[Rtk-users] About flat field correction for elekta CBCT data

[Simon Rit]

Hi,
Yes, flat field correction is possible with ITK since it's the log of the
division of two images. We do it for example for some data types (for
example the XRad small animal scanner, see here
<https://github.com/SimonRit/RTK/blob/master/include/rtkXRadRawToAttenuationImageFilter.hxx#L55-L101>).
However, Elekta already does a flat field correction in the data which are
stored on disk so I'm not sure this is the issue here. Elekta data is
processed by applying a lookup table to the raw data
https://github.com/SimonRit/RTK/blob/master/include/rtkElektaSynergyRawLookupTableImageFilter.hxx#L27-L60
and assuming that air is at 65536 then (see here
<https://github.com/SimonRit/RTK/blob/master/include/rtkProjectionsReader.hxx#L315>).
That can be improved but it mimicked what was done in the first versions of
XVI. I think it's been improved since but I'm not aware of the detail of
the improvements.
I hope it helps,
Simon

On Thu, Jan 13, 2022 at 1:54 AM 雅之 服部 <masayuki.h.0215 at gmail.com> wrote:

> Dear rtk-users
>
> I am now working on iterative reconstruction  offset detector CBCT using my elekta data.
>
> However, probably because the data is truncated , the ring artifact appears in the iterative reconstruction.
>
> One of the reasons was that flat field correction was not performed.
>
> Is flat field correction possible with RTK?
>
> I don't have an image for flat field correction, so are you predicting it? Or do I have to have a flat field correction image?
>
> Thank you very much in advance
>
> masa at japan
>
> [image: recon.jpg]
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