Figure 9.

Application of the DISCONNECT segmentation technique to the corpus callosum (CC) and fornix (Fx) fiber bundles. (A-D) Fiber tracts that terminate within the CC and Fx are dissected using the DISCONNECT segmentation technique in control B (A, C) and the traumatic coma patient (B, D) and color-coded yellow. CC fiber tract terminations are shown from a right lateral view in (A, B) and Fx fiber tract terminations are shown from a left lateral view in (C, D). Tract terminations (yellow end-points) are superimposed upon the CC (pink) and Fx (turquoise) regions of interest, respectively. Each region of interest is rendered in 3 dimensions and is semi-transparent so that the tract terminations can be seen within it. (Yellow end-points outside of the CC and Fx represent the other ends of the fiber tracts that are disrupted within these regions.) The traumatic coma patient’s Fx hemorrhage (Hem, red) is rendered in 3-dimensions and shown in (D) to demonstrate the presence of both hemorrhagic and non-hemorrhagic axonal injury within the Fx. More disconnected yellow tract end-points are seen in the CC and Fx of the traumatic coma patient than in the CC and Fx of the control. Tract terminations in the control are localized to the borders of the CC (arrows, A) and Fx (arrows, C), suggesting a technical artifact (i.e. volume averaging) due to the inability of HARDI tractography to recognize tract continuity within voxels that contain both white matter and adjacent non-white matter structures (i.e. cerebrospinal fluid).