Optimum Voxel Volume for Maximizing Contrast-to-Noise Ratio in BOLD Functional MRI

Recent studies suggest that physiological noise, which determines the SNR of the fMRI time course at commonly used spatial resolutions, is largely spatially coherent. It is theoretically shown that the ratio of such a spatially coherent physiological to thermal noise determines the optimum voxel volume for maximizing BOLD CNR, relatively independent of the size of activation.