[Gate-users] Ge68 source

Fri Aug 31 15:26:26 CEST 2012

Hi Shelley!

I think you see no Ga-68 decay because it's simply not very likely to occur within your setup.

Look at it this way: your Ge-68 source just decayed to a single Ga-68 atom. From your output, you can see the kinetic energy of the Ga-68: 8.88 x 10^-8 MeV or 1.423 x 10^-20 J. Crunching some numbers, this means that the Ga-68 atom has a velocity of 502.3 m/s. This is quite fast! Now assume that if the Ga-68 travels approximately 1 m in any direction, it will escape the scanner (or even your World, in Gate); this is somewhat reasonable to assume. How long does it stay within your scanner (or World), then? Crunching more numbers, it takes approximately 0.002 s for the Ga-68 to travel 1 m. The decay constant of Ga-68 is approximately 0.00017 s^-1. Thus, the probability that the Ga-68 will decay within 0.002 s is only (0.00017)*(0.002) = 0.000034%! Your Ge-68 source will need to produce A LOT of Ga-68 to even see one single Ga-68 decay within your simulation setup!

Does this convince you?

As for your second question: you can add new energy distribution to Gate, but be careful not to use it when you use an ion source. As the Gate User's guide says: "In the case of ions, the kinetic energy must be 0 since the ions are at rest."

If you add a new energy distribution, you would use it with the other types of sources (e.g. back-to-back or particle). But then, you will not have the realistic decay models of the ion source type.

I hope this helps!
Marc

__________________________

Marc Chamberland, MSc
PhD candidate
Department of Physics
Carleton University
Ottawa (ON)

Le 2012-08-31 à 3:59 AM, xcao <xcao at mail.ihep.ac.cn> a écrit :

