Roadmap to Design Low Frequency (20-100 kHz), Low Intensity (100 mW/cm~2) Ultrasound Applicator for Chronic Wound Treatment

摘要

Chronic wounds, such as venous and diabetic ulcers, cost the U.S healthcare system 25billionannuallyandtheirmediantreatmentexpensewasreportedtobeabout16,500 per patient. An acceleration of healing time directly translates into a reduction of healthcare costs; thus a positive clinical outcome would create a substantial societal impact. The primary goal of this work was to present a road map for design and implementation of a clinically viable ultrasound applicator that was specifically developed to treat chronic wounds; the applicator is the first truly wearable device with a proven record of successful treatment of human patients. The device operates in the kHz (20-100) range of frequencies and is intentionally designed to avoid generation of inertial cavitation and temperature elevation. To achieve these goals the peak acoustic output pressure amplitude is limited to 55 kPa, corresponding to a spatial peak temporal peak intensity of 100 mW/cm~2. This level of intensity is considered safe to apply for extended (up to four hours) periods of time. The patch-like applicator design is suitable to be embedded in wound dressing and with its light weight (<;20g), and circular (40 mm diameter) disk shape architecture, is well suited for chronic wound treatment. The quantitative absolute calibration (to within +1-10 %) of the device acoustic output is conveniently implemented making use of reciprocity calibration. The calibration permits linkage of exposure parameters with the rate of wound closure, allowing personalization of patient treatment. A small (n=8) pilot study on the effects of the applicator on diabetic ulcers healing time is also presented. The outcome of the study indicated that the average time to wound closure was 4.7 weeks for subjects treated with the active ultrasound applicator, compared to 12 weeks for subjects treated with a sham applicator, suggesting that patients with diabetic ulcers may benefit from the proposed treatment.