Optical Properties Of Human Tissue Research Articles

Development of a glass-based imaging phantom to model the optical properties of human tissue.

The fabrication of a stable, reproducible optical imaging phantom is critical to the assessment and optimization of optical imaging systems. We demonstrate the use of an alternative material, glass, for the development of tissue-mimicking phantoms. The glass matrix was doped with nickel ions to approximate the absorption of hemoglobin. Scattering levels representative of human tissue were induced in the glass matrix through controlled crystallization at elevated temperatures. We show that this type of glass is a viable material for creating tissue-mimicking optical phantoms by providing controlled levels of scattering and absorption with excellent optical homogeneity, long-term stability and reproducibility.

Novel Approach Exploiting the Hyperspectral Imaging System for Breast Cancer Therapy and Diagnosis

Background: Breast malignant growth is the most widely recognized disease in women in both highly and less developed nations where early detection is vital for life-saving and fast recovery. Recently, Photonic technologies has played a vital role in medical applications. Their satisfactory and viable implementation in therapy and diagnosis requires reliable information on the optical properties of human tissues. This study presents an outline of recent outcomes on the magnitude of breast tissue optical properties.Methods: We established two different system setups utilizing hyperspectral (HS) camera and multiple excitation source lights with wavelength (380~1050 nm) for this investigation. The first setup (Transmission Mode) was applied for light transmission measurement of ex-vivo breast sample. Thereby, we made calculations of sample absorption. The second setup (Reflection Mode) was used for the measurement of breast sample light diffuse reflectance. The outcomes of both setups were used to select the optimum spectral image to differentiate between the normal and tumoral regions in the ex-vivo breast sample by exploring the optical properties spectroscopy in the Near and visible (NIR-VIS) spectrum. Finally, we applied the custom system on the case study technique for breast tumor detection.Results: Experimental investigations results showed that due to the various excitation wavelength light source (380~1050 nm) generates variable depths of penetration depth in the ex-vivo breast sample. Consequently, experimental results of the diffuse reflectance (?d) provide the optimum spectral image at 600 nm for the diagnostic applications. However, the statistical calculation of the normalized signal validated the outcome at wavelength 680 nm. Additionally, we noticed the optimum spectral image for therapy applications at 700 nm by measurement of breast tissue transmission (?) and attenuation absorption (?) calculation. Moreover, the statistical calculation of the normalized signal validated the outcome at wavelength 760 nm.Conclusions: The proposed novel approach successfully provided promising results of the investigated breast sample optical properties in both diagnostic and therapy applications to assist the pathologist and the surgeon. The trail outcomes of the investigated case study were impressive for selecting optimum wavelength for diagnostic and treatment (680, 760 nm), respectively.

Technical note: Generation of a Cerenkov scatter function convolution kernel for a primary proton beam.

PurposeTo generate a Cerenkov scatter function (CSF) for a primary proton beam and to study the dependence of the CSF on the irradiated medium.Materials and MethodsThe MCNP 6.2 code was used to generate the CSF. The CSF was calculated for light‐pigmented, medium‐pigmented, and dark‐pigmented stratified skin, as well as for a homogeneous optical phantom, which mimics the optical properties of human tissue. CSFs were generated by binning all of the Cerenkov photons which escape the back end (end opposite beam incidence) of a 20 × 20 × 20 cm phantom. A 4 × 4 cm, 500 × 500 bin grid was used to create a histogram of the Cerenkov photon flux on the simulated medium’s back surface (surface opposite beam incidence). A triple Gaussian was then used to fit the data.ResultsFrom the triple Gaussian fit, the coefficients of the CSF for the four phantom materials was generated. The individual CSF fit coefficient errors, with respect to the Gaussian representation, were found to be between 0.92% and 4.11%. The R2 value for the fit was calculated to be 0.99. The phantom material was found to have a significant effect (63% difference between materials) on the CSF amplitude and full width at half maximum (195% difference between materials). The difference in these parameters for the three skin pigments was found to be small.ConclusionsThe CSF was obtained for a proton beam using the MCNP 6.2 code for a phantom constructed of light, medium, and dark stratified human skin, as well as for an optical phantom. The CSFs were then fit with a triple‐Gaussian function. The coefficients can be used to generate a radially symmetric CSF, which can then be used to deconvolve a measured Cerenkov image to obtain the dose distribution.

