Functional MRI neuroimaging: the effect of slice thickness and echo time

Summary form only given. To understand the number of partitions necessary to achieve an adequate sampling density and to determine when it is appropriate to use 3-D or 2-D techniques, the authors have characterized observed signal changes during stimulation of the primary visual cortex as a function of slice thickness and echo time for a gradient echo acquisition technique that is sensitive to changes in regional blood oxygenation. As expected, there is an increase in total signal with thicker slices. However, the increase in signal intensity does not lead directly to improvements in the detectability of signal change (percent change divided by standard error of the mean). Even though absolute signal intensity decreases with longer echo times, the percent signal change generally increase with increasing echo time. This effect is diminished as slice thickness increases. For time-resolved echo-planar neuroimaging of the visual cortex at 1.5 T, a slice thickness of 4 to 7 mm is acceptable