ULTRASOUND ENHANCED SKIN OPTICAL CLEARING:MICROSTRUCTURAL CHANGES

Our previous studies demonstrated the ultrasound-induced skin optical clearing enhancement with topical application of optical clearing agents on in vitro porcine skin and in vivo human skin.The objective of this study was to investigate the possible mechanisms of the enhanced skin optical clearing by ultrasound medications.Optical clearing effects of ex vivo guinea pig abdomen skin topically applied with 60% glycerol or the combination of 60% glycerol and ultrasound were studied by optical coherence tomography(OCT).Microstructure of skin surface was examined by scanning electron microscopy(SEM).Ultrasound with a frequency of 1MHz and a power of 0.75W over a 3-cm probe was simultaneously applied with glycerol solution for 15min.The combination of 60% glycerol and ultrasound results in a 19% increase in OCT 1/e light penetration depth after 30min,which is much better than 60% glycerol alone.SEM images demonstrated that changes in skin microstructure due to the tight order of the lipid bilayers in the stratum corneum disrupted and the separation of keratinocytes by the application of ultrasound contribute to the ultrasound-enhanced intact skin optical clearing effects.

Quantitative evaluation of enhanced laser tattoo removal by skin optical clearing

Lasers have been widely used for tattoo removal,but the limited light penetration depth calused by high skin scattering property restricts the therapeutic outcome of deep tattoo.Skin optical clearing method,by introducing optical clearing agent(OCA)into skin,has shown some im-provement in the effect of laser tattoo removal.In this study,the enhanced laser tattoo removal has been quantitatively assessed.OCA was applied to the skin of tattoo animal model and Q switched Nd:YAG laser(1064 nm)irradiation was used to remove the tattoo.The skin evaluation instrument(Mexameter probe,MPA580)was applied to measure the content of tattoo pigment before and after laser treatment,and then the clearance rate of pigment was calculated.Further,Monte Carlo(MC)method was utilized to simulate the efecet of skin optical clearing on light transmission in tattoo skin model.By comparing the pigment change of tattoo areas respectively treated with OCA plus laser and single laser,it was found that pigment clearance of the former tattoo area was increased by 1.5-fold.Further,the MC simulation verifed that the reduced light scattering in skin could increase the effective dose of lumninous fux reaching to the deep tattoo regions.It can be concluded from both experiment and theoretical simulations that skin optical clearing technique could improve the outcome of laser tattoo re moval,which should be beneficial for clinical laser tattoo removal and other laser pigment elimination.