In Vivo Detection of Gold Nanoshells in Tumors Using Diffuse Optical Spectroscopy

This study demonstrates the use of diffuse optical spectroscopy (DOS) for the noninvasive measurement of gold nanoshell concentrations in tumors of live mice. We measured the diffuse optical spectra (500-800 nm) using an optical fiber probe placed in contact with the tissue surface. We performed in vitro studies on tissue phantoms illustrating an accurate measurement of gold-silica nanoshell concentration within 12.6% of the known concentration. In vivo studies were performed on a mouse xenograft tumor model. DOS spectra were measured at preinjection, immediately postinjection, 1 and 24 h postinjection times, and the nanoshell concentrations were verified using neutron activation analysis.     

Extinction coefficients of hemoglobin for near-infrared spectroscopy of tissue.

Extinction coefficients of hemoglobin have been studied for five decades by clinical chemists and biochemists, particularly for laboratory spectrophotometric measurements. In the last ten to 15 years, near infrared spectroscopy (NIRS) and imaging for tissue vascular oxygenation, breast tumor detection, and functional brain imaging have been intensively developed for in vivo measurements by groups of physicists, biomedical engineers, and mathematicians. In the approach of NIRS, NIR light in the wavelength range of 650-900 nm is utilized to illuminate tissue in vivo, and the transmitted or reflected light through tissue is recorded for the quantification of hemoglobin concentrations of the measured tissue vasculature. In order to achieve mathematical conversion from the detected light intensity at different wavelengths to hemoglobin concentration, extinction coefficients of hemoglobin, /spl epsiv/, must be used. While the engineers and physicists working in the NIR field have found the correct /spl epsiv/ values to use, there has been controversy on what /spl epsiv/ values should be used for in vivo NIRS in comparison with the conventional e/spl epsiv/ that most biochemists have used in the laboratories for in vitro measurements. The purpose of this article is to address this issue and help biomedical engineers and physicists gain a better understanding of e to be used for NIRS and NIR imaging.     

Intraoperative application of optical spectroscopy in the presenceof blood

A simple but effective method of spectral processing was developed to minimize or remove the effects of the presence of superficial blood on tissue optical spectra and, hence, enhance the performance of optical-spectroscopic-based in vivo tissue diagnosis and surgical guidance. This spectral-processing algorithm was developed using the principles of absorption-induced light attenuation wherein the ratio of fluorescence intensity (F) and the hth power of diffuse reflectance intensity (Rd) at a given emission wavelength λ_m is immune to spectral distortions induced by the presence of blood on the tissue surface. Here, the exponent h is determined by the absorption coefficients of whole blood at the excitation and emission wavelengths. The theoretical basis of this spectral processing was verified using simulations and was experimentally validated. Furthermore, the optical spectra of brain tissues collected in vivo was processed using this algorithm to evaluate its impact on brain tissue differentiation using combined fluorescence and diffuse reflectance spectroscopy. Based on the simulation, as well as experimental results, it was observed that using F/Rd^h h can effectively reduce or remove spectral distortions induced by superficial blood contamination on tissue optical spectra. Thus, optical spectroscopy can also be used intraoperatively for applications such as surgical guidance of tumor resection     

应用近红外光谱方法在线测定煤中水分

应用近红外光谱方法进行煤质在线分析工作的研究,主要进行煤中水分的测定。阅读了多个光谱图,采用多元回归方法对数据进行了分析和处理,得出回归模型。模型的预测值和人工化验标准值之间的相关系数在0.97,模型的定标标准差为0.5。     

A three-dimensional modular adaptable grid numerical model forlight propagation during laser irradiation of skin tissue

Information regarding energy deposition during laser irradiation of structurally complex biological tissue is needed to understand and improve the results of clinical procedures. A modular adaptive geometry numerical model capable of simulating the propagation of laser light in a wide variety of multiple component tissues has been developed and tested. A material grid array is generated by assigning a value representing a tissue type to each of a large number of small voxels. The grid array is used to indicate optical properties in an existing variable step size, weighted-photon Monte Carlo algorithm that has been modified to account for voxels-to-voxels changes in optical properties. To test the model, simple geometric shapes and optical low coherence reflectometry images of rat skin have been used to create material grids consisting of epidermis, dermis, and blood. The model assumes 1-J/cm² irradiation of the tissue samples with a 1.0-mm diameter uniform beam at 585 nm. Computed results show good quantitative and qualitative agreement with published data. Various effects due to shading and scattering, similar to those suggested in the literature, are noted. This model provides a way to achieve more realistic representation of anatomical geometry as compared to other models, and produces accurate results     

