[Gate-users] GATE 7 metastable source definition
Josh Knowland
jknowland at lucernodynamics.com
Fri May 29 17:49:28 CEST 2020
Hi Mercedes, thank you for your reply—I think you must be right!
I hadn’t considered that, but it does make sense.
Here’s my current understanding of the situation:
So, Tc99m emits gammas at ~140keV about 88% of the time and mono-energetic electrons at ~142keV the other 12% of the time through internal conversion. For this simulation, I’m using a large single sensitive detector (water block surrounding the point source) and the digitizer has an “adder”, so all interactions from an emission will be summed into a “single”. Since the water block is large, each emission will be completely deposited and result in each “single” being ~140keV. That accounts for the edge at ~140-~142 keV in the spectrum.
Each Tc99 (non-metastable) will then also decay and emit a beta with Emax of 293.8 keV. Those betas will have a typical spread spectrum as opposed to the mono-energetic electrons from Tc99m’s internal conversion. That explains the shape seen between 140keV and ~430keV in the spectrum (140keV + 293 keV = 433 keV).
But, my remaining question is, why do the emissions from Tc99m and Tc99 add when digitized into “singles”? I would think each decay would generate its own tracking and “single” in GATE and I’d see the two spectra superimposed instead of added.
In the end, I think it’s OK because since I’m working on dosimetry, the energy will all be added together anyway.
[cid:image003.png at 01D635AF.33C473F0]
From: Mercedes Rodriguez <mercedes at fisica.unam.mx>
Sent: Tuesday, May 26, 2020 11:58 AM
To: gate-users at lists.opengatecollaboration.org; Josh Knowland <jknowland at lucernodynamics.com>
Subject: Re: [Gate-users] GATE 7 metastable source definition
Hi Josh,
I think your simulation is including the beta decay of Tc-99 to Ru-99 (Ebeta_max=294 keV). Have a look at:
http://www.lnhb.fr/nuclides/Tc-99_tables.pdf
Regards,
Mercedes
On 2020-05-26 10:08 a. m., Josh Knowland wrote:
Hi Matthew, thank you very much for the response.
I have simulated a test case using the code you gave. Here is my source def:
/gate/source/addSource src_PointSource
/gate/source/src_PointSource/gps/particle ion
/gate/source/src_PointSource/gps/ion 43 99 0 142.6832
/gate/source/src_PointSource/gps/energytype Mono
/gate/source/src_PointSource/gps/monoenergy 0 keV
/gate/source/src_PointSource/setForcedUnstableFlag true
/gate/source/src_PointSource/setForcedHalfLife 21624.129 s
/gate/source/src_PointSource/setActivity 0.027027 mCi
/gate/source/src_PointSource/gps/type Point
/gate/source/src_PointSource/gps/centre 0.000 0.000 0.000 mm
/gate/source/src_PointSource/gps/angtype iso
That point source is surrounded by a cubic meter of water that is assigned to be a sensitive detector:
/gate/world/daughters/name MeterCube
/gate/world/daughters/systemType scanner
/gate/world/daughters/insert tessellated
/gate/MeterCube/geometry/setPathToSTLFile ../STL_Files/MeterCube.stl
/gate/MeterCube/setMaterial Water
/gate/MeterCube/attachCrystalSD
Within the sensitive detector cube, I get hits which visually look right. Here is a side view:
[cid:image001.png at 01D635A2.9A62AB20]
But, the energy spectrum looks like this:
[cid:image002.png at 01D635A2.9A62AB20]
The vertical step is at the excitation energy of 143 keV.
Is that right? What is causing the odd energy spectrum?
