Can Ultrasound have a false positive for fracture?

When I see a runner who's had a sprain or a trip or a fall or something, the #1 concern is to make sure no bones are broken. 

Most of the time, what I do is I take a portable ultrasound unit with me so that I can look at the foot on the spot and try to figure out whether or not there is a fracture. 
 
I had a question about this as a comment on one of the Doc On The Run YouTube video episodes where I was talking about ultrasound imaging in the foot when you're a runner. 

The question was, “Can you get a false negative? Can you get a false positive?”
 
Can you get a false negative if you're looking for a fracture with an ultrasound unit? 

Well, that's a great question and that's what we're talking about today on the Doc On The Run Podcast.