[Rtk-users] Question about the geometry

[Arvid Piehl Lauritsen Böttiger]

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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