The DDT file contains the eigenvalues and eigenvectors, which can be easily extracted from the DDT in Matlab. The steps are:
- Download and install BVQXtools or Neuroelf from www.neuroelf.net
- Download BVdtistats.zip (or BVdtistats Dec 20) and extract to a directory where Matlab can find it (e.g. add BVdtistats to the Matlab search path).
- Analyze your DTI data to create a VDW, DDT and FA map. Save the FA map as a VMP.
- In Matlab, go to the directory where the DDT and FA map files are.
- In Matlab, call >> BVdtistats
- The function will ask to change LUT (color coding for VMP maps). On Windows, these are located in Program Files/BrainVoyager/MapLUTs. On Mac, in /Applications/BrainVoyager/(Contents/)Resources/MapLUTs.
- The function will ask for the DDT file and FA map, and will create a new VMP containing 9 extra maps:
Cl, Cp, Cs, radial diffusivity, relative anisotropy, eigenvalue maps 1,2,3 and trace(D).
Example without changing LUTs
Example with change to LUTs
Extracting values
Specific values from a map can be viewed by loading the map of interest (select the map by ticking a box in the Browse VMP window). If you move the mouse, the values will be shown in the "info tab" in BrainVoyager. Note that although the info tab will display "FA: <value>", the displayed value is in fact the map value (i.e. Eigenvalue, radial/axial diffusivity, trace etc depending on the selected map).
Values in a VOI can also be shown, by selecting the map of interest, then go to Analysis > Region of interest analysis. Select the VOI, and then go to ROI Analysis > Options > VOI details and a text box will pop up showing the values. Again these are the values of the selected map and not FA as is indicated in the text box.
Example
In this example the second eigenvalue map was selected. The values of the test voi are displayed below.
