20 week anatomy scan

I just came back from my 20 week anatomy scan, and I thought I'd get the cool 3D imaging so I could see baby's face in detail, etc. The radiologist said that they rarely do 3D scans because of the amount of radiation that they give off, and that there aren't many studies on its impact on babies. She said 2D gives all the detailed info they need, without risk. Curious if anyone else has been told this? I have a few friends who've had the 3D scan at this point...thought her feedback was a bit odd.