SignificanceLaser speckle contrast images (LSCIs) have been utilized to monitor blood flow perfusion. However, they have conventionally been observed on monitor screens, resulting in potential spatial mismatching between the imaging region of interest (IROI) and monitor screen.AimThis study proposes a projection mapping (PM) system for LSCIs (PMS_LSCI) that projects LSCIs to directly observe the blood flow perfusion in the IROI.ApproachThe PMS_LSCI consists of a camera, imaging optics, a laser projector, and graphic user interface software. The spatial matching in the regions of interest was performed by adjusting the software screen of the LSCI in the IROI and evaluated by conducting in-vitro and in-vivo studies. An additional in-vivo study was performed to investigate the feasibility of real-time PM of the LSCI.ResultsThe spatial mismatching in the regions of interest was ranged from 2.74% to 6.47% depending on the surface curvature. The PMS_LSCI could enable real-time PM of LSCI at four different blood flow states depending on blood pressure.ConclusionsThe PMS_LSCI projects the LSCI in the IROI by interacting with a projector instead of the monitor screen. The PMS_LSCI presented clinical feasibility in the in-vitro and in-vivo studies.
Skin necrosis may occur due to no blood circulation after skin grafting. In present, it may not be easy to make sure that the blood is normally circulated to the trans implanted skin flap. A real-time laser speckle imaging modality (LSIM) developed in our laboratory was utilized to evaluate early skin necrosis. Two experiments were performed: 1) in-vitro optical tissue phantom (OTP) experiment to quantitatively identify the feasibility of blood flow variation; 2) in-vivo animal skin flap surgery experiment to induce skin necrosis in mouse. In comparison of laser speckle images (spatial and temporal speckle contrast analysis) and color images after skin flap surgery, laser speckle image resulted in better efficiency in evaluating skin necrosis than the color image. In laser speckle images, the temporal contrast image was more efficient than spatial contrast image in evaluating skin necrosis. In conclusion, it may be useful employing the real-time LSIMin noninvasively evaluating blood flow variation in skin necrosis.
In clinical diagnosis, subcutaneous vein detection may be a useful method to investigate the morphological information of skin and to perform intravenous injection. Although an enhanced image may provide more effective information than a bare eye, medical doctors may feel uncomfortness due to the visual offset between the images displayed on the monitor and the actual target. This study was aimed to develop a projection based real-time subcutaneous vein detection imaging modality (PSVDIM) and to evaluate its feasibility in optical tissue phantom (OTP) and human. Projection-based technology allows users to intuitively know the size and location of the region of interest. The PSVDIM consists of a Near Infrared (NIR) camera and eight NIR LEDs, and laboratory built program based on MATLAB . The images acquired with or without PSVDIM were compared to evaluate the performance of PSVDIM. With the PSVDIM, it was possible to find blood vessels that were not clearly distinguished by bare eye.
Although the patients with cancer on pancreas or pancreaticobiliary duct have been increased, it is very difficult to detect and to treat the pancreatic cancer because of its low accessibility and obtuseness. The pancreatic cancer has been diagnosed using ultrasonography, blood test, CT, endoscopic retrograde cholangiopancreatography (ERCP), endoscopic ultrasonography (EUS) and etc. Normally, light can be delivered to the target by optical fibers through the ERCP or EUS. Diffusing optical fibers have been developed with various methods. However, many of them have mechanical and biological problems in the use of small-bend-radius apparatus or in tissue area. This study developed a therapeutic cylindrical diffusing optical fiber probe (CDOFP) for ERCP and EUS which has moderate flexibility and solidity to treat the cancer on pancreaticobiliary duct or pancreas. The CDOFP consists of a biocompatible Teflon tube and multimode glass fiber which has diffusing area processed with laser and high refractive index resin. The CDOFP was characterized to investigate the clinical feasibility and other applications of light therapy using diffusing optical fiber. The results presented that the CDOFP may be used in clinic by combining with endoscopic method, such as ERCP or EUS, to treat cancer on pancreas and pancreaticobiliary duct.