Optical characterization of tissue-simulating phantom components at 405nm

Optical properties of India ink (1950375, Parker, Quink, England) and 1-µm polystyrene microsphere (07310-15, Polysciences, USA) have been predicted at 405nm. For this purpose, a single integrating sphere system and spectrophotometric transmission spectroscopy have been used to estimate the radiometric characteristics. Radiometric measurements utilized to retrieve optical coefficients based on two different methods. Extinction coefficient has been estimated using collimated transmittance. To reconstruct absorption and scattering coefficients, total transmittance, diffuse reflectance and transmittance were measured. Polystyrene albedo was 0.9925 and was 0.1044 for ink. The agreement of PS scattering coefficient in comparison to Mie theory was obvious. Full Text: PDF ReferencesB.W. Pogue, and M.S. Patterson, "Review of tissue simulating phantoms for optical spectroscopy, imaging and dosimetry", J. Biomed. Opt. 11, 4(2006). CrossRef D. Coluccia, J. Fandino, M. Fujioka, S. Cordovi, C. Muroi, and H. Landolt, "Intraoperative 5-aminolevulinic-acid-induced fluorescence in meningiomas", Acta. Neurochir. 152 (2010). CrossRef P. Valdes et al. "https://www.spiedigitallibrary.org/conference-proceedings-of-spie/8928/892809/Quantitative-spectrally-resolved-intraoperative-fluorescence-imaging-for-neurosurgical-guidance-in/10.1117/12.2039090.short", Congress. Neuro. Surg. 10, 1(2014). CrossRef S. J. Madeson, M. S. Patterson, and B. C. Wilson, "The use of India ink as an optical absorber in tissue-simulating phantoms", Phys. Med. Bio. 37, 5(1997). CrossRef P. Ninni, F. Martelli, and G. Zaccanti, "The use of India ink in tissue-simulating phantoms", Opt. Express. 18, 26(2010). CrossRef F. Martelli, and G. Zaccanti, "Calibration of scattering and absorption properties of a liquid diffusive medium at NIR wavelengths. CW method", Opt. Express.15, 2(2007). CrossRef L. Spinelli et al. "Determination of reference values for optical properties of liquid phantoms based on Intralipid and India ink", Biomed. Opt. Express. 5, 7(2014). CrossRef Y. Liu, Y. Kim, and V. Beckman, "Development of a bioengineered tissue model and its application in the investigation of the depth selectivity of polarization gating", App.Opt. 44, 12 (2005). CrossRef B. Wilson, M. Patterson, and S. Flock, "INDIRECT VERSUS DIRECT TECHNIQUES FOR THE MEASUREMENT OF THE OPTICAL PROPERTIES OF TISSUES", Photochem. Photobiol. 46, 5(1987). CrossRef L. L. Sandell, and T. C. Zhu, "A review of in‐vivo optical properties of human tissues and its impact on PDT", J. Biophotonics. 4,(2011). CrossRef A. Shahin, M. Sayem El-Daher, and W. Bachir, "Determination of the optical properties of Intralipid 20% over a broadband spectrum", Phot. Lett. Poland. 10, 4(2018). CrossRef A. Karinov, A. Mokeeva, E. Segeeva, P. Agrba, and M. Kirillin, "Optical properties of mouse biotissues and their optical phantoms", Opt. Spec. 115, 2(2013). CrossRef C. Matzler, Matlab Functions for Mie Scattering and Absorption, version 2 (Bern, Bern university 2002). DirectLink D. Roysten, R. Poston, and S. Prahl, "Optical properties of scattering and absorbing materials used in the development of optical phantoms at 1064 nm", JBO. 1, 1(1996). CrossRef A. Shahin, and W. Bachir, "Broadband spectroscopy for characterization of tissue-like phantom optical properties", Pol. J. Med. Phys. Eng. 21, 4(2017). CrossRef

Determination of optical properties of human tissues obtained from parotidectomy in the spectral range of 250 to 800nm.

.The optical properties of human tissues are an important parameter in medical diagnostics and therapy. The knowledge of these parameters can encourage the development of automated, computer-driven optical tissue analysis methods. We determine the absorption coefficient and scattering coefficient of different tissue types obtained during parotidectomy in the wavelength range of 250 to 800 nm. These values are determined by high precision integrating sphere measurements in combination with an optimized inverse Monte Carlo simulation. To conserve the optical behavior of living tissues, the optical spectroscopy measurements are performed immediately after tissue removal. Our study includes fresh samples of the ear, nose, and throat (ENT) region, as muscle tissue, nervous tissue, white adipose tissue, stromal tissue, parotid gland, and tumorous tissue of five patients. The measured behavior of adipose corresponds well with the literature, which sustains the applied method. It is shown that muscle is well supplied with blood as it features the same characteristic peaks at 430 and 555 nm in the absorption curve. The parameter decreases for all tissue types above 570 nm. The accuracy is adequate for the purposes of providing and of different human tissue types as muscle, fat, nerve, or gland tissue, which are embedded in large complex structures such as in the ENT area. It becomes possible for the first time to present reasonable results for the optical behavior of human soft tissue located in the ENT area and in the near-UV, visual, and near-infrared areas.

