[Gate-users] Setting accolinearity with back to back source

Wed Oct 28 01:24:42 CET 2020

Dear Gate users,

I apologize for my earlier false result regarding the accolinearity of the
back-to-back gamma generator. Maxime's finding is correct that
back-to-back gamma source default is linear and accolinearity is not
enabled by default.

The reason why I came to the wrong conclusion is that I used a real PET
system in GATE to conduct the simulation which involving much scattering.
Now I updated my simulation with an ideal PET system to repeat the
simulation, the result is shown below:
[image: back-to-back angle distribution.PNG]

My understanding is that whether to simulate the accolinearity of
annihilation gammas or not is not a big deal in simulation as it can easily
be counteracted by scattering, which always happens in a real system. Just
in case someone would be interested in this, I shared my personal finding
and understanding here as well.

Thanks, Maxime.

Zhengzhi

On Mon, Oct 26, 2020 at 3:22 PM Albert Grace Lieu <albertnew2018 at gmail.com>
wrote:

> Hi Maxime,
>
> I did a simple simulation to verify whether a back-to-back gamma generator
> creates colinear or accolinear gamma pairs. I used a point source with a
> single emission direction to generate back to back gammas in a cylindrical
> PET system (in GATE 8.2). Then I collected hits file and coincidences file.
> I used valid coincidence event IDs to find its first hit position
> registered by the PET system (ideal resolution). Please note that I did not
> use any following commands:
>
>     /gate/source/NAME/setAccolinearityFlag true
>     /gate/source/NAME/setAccoValue 0.5 deg
>
>
> Here is what I found:
> It looks back-to-back gamma source has accolinearity enabled by default.
> The mean is 5.5 degrees with and a standard deviation of 4.2.
> [image: Screenshot from 2020-10-26 14-58-32.png]
>
> My question is whether back-to-back gamma source has accolinearity enabled
> by default? Maybe I shall have looked into GateBackToBack.cc, however,
> source code might have compiled with other flags which I don't know of.
>
> Thanks for your precious time answering.
>
> Zhengzhi
>
>
> On Mon, Oct 26, 2020 at 10:59 AM Albert Grace Lieu <
> albertnew2018 at gmail.com> wrote:
>
>> Hi Maxime,
>>
>> Thanks for sharing your findings regarding this accolineraity feature
>> associated with the back-to-back gamma source. I did not see
>> "setAccolinearityFlag" command in the GATE 8 and 9 manual either and am
>> skeptical about its validity. May I know your conclusion on the usage of
>> accolineraity feature in GATE? Is it still supported or dead? How can one
>> still possibly use it correctly?
>>
>> Thanks a lot.
>>
>> Sincere wishes,
>>
>> Zhengzhi
>>
>> On Wed, Jul 1, 2020 at 11:39 AM Maxime Toussaint <
>> Maxime.Toussaint at usherbrooke.ca> wrote:
>>
>>> Greetings,
>>>
>>> If one looks into the mailing list or in the Gate code, one can find
>>> that there is an option to simulate accolinearity from back to back source.
>>> The commands to use are as follow:
>>>     /gate/source/NAME/setAccolinearityFlag true
>>>     /gate/source/NAME/setAccoValue 0.5 deg
>>>
>>> In short, is this feature validated and still supported?
>>>
>>> In the following, I detail what I found from my search on that feature.
>>>
>>> This feature is not mentioned in the current openGate wiki (or at least,
>>> it was not found with the wiki search tool). I did a quick "cntrl+f" search
>>> of "setAccolinearityFlag" for the userguides available from v6.0 to the
>>> last available and I did not found a single mention of that keyword.
>>> However, if we look at the mailing list, we can find the following:
>>>
>>>    - A possible bug was found in 2011 for which the resulting thread
>>>    does not provide a clear conclusion about if the bug was corrected or if it
>>>    was a real bug [1].
>>>    - Around two years later, the feature was proposed to a user [4].
>>>    - This feature seems to be still used currently [2, 3]. In [3], the
>>>    user asked for some tips on the feature which were not answered.
>>>    - From Gate v5.0 to v6.0, a bug was found and corrected [5, 6, 7].
>>>
>>> I did try to look into the available release note of Gate and the Gate
>>> github but I did not find a mention about that feature.
>>>
>>> Currently, the option to test Gate with accolinearity validation does
>>> not work out-of-the-box with that feature. When I tried to activate the
>>> accollinearity error graph creation, the resulting graph indicated pure
>>> back-to-back events. I have built some tests by hand[*] and it showed that