This study introduces a single-channel optical video stereomicroscope based on a transparent rotating deflector (TRD) for high-resolution and high-magnification stereomicroscopy. The existing stereomicroscopes have some limitations, such as limited resolution and magnification, fixed optical channel, and the necessity to use higher quality and higher cost optical channel components compared with the conventional optical microscopes. The goal of this study was to develop a method for improved stereo imaging and stereovision for optical microscopy. Here, we demonstrate the generation of stereo video images of left and right pairs by the refraction of light passing through a motorized TRD. We estimated the corresponding rotation angles for human stereovision and the required torque. In addition, we evaluated the image quality stability under the TRD rotation.
Although numerous studies have been performed to fabricate various optical tissue phantom (OTP) models, the fabrication of OTPs that simulate skin layers is laborious and time-consuming owing to the intricate characteristics of skin tissue. This study presents various OTP models that optically and structurally simulate the epidermis–dermis skin layer. The spin-coating method was employed to reproduce a uniform thin layer that mimics the epidermis layer, and the fabrication parameters were optimized for epoxy and silicone reference materials. Various OTP models simulating blood vessels and hyperpigmentation lesions were fabricated using the two reference materials to determine their feasibility. The suitability of each of the two reference materials for OTP fabrication was qualitatively evaluated by comparing the quality of the OTP models.
A stereoscopic imaging modality was developed for the application of ophthalmology surgical microscopes. A previous study has already introduced a single-channel stereoscopic video imaging modality based on a transparent rotating deflector (SSVIM-TRD), in which two different view angles, image disparity, are generated by imaging through a transparent rotating deflector (TRD) mounted on a stepping motor and is placed in a lens system. In this case, the image disparity is a function of the refractive index and the rotation angle of TRD. Real-time single-channel stereoscopic ophthalmology microscope (SSOM) based on the TRD is improved by real-time controlling and programming, imaging speed, and illumination method. Image quality assessments were performed to investigate images quality and stability during the TRD operation. Results presented little significant difference in image quality in terms of stability of structural similarity (SSIM). A subjective analysis was performed with 15 blinded observers to evaluate the depth perception improvement and presented significant improvement in the depth perception capability. Along with all evaluation results, preliminary results of rabbit eye imaging presented that the SSOM could be utilized as an ophthalmic operating microscopes to overcome some of the limitations of conventional ones.
As the interest in skin was increased, number of studies on skin care also have been increased. The reduction of skin
density is one of the symptoms of skin aging. It reduces elasticity of skin and becomes the reason of wrinkle formation.
Low level laser therapy (LLLT) has been suggested as one of the effective therapeutic methods for skin aging as in
hasten to change skin density. This study presents the effect of a minimally invasive laser needle system (MILNS)
(wavelength: 660nm, power: 20mW) in skin density. Rabbits were divided into three groups. Group 1 didn't receive any
laser stimulation as a control group. Group 2 and 3 as test groups were exposed to MILNS with energy of 8J and 6J on
rabbits' dorsal side once a week, respectively. Skin density of rabbits was measured every 12 hours by using an
ultrasound skin scanner.
Tibial defect is very common musculoskeletal disorder which makes patient painful and uncomfortable. Many studies
about bone regeneration tried to figure out fast bone healing on early phase. It is already known that low level laser
therapy (LLLT) is very convenient and good for beginning of bone disorder. However, light scattering and absorption
obstruct musculoskeletal therapy which need optimal photon energy delivery. This study has used an interstitial laser
probe (ILP) to overcome the limitations of light penetration depth and scattering. Animals (mouse, C57BL/6) were
divided into three groups: laser treated test group 1 (660 nm; power 10 mW; total energy 5 J) and test group 2 (660 nm;
power 20 mW; total energy 10 J); and untreated control group. All animals were taken surgical operation to make tibial
defect on right crest of tibia. The test groups were treated every 48 hours with ILP. Bone volume and X-ray attenuation
coefficient were measured on 0, 14th and 28th day with u-CT after treatment and were used to evaluate effect of LLLT.
