Different types of tissue may be found in a single voxel (partial volume effects), resulting in a reduction in the value of anisotropy . Partial volume effects constitute a problem for fibre tracking techniques. The problem may be accentuated in short fibre tracts and in those close to grey matter, where white matter tends to thin out and anisotropy to diminish. Addressing partial volume effects requires spatial resolution to be increased, thus reducing the SNR. As in the previous case, the solution lies in defining the noise level tolerated by the algorithm used and in adjusting the resolution and acquisition time of the MR image.
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