[Rtk-users] Tomosynthesis reconstruction

[Simon Rit]

Indeed, the angular weighting resulting from the discretization of the back
projection occurs in rtkfdktwodweights so skipping this might help.
Simon
On 27 May 2016 5:32 p.m., "Shiras Abdurahman" <shiraska at gmail.com> wrote:

Dear Simon,

Thank you very much for the reply. I tried to reconstruct with only ramp
filtering and back projection and the results are looking good without any
weighting of the projections. I also reconstructed the volume with
rtksart with 10 iterations and the results are better than rtkfdk. With
these experiments, I also confirmed that my geometry file is accurate.

Thank you very much for your help.

With regards,
Shiras




On Thu, May 26, 2016 at 6:04 PM, Simon Rit <simon.rit at creatis.insa-lyon.fr>
wrote:

> Hi Shiras,
> I generated a volume to look at your problem:
> rtkdrawshepploganphantom --like volume.mhd -o volume.mhd --phantomscale 32
> --offset 0,0,1.7
> Then I obtained the same issue as you. I think the problem is that rtkfdk
> is meant for circular CBCT and it includes pre-weighting for displaced
> detector and short scan. I'm not sure why you don't get a warning but these
> are probably responsible for the blank output. A simple solution is to do
> only the 3 FDK steps using in order the command tools:
> rtktwodweights
> rtkramp
> rtkbackprojections
> You can also try to shunt the preweighting by modifying rtkfdk.cxx.
>
> It's interesting that you try out tomosynthesis but you'll encounter some
> problem. When I ran the above commands, I get very weird results because
> the first and the last projections get a lot more weight than the others
> since it looks at the angular weight with the previous and the next
> projections. A simple solution is to blank out these two projections.
> Good luck and keep us posted if you get interesting results,
> Simon
>
> On Thu, May 19, 2016 at 10:41 AM, Shiras Abdurahman <shiraska at gmail.com>
> wrote:
>
>> Dear all,
>>
>> I am trying to simulate Tomosynthesis reconstruction with stationary flat
>> panel detector where source rotates around Y axis to acquire 21 projections
>> (system geometry diagram is attached). Geometry file geometry.xml is
>> generated with Reg23ProjectionGeometry. I generated projection images of
>> a cube volume and then I tried to reconstruct with FDK algorithm. Even
>> though I  am able to generate projections, FDK reconstruction yields the
>> volume with all voxel values zero. The commands I used for generating
>> projections and reconstructing volume are
>>
>> rtkforwardprojections -g geometry.xml -o projections.mhd -i volume.mhd
>> --spacing 0.1518,0.1518,1 --dimension 1420,1416,21 --fp=CudaRayCast
>> rtkfdk -p . -r projections.mhd -o fdk.mhd -g geometry.xml
>> --spacing=0.25,0.25,0.25 --origin=-31.875,-31.875,25
>> --dimension=256,256,256 --hardware=cuda
>>
>> I am also attaching geometry xml file, mhd header files of the original
>> volume, projections and reconstructed volume.
>>
>> With regards,
>> Shiras
>>
>>
>>
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>>
>>
>
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