Results show that bone volume of test groups has been improved more than control group. X-ray attenuation coefficients
of each groups have slightly different. The results suggest that LLLT combined with ILP may affect on early phase of
bone regeneration and may be used in various musculoskeletal disease in deep tissue layer.
Stereoscopic retinal image can effectively help doctors. Most of stereo imaging surgical microscopes are based on dual optical channels and benefit from dual cameras in which left and right cameras capture corresponding left and right eye views. This study developed a single-channel stereoscopic retinal imaging modality based on a transparent rotating deflector (TRD). Two different viewing angles are generated by imaging through the TRD which is mounted on a motor synchronized with a camera and is placed in single optical channel. Because of the function of objective lens in the imaging modality which generate stereo-image from an object at its focal point, and according to eye structure, the optical set up of the imaging modality can compatible for retinal imaging when the cornea and eye lens are engaged in objective lens.
This study investigates the feasibility of an endoscopic laser speckle imaging modality (ELSIM) in the measurement of perfusion of flowing fluid in optical bone tissue phantom(OBTP). Many studies suggested that the change of cochlear blood flow was correlated with auditory disorder. Cochlear microcirculation occurs under the 200μm thickness bone which is the part of the internal structure of the temporal bone. Concern has been raised regarding of getting correct optical signal from hard tissue. In order to determine the possibility of the measurement of cochlear blood flow under bone tissue using the ELSIM, optical tissue phantom (OTP) mimicking optical properties of temporal bone was applied.
This paper introduces a stereoscopic video imaging modality based on a transparent rotating deflector (TRD). Sequential two-dimensional (2D) left and right images were obtained by rotating the TRD on a stepping motor synchronized with a complementary metal-oxide semiconductor camera, and the components of the imaging modality were controlled through general purpose input/output ports using a microcontroller unit. In this research, live stereoscopic videos were visualized on a personal computer by both active shutter 3D and passive polarization 3D methods. The imaging modality was characterized by evaluating the stereoscopic video image generation, rotation characteristics of the TRD. The level of 3D conception was estimated in terms of simplified human stereovision. The results show that singlechannel stereoscopic video imaging modality has the potential to become an economical compact stereoscopic device as the system components are amenable to miniaturization; and could be applied in a wide variety of fields.
Fabrication of optical tissue phantom (OTP) simulating whole skin structure has been regarded as laborious and time consuming work. This study fabricated multilayer OTP optically and structurally simulating epidermis-dermis structure including blood vessel. Spin coating method was used to produce thin layer mimicking epidermal layer, then optimized for reference epoxy and silicone matrix. Adequacy of both materials in phantom fabrication was considered by comparison the fabrication results. In addition similarities between OTP and biological tissue in optical property and thickness was measured to evaluate this fabrication process.
Although the mechanism of low level laser therapy (LLLT) is unclear, many studies demonstrated the positive clinical performance of LLLT for skin rejuvenation. An increase in dermal collagen plays an important role in skin rejuvenation and wound healing. This study aimed to investigate collagen generation after interstitial low level laser stimulation (ILLS). Rabbits were divided into two groups: surfacing irradiation and minimally invasive irradiation. 660nm diode laser of 20mW with 10J, 13J and 15J was applied to the backside of rabbits. Collagen formation was evaluated with ultrasound skin scanner every 12 hours. Results shows that ILLS groups have denser collagen density than surfacing groups.
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.
A three-dimensional stereoscopic imaging modality (3D-SIM) based on a single optical channel and detector was developed to overcome some of the limitations of conventional 3D-SIM. It produces 3-D stereoscopic images by adjusting the angle of a transparent rotating deflector (TRD) to generate disparity between left and right images. The angular effect of the TRD was demonstrated to investigate the feasibility of the proposed method in 3-D stereoscopic image generation. Results indicate that image disparity increased as a function of the rotation angles of the TRD, while maintaining adequate 3-D perception. These results are expected to facilitate the practical use of a 3D-SIM in medicine.
