What I'd like to do is to create a simple device which can mimic medical ultrasound devices. Of course, these devices are really complicated,
Sorry, Mike, can you tell me where the OP explained the scope of his project ? (what exactly is his output ?) I didn't see it. The only reference I have to go on is his reference to medical ultrasound . It isn't very useful as a medical device if it doesn't generate an image does it ? If you handed the doctor a list of analog values or whatever, would that help him ? If you are going to talk about a simple medical ultrasound , then you are by definition talking about an image as that is the whole objective of the medical device.
If you talk about a simple medical ultrasound with no medical value, then yeah go ahead, but it's not medical, it's some arduino hobbyist's weekend project, because I personally don't see how you can use the words "medical" and "ultrasound" in the same sentence without someone expecting a picture at the end. I am not being aggressive. If I were , the OP would have told me to bugger off already. XD