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Non-thermal, non-cavitational, 20kHz Ultrasound applicators in wound healing
Abstract   Open access   Peer reviewed

Non-thermal, non-cavitational, 20kHz Ultrasound applicators in wound healing

Michael T Neidrauer, Leonid A Zubkov, Michael S Weingarten, David J Margolis and Peter Andreas Lewin
Journal of therapeutic ultrasound, v 5(11), pp 10-11
01 Sep 2016
DOI: https://doi.org/10.1186/s40349-016-0079-2
Featured in Collection :   UN Sustainable Development Goals @ Drexel
url
http://nrs.harvard.edu/urn-3:HUL.InstRepos:32630527View
Published, Version of Record (VoR)CC BY V4.0,  Open
url
https://doi.org/10.1186/s40349-016-0079-2View
Published, Version of Record (VoR) Open

Abstract

Objectives: This talk examines the challenges associated with the design of clin‐ically viable ultrasound applicators operating at the relatively low fre‐quency (20 kHz) and intensity (<100 mW/cm2, spatial peak, temporal peak) levels, and tailored to treatment of chronic wounds, such as venous or diabetic ulcers. These challenges were associated with the architecture and weight, and principle and efficiency of operation, including electrical power consumption. The ultimate goal of this work was to test the efficacy of the applicators in human subjects. Methods : A fully wearable Band‐Aid™‐like, dial‐in delivery, battery‐operated ultrasound applicator was designed. The applicator included light weight (<25g) piezoelectric flexural transducer and was powered by 10‐12V fully rechargeable lithium‐ion batteries (total weight <200g); it was able to operate for up to 4 hours between re‐charging. To emphasize the uniqueness of the design, it might be useful to note that typically, the thickness of the capacitive piezoelectric element is inversely proportional to the frequency, therefore a 20 kHz element would need to be 10 cm thick. Such element would be bulky and require hundreds of volts (demanding a large power amplifier), in excitation signal thus eliminating any chance of being a portable design. To overcome this, a mechanical displacement amplifier, which translates 2 MHz ultrasound waves into 20 kHz output at the desired pressure amplitude (55 kPa; i.e. 100 mW/cm2) with only 12 volts excitation was chosen as a preferred solution. The applicators were extensively tested to ensure that the ultrasound field energy was below the level needed to generate inertial cavita‐tion and any temperature elevation that would exceed 1°C. Also, the uniformity of the acoustic field distribution was verified. The pilot study included 32 individuals between ages of 18 and 80 having venous (n=23) or diabetic (n= 9) wounds that remained open for a minimum of 8 weeks. In compliance with the IRB study protocol the subjects were randomly assigned to either treatment or control group, with an equal chance of being assigned to receive active ultrasound treatment or sham (current standard care). Treatment sessions lasted 15 minutes and were administered once a week for a period of 12 treatments, or until the wound's closure. Clinical efficacy was evaluated by measuring the reduction in wound area over time. For both etiologies, i.e. both venous and diabetic wounds the rate of closure was statistically faster (p<.05) in the treated group compared to the control group. Results : The study findings show that the ultrasound treated venous ulcer group had statistically improved (p<0.04) rate of wound size change (reduction of 14.3%/week) compared to the rate of wound size change for the control group (increase of 3.6%/week on average). Diabetic wound closure was achieved typically after 4 sessions for treated wounds, as opposed to 7 sessions for the control group. Time to heal was also statistically faster (p<.05) for treated wounds (∼5 weeks) when compared to non‐treated wounds (∼12 weeks). Conclusions : Overall, the results from this study support the notion that low fre‐quency ultrasound treatment can successfully improve healing out‐comes in chronic wounds with different morphology and etiology. The evaluated device used safe levels (<100mW/cm2 ISPTP) of ultrasound energy and featured unique portability, which opens possibility for personalized home treatment of chronic wounds in the future.

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UN Sustainable Development Goals (SDGs)

This publication has contributed to the advancement of the following goals:

#3 Good Health and Well-Being

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Domestic collaboration
International collaboration
Web of Science research areas
Engineering, Biomedical
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