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.
Methodologies to fabricate a solid optical tissue phantom (OTP) mimicking epidermal thin-layer have been developed
for in vitro human skin experiment. However, there are cumbersome and time-consuming efforts in fabrication process
such as a custom-made casting and calculation of solvent volume before curing process. In a previous study, we
introduced a new methodology based on spin coating method (SCM) which is utilized to fabricate a thin-layer OTP
analogous to epidermal thickness. In this study, a double layer solid OTP which has epidermal and dermal layers was
fabricated to mimic the morphological and optical similarity of human tissue. The structural characteristic and optical
properties of fabricated double layer OTP were measured using optical coherence tomography and inverse adding
doubling algorithms, respectively. It is expected that the new methodology based on the SCM may be usefully used in
the fabrication of double layer OTP.
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.
Skin erythema has been widely used as a diagnostic parameter in dermatology. This study describes a methodology for real-time measurement of skin erythema variation induced by negative compression. This study developed an optical measurement probe, which includes a RGB color sensor that translates in the vertical direction, with the magnitude of vertical translation dependening on the amount of skin deformation. Real-time measurement of erythema variation as a function of both negative compression and time was performed in vivo on 10 measurement sites located on the back of each of 12 volunteers who participated in this study. Negative compression was sequentially applied from −30 to −80 kPa and continuously at a constant magnitude (−80 kPa ) condition. The results showed that skin erythema was uniformly induced at the measurement sites and linearly increased as a function of both negative compression and time. A wide range of individual variation was noted for skin erythema, which may be due to variations in anisotropic skin properties between volunteers. This study demonstrated the clinical feasibility of a novel optical device for skin erythema measurement. Future studies are needed to investigate the clinical applications of this device.
Optical imaging modalities have been utilized as important tools to evaluate skin lesions. Accurate analysis of
hyper-pigmentation is important in the evaluation of sun damage, inflammation, and other skin disorders. In
this study, both cross-polarization and fluorescent color images were obtained at identical facial skin region and
hyper-pigmentation regions were extracted by applying a series of image processing. Cross-polarization image
provides subsurface skin information without specular reflection and fluorescence image emphasizes
pigmentation in epidermal region. The results were quantitatively evaluated and compared to investigate the
difference between two imaging modalities in the evaluation of hyper-pigmentation regions.
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.
Various optical tissue phantoms (OTP) have been developed and utilized for the performance test of optical device and for in vitro human skin experiments. Solid OTPs have advantages such as semi-permanent use, convenience of experimental use, and easiness of storage. However, it is difficult to fabricate epidermis layer with an extremely thin layer of about few μm thickness. This study
suggests a spin coating method to fabricate a thin layer which is similar to epidermis layer thickness of human skin (about 50 μm). By controlling specific parameters such as the concentration of matrix solution and the spin velocity for spin coating, we could design a solid OTP with extremely thin layer of about few μm and a good degree of planarization. Quantitative analysis was performed to
evaluate both the spin velocity and the concentration of OTP matrix solution used to control specific thickness of OTP. By using optimal combination of parameters a specific thin layered OTP was fabricated with a thickness of less than 50 μm. In further studies, optimal combination of parameters needs to be studied to fabricate desired thickness of layer, depending on purpose.
KEYWORDS: Teeth, Specular reflections, Color difference, Polarization, Image processing, Dentistry, Measurement devices, Digital cameras, Image segmentation, In vivo imaging
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.
Recently, tissue optical clearing (TOC) has been considered as a useful tool in low level laser therapy due to the
enhancement of photon density in deep tissue layer. In this study, glycerol injection, tissue temperature, laser pulse
modulation, and their combination methods were investigated and compared by analyzing 2D and 3D laser beam profile.
