You probably can't get closer than that without adding some words. Which words? Before we can answer that, you have to think, what do I mean by saying I'm "the" doctor? The only one in the room? The only one in the town? The one you were all expecting? The one you were told about yesterday? To translate from a language that uses definite and indefinite articles, to one that doesn't, you have to trace the thought back a little way.
Ah, thank you. The context would be 'I am the only doctor in town."
