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

[Marina Filipovic]

Hi Jakub,

You should divide your scatter rate with the size of the TOF bin converted
to mm. That's if you're using the "continuous" LM-TOF recon, which is run
if you don't specify the size of the TOF bin in the header. If you specify
the size of the TOF bin in the header, then you don't have to change your
scatter rates per bin, that's easier, I should have mentioned this option
first. The TOF resolution field is only for TOF resolution. The
documentation is maybe not so clear about these options?
Let me know if this helps.

Cheers

Marina

On Wed, 25 Aug 2021, 08:52 jbaran, <jakub.baran at ifj.edu.pl> wrote:

> Hi Marina,
>
> many thanks for your answer. could you please clarify what do you mean
> to "divide the estimated TOF bin scatter rates with the spatial width of
> the TOF bin, directly in the list-mode datafile". Once I estimate the
> scatter fraction I presume I should divide it by the TOF bin (e.g.
> 200ps)? However, I do not specify the TOF bin size in my header. Unless
> the bin size is then defined as a TOF resolution?
>
> Example of the header which I am using:
>
> Data filename: data_df.Cdf
> Number of events: 298175691
> Data mode: list-mode
> Data type: PET
> Start time (s): 0
> Duration (s): 500
> Scanner name: scanner1
> Calibration factor: 1
> Isotope: unknown
> TOF information flag: 1
> TOF resolution (ps): 200
> List TOF measurement range (ps): 3000
> Scatter correction flag: 1
>
> What is the way to proceed in that case?
>
> All the best,
> Jakub
>
> On 2021-08-18 16:54, Marina Filipovic wrote:
> > Hi Jacub,
> >
> > Have you divided the estimated TOF bin scatter rates with the spatial
> > width of the TOF bin, directly in the list-mode datafile, as explained
> > in the documentation (general and TOF-specific) ?
> >
> > Marina
> >
> > On Wed, 18 Aug 2021, 00:52 jbaran, <jakub.baran at ifj.edu.pl> wrote:
> >
> >> Dear Castor Developers and Users,
> >>
> >> I am trying to incorporate the information about the scatter
> >> correction
> >> in LM-TOF-MLEM reconstruction. I have calculated the scatter
> >> fraction
> >> for each TOF bin. The values of scatter rate are in range 1-2. I
> >> have
> >> applied them for the reconstruction, however the reconstructed
> >> images
> >> seem to be not corrected for scatter. Please find the attached
> >> screenshot. On the top panel, the reconstructed image with
> >> true+scatter
> >> coincidences is presented and on the bottom the same coincidences
> >> were
> >> used but with scatter correction applied. On the right corresponding
> >>
> >> line profiles are presented (ots - no scatter correction; corrected1
> >> -
> >> scatter correction applied)
> >>
> >> FYI: The total number of coincidences used for the reconstruction is
> >> 1
> >> order of magnitude lower than the number of possible LORs.
> >>
> >> Do you have any idea what kind of values should be applied for the
> >> scatter rate? Did you have any similar case and found the solution
> >> how
> >> the scatter rate should be calculated?
> >>
> >> All the best,
> >> Jakub
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