A thermal plate was built to control tissue temperature from 40°C through 10°C at 10°C decrement. A continuous laser
of 660 nm was modulated at the frequencies of 1, 10, 25, and 50 Hz. 95% glycerol was injected into a region of interest
of sample where laser is irradiated and its effect was analyzed after 5 min. Finally, their combination method was
evaluated. Analysis was performed with the diffusion images acquired by CCD and the optical properties measured by
double integrating sphere. Results demonstrated that average peak intensity of laser beam profile was 1) 1.57-fold higher
at 10°C than 40°C, 2) 1.79-fold higher at 10 Hz than continuous wave, 3) 1.65-fold higher with 95% glycerol injection
than no glycerol application, and 4) 2.52-fold higher at the combination method than independent methods. Average total
intensity at FWHM was 1) 1.44-fold higher with tissue cooling, 2) 1.71-fold higher at 10 Hz, 3) 1.61-fold higher with
glycerol injection, and 4) 2.19-fold higher with the combination method. In conclusion, this study implies that tissuecooling,
pulse modulation, glycerol injection, and their combination method can effectively deliver laser photon in LLLT
by enhancing the photon density in soft tissue.
Although the mechanism of laser stimulation effect in bone has not completely understood, laser stimulation is
recommended in the treatment of osteoporosis due to positive treatment efficacy. In this study, a minimal invasive laser
needle system (MILNS) was developed using a fine hollow needle in order to stimulate directly bone site by guiding an
optical fiber. In order to evaluate the MILNS as a treatment method, in-vivo animal experiment study was performed
using osteopenic mice. Twelve virginal ICR mice were employed and divided two groups: SHAM-group and LASERgroup.
SHARM-group was stimulated by only fine hollow needle and LASER-group by fine hollow needle combined
with laser stimulation. All mice were served in-vivo micro-CT images before and after treatment. Three dimensional
(3D) structural parameters and vBMD (volume bone mineral density, g/cm3) in the trabecular bone were measured.
After 2 weeks of stimulation, the vBMD, BV/TV, Tb.Th and Tb.N in LASER-group were significantly higher than those
in SHAM-group (p<0.05). Potentially, this study suggested that the MILNS might prevent the bone loss and maintains
the bone mineral density of osteopenic mice.
In this study, we quantitatively analyzed 5-ALA induced fluorescent images of actinic keratosis using digital fluorescent color and hyperspectral imaging modalities. UV-A was utilized to induce fluorescent images and actinic keratosis (AK) lesions were demarcated from surrounding the normal region with different methods. Eight subjects with AK lesion were participated in this study. In the hyperspectral imaging modality, spectral analysis method was utilized for hyperspectral cube image and AK lesions were demarcated from the normal region. Before image acquisition, we designated biopsy position for histopathology of AK lesion and surrounding normal region. Erythema index (E.I.) values on both regions were calculated from the spectral cube data. Image analysis of subjects resulted in two different groups: the first group
with the higher fluorescence signal and E.I. on AK lesion than the normal region; the second group with lower fluorescence signal and without big difference in E.I. between two regions. In fluorescent color image analysis of facial AK, E.I. images were calculated on both normal and AK lesions and compared with the results of hyperspectral imaging modality. The results might indicate that the different intensity of fluorescence and E.I. among the subjects with AK might be interpreted as different phases of morphological and metabolic changes of AK lesions.
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.
We introduce a multimodal facial color imaging modality that provides a conventional color image, parallel and cross-polarization color images, and a fluorescent color image. We characterize the imaging modality and describe the image analysis methods for objective evaluation of skin lesions. The parallel and cross-polarization color images are useful for the analysis of skin texture, pigmentation, and vascularity. The polarization image, which is derived from parallel and cross-polarization color images, provides morphological information of superficial skin lesions. The fluorescent color image is useful for the evaluation of skin chromophores excited by UV-A radiation. In order to demonstrate the validity of the new imaging modality in dermatology, sample images were obtained from subjects with various skin disorders and image analysis methods were applied for objective evaluation of those lesions. In conclusion, we are confident that the imaging modality and analysis methods should be useful tools to simultaneously evaluate various skin lesions in dermatology.
