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Pointsets

Ordered gradient directions

The sets of gradient directions provided with Camino are computed by electrostatic energy minimization (Jansons and Alexander, Inverse Problems, 2003). We have ordered a few of these sets to improve the results from partially completed scans. For each set of N gradient directions, we search for an ordering that minimizes the electrostatic energy of the first P (where 5 < P < N) directions, i.e., we want any partial set of P directions to be as evenly spread on the sphere as possible. The complete set of directions is identical to those provided with Camino in the PointSets directory, so if the scan is fully completed, the results are still optimal.

Ordered sets for 12, 18, 30, 60 and 61 directions are available here. These can be converted to Camino scheme files with the pointset2scheme command.

If you use these directions, please cite:

Cook PA, Symms M, Boulby PA and Alexander DC, Optimal acquisition orders of diffusion-weighted MRI measurements, Journal of Magnetic Resonance Imaging, 25(5), 1051-1058, 2007.