Task 1, Performing a semimanual transformation on datasets to the Talairach coordinate system

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Task 1, Performing a semimanual transformation on datasets to the Talairach coordinate system

Transforming, or converting, datasets into Talairach space provides scientists with the ability to identify important structures within the standard brain. The Talairach atlas is as much a reference system as it is a coordinate system.
The main steps involved in transforming a dataset into the Talairach coordinate system are:

  1. Performing anterior commissure and posterior commissure (AC-PC) alignment
  2. Transform the AC-PC image to Talairach alignment

Performing AC-PC alignment

In the Talairach system the anterior commissure is often referred as the "origin," because it is the origin of the Talairach grid. In this first semimanual task, you need to identify and set five separate landmark points, beginning with the anterior commissure. Setting these points aligns the anterior commissure and posterior commissure that forms the basis of the Talairach grid. The landmark points are:
AC superior edge-Top middle of anterior commissure
AC posterior margin-Rear middle of posterior commissure
PC inferior edge-Bottom middle of posterior commissure
First midsagittal point-Some point in the midsagittal plane; abbreviated as SG1
Another midsagittal point-Some other point in the midsagittal plane; abbreviated as SG2
When you've set these points, the Talairach grid is formed from these axes (refer to Figure1):
Y axis-Anterior commissure and posterior commissure.
Z axis-The longitudinal (interhemispheric or midsagittal) fissure is aligned to the yz plane, thus defining the z axis.
X axis-The right-left axis perpendicular to the y and z axes.

Figure 1. The x, y, and z planes in an image after AC-PC alignment


To perform AC-PC alignment
1 Open an image of the brain (Figure 2) that you want to put into Talairach space.

Figure 2. An image of a brain to be put in Talairach space


2 Select Image > Attributes > Edit Attributes. The Image Attributes dialog box opens.
3 Click Resolutions. The Resolutions page (Figure 3) appears.

Figure 3. Resolutions page in the Image Attributes dialog box


4 Check the resolutions in 1st dim., 2nd dim., and 3rd dim to make sure they are correct, change them if they are incorrect, and click Apply. 5 Click Orientation. The Orientation page (Figure 4) appears.

Figure 4. Orientations page in the Image Attributes dialog box


6 Check the orientation of the image to make sure it is correct.
Caution: Classical alignment problems that occur with images are that resolutions and orientation for the original image are not set properly.
7 Do one of the following:

  • If the orientation is correct, go to the next step.
  • If the orientation is incorrect:
    • Make the necessary changes.
    • Click Apply to apply the changes immediately.

8 Click Talairach. The Talairach page (Figure 5) appears.

Figure 5. Talairach page in the Image Attributes dialog box as it appears before mapping the image to AC-PC or Talairach space


9 Scroll down the window and notice that "1.0" or "1" appears in all of the fields in the ACPC group and the Talairach group. This data should change as a result of performing, first, the ACPC transformation on the image and, second, the Talairach transformation.

Select Algorithms and Brain Tools for Talairach Transform