Inobitec DICOM Viewer

5.17. Diffusion Tensor Imaging (DTI) Mode

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Functionality is available in the Pro edition
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	Tractography results cannot be used for establishing a diagnosis

The DICOM Viewer allows you to show the result of the fiber tractography for the series of Diffusion MRI. Fig. 5.12 shows tracks which are the result of brain tractography.

Figure 5.12: Result of brain tractography

The tracks which are the result of tractography are refered to as fibers in the DICOM Viewer interface and in the User Manual.

5.17.1 Open series in DTI Mode

The tractography will be performed automatically for the series made in the DTI mode when you open it in the Multiplanar Reconstruction Mode. To display fibers over the images not made in the DTI mode (for the same study):

Open the series not made in the DTI mode.
Click the DTI button on the toolbar.
In the dialog that appears, select the series made in the DTI mode.
Click Select to display fibers over the images or Cancel to cancel.

5.17.2 Select Visible Fibers

If you want to make only some fibers visible, specify the areas through which the fibers pass as visible or invisible. Use the ROI tools from the Fibers panel. The operation of these tools is similar to using ROI from the toolbar at the top of the window (see Section 2.15.5). Note that you cannot use the ROI tools from the top toolbar to adjust the visibility of the fibers.

To make some fibers visible:

Open the series made in the DTI mode or display fibers over the series not made in the DTI mode.
Select the plane and the image in which you want to specify the area through which the target fibers pass.
Open the Segmented Structure panel by clicking the Segmented structure panel button. The Fibers panel will be located at the bottom.
Specify the desired area using the ROI tools (Rectangle , Ellipse , Polygon ) on the Fibers panel. The similar tools from the toolbar at the top of the window cannot be used to adjust the visibility of the fibers. After making the ROI, only the fibers passing through the region specified by the ROI will be visible. A new group appears on the Fibers panel. This group includes the new ROI.
To delete ROI select it and click the Remove ROI button on the Fibers panel.
To make fibers which pass through the area invisible, check the Inverse box for this ROI on the Fibers panel.
To hide ROI, check the Hide ROI box for this ROI (marked with number "1" in Fig. 5.14). To hide all the ROIs in the group, check the Hide ROIs box for this group (marked with number "2" in Fig. 5.14). To hide all the ROIs, check the Hide ROIs box in the header of the table (marked with number "3" in Fig. 5.14). The visibility of the ROI does not affect the visibility of the fibers.
Make new ROIs until you see only the target fibers. Only the fibers which pass through all the ROIs are visible (or invisible if you check the Inverse box).

Figure 5.13: The Fibers Panel

Figure 5.14: ROIs visibility

When you create the first ROI, a group is automatically created for it. New ROIs are added to the same group.

The flag to the left of the name of the ROI group and the Base fibers group allows you to display or hide the relevant fibers. If the box is checked, then the fibers are displayed. This flag does not affect the visibility of fibers, it only allows you to temporarily hide them, for example, to adjust the visibility of other fiber groups.

To make other fibers visible without changing the visibility of the fibers previously made visible:

If necessary, hide the previously displayed fibers by unchecking the box to the left of the fiber group name.
Show the base fibers by checking the box on the left of the Base fibers group.
Add a new group by clicking the Add ROI group on the Fibers panel.
Add a new ROI to make only the target fibers visible. To ensure that the ROI is in the right group, this group must be selected before making a ROI.
If necessary, show some other fibers by checking the boxes to the left of the other group names.

To show the image containing a certain ROI, select this ROI in the table and click the Find ROI button on the Fibers panel.

5.17.3 Fiber Color

By default, fibers are colored in accordance with the DEC (Direction Encoded Color) scheme. It means that the color of a fiber depends on its direction. You can set color for each group manually. Color is indicated by the pictogram in the DEC mode and by the single-colored pictogram if the color is set manually.

To set color manually, uncheck the DEC box for the group, double-click the left mouse button on the color pictogram and in the dialog button that appears, select the color or leave the default color.

To switch to the DEC scheme, check the DEC box.

5.17.4 Scalar Maps

The DICOM Viewer allows to display scalar maps for series made in the DTI mode. The following types of maps are available:

Fractional Anisotropy (FA);
Mean Diffusivity (MD);
Axial Diffusivity (AD);
Radial Diffusivity (RD).

By default, the maps are not displayed. To display the map, select the target map on the drop-down list Scalar map type (Fig. 5.15). To hide the map, select an empty value from the list.

Figure 5.15: Select scalar map

5.17.5 Saving data in a file

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Functionality is available in a separate module which is activated in the Pro edition for an extra fee
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The DICOM Viewer provides an opportunity to save ROI and groups in files with .spj extension. The procedure for saving and opening files is described in Section 6.8.3. When a file is opened, the data contained in it is added to the data from the Fibers panel.