[Rtk-users] Preprocessing

[Chao Wu]

Hi Jonathan,

I do not quite understand your problem.
I think most information can be retrieved by the relationship between flux
(I) and attenuation (u):
I = I0 * exp (- integral(u * dL) )
Of course there are other effects like beam hardening and scattering
involved but this model is the basic.

Regards,
Chao

2015-11-30 17:29 GMT+01:00 Jonathan Mason <j.mason at ed.ac.uk>:

> Good afternoon RTK users,
>
> I have access to "raw data" from a Varian OBI scanner, and have
> experimented with RTK for performing its reconstruction. However, it is
> not really "raw" in the sense that the coefficients are proportional to
> the photon flux recorded at a given sensor, but is instead proportional
> to the Hounsfield attenuation along that path. With this data, it means
> that one can reconstruct using FDK and other iterative techniques, which
> assume a linear model, but the connection to the underlying physics is
> abstract.
>
> The problem I then have when trying to develop reconstruction
> techniques, is that I do not know whether I am really correcting for
> physical distortions or just correcting for Varian's preprocessing,
> which has been finely tuned for its own FDK method.
>
> My question is whether anybody has dug into the steps that manufacturers
> such as Varian or Elekta perform to arrive at these projection images?
> And if they think that if reverse engineered, could provide a richer set
> of information to facilitate advanced strategies.
>
> Best wishes,
>
> Jonathan Mason
>
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>
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