[Rtk-users] Angular weighting in gated FDK

[Simon Rit]

Hi Cyril,
I am a bit lost by what you say. FDK comes from a continous
formula and the angular weighting is the discretization of the
integral on gantry angle. I don't see how it could be smarter than the
gap with the neighbors and this is precisely why we obtain the
attenuation.
How come you have a factor 10 between projections? Isn't it regular
since heart beating is rather regular?
The only improvement I know off is to use a gating function which
takes other values than 0 and 1 but I can't remember it is accounted
for in the reconstruction.
Simon

On Tue, Sep 3, 2013 at 6:26 PM, MORY, CYRIL <Cyril.Mory at philips.com> wrote:
> Hi RTK users,
>
>
>
> I’m working on ECG-gated FDK reconstruction, and I’d like to obtain
> realistic absorption coefficients, because my gated FDK images have to
> compared to other reconstruction results which do have realistic values. In
> FDK, projections are weighted by their angular gaps. I have replaced that by
> a weighting by 1, because some angular gaps are huge in ECG-gated projection
> data, and there is no reason why a single projection should be weighed ten
> times as much as the others. But 1 obviously isn’t the right value (with a
> 20%-wide gating window, I’m getting values about ten times too high). I’m
> experimenting with smarter choices, like the minimum of the angular gaps
> (this time it’s 10 times too low), and I’ll keep experimenting until I find
> something satisfying.
>
>
>
> Does anyone know if there is a standard way of weighting the projections in
> ECG-gated FDK ? I’ve made a quick search (maybe too quick), but couldn’t
> find anything on this topic.
>
>
>
> Regards,
>
> ==========================================
>
> Cyril Mory
>
> PhD student at Philips Medisys and CREATIS
>
>
>
> Groupement Hospitalier Est
>
> Hôpital Cardiologique Louis Pradel
>
> Laboratoire CREATIS - Bât. B13
>
> CNRS UMR5220, INSERM U1044, INSA-Lyon, Univ. Lyon 1
>
> 28, Avenue du Doyen LEPINE
>
> 69677 Bron cedex FRANCE
>
>
>
> Office : +33 4 72 35 74 12
>
> Cell : +33 6 69 46 73 79
>
>
>
>
> ________________________________
> The information contained in this message may be confidential and legally
> protected under applicable law. The message is intended solely for the
> addressee(s). If you are not the intended recipient, you are hereby notified
> that any use, forwarding, dissemination, or reproduction of this message is
> strictly prohibited and may be unlawful. If you are not the intended
> recipient, please contact the sender by return e-mail and destroy all copies
> of the original message.
>
> _______________________________________________
> Rtk-users mailing list
> Rtk-users at openrtk.org
> http://public.kitware.com/cgi-bin/mailman/listinfo/rtk-users
>