Sending a follow-up thank you card? Yes. Good form is to send it to the office of admissions and they will deliver it to him / her.
Hanging around outside of his / her office to tell them thanks? Probably not.
At my first interview, they stated a protocol for contact that I think is generalizable: 1) It is OK to send thank-you cards. Send them to the office of admission and we'll be sure to get them to your specific interviewer. 2) Please refrain from emailing or calling your interviewer directly for at least 1-2 weeks after your interview. I'm thinking this has more to do with tact, and ensuring no unfair advantage if you attempt to clarify or expand upon some of your answers, as other students may not have the opportunity to do this. Also, it may just be annoying to the interviewer who sees X amounts of applicants and has either a medical practice or research they would prefer not to be consistently interrupted.
Hope that helped a little?