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Heat therapy has long been used for treatments in dermatology and sports medicine. The use of laser, RF, microwave,
and more recently, ultrasound treatment, for psoriasis, collagen reformation, and skin tightening has gained considerable
interest over the past several years. Numerous studies and commercial devices have demonstrated the efficacy of these
methods for treatment of skin disorders. Despite these promising results, current systems remain highly dependent on
operator skill, and cannot effectively treat effectively because there is little or no control of the size, shape, and depth of
the target zone. These limitations make it extremely difficult to obtain consistent treatment results. The purpose of this
study was to determine the feasibility for using acoustic energy for controlled dose delivery sufficient to produce
collagen modification for the treatment of skin tissue in the dermal and sub-dermal layers. We designed and evaluated a
curvilinear focused ultrasound device for treating skin disorders such as psoriasis, stimulation of wound healing,
tightening of skin through shrinkage of existing collagen and stimulation of new collagen formation, and skin cancer.
Design parameters were examined using acoustic pattern simulations and thermal modeling. Acute studies were
performed in 201 freshly-excised samples of young porcine underbelly skin tissue and 56 in-vivo treatment areas in 60-
80 kg pigs. These were treated with ultrasound (9-11MHz) focused in the deep dermis. Dose distribution was analyzed
and gross pathology assessed. Tissue shrinkage was measured based on fiducial markers and video image registration
and analyzed using NIH Image-J software. Comparisons were made between RF and focused ultrasound for five energy
ranges. In each experimental series, therapeutic dose levels (60degC) were attained at 2-5mm depth. Localized collagen
changes ranged from 1-3% for RF versus 8-15% for focused ultrasound. Therapeutic ultrasound applied at high
frequencies can achieve temperatures and dose distributions which concentrate in a depth profile that coincides with the
location of maximum structural collagen content in skin tissues. Using an appropriate transducer configuration produces
coverage of significant lateral area, thus making this a practical approach for treatment of skin disorders.
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