This tutorial explains how to use the DTIChecker program (in wizard mode) to check 'multiple shot' DTI images.
Requirements
You can download the DTIChecker program in our download
section
You can download sample data here
(zip format - 26Mo)
DTIChecker can process images with the following format: GIPL (.gipl), MetaImage
(.mha), Analyze (.hdr) and GE (4 or 5)
Overview - Check your data easily in 4 steps
 Step 1 - Select DTI images for each shot |
 Step 2 - Specify DTI image parameters |
 Step 3 - Specify computation options |
 Step 4 - Compute and Display artifacts |
Wizard mode
Launch DTIChecker and Click on the 'Wizard' button
Select number of shot and corresponding DTI images
Select the number of shot you have. In our example, we have 4 shots (4 DTI
images from the same patient)
Select one or more images for every shot. Select shot number and then click
on the 'add image(s)' button.
Then, select the shot #2 and click on the 'Add image(s)' buttion and select
image(s) for the second shot.
Repeat the same thing for all the shots , then click on the 'Next >>'
button
Specify DTI parameters
Now, specify the number of gradient for your DTI images (In our case 12 directions)
If your DTI images include the baseline image, you have to check this option:
Then, click on the 'Next' button to setup computation parameters
Setup computation parameters
You can check slice artifacts for each shot. This is like an intra shot checking.
You have to adjust the '% error'.
If you decrease this parameter (for example: 20), the computation will be
very sensitive to difference.
If you put a big value (for example: 75), the computation will give you slices
with very big differences only.
In our case 35 if fine.
Note: This parameter
depends mostly on the quality of the DTI images.
You can also check if the patient moves between shots. You have to specify
the maximum translation and rotation values.
DTIChecker can create an average DTI image by combining "good slices"
for the "good shots" in one image.
If patient moves, you can register "bad shots" to make all the shot
aligned.
DTIChecker uses a rigid (3 parameters for translation + 3 parameters for rotation).
Then, click on the 'Next' button to start computation
Note:
The computation could take a long time and the program will not respond but
you have to wait.
Display
results
The first thing is to adjust min/max intensity image otherwize images could
be too dark;
To do that, you have to move sliders on the left to make the image brighter.
After a long time of computation, you will have slice checking results.
You can click on the artifact list to visualize artifact.
There are 3 types of artifacts:
- Shadow artifact: Slice missing, dark slice ...
- Bright artifact: Slice brigther thatn the others.
- Motion artifacts: Slice not at the correct position (rotation or translation)
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If you
have check, the 'inter shot' computation options. You can see if the patient
moved during the acquisition.
For example, in our data, the patient moved between shot 0 and shot 2 with
the following parameters:
Translation X: 0 mm (there is translation in the X direction)
Translation Y: 0.25 mm (there is a small translation in the Y direction)
Translation Z: 0.25 mm (there is a small translation in the Z direction)
Rotation X: -1.25 mm (there is a significant (>1mm) rotation in the X direction)
Rotation Y: 0 mm (there is no rotation in the Y direction)
Rotation Z: 0.25 mm (there is a small rotation in the Z direction)
This means that
we need to remove one of the shot0 or shot2 or we can try to register them
by using the 'register image first' option.
You can visualize a single shot by selecting which shot you want to display
