Specifically, fictional doctors/professors of science and medicine on TV, who are practicing experts -- so Doctor Who's The Doctor cannot be included. You can choose ONE of my fairly extensive suggestions below, or add your own as an "other vote". Why not peruse this Wikipedia article to help jog your memory?
This poll will close on Saturday 9 April @5PM GMT. The result will be posted shortly afterwards. As always, helping to spread the word about this poll via Facebook/Twitter would be much appreciated. Or direct people here.