Taeyoon Son

Enhancement of optical skin clearing efficacy using a microneedle roller

Light scattering in biological tissues can be reduced by using optical clearing agents. Various physical methods in conjunction with agents have been studied to enhance the optical clearing efficacy of skin for diagnostic and therapeutic applications. In this study, we propose a new physical method to enhance the optical clearing potential of topically applied glycerol. A microneedle roller is used to easily create numerous transdermal microchannels prior to glycerol application. The optical clearing efficacy of skin is quantitatively evaluated with the use of a modulation transfer function target placed underneath ex vivo porcine skin samples. From cross-polarized images acquired at various time points after glycerol application, we find that samples treated with the microneedle roller resulted in an approximately two-fold increase in contrast compared to control samples 30 min after glycerol application. In conclusion, our data suggest that the microneedle roller can be a good physical method to enhance transdermal delivery of optical clearing agents, and hence their optical clearing potential over large regions of skin.

A physical method to enhance transdermal delivery of a tissue optical clearing agent: combination of microneedling and sonophoresis.

Various physical methods, such as microneedling, laser ablation, sonophoresis, and sandpaper, have been widely studied to enhance the transdermal delivery of tissue optical clearing (TOC) agents. A previous study demonstrated that the microneedling method could effectively enhance the permeability of a TOC agent through the skin barrier.

Fluorescent image analysis for evaluating the condition of facial sebaceous follicles

Background/purpose: Conventional methods, such as ‘Sebutape’ and ‘Sebumeter,’ can provide quantitative information on sebum excretion but cannot reflect the condition of sebaceous follicles that can be indirectly evaluated with fluorescent colors of sebum. The images of sebum excretion can be obtained with an ultraviolet‐A light that is generally called ‘Woods Lamp.’ In this study, we describe fluorescent image analysis methods for the detection of sebum and the color segmentation of sebum to evaluate the condition of sebaceous follicles.

Evaluation of Laser Beam Profile in Soft Tissue Due to Compression, Glycerol, and Micro-Needling

Various methods have been suggested to enhance photon density in biological tissues in an attempt to maximize the efficacy of laser therapy. In this study, the effects of tissue compression, glycerol, and micro‐needling methods on the laser beam profile (LBP) were investigated by quantitatively evaluating the spatial distribution of subsurface tissue photon density.

Contrast Enhancement of Laser Speckle Contrast Image in Deep Vasculature by Reduction of Tissue Scattering

Various methods have been proposed for enhancing the contrast of laser speckle contrast image (LSCI) in subcutaneous blood flow measurements. However, the LSCI still suffers from low image contrast due to tissue turbidity. Herein, a physicochemical tissue optical clearing (PCTOC) method was employed to enhance the contrast of LSCI. Ex vivo and in vivo experiments were performed with porcine skin samples and male ICR mice, respectively. The ex vivo LSCIs were obtained before and 90 min after the application of the PCTOC and in vivo LSCIs were obtained for 60 min after the application of the PCTOC. In order to obtain the skin recovery images, saline was applied for 30 min after the application of the PCTOC was completed. The visible appearance of the tubing under ex vivo samples and the in vivo vasculature gradually enhanced over time. The LSCI increased as a function of time after the application of the PCTOC in both ex vivo and in vivo experiments, and properly recovered to initial conditions after the application of saline in the in vivo experiment. The LSCI combined with the PCTOC was greatly enhanced even in deep vasculature. It is expected that similar results will be obtained in in vivo human studies.

Fabrication of a thin-layer solid optical tissue phantom by a spin-coating method: pilot study

Abstract. Solid optical tissue phantoms (OTPs) have been widely used for many purposes. This study introduces a spin-coating method (SCM) to fabricate a thin-layer solid OTP (TSOTP) with epidermal thickness. TSOTPs are fabricated by controlling the spin speed (250 to 2500 rpm), absorber concentration (0.2% to 1.0%), and the number of layers. The results show that the thicknesses of the TSOTPs are homogeneous in the region of interest. The one-layer TSOTP achieves maximum and minimum thicknesses of 65±0.28  μm (250 rpm) and 5.1±0.17  μm (2500 rpm), respectively, decreasing exponentially as a function of the spin speed. The thicknesses of the multilayer TSOTPs increases as a function of the number of layers and are correlated strongly with the spin speed (R2≥0.95). The concentration of the OTP mixture does not directly affect the thickness of the TSOTP; however, the absorption coefficients exponentially increase as a function of absorber concentration (R2≥0.98). These results suggest that the SCM can be used to fabricate homogeneous TSOTPs with various thicknesses by controlling the spin speed and number of layers. Finally, a double-layer OTP that combines epidermal TSOTP and dermal OTP is manufactured as a preliminary study to investigate the practical feasibility of TSOTPs.

