Noninvasive imaging of biological tissues using optical reflectance system
18 Mar 2016-pp 1-6
TL;DR: In this paper, the authors proposed reflectance systems consisting of a scanning probe with four units, each unit equipped with a photon injection port, and these ports are arranged in a straight line fashion to collect the backscattered photons from different depths.
Abstract: The noninvasive detection of inhomogeneities in biological tissues is studies using phantoms. The proposed reflectance systems consist of a scanning probe with four units. Each unit equipped with a photon injection port, and these ports are arranged in a straight line fashion to collect the backscattered photons from different depths. The inhomogeneities are placed in three different depths like 7mm, 12mm, and 17mm respectively. Through source ports light is superimposed on tissue phantom and collect the backscattered light from various depth. Red and Infrared light emitting diodes with a wavelength of 660nm and 940nm is used in the system. Twelve photodetectors are arranged in four layers with three in each. In order to obtain more information about inhomogeneities, the distance between source and detector also varies (7mm, 12mm, and 17mm). The data obtained from two different wavelength gives exact information about the location of inhomogeneities. By using the method, it is possible to detect inhomogeneities in the early stages of cancer. The advantages are time taken for scanning a given area is lower, easy to locate inhomogeneties, user-friendly, the cost of the system is less.
TL;DR: A review of reported tissue optical properties summarizes the wavelength-dependent behavior of scattering and absorption in cells and tissues.
Abstract: A review of reported tissue optical properties summarizes the wavelength-dependent behavior of scattering and absorption. Formulae are presented for generating the optical properties of a generic tissue with variable amounts of absorbing chromophores (blood, water, melanin, fat, yellow pigments) and a variable balance between small-scale scatterers and large-scale scatterers in the ultrastructures of cells and tissues.
TL;DR: In this article, a discussion of diagnostic and dosimetric optical measurements in medicine and biology is presented, including tissue optical properties, tissue boundary conditions, and invasive versus noninvasive measurements.
Abstract: A discussion is presented of diagnostic and dosimetric optical measurements in medicine and biology. Topics covered include: tissue optical properties, tissue boundary conditions, and invasive versus noninvasive measurements. Clinical applications of therapeutic dosimetry and diagnostic spectroscopy are discussed. The principles of diffuse reflectance and transmittance measurements are presented. Experimental studies illustrate reflectance spectroscopy and steady-state versus time-resolved measurements. >
TL;DR: Finite mesh-based numerical methods are introduced to calculate the diffuse light field in complex tissues with arbitrary boundaries and applications in tissue spectroscopy and imaging illustrate these theoretical and computational tools.
Abstract: A tutorial introduction to diffuse light transport is presented. The basic analytic equations of time-resolved, steady-state and modu- lated light transport are introduced. The perturbation method for han- dling slight heterogeneities in optical properties is outlined. The treat- ment of boundary conditions such as an air/tissue surface is described. Finite mesh-based numerical methods are introduced to calculate the diffuse light field in complex tissues with arbitrary boundaries. Appli- cations in tissue spectroscopy and imaging illustrate these theoretical and computational tools. © 2008 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.2967535 This report is a tutorial introduction to diffuse light transport in biological tissues. Section 1 presents the basics of diffuse light transport, showing the simple equations for time- resolved, steady-state, and modulated light transport. The per- turbation method for handling slight heterogeneities in optical properties is introduced. The treatment of an air/tissue surface boundary condition is considered. Section 2 describes numeri- cal methods for simulating light transport in complex tissues. The goal of this work is to provide the novice in biomedical optics with an introduction to diffuse light transport, and the underpinnings of how basic approaches to solving light trans- port problems can be solved.
TL;DR: Methods to improve the performance of Diffuse Optical Imaging, such as better spectral coverage with additional wavelengths, improved modelling of light transport in tissues and the use of extrinsic dyes may augment lesion detection and characterisation.
Abstract: Screening X-ray mammography is limited by false positives and negatives leading to unnecessary physical and psychological morbidity. Diffuse Optical Imaging using harmless near infra red light, provides lesion detection based on functional abnormalities and represents a novel diagnostic arm that could complement traditional mammography. Reviews of optical breast imaging have not been systematic, are focused mainly on technological developments, and have become superseded by rapid technological advancement. The aim of this study is to review clinically orientated studies involving approximately 2,000 women in whom optical mammography has been used to evaluate the healthy or diseased breast. The results suggest that approximately 85% of breast lesions are detectable on optical mammography. Spectroscopic resolution of tissue haemoglobin composition and oxygen saturation may improve the detectability of breast diseases. Results suggest that breast lesions contain approximately twice the haemoglobin concentration of background tissue. Current evidence suggests that it is not possible to distinguish benign from malignant disease using optical imaging techniques in isolation. Methods to improve the performance of Diffuse Optical Imaging, such as better spectral coverage with additional wavelengths, improved modelling of light transport in tissues and the use of extrinsic dyes may augment lesion detection and characterisation. Future research should involve large clinical trials to determine the overall sensitivity and specificity of optical imaging techniques as well as to establish patient satisfaction and economic viability.
TL;DR: In this paper, an analog single-chip pulse oximeter with 4.8mW total power dissipation is presented, which is an order of magnitude below the measurements on commercial implementations.
Abstract: Pulse oximeters are ubiquitous in modern medicine to noninvasively measure the percentage of oxygenated hemoglobin in a patient's blood by comparing the transmission characteristics of red and infrared light-emitting diode light through the patient's finger with a photoreceptor. We present an analog single-chip pulse oximeter with 4.8-mW total power dissipation, which is an order of magnitude below our measurements on commercial implementations. The majority of this power reduction is due to the use of a novel logarithmic transimpedance amplifier with inherent contrast sensitivity, distributed amplification, unilateralization, and automatic loop gain control. The transimpedance amplifier, together with a photodiode current source, form a high-performance photoreceptor with characteristics similar to those found in nature, which allows LED power to be reduced. Therefore, our oximeter is well suited for portable medical applications, such as continuous home-care monitoring for elderly or chronic patients, emergency patient transport, remote soldier monitoring, and wireless medical sensing. Furthermore, our design obviates the need for an A-to-D and digital signal processor and leads to a small single-chip solution. We outline how extensions of our work could lead to submilliwatt oximeters.