There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The diffraction tomography theorem is adapted to one-dimensional length measurement. The resulting spectral interferometry technique is described and the first length measurements using this technique on a model eye and on a human eye in vivo are presented.

Measurement of intraocular distances by backscattering spectral interferometry

Photoplethysmography and its application in clinical physiological measurement

The development of optical methods in modern medicine in the areas of diagnostics, therapy, and surgery has stimulated the investigation of optical properties of various biological tissues, since the efficacy of laser treatment depends on the photon propagation and fluence rate distribution within irradiated tissues. In this work, an overview of published absorption and scattering properties of skin and subcutaneous tissues measured in wide wavelength range is presented. Basic principles of measurements of the tissue optical properties and techniques used for processing of the measured data are outlined.

/pdf/optical-properties-of-skin-subcutaneous-and-muscle-tissues-a-wumm467r4a.pdf

Optical properties of skin, subcutaneous, and muscle tissues: a review

A survey of the literature is presented that provides an analysis of the optical properties of human skin, with particular regard to their applications in medicine. Included is a description of the primary interactions of light with skin and how these are commonly estimated using radiative transfer theory (RTT). This is followed by analysis of measured RTT coefficients available in the literature. Orders of magnitude differences are found within published absorption and reduced-scattering coefficients. Causes for these discrepancies are discussed in detail, including contrasts between data acquired in vitro and in vivo. An analysis of the phase functions applied in skin optics, along with the remaining optical coefficients (anisotropy factors and refractive indices) is also included. The survey concludes that further work in the field is necessary to establish a definitive range of realistic coefficients for clinically normal skin.

https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-17/issue-9/090901/Optical-properties-of-human-skin/10.1117/1.JBO.17.9.090901.pdf

Optical properties of human skin.

To understand the pathophysiology and to develop a new diagnostic/therapeutic technique for ischemic stroke, we performed near-infrared diffuse reflectance imaging for a rat stroke model and examined whether an infarct core and periinfarct depolarization (PID) can be visualized by detecting light-scattering signal. After middle cerebral artery occlusion, light scattering increased in the ischemic core, around which a wave-like scattering change was generated and spread over the cortex repetitively, indicating occurrence of PIDs. The region with increased scattering in the ischemic core almost corresponded to the infarct area observed by TTC staining, suggesting that the scattering increase reflected cell morphological change associated with infarction.

Near-infrared Diffuse Reflectance Imaging of Infarct Region and Peri-infarct Depolarization in a Rat Stroke Model

Cyanosis is a pathological condition that is characterized by a bluish discoloration of the skin or mucous membranes. It may result from a number of medical conditions, including disorders of the respiratory system and central nervous system, cardiovascular diseases, peripheral vascular diseases, deep vein thrombosis, and regional ischemia. Cyanosis can also be elicited from methemoglobin. Therefore, a simple, rapid, and simultaneous monitoring of changes in oxygenated hemoglobin and deoxygenated hemoglobin is useful for protective strategies against organ ischemic injury. We previously developed a red-green-blue camera-based spectral imaging method for the measurements of melanin concentration, oxygenated hemoglobin concentration (CHbO), deoxygenated hemoglobin concentration (CHbR), total hemoglobin concentration (CHbT) and tissue oxygen saturation (StO2) in skin tissues. We leveraged this approach in this study and extended it to the simultaneous quantifications of methemoglobin concentration (CmetHb), CHbO, CHbR, and StO2. The aim of the study was to confirm the feasibility of the method to monitor CmetHb, CHbO, CHbR, CHbT, and StO2. We performed in vivo experiments using rat dorsal skin during methemoglobinemia induced by the administration of sodium nitrite (NaNO2) and changing the fraction of inspired oxygen (FiO2), including normoxia, hypoxia, and anoxia. Spectral diffuse reflectance images were estimated from an RGB image by the Wiener estimation method. Multiple regression analysis based on Monte Carlo simulations of light transport was used to estimate CHbO, CHbR, CmetHb, CHbT, and StO2. CmetHb rapidly increased with a half-maximum time of less than 30 min and reached maximal values nearly 60 min after the administration of NaNO2, whereas StO2 dramatically dropped after the administration of NaNO2, indicating the temporary production of methemoglobin and severe hypoxemia during methemoglobinemia. Time courses of CHbT and StO2, while changing the FiO2, coincided with well-known physiological responses to hyperoxia, normoxia, and hypoxia. The results indicated the potential of this method to evaluate changes in skin hemodynamics due to loss of tissue viability and vitality.

https://www.mdpi.com/1422-0067/22/4/1528/pdf

In Vivo Transcutaneous Monitoring of Hemoglobin Derivatives Using a Red-Green-Blue Camera-Based Spectral Imaging Technique.

To evaluate the functional pigments in the tomato fruits nondestructively, we propose a method based on the
multispectral diffuse reflectance images estimated by the Wiener estimation for a digital RGB image. Each pixel of the
multispectral image is converted to the absorbance spectrum and then analyzed by the multiple regression analysis to
visualize the contents of chlorophyll a, lycopene and β-carotene. The result confirms the feasibility of the method for in
situ imaging of chlorophyll a, β-carotene and lycopene in the tomato fruits.

In situ nondestructive imaging of functional pigments in Micro-Tom tomato fruits by multi spectral imaging based on Wiener estimation method

/pdf/application-of-optical-coherence-tomography-to-monitoring-of-154con2zue.pdf

Application of Optical Coherence Tomography to Monitoring of Brain Viability

Similarity in skin reflectance spectra with different combination of absorption and scattering conditions makes erroneous estimation of parameters for any measured spectrum through the database containing simulated spectra. In this study, such similar reflectance spectra are investigated by Monte Carlo simulation and phantom experiment.

Izumi Nishidate

Papers

Near-infrared Diffuse Reflectance Imaging of Infarct Region and Peri-infarct Depolarization in a Rat Stroke Model

In Vivo Transcutaneous Monitoring of Hemoglobin Derivatives Using a Red-Green-Blue Camera-Based Spectral Imaging Technique.

In situ nondestructive imaging of functional pigments in Micro-Tom tomato fruits by multi spectral imaging based on Wiener estimation method

Application of Optical Coherence Tomography to Monitoring of Brain Viability

Skin reflectance spectra with different parameter conditions in Monte Carlo simulation and agarose-gel phantom experiment