[Rtk-users] Gantry rotation direction and artefacts

[Vincent Libertiaux]

Hi Simon,

I am afraid I was no clear enough. Please find a picture of the real 
object and the reko at that link:

https://www.dropbox.com/sh/ul0oy9kv3us4ey7/AABQ5Y4R1PR-jcRawGFKOUK4a?dl=0


So you can see that on the part, the serial number is on the "head" side 
while it is on the "tail" side on the reconstruction, using the "direct" 
geometry.  That is what I call the mirror image.  The rotation axis is 
along the vertical direction of the image.  I could easily reorder the 
reconstructed slice to get it in the right orientation, but I was 
wondering where the issue comes from.

Best regards,
Vincent

On 28.08.20 12:13, Simon Rit wrote:
> Mirror in which direction? Depending on the direction, it can also be 
> a 180° offset of the angle. If it reconstructs well, I would assume 
> that the direct direction is the correct one but there is something 
> else you need to understand...
>
> On Fri, Aug 28, 2020 at 10:44 AM Vincent Libertiaux <vl at xris.eu 
> <mailto:vl at xris.eu>> wrote:
>
>     Hi Simon,
>
>     thank you for testing my dataset.
>
>     I get the same results you describe and I am quite happy with the
>     first result. However, the reconstructed volume is a "mirror" view
>     of the real object, and my guess was that the rotating plate was
>     going in the opposite direction assumed by rtk. Is it the wrong
>     assumption?
>
>     Thank you again for your help,
>
>     best regards,
>
>     Vincent
>
>
>     Thanks for the dataset. When I run
>       rtkfdk -p . -r ^proj.mha$ -g direct.xml --spacing 0.5 -d 300
>     --hardware cuda -o fdk.mha
>     The result looks good to me. Obviously, when I run
>       rtkfdk -p . -r ^proj.mha$ -g inverse.xml --spacing 0.5 -d 300
>     --hardware cuda -o fdk.mha
>     the result is bad since the correct rotation direction seems to be
>     the direct one. Did you expect the second line to produce the
>     correct result? Or is the first line not producing a good enough
>     result in your opinion?
>

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