[Gate-users] Positron range simulation - inconsistency between GATE 8.0/ 9.0 and between source types

[Minh Phuong Nguyen]

Hi Cassandra,

Thank you for your reply. I use the following standard definition for the
physics list. I also put the definition of the I-124 point source below.
How do you set the energy cuts? Do you mean the production threshold:
https://opengate.readthedocs.io/en/latest/cut_and_variance_reduction_technics.html?highlight=range%20cut#production-threshold

#  P H Y S I C S
/gate/physics/addPhysicsList emstandard
/gate/physics/addProcess RadioactiveDecay
/gate/physics/processList Enabled
/gate/physics/processList Initialized

# S O U R C E:  I-124
/gate/source/addSource pointsource
/gate/source/pointsource/gps/particle ion
/gate/source/pointsource/gps/ion 53 124 0 0
/gate/source/pointsource/gps/monoenergy 0. keV
/gate/source/pointsource/gps/angtype iso
/gate/source/pointsource/gps/mintheta 0 deg
/gate/source/pointsource/gps/maxtheta 180 deg
/gate/source/pointsource/gps/minphi -180 deg
/gate/source/pointsource/gps/maxphi 180 deg
/gate/source/pointsource/gps/centre 0 0 0 mm
/gate/source/pointsource/setActivity 30000000 Bq

Best,
Minh

On Mon, Nov 9, 2020 at 11:21 PM Cassandra Miller <
cassandramiller at phas.ubc.ca> wrote:

> Hi Minh,
>
> I don't have a solution to your problem, but is it possible that your
> energy cuts are too high and hence your positrons are stopping too early
> and depositing all of their energy? Also, what physics list are you
> using?
>
> Best,
> Cassandra
>
> On 2020-11-09 07:27, Minh Phuong Nguyen wrote:
> > Can anyone help me with this?
> >  The inconsistency in the positron range simulation with GATE appears
> > to be an existing problem.
> > Several related posts in the gate-user archive have not received a
> > final answer either.
> >
> > Minh
> >
> > On Thu, Nov 5, 2020 at 10:29 AM Minh Phuong Nguyen <mipbkhn at gmail.com>
> > wrote:
> >
> >> Dear GATErs,
> >>
> >> I simulated positron ranges for several isotopes such as F-18 and
> >> I-124 with GATE. The setup was very simple with a point source at
> >> the centre of a water environment (20-cm-radius sphere). The sphere
> >> was that large to make sure that the positrons do not escape the
> >> water volume.
> >>
> >> The obtained mean/max positron range from this simulation was
> >> shorter than what I found in literature. Then I tested with
> >> different GATE versions (8.0/ 9.0 with corresponding GEANT4 versions
> >> as stated in the GATE documentation), and different ways of defining
> >> the source (ion, e+, fastI124). I observed that the positron range
> >> result was not consistent when changing these parameters (attached
> >> figures).
> >>
> >> Looking at the range distributions (attached figures), GATE 8.0 with
> >> ion source produced a lot of annihilations near the decay locations
> >> (range ~ 0 mm). This was not the case with GATE 9.0 and e+ or
> >> fastI124 sources.
> >>
> >> Does anybody know:
> >> - why positron range from GATE is shorter than in literature?
> >>
> >> - which changes in the new GATE version makes the discrepancy in
> >> positron range simulation result?
> >> - what makes the difference in positron range between the ion source
> >> and other type sources?
> >>
> >> Thank you.
> >> Kind regards,
> >> Minh Phuong Nguyen
> > _______________________________________________
> > Gate-users mailing list
> > Gate-users at lists.opengatecollaboration.org
> > http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
>
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