The Anisotropic Bias of Fractional Anisotropy in Anisotropically Acquired DTI Data

Sjoerd B. Vos¹, Max A. Viergever¹, Alexander Leemans¹

In order to reduce DTI scan time, slice thickness is often increased while maintaining a high in-plane resolution. The resulting anisotropic voxel size means that the orientation-dependent diffusion information is sampled in a higher resolution in-plane than through-plane. In this work we show that the bias in fractional anisotropy, introduced by anisotropically acquired DTI data, is dependent on the orientation of the fiber bundle of interest. Furthermore, we demonstrate that the diffusion bias is not solely determined by the anisotropy of the voxel size, but strongly depends on the relation between the fiber bundle and the data grid as well.