[dba-SQLServer] c# - Report server databases

I am using SMO to get lists of databases, tables in databases etc.  I never operate on the system 
databases so I filter out the system databases using the Database.IsSystemObject property.  That 
brought into focus the ReportServer and ReportServerTempDB databases, which oddly are not inside of 
the system folder and apparently are not system objects.

Other than filtering them out by their name, is there a way to know that they are not user defined 
databases?

-- 
John W. Colby
www.ColbyConsulting.com