Comparison of block and event‐related experimental designs in diffusion‐weighted functional MRI. Issue 2 (29th October 2013) - Williams, Rebecca J.
Abstract Purpose To compare diffusion‐weighted functional magnetic resonance imaging (DfMRI), a novel alternative to the blood oxygenation level‐dependent (BOLD) contrast, in a functional MRI experiment. Materials and Methods Nine participants viewed contrast reversing (7.5 Hz) black‐and‐white checkerboard stimuli using block and event‐related paradigms. DfMRI (b = 1800 mm/s2) and BOLD sequences were acquired. Four parameters describing the observed signal were assessed: percent signal change, spatial extent of the activation, the Euclidean distance between peak voxel locations, and the time‐to‐peak of the best fitting impulse response for different paradigms and sequences. Results The BOLD conditions showed a higher percent signal change relative to DfMRI; however, event‐related DfMRI showed the strongest group activation (t = 21.23, P < 0.0005). Activation was more diffuse and spatially closer to the BOLD response for DfMRI when the block design was used. DfMRIevent showed the shortest TTP (4.4 ± 0.88 sec). Conclusion The hemodynamic contribution to DfMRI may increase with the use of block designs. J. Magn. Reson. Imaging 2014;40:367–375. © 2013 Wiley Periodicals, Inc.