Given the several difficulties associated with histology, including difficulty in continuous monitoring, this study aimed to investigate the feasibility of optical imaging modalities—cross-polarization color (CPC) imaging, erythema index (EI) imaging, and laser speckle contrast (LSC) imaging—for continuous evaluation and monitoring of arthritis in animal models. C57BL/6 mice, used for the evaluation of arthritis, were divided into three groups: arthritic mice group (AMG), positive control mice group (PCMG), and negative control mice group (NCMG). Complete Freund’s adjuvant, mineral oil, and saline were injected into the footpad for AMG, PCMG, and NCMG, respectively. LSC and CPC images were acquired from 0 through 144 h after injection for all groups. EI images were calculated from CPC images. Variations in feet area, EI, and speckle index for each mice group over time were calculated for quantitative evaluation of arthritis. Histological examinations were performed, and the results were found to be consistent with those from optical imaging analysis. Thus, optical imaging modalities may be successfully applied for continuous evaluation and monitoring of arthritis in animal models.
An imaging system was developed based on single-channel and transparent rotating deflector (TRD) to achieve stereoscopic video imaging. To acquire images at high frame rate, a CMOS camera was used with triggering function allowing image acquisition at certain time point. Stepping motor was controlled to rotate in an arc, stopping at the edge for image acquisition. The acquired 2D images were displayed in stereoscopic 3D using active shutter glasses and conventional display monitor. Using microcontroller (MCU) as centralized control system, system components were controlled and synchronized through using general purpose input/output (GPIO) ports. The created system was evaluated for two factors: motor rotation analysis based on MCU signal generation; and image property based on coefficient of variation calculation.
Arthritis is a chronic inflammatory disease that induces potentially damaging and commonly disabling. Various imaging modalities have been used for the evaluation of arthritis. This study aimed to investigate the feasibility of laser speckle contrast image (LSCI) in the evaluation of the severity and early stage of arthritis in animal model. Arthritis was induced on mouse foot and evaluated by a trained expert and the LSCI. The arthritis severity was quantitatively evaluated by speckle index (SI) computed from LSCI. In visual inspection by an expert, it was difficult to evaluate the arthritis because there was no noticeable different between control mouse group (CMG) and arthritis mouse group (AMG) in erythema. However, arthritis was easily evaluated by significant SI different between the CMG and AMG. In addition, the LSCI also successfully evaluated the early stage of arthritis, presenting different SI distribution depending on lesion.
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 (R 2 ≥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 (R 2 ≥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.
The laser scattering in tissue is significant in diagnostic and therapeutic purposes of laser. Many studies have been
conducted to minimize laser scattering in tissue and therefore, to maximize the clinical efficacy by enhancing photon
density. Optical clearing agents (OCAs) have been employed for optical tissue clearing (OTC). This study was aimed to
investigate the optimal concentration of an OCA, glycerol, in topical application,, so that it can be utilized for clinical
diagnosis and therapy in dermatology. Glycerol was topically applied to avoid possible edema caused by dermal
injection. The effect of OTC was quantitatively evaluated as a function of the concentration of glycerol with various
methods. Optical methods such as optical coherence tomography (OCT) and an integrating sphere were used to assess
the enhancement of light penetration depth and refractive index matching. In addition, a non-optical method, ultrasound
scanner, was utilized to evaluate quantitatively collagen dissociation. The results revealed that 70 % glycerol was the
optimal concentration of OTC for topical application. This study may provide a guideline regarding to the use of
glycerol for optimal diagnostic and therapeutic effects in dermatology.
