High intensity focused ultrasound and non-invasive body contouring
Liposuction (lipoplasty) first appeared as a procedure approximately 25 years ago as a technique to produce contour improvements with a minimally invasive approach. When it was introduced, it represented a quantum leap from the Pitanguy-style body contouring through excision of skin and fat deposits. Today, it remains a mainstay of esthetic surgery and one of the most requested esthetic procedures. Although a variety of attempts at noninvasive body contouring with energy-based technologies have been proposed, most had technological shortcomings, poorly-characterized outcomes, and/or a poor risk-benefit profile. Even in situations where multimodal approaches of mechanical force, laser, and radiofrequency energy have been used simultaneously, patients have not achieved uniformly satisfactory results. The theory of a noninvasive approach for body contouring optimally involves the application of some sort of energy to ablate adipocytes and tighten collagen that is found within the midlamellar matrix of tissue (MLM). The question that follows is how does one accomplish this task and at the same time avoid fundamental problems with tissue thermodynamics from bulk heating of tissue or full-thickness epidermal injury. Energybased systems that utilize bulk heating of tissue appear only minimally better than lipoplasty, but with substantive risk of tissue necrosis, chronic inflammation, and occlusion of vascular structures. Transcutaneous radiofrequency technologies become problematic due to treatment discomfort and risks of thermal injury to skin. Pharmacologic approaches (injection lipolysis or "mesotherapy") have been considered, yet remain problematic because of the small areas that are treated and the presence of chronic inflammation in tissues. 1 Cold-based devices may improve contour, yet cannot be expected to tighten collagen in the MLM. These heat subtraction treatment devices appear to produce contour improvements through reduction of superficial fat and skin retraction only. External low-level or "cold" laser techniques have been reported as applicable for body contouring, yet with poorly-controlled studies and short, meaningless follow up periods. This chapter will cover what appears to be a promising technology of high-intensity focused thermal ultrasound that is designed to improve body contour.