Accurate measurement of total attenuation coefficient of thin tissue with optical coherence tomography

Noninvasive accurate measurements of tissue optical properties are needed for many diagnostic and therapeutic applications. Optical coherence tomography (OCT) recently proposed for high-resolution imaging in tissue can potentially be applied for accurate, noninvasive, and high-resolution measurement of tissue total attenuation coefficient. However, confocal function (dependence of OCT sensitivity on the distance of probed site from the focal plane of the objective lens) and multiple scattering substantially limit the accuracy of the measurement with the OCT technique. We studied the influence of the confocal function and multiple scattering on the accuracy of the measurement and proposed methods that provide measurement of the total attenuation coefficient with a significantly reduced systematic error. Experiments were performed in tissue phantoms and porcine and human skin in vitro and in vivo. Our data indicate that the tissue total attenuation coefficient can noninvasively be measured in vivo with the accuracy of 5%-10% in the range from 0.5 to 17 mm/sup -1/ and about 20% in the range up to 40 mm/sup -1/. These results suggest that the proper correction of the OCT-based measurement for the confocal function and multiple scattering provides absolute values of tissue total attenuation coefficient with high accuracy and resolution that may not be achievable by other optical techniques in vivo.     

Noninvasively measuring blood glucose using saliva

Self-measurement of blood glucose level is a very important aspect in monitoring the health quality of diabetic patients who require insulin therapy. Typically, a blood sample for analysis is obtained via a finger stick or other such invasive procedure. Often, this blood collecting causes physical and mental stress to the patient. For this reason, it is desirable to establish a noninvasive bloodless procedure to monitor the blood glucose level (BGL). Here, the authors discuss the correlation between BGL and saliva glucose level and then present an approach that uses an enzyme-sensor system to noninvasively measure blood glucose using saliva     

Near-infrared (NIR) tomography breast image reconstruction with a priori structural information from MRI: algorithm development for reconstructing heterogeneities

A combined magnetic resonance and near-infrared (MRI-NIR) imaging modality can potentially yield high resolution maps of optical properties from noninvasive simultaneous measurement. The main disadvantage of near-infrared (NIR) tomography lies in the low spatial resolution resulting from the highly scattering nature of tissue for these wavelengths. MRI has achieved high resolution, but suffers from low specificity. In this study, NIR image reconstruction algorithms that incorporate a priori structural information provided by MRI are investigated in an attempt to optimize recovery of a simulated optical property distribution. The effect of high levels of tissue heterogeneity are evaluated to determine the limitations of incorporating prior information into a realistic set of patient breast images. We assume absorption coefficient (/spl mu//sub a/) variations near /spl plusmn/40%, and transport scattering coefficient (/spl mu//sub s//sup //) variations near /spl plusmn/20%, in a coronal breast MRI geometry. Changes in tissue pathology due to tumor growth can be observed with NIR tompgraphy, and so the goal here is to determine how best to quantify these tumor-based contrast regions within the presence of high tissue heterogeneity. By applying knowledge of tissue's layered structure in reconstruction through various constraints in the iterative algorithm, quantitative recovery of the tumor optical properties improves from 69% to 74%, and localization improves as well. However, only when the true heterogeneity of the tissue distribution was included was accurate quantification of the tumor region possible. Using a good initial guess of /spl mu//sub a/ and /spl mu//sub s//sup //, derived from the regional structure of the model, quantification of the region reaches 99% of the true value, and spatial resolution retains a similar value to the original MRI image.     

应用近红外光谱分析技术测量煤质发热量

主要进行煤质发热量的测定,在阅读了多个光谱图的基础上,采用多元线性回归方法对数据进行了分析和处理,建立了多元线性模型,采用该模型得出的煤质发热量的预测值与人工化验标准值之间的相关系数为0.92,所建模型的定标标准差为1.58。     

Integrated optical sensor in glass for optical coherence tomography(OCT)

The in vivo examination of tissue structures (e.g., human skin, eye retina) by optical coherence tomography is a powerful tool for pharmaceutical and medical research for the development of new drugs and new diagnostic methods. The parallel integration of eight Michelson interferometers including all reference light paths in one small glass chip is the basis of a compact sensor system with a high resolution, short measurement time, and a large penetration depth especially in almost opaque tissue such as the human skin. The interferometer array is fabricated with silver ion exchanged waveguides     