Recently, it has become more important to objectively analyze teeth color in terms of esthetical point of view. In the
evaluation of tooth color, the specular reflection caused by saliva on tooth may cause artifacts in analysis. In this study,
a polarization dental imaging modality (PDIM) was developed to address the specular reflection problems. Clinical
validity was evaluated by performing three studies such as shade-guide selection for implant, plaque distribution
detection, and evaluation of tooth whitening. In the selection of shade-guide, in-vivo human teeth and shade-guide
color images were obtained. The minimum color difference between shade-guide and tooth was calculated using
Euclidian distance. In the plaque distribution detection, teeth disclosing agent was used to differentiate plaque from
teeth and images were taken. In the evaluation of whitening, whiteness indices were calculated using 29 shade-guide
images. Results presented that the new imaging modality could provide reproducible images by effectively removing
the specular reflection on teeth surface and therefore, minimize artifacts in the quantitatively analysis of shade-guide
selection, plaque detection, and tooth whitening. In conclusion, the PDIM potentially proved its clinical efficacy as a
new imaging modality.
Noninvasive low-level laser devices have been introduced for therapeutic purpose in medicine. However, low-level laser
cannot deliver enough photon density to expect positive therapeutic results in deep tissue layer due to light scattering
property in tissue. In order to overcome the limitation, this study was aimed to develop a negative pressure applied low-level
laser probe to enhance laser transmission and, therefore, photon density in soft tissue. In order to evaluate clinical
feasibility of developed laser probe, ex-vivo experiments were performed with porcine skin samples and laser
transmissions were quantitatively measured as a function of tissue compression. The laser probe has an air suction hole
to apply negative pressure to skin, a transparent plastic body to observe tissue deformation, and a small metallic optical
fiber guide to support the optical fiber when negative pressure was applied. By applying negative pressure to the laser
probe, the porcine skin under the fiber guide is compressed down and, low-level laser is emitted into the skin. Diffusion
images of laser in the skin samples were acquired with a CCD camera and analyzed. Compared to the intensity without compression, the peak intensity of laser beam profiles increased about 2~2.5 times and FWHM (Full Width at Half Maximum) decreased about 1.67~2.85 times. In addition, the peak intensity was linearly increased as a function of
compression. In conclusion, we verified the enhancement of laser transmission and therefore, photon density in tissue by
applying negative pressure to the developed low-level laser probe and its potential for clinical usefulness.
The light does not penetrate deeply into the skin tissue because of tissue turbidity. Light penetration depth in skin tissue can be increased by using optical clearing agents such as glycerol, glucose and dimethyl sulfoxide(DMSO). The stratum corneum prevents most optical skin clearing agent from diffusing into the tissue. Previous studies demonstrated the optical tissue clearing effect using optical clearing agents and presented several physical methods to improve transdermal delivery of optical clearing agents. In previous study, we introduced a micro-needling method to enhance optical clearing efficacy against skin barrier and suggested quantitative analysis method to evaluate the optical tissue clearing efficacy. In this study, we present a new physical micro-needling method combined with sonophoresis to further enhance the optical tissue clearing efficacy. The optical tissue clearing effect was quantitatively evaluated with a modulation transfer function target placed under ex-vivo porcine skin samples. To improve transdermal delivery of glycerol, 70% glycerol solution as optimal concentration was topically applied. In conclusion, the samples treated with micro-needling method and sonophoresis resulted in noticeable optical tissue clearing effect.
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.
Laser speckle imaging modality is one of widely used methods to evaluate blood flow because of its simplicity.
However, laser speckle image has a limitation in the evaluation of subcutaneous blood flow due to its low contrast
perfusion image. Various methods have been tried to enhance the perfusion image contrast. Such methods presented
positive results in some degree. However, it could not be fundamental solutions due to low penetration depth of lasers
restricted by optical tissue scattering property. This study suggests a method to enhance the perfusion image contrast of
laser speckle imaging modality by increasing the penetration depth of lasers. An optical clearing agent (glycerol) was
topically applied on skin treated with micro-needle roller in order to reduce the time period of optical tissue clearing and
therefore, enhance the penetration depth of laser. In this study, we investigated the effect of glycerol and micro-needling
methods in the contrast enhancement of laser speckle perfusion skin image and presented the results of in-vitro
and in-vivo animal experiment.