Agreed. You could substitute ultrasound waves with electromagnetic waves in this same conversation. We use EM waves every day for diagnotics -- at the 740-380nm

Agreed. You could substitute ultrasound waves with electromagnetic waves in this same conversation. We use EM waves every day for diagnotics -- at the 740-380nm range because that's visible light. 10x-100x frequency of that is ultraviolet, which is harmful. And as for resonant frequencies, it doesn't seem unreasonable to me that certain frequencies could denature certain proteins or have other effects.