We need to improve the accuracy of the alignment and we are unable to do it so far.
Can someone help us with accurate alignment/superimposition of the two scans ?
Next we need to measure the change in the bone volumes in the circled region. That is the difference of bone volume in preoperative and postoperative scans.
Perhaps you could try ROI registration around those small tube looking bits which seem to be common to both models. To be honest with some models I just cant get automatic registration to work well enough. With a bit of time I can get a better result using manual registration of the two models.
You can manually move one model around using the “Transforms” module. It helps to make the models visible in the slice view which you can do under the “Models” module. Remember that the rotation seems to always be about the origin or 0,0,0 coordinate in the 3d space. So it helps a lot if your model is centered over the origin (0,0,0) point before you start moving it. Click local coordinate button in the transforms module to keep the rotation point around the centre of the model as you move it around.
If you can accurately identify landmark points then you may use Fiducial registration wizard module (in SlicerIGT extension) to register based manually placed landmarks. See U-12 SlicerIGT tutorial for step-by-step instructions.
Dear Prof Lasso,
I used the as you suggested but this is my results and went through the tutorial as well. I can’t figure out , how to get it to transformed.
Registration result is a transform (not a transformed model node). You can apply this transform to models, markups, images, etc. to align them.
An easy way to preview transformation result and apply it to the model is to choose the moving model node in “Preview transform” section and click “Apply”.
It seems that your point pattern is not unique enough for the automatic point matching to work reliably. Disable automatic point matching and instead make sure you mark corresponding points in the same order.
It is the root mean square of the residual error after fitting the landmark points. It characterizes how well the points can be aligned by the chosen transformation. Lower values are better.
According to the opinion of the guys here which you think is better aligned ?
And my second problem is to measure the difference in Volume ? (this is the old photo but the idea remains the same to ilustrate where exactly i want the volume difference in )
Also i want to create a colour map like this one using 3D Slicer. (this was not created with the 3D Slicer)
I tried the https://www.youtube.com/watch?v=FCCa2A77fV8 but i cannot find the 3Derror metric plugin in my slicer as shown in the video here. So i dont’ know how to proceed.
Looking for the help again by anyone who is interested.
We need to improve the accuracy of the alignment and we are unable to do it so far.
Can someone help us with accurate alignment/superimposition of the two scans ?
Next we need to measure the change in the bone volumes in the circled region. That is the difference of bone volume in preoperative and postoperative scans.
Current surface-to-surface methods require cutting off non-common surfaces, which will be much easier with the new surface cutting module that @Sunderlandkyl is working on (that will allow cutting with plane widgets and surface curves).
There is also the option of doing landmark registration.
Integration of more robust surface matching algorithm from OpenCV could allow surface matching without the need to cut off non-common surfaces - this should not be too much work, but would require dedicated funding (or maybe you may ask SlicerCMF developers if it is potentially in the scope of their project).
Volume measurement: You need to register the surfaces, then close them (for example, cut off excess parts, thicken it using vtkLinearExtrusionFilter, then cut off the back side). We did this for surface-scan based volumetric fat resorption monitoring after breast lipofilling (see details in this thesis and implementation in this repository). It would be not too hard to adapt this to dental scans, but probably would require dedicated project. SlicerCMF and others, such as @cpinter might be potentially interested in collaborating or could help out if you can secure some funding.
Volume measurement between two intraoral or breast STL files which are generally not closed need manual adjustments to close the surface…
In the thesis provided an extrusion of the surface was performed. Wouldn’t bridging (joining) the two surfaces provide the same results in case you have multiple follow up scans e.g. to measure postop swelling and would like to detect the % reduction over time?