Optical oximetry sensors for whole blood and tissue

This article reviews the optical techniques applied to the determination of intravascular hemoglobin oxygen saturation as well as the noninvasive estimation of arterial and tissue saturation. Although in skeletal muscles and brain tissues myoglobin and cytochrome analyses have been demonstrated (F.F. Jobis et al., 1977; K. Kariman et al., 1983), their effects upon absorption and reflection spectra of tissues are small. Thus, this review is focused only upon measurement of hemoglobin saturation     

An RCL sensor for measuring dielectrically lossy materials in the MHz frequency range. Part I. Comparison of hydrogel model simulation with actual hydrogel impedance measurements

There is a requirement for the development of non-invasive continuous blood glucose monitoring devices to meet the clinical demands of the rapidly increasing number of people currently developing diabetes mellitus. Impedance spectroscopy is a technology that meets the requirements of such devices. An NI CGMD is being developed as a device that couples a sensor to the skin to form an RCL sensor. The reliability of such an RCL sensor model has been investigated by comparing electrodynamical simulations to in-vitro measurements of dielectrically "lossy" materials. The sensor has been modeled and simulated in FEMLAB (finite element modeling laboratory). In-vitro measurements are performed on hydrogels, representing the lossy material, by the aid of a Rohde & Schwarz VNA (vector network analyzer). From the quantitative agreement of the results we conclude, that the proposed qualitative model is appropriate for the characterization of the RCL sensor and suggests that more detailed models can be used to elucidate the behavior of human skin tissue.     

Glucose monitoring using implanted fluorescent microspheres

The authors are working toward a minimally invasive means for diabetics to better monitor glucose levels. A fiber-optic probe was fabricated for delivery and collection of light to an implanted sensor. The probe and associated optical system has high sensitivity and allows for flexible, remote measurements. The system was used to collect data with sensor solutions similar to what is envisioned for the implantable system, and the recorded spectra were processed in an attempt to predict glucose concentrations from fluorescence measurements. Despite the availability of sophisticated multivariate calibration methods, the best prediction results were obtained using polynomial regression with regression coefficient ratios. The measurements are far from perfect, but they do meet the requirements for clinical use and show promise for further improvement in the future. In vivo experiments were conducted using "simulated" sensors that had constant fluorescence characteristics. Results of implantation in excised skin and in live animals indicate that, while very strong fluorescence signals were measured for implanted particles, the current sensor chemistry must be improved for adequate resolution. In addition, difficulty in achieving repeatable injection depths and homogeneity of mixtures containing different colored spheres confounded attempts to make true quantitative measurements.     

Optical coherence tomography for in vitro monitoring of wound healing after laser irradiation

We demonstrate a novel application of optical coherence tomography (OCT) to monitor post-laser irradiation collagen injury in model skin. An artificial skin model (RAFT), which closely approximates human skin, was irradiated with a Perovskite laser (/spl lambda/=1341 nm), which is under investigation for potential use as a nonablative laser skin rejuvenation device (NALSR). OCT was used to determine the extent of laser injury immediately post irradiation and, subsequently, to monitor tissue recovery over a seven-day period. OCT images clearly delineated areas of post-irradiation collagen injury and allowed noninvasive monitoring of the wound healing process. Histology was used for comparison and correlated well with OCT images. OCT offers advantages over standard histology as it is noninvasive and allows serial monitoring at the same site over time. Our results indicate that OCT has potential as a method for characterization of collagen injury post-laser irradiation and may be a useful tool for determination of optimal parameters for NALSR using different devices under investigation for this indication.     

Evaluation of a mobile NMR sensor for determining skin layers and locally estimating the T2eff relaxation time in the lower arm

Object

The nuclear magnetic resonance (NMR) mobile-universal-surface-explorer (MOUSE) was evaluated in a pilot study to determine its ability to detect physiological changes in human skin caused by physical or pharmacological interventions.

Materials and methods

The left lower arm skin thicknesses of ten male subjects were measured five times using a Profile NMR-MOUSE^? (¹H, 19?MHz) before and after a venous occlusion manoeuvre. In five of the subjects, the T_2eff relaxation times were derived from a bi-exponential fitting and were determined in the dermis and subcutis before and after applying a salve containing capsaicin.

