The CTKBarCamp community lives on Google plus: https://plus.google.com/communities/105094033241300780178
The main idea behind this community is to share facts, idea and news related the medical imaging field and the open-source library CTK
You will find below a template of message to send to confirm the interest of folks requesting to join. Make sure to change <FUTURE_MEMBER_NAME> and <YOUR_NAME> with the appropriate value.
Dear <FUTURE_MEMBER_NAME>, You recently requested to join the CTK BarCamp community on Google plus. Before approving your request to join the CTKBarCamp, I am reaching to you to make sure this community aligns with your interests. The main idea behind this community is to share facts, idea and news related the medical imaging field and the open-source library CTK  Let me know if you are still interested and will gladly approve your request, Best, <YOUR_NAME> on behalf of the CTK community  http://www.commontk.org
If few days/weeks later, you haven't heard back you could send the following message:
Dear <FUTURE_MEMBER_NAME>, Not having heard back from you I will cancel your request. If you think this is a mistake, do not hesitate to contact us on the CTK mailing list. See http://commontk.org/index.php/Getting_Started Best, <YOUR_NAME> on behalf of the CTK community