Special Issue "Tissue Optics"

A special issue of Photonics (ISSN 2304-6732). This special issue belongs to the section "Biophotonics and Biomedical Optics".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 17264

Special Issue Editors

Prof. Dr. Walter Blondel
E-Mail Website
Guest Editor
Research Center for Automatic Control in Nancy (CRAN), UMR 7039, University of Lorraine - CNRS, 54518 Vandoeuvre-lès-Nancy CEDEX, France
Interests: UV-Vis-NIR optical spectroscopy; processing of multidimensional spectroscopic data; image processing; light–tissue interactions modelling
Prof. Dr. Dan Zhu
E-Mail Website
Guest Editor
Wuhan National Laboratory for Optoelectronics, Britton Chance Center for Biomedical Photonics, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: tissue optical clearing imaging; in vivo skull/skin optical clearing methods; in vitro optical clearing methods; laser speckle contrast imaging; hyperspectral imaging
Prof. Dr. Valery V. Tuchin
E-Mail Website
Guest Editor
Research-Educational Institute of Optics and Biophotonics, Saratov State University, 410012 Saratov, Russia
Interests: biological and medical physics; biophotonics; biomedical optics; laser spectroscopy and imaging in biomedicine; nonlinear dynamics of laser and optical systems; physics of optical and laser measurements; nanobiophotonics
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Special Issue Information

Dear Colleagues,

Tissue optics is the cornerstone of biophotonics and biomedical optics research exploiting the interactions of light with biological tissues to deepen our knowledge of their Optical Properties (OP) and targeting the development of innovative optical methods and medical devices to improve health care. This is a multidisciplinary field combining biology, photonics and data science to characterize and analyze the OP of biological tissues on subcellular, cellular and tissue scales and their changes related to metabolic and morphological pathological modifications. Tissue optics is at stake in a wide range of applications, from the ex vivo spectral characterization of absorption, scattering, fluorescence and/or polarization properties, to in vivo photodiagnosis or perioperative surgical guiding, through therapeutic use of light.

This Special Issue on “Tissue Optics” will welcome basic, methodological and applied cutting-edge research contributions, as regular and review papers, dealing with:

  • The development and validation of spectroscopic and/or imaging instrumentations on phantoms and on ex vivo and in vivo tissues;
  • The modelling of light–tissue interactions, including inverse problem solving and OP estimation;
  • The processing of multidimensional data using classification and machine learning methods;
  • The development of multimodal, multispectral and/or multiscale approaches;
  • The modifications of tissue OP, including optical clearing;
  • The validation of the methods and tools developed in the frame of preclinical and clinical studies.

Prof. Dr. Walter Blondel
Prof. Dr. Dan Zhu
Prof. Dr. Valery V. Tuchin
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Biological tissue optics and tissue optical properties
  • Biomedical optics and biophotonics
  • Interactions of light with biological tissues
  • Theoretical and experimental modelling
  • Multidimensional data processing and machine learning
  • Spectroscopic and imaging techniques
  • Multimodality and multiscale approaches
  • Optical clearing
  • Basic research and translational research (clinical applications)
  • Photodiagnosis, surgical guiding and therapeutic methods

Published Papers (21 papers)