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.
Over the last two decades, optical polarimetry method has been applied for glucose concentration monitoring in biological media such as aqueous humor and cell culture media as a non-invasive alternative method. Compared to glucose analyzer and electronic analyte sensor, the advantages of polaimetry method are non-ionizing radiation to interrogate the sample, non-interference with the sample, needless of consumable reagents, use of readily available sources, and prospect of miniaturizing the optics. Commercial polarimeter is widely used to measure the concentration of chemical compounds with optical activity. However, this device was based on off-line measurement so that it needs sample extraction process to measure the concentration of sample. This process does not reflect the real-time status of sample concentration and sample contamination can be occurred during sample extraction when applied to cell culture process. In polarimetry method, the measurement sensitivity can be controlled by varying optical path length. However, in current polarimeter, the sample cell should be exchanged to vary the optical path length. This process is a time consuming and might cause sample contamination in cell culture process. Therefore, it is necessary to develop a new polarimetry method which can measure the real-time status of sample concentration without sample extraction. In this paper, we introduce a new polarimetry probe system which might be utilized to monitor glucose concentration during cell culture process. It was designed to have variable optical path lengths to control the optical rotation angle of polarized light. We describe the feasibility of the system and the preliminary results.
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.
In dermatology, various digital imaging modalities have been used as an important tool to quantitatively evaluate the
treatment effect of skin lesions. Cross-polarization color image was used to evaluate skin chromophores (melanin and
hemoglobin) information and parallel-polarization image to evaluate skin texture information. In addition, UV-A
induced fluorescent image has been widely used to evaluate various skin conditions such as sebum, keratosis, sun
damages, and vitiligo. In order to maximize the evaluation efficacy of various skin lesions, it is necessary to integrate
various imaging modalities into an imaging system. In this study, we propose a multimodal digital color imaging system,
which provides four different digital color images of standard color image, parallel and cross-polarization color image,
and UV-A induced fluorescent color image. Herein, we describe the imaging system and present the examples of image
analysis. By analyzing the color information and morphological features of facial skin lesions, we are able to
comparably and simultaneously evaluate various skin lesions. In conclusion, we are sure that the multimodal color
imaging system can be utilized as an important assistant
tool in dermatology.
Current methods for analysis of sebum excretion have limitations, such as irreproducible results in repeatable
measurements due to the point measurement method, user-dependent artifact due to contact measurement or qualitative
evaluation of the image, and long measurement time. A UV-induced fluorescent digital imaging system was developed
to acquire facial images so that the distribution of sebum excretion on the face could be analyzed. The imaging system
consisted of a constant UV-A light source, digital color camera, and head-positioning device. We describe the system
characterization for acquisition of a fluorescent facial image and the image analysis method. The imaging modality
provided uniform light distribution on the facial mannequin model and presented a discernible color fluorescent image.
Valuable parameters of sebum excretion were obtained after image analysis. The imaging system, which provides a non-contact
method, was proven to be a useful tool to evaluate sebum excretion and to characterize the pattern of sebum
excretion. When compared to conventional "Wood's lamp" and "Sebutape" methods that provide similar parameters for
sebum excretion, the method described herein is simpler and more reliable to evaluate the dynamics of sebum excretion
in nearly real-time.
Current methods for analysis of sebum excretion have limitations, such as irreproducible results in repeatable measurements due to the point measurement method, user-dependent artifacts due to contact measurement or qualitative evaluation of the image, and long measurement time. A UV-induced fluorescent digital imaging system is developed to acquire facial images so that the distribution of sebum excretion on the face could be analyzed. The imaging system consists of a constant UV-A light source, digital color camera, and head-positioning device. The system for acquisition of a fluorescent facial image and the image analysis method is described. The imaging modality provides uniform light distribution and presents a discernible color fluorescent image. Valuable parameters of sebum excretion are obtained after image analysis. The imaging system, which provides a noncontact method, is proved to be a useful tool to evaluate the amount and pattern of sebum excretion. When compared to conventional “Wood's lamp” and “Sebutape” methods that provide similar parameters for sebum excretion, the described method is simpler and more reliable to evaluate the dynamics of sebum excretion in nearly real-time.
