Fractions of white matter voxels with single and multiple fibers for different values of threshold. The ODF peak threshold was labeled as N (N ranges from 0 to 10) times standard deviation above the mean of the noise peaks. Data from subjects 1 and 2 (a, b) were acquired with the same imaging protocol No. 1, where number of diffusion directions in the 1k, 3k, 5k, and 10k shells was 64, 64, 128, and 256, respectively; data from subject 3 (c) were acquired with protocol No. 2, with 256 diffusion directions in all three shells.