Below is the full listing of my code:
/gate/geometry/setMaterialDatabase ../my_Materials.txt
/gate/world/geometry/setXLength 1000 mm
/gate/world/geometry/setYLength 1000 mm
/gate/world/geometry/setZLength 1000 mm
/gate/world/setMaterial Water
/gate/world/daughters/name MeterCube
/gate/world/daughters/systemType scanner
/gate/world/daughters/insert tessellated
/gate/MeterCube/geometry/setPathToSTLFile ../STL_Files/MeterCube.stl
/gate/MeterCube/setMaterial Water
/gate/MeterCube/attachCrystalSD
/gate/physics/addPhysicsList emstandard_opt4
/gate/physics/addProcess RadioactiveDecay
/gate/random/setEngineName MersenneTwister
/gate/random/setEngineSeed auto
/gate/run/initialize
/gate/source/addSource src_PointSource
/gate/source/src_PointSource/gps/particle ion
/gate/source/src_PointSource/gps/ion 43 99 0 142.6832
/gate/source/src_PointSource/gps/energytype Mono
/gate/source/src_PointSource/gps/monoenergy 0 keV
/gate/source/src_PointSource/setForcedUnstableFlag true
/gate/source/src_PointSource/setForcedHalfLife 21624.119140625 s
/gate/source/src_PointSource/setActivity 0.027027 mCi
/gate/source/src_PointSource/gps/type Point
/gate/source/src_PointSource/gps/centre 0.000 0.000 0.000 mm
/gate/source/src_PointSource/gps/angtype iso
/gate/digitizer/Singles/insert adder
/gate/output/ascii/enable
/gate/output/ascii/setFileName Test_
/gate/output/ascii/setOutFileSinglesFlag 1
/gate/output/ascii/setOutFileHitsFlag 0
/gate/output/allowNoOutput
/gate/application/setTimeSlice 1.0 s
/gate/application/setTimeStart 0.0 s
/gate/application/setTimeStop 1.0 s
/gate/application/startDAQ
From: Matthew Strugari <matthew.strugari at dal.ca><mailto:matthew.strugari at dal.ca>
Sent: Tuesday, May 26, 2020 9:58 AM
To: Josh Knowland <jknowland at lucernodynamics.com><mailto:jknowland at lucernodynamics.com>; Christopher Watanabe <ge69kec at mytum.de><mailto:ge69kec at mytum.de>; gate-users at lists.opengatecollaboration.org<mailto:gate-users at lists.opengatecollaboration.org>
Subject: Re: [Gate-users] GATE 7 metastable source definition
Hi Josh,
There are a couple options for simulating gamma emissions from Tc-99m. One of which uses the ion source:
/gate/source/ [ source name ] /gps/particle ion
/gate/source/ [ source name ] /gps/ion 43 99 0 142.6832
/gate/source/ [ source name ] /setForcedUnstableFlag true
/gate/source/ [ source name ] /useDefaultHalfLife
/gate/source/ [ source name ] /setActivity 10 MBq
An alternative and speedier option, if you are not concerned about dosimetry within your source volume, would be to use a gamma source defined in the UserSpectrum:
/gate/source/ [ source name ] /gps/particle gamma
/gate/source/ [ source name ] /gps/energytype UserSpectrum
/gate/source/ [ source name ] /gps/setSpectrumFile data/energy_spectrum_Tc99m.txt
/gate/source/ [ source name ] /setForcedHalfLife 21625.848 s
/gate/source/ [ source name ] /setActivity 8.85244 MBq
Here, your energy spectrum file would look like:
# Gamma spectrum for Technetium 99m from LNE-LNHB/CEA Table de Radionucleides
# (first line is 1 0 to say it is a discrete spectrum)
# Three next lines : 89.6 keV, 140.511 keV, and 142.675 KeV
1 0
0.0896 0.000014
0.140511 0.885
0.142675 0.00023
Both configurations above would simulate a 10 MBq Tc-99m source. In the former case, you would set your activity as desired. In the latter case, you would scale your activity by the sum of all branching ratios to account only for the gamma portion of radioactivity.
Cheers,
Matthew
________________________________
From: Gate-users <gate-users-bounces at lists.opengatecollaboration.org><mailto:gate-users-bounces at lists.opengatecollaboration.org> on behalf of Josh Knowland <jknowland at lucernodynamics.com><mailto:jknowland at lucernodynamics.com>
Sent: May 26, 2020 10:35 AM
To: Christopher Watanabe <ge69kec at mytum.de><mailto:ge69kec at mytum.de>; gate-users at lists.opengatecollaboration.org<mailto:gate-users at lists.opengatecollaboration.org> <gate-users at lists.opengatecollaboration.org><mailto:gate-users at lists.opengatecollaboration.org>
Subject: Re: [Gate-users] GATE 7 metastable source definition
CAUTION: The Sender of this email is not from within Dalhousie.