> hi，Marc!
>  
> You suggestion give me much help and understanding. I'll test GateLab, hope it will work.
>  
> Just as you say, for Ge-68, electron capture branching rations is included. But there are still something confused me.
> I change the verbose to get more information of output, and find that, for Ge-68, it will produce Ga-68, but Ga-68 will not decay,
> I can't understand why? In the attachment is the out of Ge-68 source and pure Ga-68 source.
>  
> Another question is, whether can I put the enengy spectrum produced by "ion source" of Ga-68 into the Gate code of source/physics/src/GateSPSEneDistribution.cc,  the use a new energytype? This will also can save simulation time.
>  
> Thank you very much!
>  
> Shelley!
>  
>  
> 2012-08-31
> xcao
> 发件人： Marc Chamberland
> 发送时间： 2012-08-30  20:58:42
> 收件人： xcao
> 抄送： gate-users at lists.opengatecollaboration.org
> 主题： Re: [Gate-users] Ge68 source
> (Re-sent to include the Gate Users mailing list.)
> 
> Hi Shelley!
> 
> According to the Geant4 9.4 Physics Reference Manual, electron capture is included in radioactive decay (look at Chapter 37 in the PDF) : http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/BackupVersions/V9.4/fo/PhysicsReferenceManual.pdf
> 
> Also, if you look at the RadioactiveDecay data file for Ge-68 (z32.a68), you'll see the electron capture branching ratios is included.
> 
> As for the simulation time, my first suggestion would be to use the cluster tools included with Gate. If you don't have access to a computer cluster, maybe you can check if GateLab would work for you: http://www.opengatecollaboration.org/GateLab
> 
> Also, I'm no expert in PET, but couldn't you do attenuation correction simply with a back-to-back gamma source instead? This would be way faster. Of course, for your actual PET simulations you would use a more realistic source.
> 
> I hope this helps!
> 
> Marc
> 
> 
> 
> __________________________
> 
> Marc Chamberland, MSc
> PhD candidate
> Department of Physics
> Carleton University
> Ottawa (ON)
> 
> Le 2012-08-30 à 8:56 AM, Marc Chamberland <MarcChamberland at cmail.carleton.ca>
>  a écrit :
> 
>> Hi Shelley!
>> 
>> According to the Geant4 9.4 Physics Reference Manual, electron capture is included in radioactive decay (look at Chapter 37 in the PDF) : http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/PhysicsReferenceManual/BackupVersions/V9.4/fo/PhysicsReferenceManual.pdf
>> 
>> Also, if you look at the RadioactiveDecay data file for Ge-68 (z32.a68), you'll see the electron capture branching ratios is included.
>> 
>> As for the simulation time, my first suggestion would be to use the cluster tools included with Gate. If you don't have access to a computer cluster, maybe you can check if GateLab would work for you: http://www.opengatecollaboration.org/GateLab
>> 
>> Also, I'm no expert in PET, but couldn't you do attenuation correction simply with a back-to-back gamma source instead? This would be way faster. Of course, for your actual PET simulations you would use a more realistic source.
>> 
>> I hope this helps!
>> 
>> Marc
>> 
>> 
>> 
>> __________________________
>> 
>> Marc Chamberland, MSc
>> PhD candidate
>> Department of Physics
>> Carleton University
>> Ottawa (ON)
>> 
>> Le 2012-08-30 à 3:54 AM, xcao <xcao at mail.ihep.ac.cn>
>>  a écrit :
>> 
>>> hi, Marc!
>>>  
>>>    Thank you for you reply.
>>>    Yes, using "ion source" will solve this problem, I have tested, but should use Ga-68 instead of Ge-68.
>>> I think the reason maybe the physical process of electron capture is not include. Even so, Ga-68 will be ok.
>>>  
>>> Another problem is what you have mentioned, using "ion source" will slow down simulations.
>>> I want to using Ge-68 source to do attenuation correction on PET,  this will need plenty of data samples.
>>> So simulation time is also very important. If you have any better suggestion for simulation time.
>>>  
>>> Thank you very much!
>>> Shelley
>>>  
>>> 2012-08-30
>>> xcao
>>> 发件人： Marc Chamberland
>>> 发送时间： 2012-08-29  21:15:54
>>> 收件人： xcao
>>> 抄送： gate-users at lists.opengatecollaboration.org
>>> 主题： Re: [Gate-users] Ge68 source
>>> Hi!
>>> You can define a Ge-68 source in Gate by using the "ion source" type. See the documentation here: http://wiki.opengatecollaboration.org/index.php/Users_Guide_V6.1:Source#Defining_the_type_of_source
>>> So for Ge-68, you would do it like this:
>>> /gate/source/NAME/gps/particle ion 
>>> /gate/source/NAME/gps/ion 32 68 0 0 
>>> /gate/source/NAME/gps/monoenergy 0. keV 
>>> /gate/source/NAME/setForcedUnstableFlag true 
>>> /gate/source/NAME/setForcedHalfLife 23410080 s
>>> You also need to add the RadioactiveDecay process in your physics list (before initialization):
>>> /gate/physics/addProcess RadioactiveDecay
>>> Note that using an ion source will slow down your simulations.
>>> Cheers!
>>> Marc
>>> __________________________
>>> Marc Chamberland, MSc
>>> PhD candidate
>>> Department of Physics
>>> Carleton University
>>> Ottawa (ON)
>>> Le 2012-08-28 à 10:40 PM, xcao <xcao at mail.ihep.ac.cn>
>>>  a écrit :
>>> > hello, gate-users
>>> > 
>>> >    If anyone have used the source of germanium-68, I want to know how to define it.
>>> > Can anyone offer me some help.
>>> > 
>>> > Thank you very much! 
>>> > 
>>> > 2012-08-29 
>>> > 
>>> > 
>>> > 
>>> > xcao 
>>> > _______________________________________________
>>> > Gate-users mailing list
>>> > Gate-users at lists.opengatecollaboration.org
>>> > http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
>>> > 
>> 
> 
> <output_info_of_Ge_and_Ga.txt>