I still have problems measuring my vessel wall thickness. Can you make marker points smaller so that a more precise measurement is possible? Due to the large marking points, there is also a great risk of measurement deviation.
Another problem with the measurement is the placement of the measuring points. I have little control over where the measuring points are placed and whether they also run in a horizontal line, since the measuring line between the marking points cannot be recognized by the vessel model.
Readjustment is made considerably more difficult.
For precise point marking, I would recommend Glyph Type -> “Cross2D” or “CrossDot2D” or “StarBurst2D” and adjustment of Line thickness, maybe also Opacity.
Measuring at a few positions will be inevitably quite inaccurate and subjective. It may be more accurate to segment the structure in 3D or draw curves on two sides and compute min/max/mean distance between the contours with a 2-3-line Python script.
Vessel wall thickness is typically not visible on clinical images (except maybe IVUS or OCT). What imaging modality do you work with? Can you post a screenshot of a typical image and what you want to measure? Why do you want to measure vessel wall thickness? What accuracy is needed? What is the resolution of your images?
Thank you for the quick response and illustration.
1) What imaging modality do you use?
my imaging modality is brain vessel angiography.
2) Can you post a screenshot of a typical image and its measurements?
Attached you can see the screenshot with the attempt to measure.
Another problem is that I cannot create an exact cutting path, but only cut freely with the scissors, which leads to serious measurement errors.
3) Why do you want to measure the wall thickness of the container?
The vessel should ultimately be printed three-dimensionally as a silicone model. With a calculated expansion behavior, which I only have from a certain wall thickness, so it is important not to get too large nominal deviations of the “shell”. (continuous and uniform wall thickness in the entire course of the vessel)
4) What accuracy is required?
I would like to see how exact the set wall thickness (e.g. 0.5 mm) actually is in different sections and places.
I try, as you recommended, to choose the “Spacing Scale” 4-6 x smaller with the help of “Crop Volume” in order to get the most exact wall thickness possible.
5) What is the resolution of your pictures?
Unfortunately, I do not know the resolution of my clinical DICOM data sets. You may be able to tell me where I can find it.
Many thanks for your help
You don’t need to cut the model. You can measure directly in slice views. You can rotate the slice views using Ctrl+Alt+Left-click-and-drag (after enabling “Slicer intersections” in crosshair toolbar), or reorient your slice view to show the exact cross-section of the vessel automatically using Cross-section analysis module (in SlicerVMTK extension).
See Volumes module / Volume information section / Spacing. To measure a distance accurately, you would need approximately a magnitude smaller voxel size (it would still mean that you have 10-20% error in the measurement, just because of limited spatial resolution). So, for accurate wall thickness measurement of 0.5mm, you would need voxel size of 0.05mm or smaller, which I think is beyond of what is feasible in current clinical practice. To improve accuracy, you may measure at thousands of positions instead of a handpicked few, by segmenting the inner and outer surface of the vessel and compute average surface-to-surface distance.