Results

The dermis (including the epidermis) showed rather homogeneous signal amplitudes. The subcutis was characterised by higher and more variable amplitudes. The full-skin thickness values were affirmed by ultrasound imaging. The NMR profiles did not show significant skin swelling due to venous occlusion. In the dermis, capsaicin caused significant (p?<?0.05) decreases in both components of T _2eff (100?±?19?ms?C19?±?10?ms; 9.5?±?0.5?ms?C7.2?±?1.6?ms). In the subcutis, the T _2eff was not affected.

Conclusion

In principle, NMR-MOUSE profiles are capable of detecting skin structure. However, precise measurements are jeopardised by poor reproducibility, long acquisition times, and incompatibility between the geometries of the sensitive area of the instrument and the non-planar structure of the skin. In the dermis, T _2eff contrast could be used to detect the changes in tissue composition caused by inflammatory reactions.     

Electrical and chemical diagnostics of transformers insulation. A.Aged transformer samples

This paper describes the application of two relatively new diagnostic techniques for the determination of insulation condition in aged transformers. The techniques are: (a) measurements of interfacial polarization spectra by a DC method; and (b) measurements of molecular weight and its distribution by gel permeation chromatography. Several other electrical properties of the cellulose polymer were also investigated. Samples were obtained from a retired power transformer and they were analysed by the developed techniques. Six distribution transformers were also tested with the interfacial polarization spectra measurement technique, and the molecular weight of paper/pressboard samples from these transformers were also measured by the gel permeation chromatography. The variation of the results through different locations in a power transformer is discussed in this paper. The possible correlation between different measured properties was investigated and discussed in this paper     

LED灯光辐射对人皮肤的影响

目的:产生评价演播室中使用的一种LED光源对人皮肤颜色和皮肤屏障功能的影响。方法:选择了30名健康女性志愿者,以照度为2800lxLED光源照射上臂屈侧的皮肤,照射时间15分钟,每天照射一次,连续照射30天。比较照射前后反应皮肤颜色的L*a*b*值、M和E值以及角质层含水量和经皮水分丢失。结果:照射前后L*a*b*值、M和E值以及角质层含水量和经皮水分丢失均无统计学差异。结论:演播室中使用的此种LED光源短期照射对人体肤色和皮肤含水量无影响。     

Noninvasive detection of coronary artery disease using parametricspectral analysis methods

The detection of coronary artery disease by noninvasive analysis of isolated diastolic heart sounds is considered. It is based on identifying features associated with turbulent blood flow in partially occluded coronary arteries. The application of two types of parametric spectral analysis-autoregressive methods and eigenvector methods-to identify the additional signal components is discussed. Results obtained with one eigenvector method, (the MUSIC method) for spectra obtained from an angioplasty patient and results obtained with the autoregressive model in a comparison study of ten diseased and five normal patients are presented and discussed.     

Evaluation of dynamics of forehead skin temperature under induced drowsiness

Drowsiness is one of the leading causes of traffic accidents. A technique for fast and easy measurement of the level of drowsiness is desirable. The objective of the present paper is to evaluate the dynamics of forehead skin temperature (FHT) under induced drowsiness. With a precursory change associated with drowsiness from the FHT, which is a noninvasive measurement, drowsiness can be detected at an early stage and, possibly, traffic accidents can be prevented. In this study, the measured FHTs were categorized into five drowsiness levels according to facial expressions (Level 1 is awake and Level 5 is extremely drowsy). In an experiment, the thermoregulation process of drowsiness was represented by a decrease in the total peripheral resistance, elevation of the nasal skin temperature, and decline in the tympanum temperature. The experimental results showed a significant decrease in FHT for drowsiness Levels 3–5 compared to the rest state (Mann–Whitney U‐test, p < 0.01). Because FHT did not increase in accordance with the process for nasal skin temperature, FHT could represent both skin and core temperatures. The results suggest that FHT can be an indicator for predicting drowsiness. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

一种线性测量电光相位延迟的光学电压传感器

提出了一种采用晶体劈直接线性测量电光相位延迟的新型光学电压传感器,将晶体的电光相位延迟转换为光斑条纹的移动,通过测量光斑的位移量获得相位延迟。理论上分析推导了光斑位移量与晶体电光相位延迟角之间的线性关系,给出了光斑位移量的计算方法,并进行了实验验证。实验结果表明,新型光学电压传感器能够测量的相位延迟角达到320°,线性度良好。