[Castor-users] Scatter rate estimation for LM-TOF-MLEM

[STUTE Simon]

Hi,

OK thanks for the explanations.

Why ignoring the frame duration in the reconstruction ?

As the scatter correction is supplied as a rate, you really need the frame duration to rescale the scatters to the prompt coincidences.

Could you try to reconstruct with the frame duration taken into account ?

How did you translate the estimation of the scatter rates based on a sinogram to the list-mode data ? Did you take the binning size into account ? You need to divide your scatter rate for a TOF bin by the size of the TOF bin to get an "almost" continuous measurement.

Simon

________________________________________
De : jbaran <jbaran at ifj.edu.pl>
Envoyé : mardi 7 décembre 2021 10:59
À : STUTE Simon
Cc : Castor Users
Objet : Re: [Castor-users] Scatter rate estimation for LM-TOF-MLEM

Hi Simon,

many thanks for the quick response. The answers are as follows:


On 2021-12-07 09:56, STUTE Simon wrote:
> Hello Jakub,
>
> Thanks for the detailed email !
>
> Do you take the scan duration into account in the datafile header ?

Yes, I added the information about the scan duration in the header. On
the other hand in the reconstruction I used -ignore-corr fdur option.

>
> You say that you estimated the scatter rate for each TOF bin
> independently to be 1-2. Is it "1 or 2" (which would be insanely high)
> or "e-2" ?

I was not explicit here. The scatter rate passed to the castor lm is
ranging from 0 to 2. However most values are in the range from 1e-3 to
1e-1.

>
> How did you compute this estimated scatter rate ?

We made basic estimation based on Monte Carlo simulations - NEMA IEC
study. For the cubic study we use -sc flag during the conversion of the
ROOT data to CASToR. For this the scatter rate is at the level of  about
1e-4.

>
> And how did you translate this information into your list-mode file ?

We adapt the CASToR code to read the scatter correction rate factor from
the matrix provided by ourselves.

>
> Best
> Simon

All the best,
Jakub