Task 6, Calculating statistics on VOIs

1 Select a segmented image that was produced in task 5.
2 Select VOI > Statistics Generator in the main MIPAV window. The Calculate Statistics on VOI Groups window opens and displays the VOI Selection page (Figure 1).
The VOI group list on the left of the window lists all of the VOIs that are in the image.
3 Make sure that the path and file name listed in VOI Statistic File Destination is correct. The path indicates where MIPAV should place the statistics file; the file name is the name of the statistics file.
To change the path and file name, do either of the following:

• Click Browse to navigate to the correct directory and file name.
  
• Type the correct path and file name over the current path and file name.
  

4 Select the VOIs in the VOI group list on which you want to generate statistics (Figure 1).
5 Click the right arrow. MIPAV moves the selected VOIs to the list on the right (Figure 1).
6 Select the Statistics Options tab. The Statistics Options page (Figure 2) opens.
7 Select the statistics that you want to be generated in Statistics to Calculate list.
8 Select Exclude pixels from calculation.
9 Change the value of Exclude Pixels from Between to Outside.

Figure 1. Calculate Statistics on VOI Groups window showing four VOIs that were moved to the right list

Figure 2. Statistics Options page in the Calculate Statistics on VOI Groups window

To check the intensity level of the pixels in the image, click on any point within one of the VOIs (Figure 3). MIPAV displays the intensity level at that point on the left bottom of the MIPAV main window.

Figure 3. Finding the intensity level

Example: If the intensity level of the gray matter is 2, exclude pixels outside the range 1.5-2.5 or 1.9-2.1.
The Logging page (Figure 4) opens showing a table of the statistics.
Note:If a message appears asking you whether to overwrite the file, refer to "Overwriting the VOI Statistics File".

Figure 4. Logging page in the Calculate Statistics on VOI Groups window showing a table of the generated statistics

Overwriting the VOI Statistics File If statistics were written to the statistics file in the past, a message may appear asking whether to overwrite the previous statistics table.
To overwrite the file, click Overwrite. To cancel, click Cancel, and change the file name in VOI Statistic File Destination on the VOI Selection page. To always overwrite the statistics file, either select Options > Overwrite file automatically or press Alt O. To clear the Logging page, either select Options > Clear Log Window or press Alt C.

Viewing the Talairach grid on Talairach images