[Rtk-users] Gantry rotation direction and artefacts

[Vincent Libertiaux]

Hi Simon,

Yes, we have very decent reconstructions in the opposite direction.

If you want to have a look, here is a link towards the sinogram and the 
two geometry files:

https://www.dropbox.com/sh/xtzof23ar89vutm/AAASZhDBcCez_c1BN2ed74H_a?dl=0

I downsampled the projections so that the file size remains reasonable.

Thank you very much for you help,
Vincent

On 27.08.20 17:02, Simon Rit wrote:
> Hi Vincent,
> This sounds like a typical geometry problem. It's hard to guess what 
> could be the problem without data. Is it a system for which you're 
> able to reconstruct in the opposite direction?
> Simon
>
> On Thu, Aug 27, 2020 at 2:17 PM Vincent Libertiaux <vl at xris.eu 
> <mailto:vl at xris.eu>> wrote:
>
>     Dear RTK users,
>
>     I am trying to reconstruct a volume using the opposite rotation
>     direction; I basically defined my rotation angle to be -360
>     degrees and
>     my initial angle to be 359.6 (I have 900 projections).
>
>     The results present artefacts, mostly important blurs compared to the
>     "original" reconstruction.  To be sure I was not misinterpreting
>     the way
>     rtk deals with the geometry, I performed the same reconstruction with
>     the "direct" rotation direction (from 0 to 359.6) but reordering my
>     projections instead, which yields in the same blurry results.
>
>     I feel I am missing some basic understanding of what is happening,
>     any
>     help you can provide would be much appreciated !
>
>     Best regards,
>
>     Vincent
>
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