Even though it may seem like a dream job, the interviewer wants to know that you have realistic expectations of the role and that you will not be blindsided if problems or challenges present themselves. Keep your answer simple. It is okay to ask for clarification on the position if you do not fully understand what challenges are in store for you.
"I think the greatest challenges in this role will be to learn the proper operation of the equipment. Another challenge will be the physical aspect of the position as I will be required to stand and walk around most of the day. I will be sure to pay keen attention to training and ask questions along the way. In regards to the physical component - I will get used to the additional activity after just a couple of days, I'm sure."
"I think the added responsibility of running one of the highest volume departments in the hospital will be an adjustment, but it's a welcome challenge. I am looking forward to tackling it head on and growing through the challenges, because I know on the other side of those challenges, of that responsibility, are the biggest opportunities."