Although human research is limited, I don't believe there is enough evidence to disgard the use of U/S in PT all together either. It completely depends on your target tissue and goal of treatment. If you are targeting a relatively superficial tissue that is higher in collagen content (such as ligament or tendon), I believe the use of continuous U/S as an adjunct to other therapies- manual and especially therapeutic exercise could very well be warranted. As long as you've taking proper precautions- I think the possible benefits outweigh the harm. Also, you can always monitor patient response and alter your treatment approach from there. If you are seeing no improvements re-evaluation would be appropriate.