Fig 1.
An example of the input data and ROIs used for fiber tracking.
The seeding/target ROIs are overlaid on registered anatomical images. (A-C) ROIs in the axial, sagittal and coronal planes include the LGN seed (blue), V1 target (red) and waypoint (green) areas, a frontal/midline exclusion zone (yellow) and an atlas-defined OR probability map (red/yellow) overlaid on the MNI152 standard brain. (D-F) Representative axial, sagittal and coronal slices of the ADC map. (G-I) Representative axial, sagittal, and coronal slices of an FA map. (J-L) FOD plots for each voxel and the optic radiation (yellow) overlaid on the FA map in the region of Meyer’s loop indicated by the cross-hairs in (G-I).
Fig 2.
Complete CSD and B&S (probtrackX) tractography results for a single subject.
(A) Without using a threshold to remove voxels of low connectivity. The unthresholded CSD streamline reconstructions of the OR (yellow) in three planes are shown together with whole brain color-coded CSD tracks for visual reference. (B) The unthresholded B&S SDIs (green) overlaid on anatomical T1 weighted images in three planes. (C) Final thresholded CSD SDI. (D) Final thresholded B&S SDI. An optimal threshold (Table 1) was used to remove voxels of low connectivity such that the median FPR across all patients was 2.1%.
Table 1.
Tractography results and ROC analysis compared to previous studies.
Fig 3.
Left optic radiation SDIs for a single subject.
The OR of the same subject as in Fig. 2 is shown with no threshold (left), the optimal SDI threshold (middle) and 10 times the optimal SDI threshold (right). (A) SDIs based on the CSD model. (B) SDIs based on the B&S model.
Fig 4.
Group results of optic radiation fiber tracking.
(A) The mean ROC curves with 95% confidence intervals (dashed lines) for the CSD and B&S based tractography. A line of unity is shown for comparison. (B) Box plot of the AUCs for the CSD and B&S tractography algorithms. The CSD algorithm resulted in a significantly (p<0.05) greater AUC than the B&S algorithm. (C) Box plots of the MLA-TP distances as calculated from the CSD and B&S thresholded streamline density maps. The dashed line indicates the median distance calculated from a previous dissection study [2].
Table 2.
Distances between the anterior tip of Meyer’s loop and anatomical landmarks.
Fig 5.
Dependence of OR tractography results on the number of diffusion directions in a single subject.
Tractography was performed on a single subject from the human connectome project (www.humanconnectomeproject.org). The CSD tractography was performed on pre-processed 90 direction diffusion data, with a b-value of 3000 and 1.25mm isotropic voxel resolution, subsampled between 20 and 88 directions. The sensitivity, specificity and similarity indices were all computed using the fully sampled DWI data as the gold standard. All MLA-TP distances were within one standard deviation (dashed lines) of the median dissection distance (solid line).