How can I hide Main Themes and only show Child Themes with Theme Manager

Hi there heroes.

We are using several Multisite Theme Manager and Child Themes for our Blogs. When a Blog Admin go to Themes, he will see both Themes and Child Themes.

Is there any way we can hide main themes and only show Child Themes?

Child Themes contain tweaks we have made to simplify Blog Admins from having to customize specific details on each blog.

Thanks for your help!