Measurement of tissue optical properties in the context of tissue optical clearing.

Nowadays, dynamically developing optical (photonic) technologies play an ever-increasing role in medicine. Their adequate and effective implementation in diagnostics, surgery, and therapy needs reliable data on optical properties of human tissues, including skin. This paper presents an overview of recent results on the measurements and control of tissue optical properties. The issues reported comprise a brief review of optical properties of biological tissues and efficacy of optical clearing (OC) method in application to monitoring of diabetic complications and visualization of blood vessels and microcirculation using a number of optical imaging technologies, including spectroscopic, optical coherence tomography, and polarization- and speckle-based ones. Molecular modeling of immersion OC of skin and specific technique of OC of adipose tissue by its heating and photodynamic treatment are also discussed.

Tissue oximetry by diffusive reflective visible light spectroscopy: Comparison of algorithms and their robustness

It is essential to measure tissue oxygen saturation (StO2 ) locally and in thin layers of tissue, for example, the bronchial mucosa, skin flaps and small bones. Visible light spectroscopy (VLS) with a shallow penetration depth is suitable method. Although several VLS algorithms have been developed and described, they have not yet been compared to each other. This hinders attempts to compare the clinical results obtained by different algorithms. To address this issue, we compared the algorithms of Harrison, Knoefel, Pittman-Duling, Sato and our OxyVLS oximeter, which applies the algorithm from Wodick and Lübbers, in a liquid phantom with optical properties of human tissue. We generally observed considerable differences between the algorithms, which were StO2 dependent. Exceptions were OxyVLS and Sato, showing a high level of agreement with negligible StO2 dependency. In spite of the considerable deviation between the other algorithms, the difference of StO2 between them in clinically normal StO2 was <10%. We did not observe any dependency of the algorithms on hemoglobin content of the phantom or temperature.

Mixed Total Variation and L1 Regularization Method for Optical Tomography Based on Radiative Transfer Equation.

Optical tomography is an emerging and important molecular imaging modality. The aim of optical tomography is to reconstruct optical properties of human tissues. In this paper, we focus on reconstructing the absorption coefficient based on the radiative transfer equation (RTE). It is an ill-posed parameter identification problem. Regularization methods have been broadly applied to reconstruct the optical coefficients, such as the total variation (TV) regularization and the L1 regularization. In order to better reconstruct the piecewise constant and sparse coefficient distributions, TV and L1 norms are combined as the regularization. The forward problem is discretized with the discontinuous Galerkin method on the spatial space and the finite element method on the angular space. The minimization problem is solved by a Jacobian-based Levenberg-Marquardt type method which is equipped with a split Bregman algorithms for the L1 regularization. We use the adjoint method to compute the Jacobian matrix which dramatically improves the computation efficiency. By comparing with the other imaging reconstruction methods based on TV and L1 regularizations, the simulation results show the validity and efficiency of the proposed method.

Cherenkov radiation from electrons passing through human tissue

A method for investigating the optical properties of human tissues is suggested. The method is based on the measurement of Cherenkov radiation produced by relativistic electrons passing through the tissue. Monte-Carlo simulation of visible photon emission and propagation is carried out taking into account multiple electron and photon scattering processes. Sensitivity of the Cherenkov radiation to the optical characteristics of human tissues is demonstrated.

Characterisation of signal enhancements achieved when utilizing a photon diode in deep Raman spectroscopy of tissue.

We characterise the performance of a beam enhancing element ('photon diode') for use in deep Raman spectroscopy (DRS) of biological tissues. The optical component enhances the number of laser photons coupled into a tissue sample by returning escaping photons back into it at the illumination zone. The method is compatible with transmission Raman spectroscopy, a deep Raman spectroscopy concept, and its implementation leads to considerable enhancement of detected Raman photon rates. In the past, the enhancement concept was demonstrated with a variety of samples (pharmaceutical tablets, tissue, etc) but it was not systematically characterized with biological tissues. In this study, we investigate the enhancing properties of the photon diode in the transmission Raman geometry as a function of: a) the depth and b) the optical properties of tissue samples. Liquid tissue phantoms were employed to facilitate systematic variation of optical properties. These were chosen to mimic optical properties of human tissues, including breast and prostate. The obtained results evidence that a photon diode can enhance Raman signals of tissues by a maximum of × 2.4, although it can also decrease the signals created towards the back of samples that exhibit high scattering or absorption properties.

