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Evaluation of biological chromophore levels is useful for detection of various skin diseases, including cancer, monitoring of health status and tissue metabolism, and assessment of clinical and physiological vascular functions. Clinically, it is useful to assess multiple different chromophores in vivo with a single technique or instrument. To investigate the possibility of estimating the concentration of four chromophores, bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin from diffuse reflectance spectra in the visible region. A new diffuse reflectance spectroscopic method based on the multiple regression analysis aided by Monte Carlo simulations for light transport was developed to quantify bilirubin, oxygenated hemoglobin, deoxygenated hemoglobin, and melanin. Three different experimental animal models were used to induce hyperbilirubinemia, hypoxemia, and melanogenesis in rats. The estimated bilirubin concentration increased after ligation of the bile duct and reached around 18 mg / dl at 50 h after the onset of ligation, which corresponds to the reference value of bilirubin measured by a commercially available transcutaneous bilirubin meter. The concentration of oxygenated hemoglobin and that of deoxygenated hemoglobin decreased and increased, respectively, as the fraction of inspired oxygen decreased. Consequently, the tissue oxygen saturation dramatically decreased. The time course of melanin concentration after depilation of skin on the back of rats was indicative of the supply of melanosomes produced by melanocytes of hair follicles to the growing hair shaft. The results of our study showed that the proposed method is capable of the in vivo evaluation of percutaneous bilirubin level, skin hemodynamics, and melanogenesis in rats, and that it has potential as a tool for the diagnosis and management of hyperbilirubinemia, hypoxemia, and pigmented skin lesions. [ABSTRACT FROM AUTHOR]

Bright light therapy is a treatment modality for seasonal affective disorder and circadian rhythm disorders in which artificial light of 2,500 lux or higher at the eye is effective. Although short-wavelength visible light is more effective than long-wavelength visible light, it may be hazardous to the retina. Recently, light-emitting diodes (LEDs) have been used as the light source in bright light therapy apparatuses. We developed goggles for bright light therapy equipped with LEDs as the light source. The aim of this study was to examine the efficacy and safety of our goggles when emitting 10,000-lux light with its short-wavelength light content reduced by 30% or 50% (denoted as 30%-cut and 50%-cut light, respectively, henceforth). Six healthy young males participated in this study. They were administered no light, 50%-cut light, and 30%-cut light for 30 min early in the morning for 4 days each. Subjective sleepiness and sleep quality were evaluated by the Stanford Sleepiness Scale (SSS) and the Oguri–Shirakawa–Azumi sleep inventory MA version (OSA-MA), respectively. Subjective sleepiness evaluated by the SSS and the subscale of the OSA-MA significantly decreased with 30%-cut light compared with no light. Psychomotor performance evaluated by a calculation task improved with the 30%-cut light, although not significant after multiple comparisons were considered. No abnormality was found by ophthalmoscopy and the vision test. In conclusion, our goggles with 30%-cut light may be safe and have an awakening effect. [ABSTRACT FROM AUTHOR]

Dynamic speckle patterns can be used for imaging of relative velocity of moving objects in fields of biomedical and mechanical measurements. In spite of the widespread use of this method, the effect of speckle size on velocity sensing has not fully been estimated so far. In addition, effects of speckle contrast and random noises on the sensitivity of velocity sensing have not been investigated yet. In the present study, we estimated condition of image processing of speckle patterns for reducing effects of random noises with relation to linearity and sensitivity in velocity sensing. We further introduced binarization of the speckle pattern to improve the sensitivity in velocity sensing. Experiments were conducted for sample models using a diffusive plate and fluid flows to confirm the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Imaging technique based on bio-speckles is useful for visualizing blood flow distribution. We have proposed so far temporal contrast factor (TCF) and inversed temporal contrast factor (ITCF) for imaging of slow and fast blood flows, respectively. However, selection of TCF and ITCF depends on user’s experience. Additionally, these parameters are significantly influenced by the speckle contrast and random noises. In the present study, we propose a method for automatic selection of a proper parameter for imaging blood flow in an unknown velocity region with reduced effects of speckle contrast and random noises. Experiments are conducted for a sample model using ground-glass plates, human wrist, and human finger to confirm the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Modified LDV method is proposed for measuring the diameter and absorption coefficient of a single moving particle by applying the Lambert–Beer’s law to dual burst Doppler signal. The diameter and absorption coefficient of a particle are determined simultaneously from the time difference and intensity ratio between burst components of reflected and refracted rays in a dual burst Doppler signal, using only a single photodetector. This method can be applied to a particle larger than the cross-sectional area of an illuminating beam. The optimum conditions of an optical system were estimated theoretically. Experiments were performed with polystyrene particles in water, water droplets, and water-black ink droplets to confirm usefulness of the proposed method. [ABSTRACT FROM AUTHOR]

A multi-spectral diffuse reflectance imaging method based on a single snap shot of Red-Green-Blue images acquired with the exposure time of 65 ms (15 fps) was investigated for estimating melanin concentration, blood concentration, and oxygen saturation in human skin tissue. The technique utilizes the Wiener estimation method to deduce spectral reflectance images instantaneously from an RGB image. Using the resultant absorbance spectrum as a response variable and the extinction coefficients of melanin, oxygenated hemoglobin and deoxygenated hemoglobin as predictor variables, multiple regression analysis provides regression coefficients. Concentrations of melanin and total blood are then determined from the regression coefficients using conversion vectors that are numerically deduced in advance by the Monte Carlo simulations for light transport in skin. Oxygen saturation is obtained directly from the regression coefficients. Experiments with a tissue-like agar gel phantom validated the method. In vivo experiments on fingers during upper limb occlusion demonstrated the ability of the method to evaluate physiological reactions of human skin. [ABSTRACT FROM AUTHOR]

It has been shown in previous studies that fractal speckles can be produced in an image plane by using as a pupil filter in the imaging system a spatial light modulator with an intensity transmittance obeying a negative power-law. However, this method has a disadvantage in that the intensity distributions of such speckles are very low due to the pupil filter giving a lower total transmittance. To overcome this disadvantage, we propose here the use of digital holography to generate fractal speckles. The theoretical background is explained briefly, and experimental results are shown. [ABSTRACT FROM AUTHOR]