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

Albert Grace Lieu albertnew2018 at gmail.com
Mon Oct 26 23:22:45 CET 2020

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.


On Mon, Oct 26, 2020 at 10:59 AM Albert Grace Lieu <albertnew2018 at gmail.com>

> 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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