Radiative transfer equation modeling by streamline diffusion modified continuous Galerkin method.

Optical tomography has a wide range of biomedical applications. Accurate prediction of photon transport in media is critical, as it directly affects the accuracy of the reconstructions. The radiative transfer equation (RTE) is the most accurate deterministic forward model, yet it has not been widely employed in practice due to the challenges in robust and efficient numerical implementations in high dimensions. Herein, we propose a method that combines the discrete ordinate method (DOM) with a streamline diffusion modified continuous Galerkin method to numerically solve RTE. Additionally, a phase function normalization technique was employed to dramatically reduce the instability of the DOM with fewer discrete angular points. To illustrate the accuracy and robustness of our method, the computed solutions to RTE were compared with Monte Carlo (MC) simulations when two types of sources (ideal pencil beam and Gaussian beam) and multiple optical properties were tested. Results show that with standard optical properties of human tissue, photon densities obtained using RTE are, on average, around 5% of those predicted by MC simulations in the entire/deeper region. These results suggest that this implementation of the finite element method-RTE is an accurate forward model for optical tomography in human tissues.

Radiative heating of superficial human tissues with the use of water-filtered infrared-A radiation: A computational modeling

A computational model of both the absorbed radiation and transient temperature fields in multilayer superficial human tissues in the case of an external water-filtered infrared-A irradiation is developed. A novel simplified model for radiative transfer is based on local 1-D solutions taking into account the oblique incidence of radiation at the periphery of the heated region. The computational study of a model problem at typical geometrical, optical, and thermal parameters confirms the acceptable accuracy of the 1-D solution for the temperature field formed in human tissues during thermal treatment with periodic infrared irradiation. The effects of uncertainties in spectral absorption coefficients and thermal conductivity of biological tissues on thermal treatment parameters are analyzed. It is shown that the temperature response to periodic water-filtered infrared-A heating can be used to estimate optical properties of human tissues. The calculations show that the decrease in convective heat transfer with the heating of air in the gap between the radiation source and the body surface has to be taken into account.

A review of in-vivo optical properties of human tissues and its impact on PDT.

A thorough understanding of optical properties of biological tissues is critical to effective treatment planning for therapies such as photodynamic therapy (PDT). In the last two decades, new technologies, such as broadband diffuse spectroscopy, have been developed to obtain in vivo data in humans that was not possible before. We found that the in vivo optical properties generally vary in the ranges μ(a) = 0.03-1.6 cm⁻¹ and μ'(s) = 1.2-40 cm⁻¹, although the actual range is tissue-type dependent. We have also examined the overall trend of the absorption spectra (for μ(a) and μ'(s)) as a function of wavelength within a 95% confidence interval for various tissues in vivo. The impact of optical properties on light fluence rate is also discussed for various light application geometries including superficial, interstitial, and within a cavity.

Validity of the semi-infinite tumor model in diffuse reflectance spectroscopy for epithelial cancer diagnosis: a Monte Carlo study

The accurate understanding of optical properties of human tissues plays an important role in the optical diagnosis of early epithelial cancer. Many inverse models used to determine the optical properties of a tumor have assumed that the tumor was semi-infinite, which infers infinite width and length but finite thickness. However, this simplified assumption could lead to large errors for small tumor, especially at the early stages. We used a modified Monte Carlo code, which is able to simulate light transport in a layered tissue model with buried tumor-like targets, to investigate the validity of the semi-infinite tumor assumption in two common epithelial tissue models: a squamous cell carcinoma (SCC) tissue model and a basal cell carcinoma (BCC) tissue model. The SCC tissue model consisted of three layers, i.e. the top epithelium, the middle tumor and the bottom stroma. The BCC tissue model also consisted of three layers, i.e. the top epidermis, the middle tumor and the bottom dermis. Diffuse reflectance was simulated for two common fiber-optic probes. In one probe, both source and detector fibers were perpendicular to the tissue surface; while in the other, both fibers were tilted at 45 degrees relative to the normal axis of the tissue surface. It was demonstrated that the validity of the semi-infinite tumor model depends on both the fiber-optic probe configuration and the tumor dimensions. Two look-up tables, which relate the validity of the semi-infinite tumor model to the tumor width in terms of the source-detector separation, were derived to guide the selection of appropriate tumor models and fiber optic probe configuration for the optical diagnosis of early epithelial cancers.