>>> a Gaussian angular error was indeed simulated which is good. However, when
>>> I compared the accolinearity error resulting from that feature to when
>>> using a positron source[**], the profile were clearly different. The latter
>>> being Gaussian-like, as expected. It would seems that something unexpected
>>> happens when the angular error is applied to the gamma pairs momentum with
>>> that feature. While I did try to make sense of the code in the method
>>> "GenerateVertex" of GateBacktoBack.cc, I must admit I fail to comprehend
>>> all the steps it does.
>>>
>>> Thus, it seems that this feature might have some problems or that it is
>>> not completely supported. If it is indeed the case, I will propose a
>>> modification to the wiki such that it mention the existence of that feature
>>> but warns the users that it might not work as intended. If it should work,
>>> I will try to make a MWE of my tests and ask for validation.
>>>
>>> Best,
>>> Maxime Toussaint
>>>
>>>
>>> [1]
>>> http://lists.opengatecollaboration.org/pipermail/gate-users/2011-February/004842.html
>>> <https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.opengatecollaboration.org%2Fpipermail%2Fgate-users%2F2011-February%2F004842.html&data=02%7C01%7CMaxime.Toussaint%40USherbrooke.ca%7C25315ca43ca74ed7ad0608d81de0a462%7C3a5a8744593545f99423b32c3a5de082%7C0%7C0%7C637292197959885713&sdata=hErgjKVo%2BGaOLEjOHvH8hG1YyI5lN5dqKYuGGQwOx7A%3D&reserved=0>
>>> [2]
>>> http://lists.opengatecollaboration.org/pipermail/gate-users/2020-June/011680.html
>>> <https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.opengatecollaboration.org%2Fpipermail%2Fgate-users%2F2020-June%2F011680.html&data=02%7C01%7CMaxime.Toussaint%40USherbrooke.ca%7C25315ca43ca74ed7ad0608d81de0a462%7C3a5a8744593545f99423b32c3a5de082%7C0%7C0%7C637292197959895705&sdata=2r8SoyW0IZrf%2Btztjjbk9BW55g2tRu1cEOv56fwnhW4%3D&reserved=0>
>>> [3]
>>> http://lists.opengatecollaboration.org/pipermail/gate-users/2019-December/011222.html
>>> <https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.opengatecollaboration.org%2Fpipermail%2Fgate-users%2F2019-December%2F011222.html&data=02%7C01%7CMaxime.Toussaint%40USherbrooke.ca%7C25315ca43ca74ed7ad0608d81de0a462%7C3a5a8744593545f99423b32c3a5de082%7C0%7C0%7C637292197959895705&sdata=H%2BAvIhdArNubUAJJXV9l4Wzq18IozEXcLOu8jP%2FZweA%3D&reserved=0>
>>> [4]
>>> http://lists.opengatecollaboration.org/pipermail/gate-users/2012-November/006068.html
>>> <https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.opengatecollaboration.org%2Fpipermail%2Fgate-users%2F2012-November%2F006068.html&data=02%7C01%7CMaxime.Toussaint%40USherbrooke.ca%7C25315ca43ca74ed7ad0608d81de0a462%7C3a5a8744593545f99423b32c3a5de082%7C0%7C0%7C637292197959905700&sdata=%2B1j5zAFPGqBNayNUn1I6uf7joGaLYCdPOT5vbnRbuO0%3D&reserved=0>
>>> [5]
>>> http://lists.opengatecollaboration.org/pipermail/gate-users/2010-November/004684.html
>>> <https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.opengatecollaboration.org%2Fpipermail%2Fgate-users%2F2010-November%2F004684.html&data=02%7C01%7CMaxime.Toussaint%40USherbrooke.ca%7C25315ca43ca74ed7ad0608d81de0a462%7C3a5a8744593545f99423b32c3a5de082%7C0%7C0%7C637292197959905700&sdata=DAVufxRn3d%2BCb7VxOULE9siiR9FQ6pWBzo2nb%2FrYA3k%3D&reserved=0>
>>> [6]
>>> http://lists.opengatecollaboration.org/pipermail/gate-users/2010-November/004683.html
>>> <https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.opengatecollaboration.org%2Fpipermail%2Fgate-users%2F2010-November%2F004683.html&data=02%7C01%7CMaxime.Toussaint%40USherbrooke.ca%7C25315ca43ca74ed7ad0608d81de0a462%7C3a5a8744593545f99423b32c3a5de082%7C0%7C0%7C637292197959915693&sdata=wTA7OwcDUmICDa%2FOLyAgP%2FiRPIWTO%2FwIWt27j1GKcIY%3D&reserved=0>
>>> [7]
>>> http://lists.opengatecollaboration.org/pipermail/gate-users/2010-October/004599.html
>>> <https://can01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.opengatecollaboration.org%2Fpipermail%2Fgate-users%2F2010-October%2F004599.html&data=02%7C01%7CMaxime.Toussaint%40USherbrooke.ca%7C25315ca43ca74ed7ad0608d81de0a462%7C3a5a8744593545f99423b32c3a5de082%7C0%7C0%7C637292197959915693&sdata=F%2Fwogp5s9hJC1WtE2CujQWvG3GW%2BapOOIGMIJGiQnh8%3D&reserved=0>
>>>
>>> [*] Outputting the "dev" variable from the file GateBacktoBack.cc
>>> [**] Outputting the momentum from the file GateBacktoBack.cc and
>>> GatePositronAnnihilation.cc, and extracting the photon pairs accolinearity.
>>>
>>> _______________________________________________
>>> Gate-users mailing list
>>> Gate-users at lists.opengatecollaboration.org
>>> http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
>>
>>
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