Table 1.

Selection criteria for DTI studies in Alzheimer's disease included in the present review and additional guidelines for future studies.

Essential (inclusion criteria for this review)
DTI ACQUISITION
✓ Number of diffusion-encoding directions equal to or greater than 30
✓ Quasi-isometric voxels—ratio between in-plane resolution and slice thickness greater than 0.75, i.e., the geometry of 1.875 × 1.875 × 2.5 mm3 voxels is at the lower limit
✓ Voxels smaller than 20 mm3, i.e., image resolution 2.7 × 2.7 × 2.7 mm3 is at the upper limit
✓ Maximum b-value equal to or greater than 900 s/mm2
STUDY COHORT
✓ (i) Clinical diagnosis of probable AD (at acquisition or through clinical follow-up), (ii) positive CSF analysis for AD (iii) positive amyloid-PET, or (iv) autosomal dominantly inherited mutation carriers
✓ Number of subjects equal or greater than N = 10 in each group
DATA ANALYSIS
✓ Voxel-/cluster-wise (or region-average) whole-brain TBSS
✓ Show results for both FA and MD (at least)
✓ Demonstrate results are robust against multiple testing effects
Desirable (additional suggested criteria for future studies)
DTI ACQUISITION
+ Studies performed on a single scanner
+ Use of multiple b-values, i.e., Nb≥ 2
+ If Nb = 1, total number of measurements greater than 60, i.e., Nm > 60
+ Ensure stable S0 measurement, i.e., Nb0 ≥ 5
+ Voxels equal to or smaller than 8 mm3, i.e., image resolution 2 × 2 × 2 mm3 or finer
+ Perfect voxel symmetry (or within 90%)
DATA ANALYSIS
+ Avoidance of RS-TBSS pipelines