Answer:
There is no mention of the use of external ultrasound in liposuction in any of the consulted texts. Based on the biologic effect of ultrasound waves on tissue, it is known that lower levels of energy are needed to disrupt low density tissues such as fat, where molecular cohesion is weaker. Common sense suggests that external ultrasonic waves which need to traverse the skin barrier would be less effective than ultrasonic energy delivered directly to subcutaneous fat via a probe, however there is no study comparing these two methods.