[Rtk-users] Question about the geometry

[Chao Wu]

Hi Arvid,

Is the origin and spacing of your projection data correct? What is your
projection pixel size?

Regards, Chao

2015-10-16 9:12 GMT+02:00 Arvid Piehl Lauritsen Böttiger <bottiger at gmail.com
>:

> Dear all. Hello again.
>
> I writing to you again because I need some help to understand how to
> declare the geometry of the system.
>
> Cyril redirected me towards this document (
> http://www.creatis.insa-lyon.fr/~srit/geometry.pdf ) which helped a
> lot, but unfortunately it has not been enough to make me reconstruct a
> tomogram.
>
> I have attached a drawing of my setup (setup.jpg). The
> source-to-detector distance is around 1600 mm. I just rotate the
> sample instead of the source, and the sample-detector distance is 15
> cm which makes the isocenter distance 1450. The field of view is
> around 2 cm.
>
> The aligned projections are located here:
> https://www.dropbox.com/s/ycg41qkeym61kec/cylinder-a.mha?dl=0
> and the raw tiffs are here:
> https://www.dropbox.com/s/hb67pkueyb3zcc3/tiffs.zip?dl=0
>
> I would say the input data looks as nice, but when reconstructing I'm
> still just getting noise:
>
> This is how I perform my "reconstruction"
>
> # 361 projections from 0 to 360 degrees. The source-detector distance
> is 1.6 m and the
> # sample-detector distance is 15 cm
> # I have tried with many variations of --ssd and --sid but I think
> they all look the same
> rtksimulatedgeometry.exe -f 0 -n 361 -a 360 --sdd 1600 --sid 1450 -o
> c:\Work\out_dir\geometry_real.xml
>
> # make a mha file out of the tiff files
> rtkprojections.exe --path c:\Work\tomography_data\tiffs\ --output
> c:\Work\out_dir\cylinder-a.mha --regexp .tif
>
> # "Reconstruct" the data.
> rtkfdk.exe -p c:\Work\out_dir\ -r cylinder-a.mha -o
> c:\Work\out_dir\cylinder_a_recon.mha -g
> c:\Work\out_dir\geometry_real.xml --spacing 2 --dimension 256
>
> The result can be viewed in the recon_result.PNG attachment.
> The reconstrcution can be found here:
> https://www.dropbox.com/s/cbwwnbbzvhqiyvy/cylinder_a_recon.mha?dl=0
>
> Can someone please help me what I am doing wrong?
>
> best
>
> Arvid
>
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>
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