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Re: [shapeworks-users] Shapeworks does not seem to properly place particles on specimens with different sizes. How can we fix that?


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  • From: "Savriama, Yoland F" <yoland.savriama@helsinki.fi>
  • To: Praful Agrawal <prafulag@cs.utah.edu>, "Shapeworks-users@sci.utah.edu" <Shapeworks-users@sci.utah.edu>
  • Subject: Re: [shapeworks-users] Shapeworks does not seem to properly place particles on specimens with different sizes. How can we fix that?
  • Date: Thu, 18 May 2017 09:24:38 +0000
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Hi Praful!


Thanks a lot for your quick and thorough message! 


Yes, I have read that there is a Procrustes superimposition included in ShapeWorks. I used the .wpts coordinates to redo a PCA on the femur data and I found the same values for eigenvectors and eigenvalues. 


We work on volume data and we decided to save these data as .tiff stack that are later converted as .nrrd files via Fiji. So, we actually align the .tiff stacks using one of Amira's tools for alignment (center) and we used a common bounding box to produce .tiff stacks with the same dimensions. However, way too many extra slices (empty) are produced for the smallest specimens. I can later reslice them using "slice keeper" in fiji to keep the same number of slices for all specimens. This is way to reduce file sizes, but it is a quite tedious one. We also have them as .ply files and we can align these surfaces using an algorithm similar to the ICP one that you mention here. 


I was wondering if you happen to know a better pipeline to import these data in ShapeWorks (from volume or surface data, aligned and converted as .nrrd files)?


Also, is there a way to convert .ply files or save them as .nrrd files?


I much appreciate your recommandations. I have tried several settings (there was even a case in which the smallest specimen has been flipped) and I am sending you screenshots of one setting which gives sensible results, albeit the coverage is still not optimum. You can see that some regions are left empty. Please, see attached screenshots for the reconstructed shapes and the shape changes exhibited for extreme negative and positive values of PC1.


Best!

Yoland



From: Praful Agrawal <prafulag@cs.utah.edu>
Sent: Monday, May 15, 2017 7:23:30 PM
To: shapeworks-users@sci.utah.edu; Savriama, Yoland F
Subject: Re: [shapeworks-users] Shapeworks does not seem to properly place particles on specimens with different sizes. How can we fix that?
 
Okay.

Shapeworks has an implicit procrustes scaling for shapes with varying sizes, the points being visualized are local coordinate points (local to the input shapes). If world coordinate points (transformed space with all shapes scaled and rigid aligned by generalized procrustes) are visualized, they should have common size.

Usually in our experiments, we do an ICP registration to align all shapes (Amira should have an option). Once aligned, it should be okay to run in ShapeWorks.

Following parameters should be tuned for good correspondence model:

Relative Weighting - Should be tuned if mean shape looks somewhat like the expected shape with some bad corresponding regions (indicated by distortions in mean shape)
Starting Regularization -
Ending Regularization  - These should be tuned if mean shape seems completely random.

Also, I would recommend to use atleast 2-3K iterations.

Good Luck!
Praful

On May 15, 2017, at 9:17 AM, Savriama, Yoland F <yoland.savriama@helsinki.fi> wrote:

Hi Praful,

Thanks for getting in touch. Here are the snapshots of the parameters for Grooming and Optimize.

Best,
Yoland
From: Praful Agrawal <prafulag@cs.utah.edu>
Sent: Monday, May 15, 2017 5:49:44 PM
To: shapeworks-users@sci.utah.edu; Savriama, Yoland F
Subject: Re: [shapeworks-users] Shapeworks does not seem to properly place particles on specimens with different sizes. How can we fix that?
 
Hi Yoland,

Please share the snapshot of Optimization tab with parameters, it could be very helpful in debugging these results.

Thanks,
Praful
On May 15, 2017, at 8:39 AM, Savriama, Yoland F <yoland.savriama@helsinki.fi> wrote:


Greetings,

I have been recently using the latest version of ShapeWorksStudio on a Mac Book Pro with Mac Os X 10.16.6 and I am dealing with brains of snakes and lizards. The volumes have been reconstructed and aligned with Amira. In our dataset, brains can have very different shapes and also very different sizes. When I use 200 particles placed on a couple of specimens, it is obvious that the coverage is more than enough for the smallest specimen, and it is problematic for the much larger one since it is clear that the coverage is not the same for both specimens. 

Please see attached screenshots that illustrate this issue.

I was wondering if all specimens have to be somehow scaled to a common unit size such that they can properly treated in ShapeWorks? If so, could you explain to me the procedure for this scaling in Amira, please?

Also, does the color of particles have a meaning? For instance, does the color reflect the "homology" in placing a given particle on different surfaces?

Best wishes,
Yoland Savriama, PhD
P/O Jernvall
Institute of Biotechnology
P.O. Box 56 (Viikinkaari 5)
FIN-00014 FINLAND

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