Sonophoretic delivery for contrast and depth improvement in skin optical coherence tomography

Our previous studies demonstrated the feasibility of using a sonophoretic delivery method to enhance skin light transmittance with topical application of optical clearing agents using spectroscopy. In this study, we examined the effect of ultrasound [surgeon-performed (SP)] on optical coherence tomography (OCT) imaging depth and contrast of in vitro and in vivo skin. Sixty percent glycerol (G) and SP with a frequency of 1 MHz and a power of 0.75 W over a 3 cm probe was simultaneously applied for 15 min. We find that 60% G/SP results in a twofold increase in achievable OCT imaging depth for in vitro porcine skin and induces 11% shrinkage of the skin. For in vivo human skin, OCT imaging depth and contrast is significantly improved within 30 min of treatment. Imaging depth is increased from 1.4 to 2 mm, and dermal vasculature is clearly visualized in the deeper tissue. OCT imaging of the skin treated with 60% glycerol shows little enhancement in contrast or imaging depth over 60 min. We first demonstrate the superb ability of sonophoretic delivery for in vivo human skin optical clearing, particularly in accelerating the clearing rate. The greater clearing efficiency of glycerol implemented with ultrasound may be attributed to more effective dehydration.