KEYWORDS: Camera shutters, Temperature metrology, Skin, Calibration, Radiometry, In vivo imaging, Black bodies, Laser therapeutics, Infrared detectors, Pulsed laser operation
In laser therapy of port wine stain (PWS) birthmarks, measurement of maximum temperature rise is important to determine the maximum permissible light dose for PWS laser therapy. To measure maximum temperature rise on arbitrary PWS skin site, we developed a handheld pulsed photothermal radiometry (PPTR) system, which overcomes in
vivo measurement limitations of bench-top PPTR systems. The developed PPTR system consists of an IR lens, an AC-coupled thermoelectrically cooled IR detector, a laser handpiece holder, and a fixed distance measurement port. With system characterization, experimental results were in good agreement with theoretical calculations. Preliminary results for maximum temperature rise demonstrate the feasibility of the PPTR system for PWS skin characterization in the clinic.
KEYWORDS: Skin, In vivo imaging, Reflectivity, Optical spheres, In vitro testing, Diffuse reflectance spectroscopy, Laser therapeutics, Color difference, Visualization, Spectrometers
For quantitative prediction and evaluation of pulsed dye laser therapy of port wine stain (PWS) skin, the CIE L*a*b* color difference, ΔE*, has been utilized to characterize numerically the color differences between normal untreated and treated PWS skin. Three optical instruments (Minolta chromameter CR-200, a cross-polarized diffuse reflectance imaging system, and visual reflectance spectrometers) are compared to investigate their clinical feasibility for quantitative color assessment. Compared to the chromameter as a standard measurement instrument, other instruments also provide valuable measurements of skin color for the relative quantification of PWS treatment outcome. The fiber-optic visual reflectance spectrometer is preferable for continuous measurement of a small area of skin. The cross-polarized imaging system is useful as a simple non-contact measurement technique to provide spatially resolved color difference images.
KEYWORDS: Temperature metrology, Calibration, Infrared cameras, Black bodies, Infrared imaging, Profiling, Radiometry, Imaging systems, Tissues, Control systems
The effects of varying lens housing temperature on subsurface temperature profiling of a tissue-simulating phantom were studied using pulsed photothermal radiometry (PPTR). A temperature feedback system was used to control systematically the infrared (IR) detector lens housing temperature. Temperature feedback system maintained lens housing temperature at constant level for external temperature fluctuation. The radiometric signal intensity and temperature calibration was substantially affected by lens housing temperature change. Temperature values as a function of depth profiles reconstructed from pulsed photothermal radiometry measurements increased when lens housing temperatures were elevated during the radiometric temperature calibration run. These experiments demonstrate that lens housing temperature fluctuations affect the accuracy of radiometric subsurface temperature measurements using an infrared camera system.
In quantitative evaluation of facial skin chromophore content using color imaging, several factors such as view angle and facial curvature affect the accuracy of measured values. To determine the influence of view angle and facial curvature on the accuracy of quantitative image analysis, we acquire cross-polarized diffuse reflectance color images of a white-patched mannequin head model and human subjects while varying the angular position of the head with respect to the image acquisition system. With the mannequin head model, the coefficient of variance (CV) is determined to specify an optimal view angle resulting in a relatively uniform light distribution on the region of interest (ROI). Our results indicate that view angle and facial curvature influence the accuracy of the recorded color information and quantitative image analysis. Moreover, there exists an optimal view angle that minimizes the artifacts in color determination resulting from facial curvature. In a specific ROI, the CV is less in smaller regions than in larger regions, and in relatively flat regions. In clinical application, our results suggest that view angle affects the quantitative assessment of port wine stain (PWS) skin erythema, emphasizing the importance of using the optimal view angle to minimize artifacts caused by nonuniform light distribution on the ROI. From these results, we propose that optimal view angles can be identified using the mannequin head model to image specific regions of interest on the face of human subjects.