Cultured human keratinocytes for optical transmission measurement

The challenges of measuring optical properties of human tissues include the thickness of the sample, homogenization, or crystallization from freezing of the tissue. This investigation demonstrates a method to avoid these problems by growing optically thin samples of human keratinocytes as a substitute for ex vivo epidermis samples. Several methods of growth were investigated. Resulting samples were measured on a spectrophotometer for transmission between 300 nm and 2600 nm. The efficacy of the cell growth was confirmed with histological examination of several cultured keratinocyte samples. Limitations were the requirement to measure samples immediately after removal from the incubation environment, and the absence of the irregular structures of normal skin such as hair and glands.

Modified Beer's Law – historical perspectives and relevance in near-infrared monitoring of optical properties of human tissue

Studying the interaction of light with human tissue is important in understanding functional changes and oxidative metabolism of tissue (e.g., skeletal muscle, brain). This manuscript focuses on the development of quantitative absorption laws of light energy, from the inception of Bouguer Law to Beer's Law, to gain a perspective on the present application of the absorption concepts in investigating optical properties of light absorbing chromophores of human tissue. Although these absorption laws are applicable to determine the absolute concentration of substances present in solids or solvents, these laws do not take into consideration of either reflection or scattering of incident light that accounts for the loss of transmitted light intensity. Importance of light energy in the near-infrared window of 700–1300 nm compared to that of other regions in the electromagnetic spectrum for determination of optical tissue properties in vivo is emphasized. Since human tissue is a highly scattering non-homogenous medium, limitations of Beer's Law with respect to studying human tissue chromophores are presented. Finally, modifications of Beer's Law to investigate the relationship between changes in absorbency and concentrations of light absorbing chromophores within the medical spectral window (700–900 nm) in human tissue are discussed. Relevance to industry As light propagates through human tissue, concentration of some chromophores varies in time within the medical spectral window, implying physiological changes in the tissue. Utilization of this optical principle in biomedical (non-invasive) research of the health and disease of human tissue has increased in the last two decades. While impressive in clinical applications, researchers in the field of ergonomics and human factors have been slow in exploiting the potential of examining optical properties of tissue relevant to human performance at the workplace.

ESTIMATION AND MEASUREMENT OF BIOLOGICAL TISSUES USING OPTICAL SIMULATION METHOD

This paper deals with the optical properties of human tissues that are measured using laser reflectometry method. The result is compared with the phantom and simulation values to get accurate result. The surface Backscattering was determined by laser reflectometry. The tissue equivalent phantom would be prepared with the help of white paraffin wax mixed with various colour pigments in multiple proportions. A familiar Monte Carlo Simulation is used for the analysis of the optical properties of the tissue. The normalized backscattered intensity(NBI) signals from the tissue surface, measured by the output probes after digitization are used to reconstruct the reflectance images of tissues in various layers below the skin surface. From NBI profiles measured at various locations of the tissues on the forearm the corresponding optical parameters, the scattering (ms ) and absorption(ma) coefficient and the anisotropy parameter (g) ,by matching these with profiles as simulated by Monte Carlo procedure are determined.

Catalogue of human tissue optical properties at terahertz frequencies.

Recently published studies suggest thatterahertz pulsed imaging will have applications inmedicine and biology, but there iscurrently very little information about the opticalproperties of human tissue at terahertzfrequencies. Such information would be useful forpredicting the feasibility of proposedapplications, optimising acquisition protocols,providing information about variability ofhealthy tissue and supplying data for studies of theinteraction mechanisms. Research ethicscommittee approval was obtained, andmeasurements made from samples of freshlyexcised human tissue, using a broadbandterahertz pulsed imaging system comprisingfrequencies approximately 0.5 to 2.5 THz.Refractive index and linear absorptioncoefficient were found. Reproducibility wasdetermined using blood from one volunteer,which was drawn and measured on consecutivedays. Skin, adipose tissue, striatedmuscle, vein and nerve were measured (to date, from oneindividual). Water had a higher refractiveindex (2.04 ± 0.07) than any tissue.The linear absorption coefficient was higher formuscle than adipose tissue, as expectedfrom the higher hydration of muscle. As these samples camefrom a single subject, there is currentlyinsufficient statistical power to draw firmconclusions, but results suggest that in vivo clinical imaging will be feasible in certainapplications.

Laser photomedicine

The optical properties of human tissue are reviewed and the effects of UV and visible radiation on human tissue summarized. Therapeutic photomedicine using lamp sources is reviewed and current applications using lasers are discussed. Techniques for achieving selective thermal effects are summarized; these include the use of endogenous and exogenous chromophores as targets and the use of pulsed radiation to confine the heating effects to the targets. Future therapeutic uses of lasers may depend on these target-specific effects.