# Problem with CT reconstruction

**URL:** <https://castor-project.discourse.group/t/problem-with-ct-reconstruction/168>\
**Category:** General Discussions\
**Created:** [September 4, 2020, 10:00am UTC](https://castor-project.discourse.group/t/problem-with-ct-reconstruction/168 "2020-09-04T10:00:55Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Konstantinos\_P\_Chatz](https://avatars.discourse-cdn.com/v4/letter/k/ac8455/32.png) [@Konstantinos\_P\_Chatz](https://castor-project.discourse.group/u/Konstantinos_P_Chatz)\
**Post date:** [September 4, 2020, 10:00am UTC](https://castor-project.discourse.group/t/problem-with-ct-reconstruction/168/1 "2020-09-04T10:00:55Z")

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Hello to the CASToR community.!

I have run some MC simulations using GATE and the Moby mouse phantom. For the reconstruction I use MLTR and distanceDriven algorithms. The final reconstruction, after 8 sets and 25 subsets, still includes some artifacts that I cannot understand.

Any help to get rid of the artifacts could be reaaaaally useful.!

cdh/cdf that used with castor, the output hdr/img and the geom file of the scanner have been uploaded here:  
[https://drive.google.com/drive/folders/1RX6BdyHHoetqUo0LXrQiXyXE1twvyoys?usp=sharing](https://drive.google.com/drive/folders/1RX6BdyHHoetqUo0LXrQiXyXE1twvyoys?usp=sharing)

The command that we used is:  
./castor-recon -df /path/to/ct\_header\_1deg.cdh -dout /path/to/reconMLTR\_1deg\_181 -it 8:25 -vb 2 -proj distanceDriven -opti MLTR -dim 181,181,512 -vox 0.2375,0.2375,0.240625

Kind Regards,  
Konstantinos

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**Author:** ![FILIPOVIC\_PIERUCCI\_M](https://avatars.discourse-cdn.com/v4/letter/f/8491ac/32.png) [@FILIPOVIC\_PIERUCCI\_M](https://castor-project.discourse.group/u/FILIPOVIC_PIERUCCI_M)\
**Post date:** [September 15, 2020, 3:06pm UTC](https://castor-project.discourse.group/t/problem-with-ct-reconstruction/168/2 "2020-09-15T15:06:12Z")

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Hi,

I had a quick look, I wouldn't call these artefacts, it's more of a nice artwork :). Something seems to have gone rather wrong, are you sure the matching between scanner description and event indices is correct? I have no other clues currently.

Best

Marina

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**Author:** ![tmerlin](https://yyz2.discourse-cdn.com/free1/user_avatar/castor-project.discourse.group/tmerlin/32/216_2.png) [@tmerlin](https://castor-project.discourse.group/u/tmerlin)\
**Post date:** [September 21, 2020, 7:16pm UTC](https://castor-project.discourse.group/t/problem-with-ct-reconstruction/168/3 "2020-09-21T19:16:56Z")

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Hi Konstantinos,

I noticed there is no blank mesurements correction in your data. I don't know if they would be required for CT simulations with GATE, but maybe your artifacts could be related to that ?

Thibaut

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**Author:** ![sstute](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@sstute](https://castor-project.discourse.group/u/sstute)\
**Post date:** [September 22, 2020, 1:55pm UTC](https://castor-project.discourse.group/t/problem-with-ct-reconstruction/168/4 "2020-09-22T13:55:32Z")

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Hi,

You are right Thibaut, this is likely due to that.

It is required even with GATE as the detection sensitivity depends on the direction of photons and the position of the detection elements within the panel.

Simon