A new sonographic method for the evaluation of skin permeability changes after irradiation with low-frequency ultrasound

Abstract

The irradiation of the skin with low-frequency ultrasound (42 MHz) increases the skin permeability, allowing the US stimulated drug delivery (sonophoresis). The changes in the skin permeability is generally demonstrated with the measurement of corneometry and transepidermal water loss (TEWL). A novel ultrasound scanner with a 50 MHz probe was used for acquiring images of the skin (penetration depth few millimeters). The images show the different epidermal and dermis layers. A specially designed plexiglas basin containing an US transducer was used. Water was used as matching medium. The transducer was set to generate a 42 MHz continuous wave US beam with an intensity of 150 mW/cm2 for a chosen preset time. Ninety healthy volunteers were submitted to exposure of the back of the hand. The back of the hand of each person was scanned at 50 MHz before the irradiation and after 1, 15 and 60 minutes. A significant variation of the stratum corneum and the derma on the sonographic image was found. A particular software code was developed in order to quantify the amount of the variation in the image, using different parameters (entropy, energy, skewness, kurtosis, etc.) related to the pixel value in different regions of interest and to the cumulated profile along lines perpendicular to the skin surface. The variations in the parameters so defined were demonstrated to be statistically significant and with a sensibility much higher than corneometry and TEWL. This new approach allow to better understand the mechanism and quantify the changes in the skin permeability.

Low‐Frequency Low‐Intensity Ultrasounds Do Not Influence the Survival and Immune Functions of Cultured Keratinocytes and Dendritic Cells

“…To this end, the effects of low-frequency US were analyzed on keratinocyte cultures established from skin biopsies of healthy donors. US were employed on cell cultures at frequency (42 KHz) and intensity (0.15 W/cm 2 ) values known to be effective in enhancing human skin permeation in vivo [ 12 ]. We firstly investigated on the US effects on keratinocyte expression and activation of ERK1/2 proteins, which sustain proliferative and self-protective programs in keratinocytes [ 18 ].…”

“…In this study, we investigated whether application of low-frequency US influenced the physiological and immune functions of human keratinocytes and DC in vitro. Low-frequency US were used at frequency (42 KHz) and intensity (0.15 W/cm 2 ) values known to be effective in enhancing human skin permeation in vivo [ 12 ]. It has been widely documented that, during inflammatory skin reactions, following exposure to lymphokines, especially IFN- γ and TNF- α , epidermal keratinocytes become an important source of inflammatory molecules [ 14 , 15 ].…”