Yeah mine was about 15 mins. Exactly like first PP said, they measure head/brain, heart, stomach, spine, legs, your ovaries and cervix too, as well as the placenta.
I had to drink 32oz water an hour before and had to hold it until afterwards. It was slightly uncomfortable but once you see your little baby its not a bother. When they're done tho you'll feel you're going to explode lol
Mine was only abdominal, but I've read they can do tv if they need better images of your cervix
It was the best 15 mins of my life!!