Interactive Fiber Tracking
Real-time interactive fiber tracking provies a useful exploratory approach to estimate and visualize fiber tracts. In this approach, fibers are estimated directly from a point selected with a mouse click on a visualized sagittal, coronal or axial slice plane. To prepare interactive fiber tracking, a VMR file and a matching DDT file must be loaded first. After switching to the surface module, one or more slice cut planes must be selected. To start fiber tracking, the Fiber Tracking and Rendering dialog should be invoked by clicking the Fiber Tracking and Rendering item in the DTI menu. This sets the surface window in "fiber tracking" mode and any subsequent Ctrl-Left-Mouse-Button (Ctrl-LMB) click will be interpreted as specifying a seed point for fiber tracking. After clicking on a cut plane, you will immediately see a fiber bundle emanating from the selected seed point. Note that the appearing fibers are constructed on the fly and are not simply selected from previously calculated fiber tracts. You may start fiber tracking also directly (without opening first the Fiber Tracking and Rendering dialog) after showing a cut plane by using the Ctrl-Alt-LMB key combination. This command will call the Fiber Tracking and Rendering dialog and starts tracking from the selected seed point. After an initial Ctrl-Alt-LMB click, subsequent seeds can be specified by using the Ctrl-LMB key combination.
After clicking on a point on a slice cut plane, a set of surrounding positions is used to define multiple seed points for fiber tracking. From each of the determined seed points, tracking is performed in two opposing directions along the axis given by the voxel's largest eigenvector. All fibers tracked from the seed points are assigned to the current fiber group. Each fiber group gets its own set of properties, including a color, a visibility flag (whether the fiber group should be shown or not) and a fiber thickness display parameter. The Fiber Tracking and Rendering dialog in combination with the Fiber Table dialog allow to select and change different display options.
Different fiber visualization styles may be selected in the Rendering options field of the Fiber Tracking and Rendering dialog. As default, the Render as lines option is turned on rendering fibers as a connected set of line segments. Since this is the fastest way to render fibers, this style is the recommended visualization mode for interactive fiber tracking allowing (near) real-time display of even large amounts of fibers. To obtain more beautiful shaded renderings of fibers, switch to the Render as tubes option. This option renders fibers as a connected set of tubes with a certain diameter, which can be specified in the Tube thickness text box before creating fibers or in the Fibers Table dialog for existing fiber groups. You may start a new fiber bundle by turning on the Start new group option. You may also select a color for the fibers created under the new fiber group by clicking on the Color button. You may also enter a name for the new fiber group by editing the Name text field. Fibers of a group are shown in the group color in case that the Show color of fiber groups option is selected.This option aids in separating different fiber bundles from each other. The snapshot above shows two interactively tracked fiber bundles shown in the specified fiber group colors (blue for bundle 1, yellow for bundle 2). In case that the Show color of fiber elements (direction coding) option is turned on instead, fiber segments are assigned a color as determined by the orientation with respect to the cardinal X, Y, Z axes. If you want to (temporarily) hide fibers from view, deselect the Show fibers option.
Copyright © 2021 Rainer Goebel. All rights reserved.