Manish Amin^{1} and Thomas Mareci^{2}

With improvements in MRI technology, more informative diffusion acquisitions can be obtained to improve tissue microstructure analysis. In this study, a Multi-shell Acquisition with Increased b-Shells and Sparse ORientations (MAISSOR) is proposed to optimize diffusion acquisition. The scheme improves diffusion signal decay fitting while simultaneously improving fiber orientation distribution1 (FOD) calculations as well as diffusivity metrics, such as those derived from diffusion tensor imaging2 (DTI).

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Figure 1: The direction and number
of shells used for each dataset. The
left image indicates the ground truth (full) dataset. The top row shows the two
MAISSOR acquisitions and the bottom row shows two common diffusion acquisitions.

Figure 2: The bar
graph shows the mean (blue bar) and standard deviation (white line) of FA across
the white matter, and the difference (orange) between the mean of the FA values
and the ground truth FA value. The differences between the FA values and the
ground truth FA value were calculated for each voxel in the voxel then averaged.

Figure 3: The top graph displays the norm differences between the FOD
spherical harmonic coefficients calculated for each dataset and the full data
set (ground truth). Bottom graph displays the Orientation error of the
principle direction of the FOD calculated using each dataset. Both the norm
differences and the orientation error were calculated in each voxel, and then
averaged across the entire white matter.

Figure 4: Signal vs.
gradient strength for the various acquisition schemes. The signal is normalized
to the value at b = 0. The graphs show the principle-direction FOD signal vs. b
in a voxel within the corpus callosum (left column) and the internal capsule
(right column). The curve was fit using
a mono-exponential fitting.