I'm assuming you mean one of the avatars that either comes with the application or in a Reallusion content pack?  If so, then no, there is no way to edit them directly.  CrazyTalk isn't really about modifying avatars, it's more about creating new avatars from ANY photograph.  So if you need a medical avatar, take a picture of a doctor and import it into CrazyTalk to animate it however you want.

However, with that said...  if it must be a specific avatar that you absolutely must have, render out  1 frame of your chosen avatar, open it in Photoshop, modify and edit to your hearts content, then re-import into CrazyTalk, go thru the photo fitting, and boom your customized avatar.