (Hu et al, 1995) was found to increase the test-retest reproducibility at 4T (Tegeler et al, 1999).…”