Gate Users,
Is there any update on this? Simulation of Tc99m without going through Mo-99 decay?
What is the best practice for this situation?
-josh
From: Gate-users <gate-users-bounces at lists.opengatecollaboration.org><mailto:gate-users-bounces at lists.opengatecollaboration.org> On Behalf Of Christopher Watanabe
Sent: Thursday, January 30, 2020 3:53 PM
To: gate-users at lists.opengatecollaboration.org<mailto:gate-users at lists.opengatecollaboration.org>
Subject: Re: [Gate-users] GATE 7 metastable source definition
Hi all,
I was wondering, given that the original post here was 5 years ago, whether methods now exist for simulating the metastable Tc99m, without simulating the Mo-99 decay scheme. This, for a Tc99m SPECT imaging simulation.
I realize in the GATE examples, this is simulated using a pure gamma, but I’m interested in checking the dose, minimal though it may be, of tissue as well.
Thank you!
Chris
/----------------------------------------------------------------------------------------------------------
Hi,
you should take Mo-99, i.e. Z=42, A=99 instead, since Tc-99m
is part of the Mo-99 decay scheme. I have just tried it with
the Spectro-example of EduGATE and it gives a useful spectrum!
Also, if you use the physicslist mechanism for the physical processes you need to add:
/gate/physics/addPhysicsList emstandard
/gate/physics/addProcess RadioactiveDecay
Hope this is helpful for you!
Kind regards,
Uwe Pietrzyk
/----------------------------------------------------------------------
Prof. Dr. Uwe Pietrzyk
Diplom-Physiker
Institut für Neurowissenschaften und Medizin / INM-4
Forschungszentrum Jülich GmbH
52425 Jülich
Tel: +49-2461-61 4763
Fax: +49-2461-61 2820
Mobil: +49-162-103-4871
eMail: U.Pietrzyk at fz-juelich.de<http://lists.opengatecollaboration.org/mailman/listinfo/gate-users><mailto:U.Pietrzyk at fz-juelich.de<http://lists.opengatecollaboration.org/mailman/listinfo/gate-users>>
http://www.fz-juelich.de/inm/inm-4/DE/Home/home_node.html
&
Bergische Universität Wuppertal
Fachbereich C - Physik / D.08.01
Gaußstr. 20
42097 Wuppertal
Tel: +49-(0)202-439-3523
Fax: +49-(0)202-439-2811
eMail: Uwe.Pietrzyk at physik.uni-wuppertal.de<http://lists.opengatecollaboration.org/mailman/listinfo/gate-users><mailto:Uwe.Pietrzyk at physik.uni-wuppertal.de<http://lists.opengatecollaboration.org/mailman/listinfo/gate-users>>
http://www.medizinphysik.uni-wuppertal.de<http://www.medizinphysik.uni-wuppertal.de/<http://www.medizinphysik.uni-wuppertal.de%3chttp:/www.medizinphysik.uni-wuppertal.de/>>
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On 30 Jan 2015, at 21:17, Xinchi Hou <monicaxinchi at gmail.com<http://lists.opengatecollaboration.org/mailman/listinfo/gate-users><mailto:monicaxinchi at gmail.com<http://lists.opengatecollaboration.org/mailman/listinfo/gate-users>>> wrote:
Dear Gate-users,
I am using GATE 7 for SPECT simulations. For some reason, GATE 7 seems can not recognize metastable source by defining an ion source (shows below,Tc-99m as an example), which can be successfully run by GATE 6.1:
/gate/source/SourceTC99m/gps/particle ion
/gate/source/SourceTC99m/gps/ion 43 99 0 142.6833
/gate/source/SourceTC99m/gps/monoenergy 0 keV
/gate/source/SourceTC99m/setForcedUnstableFlag true
/gate/source/SourceTC99m/setForcedHalfLife 21640 s
I know we can define 140keV gamma as a source instead of using ion source. However, I need to use many of other metastable isotopes as sources which usually have multiple gamma energies for each of them.
I really appreciate if somebody could share his/her experience on similar problems.
My best regards,
Monica
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--
Mercedes Rodriguez-Villafuerte, PhD
Instituto de Fisica, UNAM
AP 20-364, 01000 CDMX
Mexico
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