Ultrasound energies for therapy in a theoretical model of the skin

Adipocytes in the white adipose tissue underneath the skin are believed to be involved in dermatological pathologies, such as atopic dermatitis and psoriasis. As these cells are sensitive to temperature alteration, researchers have considered using temperature to manipulate adipocyte biology for the treatment of various skin conditions. Very high frequency ultrasound is one method for concentrating energy within a small area to influence adipocytes. Biophysicist Ilja Kruglikov has investigated the optimal clinical ultrasound range and reports his findings in AIP Advances.

Kruglikov utilized a thermodynamic model and ran simulations using an in-house code to calculate the temperature fields in the skin, aiming to identify ultrasound applications that induce high temperature gradients without damaging the skin. Kruglikov emphasizes the importance of the model’s layering in accurately assessing the temperature fields induced by ultrasound waves. He explains that differing absorption between layers determines the distribution of energy, especially in the boundary between skin and adipose layers.

Calculations were made at three frequencies, 3, 10 and 19MHz. The temperature gradient was low after 3MHz applications but as high as 7.5°C/mm at 10MHz and 14.0°C/mm at 19MHz for intensities of 10.0 W/cm². Many other variables were considered in the calculations, including skin thickness and blood flow rate. It was found that 19MHz was the optimal ultrasound frequency for concentrating energy near the interface. The results also identified the upper limits of ultrasound frequencies and intensities within set time frames.

Kruglikov describes his work as “an important step for the clinical applications of these modalities” and that in vitro experiments would now proceed. He also mentioned the potential to investigate a combination of ultrasound and radio-waves in treating skin conditions.

Source: “Modeling of the spatiotemporal distribution of temperature fields in skin and subcutaneous adipose tissue after exposure to ultrasound waves of different frequencies,” by Ilja L. Kruglikov, AIP Advances (2017). The article can be accessed at https://doi.org/10.1063/1.4997833 .