Sub-millimeter fMRI at 1.5 Tesla: Correlation of high resolution with low resolution measurements

Functional magnetic resonance imaging of the visual cortex with an in-plane resolution of 0.4 x 0.4 mm(2) was performed using a simple visual stimulus resulting in clear maps of activation, A collapsing filter was used to com pare these high-resolution images with low-resolution images collected duri ng the same session. A good correspondence between the high- and low-resolu tion functional maps was found with respect to the center of localization o f activation. However, only 20% of the size of activated areas in the low-r esolution experiment was observed at high resolution, which was partly caus ed by the difference in signal-to-noise ratio. The high-resolution images p roduce signal changes much higher than the low-resolution images due to red uced partial volume effects, Additionally, the high-resolution functional m aps were compared with detailed anatomical and venous information. The acti vated areas were predominantly observed at venous vessels within the sulci with a diameter on the order of the pixel size. (C) 1999 Wiley-Liss, Inc.