Talairach Coordinate Configuration

 

  
Figure 37: Talairach Load/Save menus

The following is the procedure to configure the Talairach Coordinate feature.

1. The first step is to input three cardinal orientation image volumes of the subject brain using the button (36-9). This is accomplished by pulling down the load menu as shown in Figure 37 and sequentially selecting each orientation menu item (i.e. Sag, Ax & Cor). As each orientation menu item is selected the file browser popup window will be displayed (See Section 5). When loaded, the image filename appears under the respective display window (36-2).
2. The contrast and brightness of the images can be adjusted using the button (36-6) to display the graphical tool as shown in Figure 13. After adjusting the LUT mapping, pressing the button (36-7) will recalculate the LUT indices as discussed in Section 8.
3. The orientations can be checked by selecting the option (36-13) as shown in Figure 38 and described in Table 4. A summary of the orientation conventions is provided below each image (36-4). Also shown in Figure 38 is the effect of the option (36-13). The relationship between the image planes is displayed as a vertical and horizontal lines as described in Table 9. When any of the planar indices (36-3) are changed, the corresponding plane of the image volume is displayed and the planar lines in the other two image display windows are moved accordingly.
4. Each of the Talairach landmarks listed in Table 8 must be specified on the indicated plane. To specify a landmark, select one of the landmark choices (36-4) and click the mouse in the corresponding planar image at the proper anatomic location. If the option (36-13), is selected a crosshair will appear to indicate the chosen location as shown in Figure 39. The images can be resized by powers of two as specified in (36-14) and landmark adjustments can be made by repeated mouse clicks. Note that the landmark crosshair only appears on the planar image where the mouse was clicked. If a planar index (36-3) is changed, the landmark crosshair will not be seen. However the line between related pairs of landmarks will continue to be displayed.
5. The landmark crosshairs can be replace with its acronym when the and options (36-13) are chosen as shown in Figure 40. The interhemispherical medial plane is calculated by the cross product of the line between the AP and PP and the line between the SP and IP. The specified AC and PC locations are then projected onto this plane. The projected AC and PC points can be seen on the Axial slice when the option (36-13) is selected. Similarly, the RM and LM points are projected normal from the medial plane at the AC location.
6. Once the landmarks are accurately specified, the option (36-13) will overlay a Talairach proportional grid on the planar images. Each particular parallelogram has a unique identifier using the axis index labeling scheme as described in Table 10. When the mouse is moved into a grid, the location of the corresponding parallelogram is displayed in field (36-12). The , and fields (36-12) display the mouse location using the image field of view.
7. To more precisely define a location in the Talairach grid, the normalized dimensions can be specified by pressing the button (36-8). The popup window (Figure 41) will then be displayed. Except for the PP dimension, each dimension is relative to the AC point. Hence the AC dimension must necessarily always be zero. The PP dimension is relative to the PC point. After entering the dimensions in the fields (41-1), the button (41-2) must be pressed. The field (36-11) will then display the mouse location in normalized dimensions.
8. When the Talairach coordinates are fully configured, the landmarks and normalized dimensions can be saved to a file using the button (37-2). Subsequently, they can be retrieved using the ``tala'' menu item under the button (37-1).

  
Table 8: Talairach Landmark Acronyms and Specification Planes.

  
Table 9: Relationship between the Horizontal and Vertical Lines of the Plns option to that of the orientation of the image plane.

  
Table 10: Talairach Grid Axis Index Labels.

  
Figure 38: Talairach Image Windows with Axis and Plns options.

  
Figure 39: Talairach Image Windows with Pts option.

  
Figure 40: Talairach Image Windows with Pts, Proj and Label options.

  
Figure 41: Talairach Dimensions popup window.