Dermatological feasibility of multimodal facial color imaging modality for cross-evaluation of facial actinic keratosis

Background/Purpose: Digital color image analysis is currently considered as a routine procedure in dermatology. In our previous study, a multimodal facial color imaging modality (MFCIM), which provides a conventional, parallel‐ and cross‐polarization, and a fluorescent color image, was introduced for objective evaluation of various facial skin lesions. This study introduces a commercial version of MFCIM, DermaVision‐PRO, for routine clinical use in dermatology and demonstrates its dermatological feasibility for cross‐evaluation of skin lesions.

Sonophoresis Using Ultrasound Contrast Agents: Dependence on Concentration

Sonophoresis can increase skin permeability to various drugs in transdermal drug delivery. Cavitation is recognized as the predominant mechanism of sonophoresis. Recently, a new logical approach to enhance the efficiency of transdermal drug delivery was tried. It is to utilize the engineered microbubble and its resonant frequency for increase of cavitation activity. Actively-induced cavitation with low-intensity ultrasound (less than ~1 MPa) causes disordering of the lipid bilayers and the formation of aqueous channels by stable cavitation which indicates a continuous oscillation of bubbles. Furthermore, the mutual interactions of microbubble determined by concentration of added bubble are also thought to be an important factor for activity of stable cavitation, even in different characteristics of drug. In the present study, we addressed the dependence of ultrasound contrast agent concentration using two types of drug on the efficiency of transdermal drug delivery. Two types of experiment were designed to quantitatively evaluate the efficiency of transdermal drug delivery according to ultrasound contrast agent concentration. First, an experiment of optical clearing using a tissue optical clearing agent was designed to assess the efficiency of sonophoresis with ultrasound contrast agents. Second, a Franz diffusion cell with ferulic acid was used to quantitatively determine the amount of drug delivered to the skin sample by sonophoresis with ultrasound contrast agents. The maximum enhancement ratio of sonophoresis with a concentration of 1:1,000 was approximately 3.1 times greater than that in the ultrasound group without ultrasound contrast agent and approximately 7.5 times greater than that in the control group. These results support our hypothesis that sonophoresis becomes more effective in transdermal drug delivery due to the presence of engineered bubbles, and that the efficiency of transdermal drug delivery using sonophoresis with microbubbles depends on the concentration of microbubbles in case stable cavitation is predominant.

Cross-evaluation of optimal glycerol concentration to enhance optical tissue clearing efficacy

The efficacy of light therapeutic and diagnostic applications can be enhanced by employing optical tissue clearing (OTC) agents to minimize light scattering in tissue. This study aimed to investigate the optimal concentration of glycerol, so that it can be efficiently used as an OTC agent in dermatology.

Development of polarization dental imaging modality and evaluation of its clinical feasibility.

OBJECTIVES In the evaluation of tooth color, the specular reflection caused by roughness or saliva on the tooth surface may cause artefacts in image analysis. In this study, a polarization dental imaging modality (PDIM) was developed to obtain cross-polarized images and, therefore, to address the problem of specular reflection. Its clinical validity was evaluated by performing 3 studies of shade tab selection for implant, plaque distribution detection, and evaluation of tooth whitening. METHODS In vivo human tooth and shade guide color images were obtained, and the minimum color difference between them was calculated for the best color matching shade tab selection. A dental plaque disclosing agent was used to differentiate plaque regions on teeth, and plaque distribution was detected by applying the K-means algorithm. In vivo human teeth were treated with a commercial tooth whitening gel, and tooth whitening was quantitatively evaluated using the PDIM images. RESULTS The PDIM produced repeatable glare-free tooth color images by effectively removing the specular reflection from the tooth surface. The cross-polarized tooth images were successfully utilized for shade guide selection, plaque detection, and tooth whitening by minimizing artefacts in the quantitative image analysis. The PDIM could simultaneously provide both qualitative and quantitative assessment of the tooth condition in clinical diagnosis. CONCLUSIONS The clinical feasibility of the PDIM was successfully verified in 3 clinical studies by showing its clinical efficacy as a new imaging modality.