[Rtk-users] wrong projection geometry?

[Simon Rit]

Hi,
>From what I see in your reconstruction screenshot, you have mainly one
projection. 180° is too short for a short scan so I suggest to have at
least 180°+cone angle. Don't you get a warning when launching the command
line? It's hard to anticipate what happens if you don't use this amount of
data.
Since it's a Gate simulation, I suggest to start with a full acquisition to
check that everything else is correct (distances, rotation direction, etc).
Don't hesitate to share your Gate macro if you want us to check the
geometry.
Note that your spacing and origin parameters need commas instead of spaces
or quotes to be adequately interpreted
Simon

On Sun, Jul 28, 2019 at 5:15 PM Howard <lomahu at gmail.com> wrote:

> Hi,
>
> I tried to run the application rtkfdk to reconstruct CBCT from 180
> projections (from 0 degree to 180 degree only) that were generated using
> Gate simulation. Here is the geometry of the simulation:
>
> a cylindrical phantom (radius=8mm, height=20mm) sitting on a turntable
> X-ray source to isocenter (center of the cylindrical phantom) = 80mm (SAD)
> Flat panel imager (60mm x 60mm) to isocenter = 80mm (SDD=160mm)
>
> x direction: perpendicular to y direction which is the direction from
> detector to X-ray source;
> z direction: turntable rotation axis and pointing upward
>
> I used rtksimulatedgeometry application to generate the geometry xml file
> following the simulation geometry with the command:
> rtksimulatedgeometry -n 180 --arc 180 -o geo.xml --sid 80 -sdd 160
> --proj_iso_x -30 --proj_iso_y -30
>
> Subsequently the CBCT was reconstructed with the rtkfdk application with
> the command:
> rtkfdk -g geo.xml -p . -r proj.mha -o test.mha --spacing 0.1 0.1 0.2
> --dimension 160,160,100 --origin -8 -8 -10
>
> However, the reconstruction result does not look correct. Particularly the
> axial and sagittal views have a lot of streaks. For your reference, I am
> sharing the snapshots of the projections and the reconstructed CBCT in the
> following link:
>
> projection screenshot:         https://ibb.co/PCTjzrt
> reconstruction screenshot:  https://ibb.co/QCjjvQt
>
> What did I do wrong or miss? Or streaks are due to partial projections,
> ie, only 180 views? Your help would be greatly appreciated.
>
> Best,
> Howard
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