Does Ultherapy cause apoptosis of healthy cells+healing by scar tissue? I'm a med resident, please explain scientifically

I understand that some drs will always stand by ultherapy. But can someone give a scientific explanation of what happens? Does it in fact cause injury and therefore apoptosis to healthy cells, and the response is hard to control so you dont know how the ultrasound waves will bounce around? How can you be a 100% sure there will be no scarring/internal damage? There are no long term clinical trials. What if it does indeed cause damage longterm, but short term it "appears" to create a tighter look?