Fiber estimation errors incurred from truncated sampling in q-space diffusion magnetic resonance imaging

ABSTRACT The effect of truncated sphere sampling commonly used in Diffusion Spectrum Imaging to estimate single fiber orientation errors is simulated using fully-sampled (7x7x7) q-space data (343 samples), truncated sphere sampling (203 samples), and zero-padding (to 21x21x21 samples), in both noise-free and noisy (SNR = 30) scenarios. We show that the error of resolving a single fiber direction depends on the fiber orientation relative to the “corners of q-space”, which are not sampled when truncated sampling schemes are used, and th at corner-samples help reduce the error in estimating a single fiber orientation (mean error 3.5° versus 3.9° for the noise case and zero-padding used). As truncated sphere sampling requires 40% less acquisition time, its use could jus tify the small increase in error (0.4°). A simulation of the FiberCup phantom was used to assess the significance of truncated sampling on fiber orientation estimation errors over a continuous space of voxels by examining differences in resulting tractography. Keywords: diffusion spectrum imaging, truncated sphere sampling, fiber estimation errors, simulated FiberCup phantom, tractography