We present an initial study on applying genetic algorithms (GA) to retrieve human skin optical properties using visual reflectance spectroscopy (VRS). A three-layered skin model consisting of 13 parameters is first used to simulate skin and, through an analytical model based on optical diffusion theory, we study their independent effects on the reflectance spectra. Based on a preliminary analysis, nine skin parameters are chosen to be fitted by GA. The fitting procedure is applied first on simulated reflectance spectra with added white noise, and then on measured spectra from normal and port wine stain (PWS) human skin. A normalized residue of less than 0.005 is achieved for simulated spectra. In the case of measured spectra from human skin, the normalized residue is less than 0.01. Comparisons between applying GA and manual iteration (MI) fitting show that GA performed much better than the MI fitting method and can easily distinguish melanin concentrations for different skin types. Furthermore, the GA approach can lead to a reasonable understanding of the blood volume fraction and other skin properties, provided that the applicability of the diffusion approximation is satisfied.
In cutaneous vascular laser surgery, hemoglobin and melanin are important skin chromophores that influence treatment of port wine stain (PWS) birthmarks. A potential problem in quantitative chromorphore evaluaton is the error in image analysis associated with a number of factors, including nonuniform illumination and skin curvature. In this study, we used a mannequin head model to investigate how the accuracy of image analysis is influenced by view angle and facial curvature. Our results indicate that view angle and facial curvature affect the accuracy of the recorded color information. From this analysis, we propose that optimal view angles can be determined on an individual patient basis to analyze features on different regions of the face.
Previous studies suggest that optimal port wine stain (PWS) laser treatment parameters require knowledge of skin characteristics such as blood vessel size, depth, and distribution. Effective and rapid imaging modalities are not widely available. In the present study, photothermal tomography (PTT) images of an in vivo hamster window model and human PWS skin were obtained and analyzed. Subtherapeutic laser light pulses at 585 and 600 nm were applied to skin surface and image sequences acquired with an infrared camera. A nonnegatively constrained conjugate gradient algorithm was used to reconstruct a PTT image of the initial temperature distribution immediately following pulsed laser irradiation. Vessel dimensions determined from PTT images of hamster window model skin compared well with those measured directly using video microscopy. PTT images of human PWS skin contained vessels with estimated diameters of 200-250 μm over a 250-320 μm depth range. Use of dual wavelength excitation (DWE) analysis allowed for imaging of shallow vessels.
The noninvasive monitoring of sugars, and in particular, glucose using near-IR (NIR) spectroscopy would be useful for a number of applications including regulating the nutrients in cell culture medium, monitoring on-line processes in the food industry, and in vivo monitoring for control of glucose in DIabetic patients. The focus of this research was the investigation of the temperature effects across a 10.6 to 40.4 degrees C range on Fourier filtered and unfiltered single-beam as well as absorbance glucose and water NIR spectra. It is known that the positions of water absorption bands centered at 1.923 and 2.623 micrometers depend heavily on temperature effects while the glucose bands are temperature insensitive across this range. The water absorption bands were shown to shift to lower wavelengths while the distance between these bands increased with increasing temperatures. Partial least squares (PLS) calibration models were constructed at five separate temperatures, 15.7, 20.5, 25.5, 35.6, and 40.4 degrees C. When absorbance spectra were used with reference scans taken at the same temperature and PLS models were used, no significant difference in the standard error of prediction (SEP) was noted with temperature. Using PLS calibration with single-beam spectra at one temperature showed large SEPs at the other temperatures. The use of Fourier filtered single-beam spectra reduced the SEP but still showed an increase as large temperature differences were produced and the filtered single beam approach did not reduce the SEP to the level achieved with the absorbance spectra.
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