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Research

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Article
Probing Dynamic Variation of Layered Microstructure Using Backscattering Polarization Imaging
Photonics 2022, 9(3), 153; https://doi.org/10.3390/photonics9030153 - 04 Mar 2022
Viewed by 511
Abstract
Polarization imaging can quantitatively probe the microscopic structure of biological tissues which can be complex and consist of layered structures. In this paper, we established a fast-backscattering Mueller matrix imaging system to characterize the dynamic variation in the microstructure of single-layer and double-layer [...] Read more.
Polarization imaging can quantitatively probe the microscopic structure of biological tissues which can be complex and consist of layered structures. In this paper, we established a fast-backscattering Mueller matrix imaging system to characterize the dynamic variation in the microstructure of single-layer and double-layer tissues as glycerin solution penetrated into the samples. The characteristic response of Mueller matrix elements, as well as polarization parameters with clearer physics meanings, show that polarization imaging can capture the dynamic variation in the layered microstructure. The experimental results are confirmed by Monte Carlo simulations. Further examination on the accuracy of Mueller matrix measurements also shows that much faster speed has to be considered when backscattering Mueller matrix imaging is applied to living samples. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Fast Estimation of the Spectral Optical Properties of Rabbit Pancreas and Pigment Content Analysis
Photonics 2022, 9(2), 122; https://doi.org/10.3390/photonics9020122 - 21 Feb 2022
Viewed by 377
Abstract
The pancreas is a highly important organ, since it produces insulin and prevents the occurrence of diabetes. Although rare, pancreatic cancer is highly lethal, with a small life expectancy after being diagnosed. The pancreas is one of the organs less studied in the [...] Read more.
The pancreas is a highly important organ, since it produces insulin and prevents the occurrence of diabetes. Although rare, pancreatic cancer is highly lethal, with a small life expectancy after being diagnosed. The pancreas is one of the organs less studied in the field of biophotonics. With the objective of acquiring information that can be used in the development of future applications to diagnose and treat pancreas diseases, the spectral optical properties of the rabbit pancreas were evaluated in a broad-spectral range, between 200 and 1000 nm. The method used to obtain such optical properties is simple, based almost on direct calculations from spectral measurements. The optical properties obtained show similar wavelength dependencies to the ones obtained for other tissues, but a further analysis on the spectral absorption coefficient showed that the pancreas tissues contain pigments, namely melanin, and lipofuscin. Using a simple calculation, it was possible to retrieve similar contents of these pigments from the absorption spectrum of the pancreas, which indicates that they accumulate in the same proportion as a result of the aging process. Such pigment accumulation was camouflaging the real contents of DNA, hemoglobin, and water, which were precisely evaluated after subtracting the pigment absorption. Full article
(This article belongs to the Special Issue Tissue Optics)
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Communication
Quantitative Photoacoustic Reconstruction of the Optical Properties of Intervertebral Discs Using a Gradient Descent Scheme
Photonics 2022, 9(2), 116; https://doi.org/10.3390/photonics9020116 - 18 Feb 2022
Viewed by 330
Abstract
The intervertebral discs (IVD) are among the essential organs of the human body, ensuring the mobility of the spine. These organs possess a high proportion of water. However, as the discs age, this content decreases, which can potentially lead to various diseases called [...] Read more.
The intervertebral discs (IVD) are among the essential organs of the human body, ensuring the mobility of the spine. These organs possess a high proportion of water. However, as the discs age, this content decreases, which can potentially lead to various diseases called degenerative disc diseases. This water content is therefore an important indicator of the well-being of the disc. In this paper, we propose photoacoustic imaging as a means of probing a disc and quantitatively recovering its molecular composition, which should allow concluding on its state. An adjoint-assisted gradient descent scheme is implemented to recover the optical absorption coefficient in the disc, from which, if spectroscopic measurements are performed, the molecular composition can be deduced. The algorithm was tested on synthetic measurements. A realistic numerical phantom was built from magnetic resonance imaging of an actual IVD of a pig. A simplified experiment, with a single laser source, was performed. Results show the feasibility of using photoacoustics imaging to probe IVDs. The influences of exact and approximate formulations of the gradient are studied. The impact of noise on the reconstructions is also evaluated. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Evaluation of Mannitol Intervention Effects on Ischemic Cerebral Edema in Mice Using Swept Source Optical Coherence Tomography
Photonics 2022, 9(2), 81; https://doi.org/10.3390/photonics9020081 - 30 Jan 2022
Cited by 1 | Viewed by 741
Abstract
Cerebral edema is a serious complication of ischemic cerebrovascular disease and mannitol is a commonly used dehydrating agent for relieving cerebral edema. However, the edema state and surrounding vascular perfusion level during mannitol treatment remains unclear, which affects the clinical application of the [...] Read more.
Cerebral edema is a serious complication of ischemic cerebrovascular disease and mannitol is a commonly used dehydrating agent for relieving cerebral edema. However, the edema state and surrounding vascular perfusion level during mannitol treatment remains unclear, which affects the clinical application of the medicine. In this paper, we demonstrated the role of swept-source optical coherence tomography (OCT) in the evaluation of mannitol efficacy using mouse models. The OCT-based angiography and attenuation imaging technology were used to obtain the cerebral vascular perfusion level and cerebral edema state at different times. Vascular parameters and edema parameters were quantified and compared. Experimental results show that mannitol can significantly reduce the water content in the central region of edema, effectively inhibiting the rapid growth of the edema area, and restoring cerebral blood flow. On average, the edema area decreased by 33% after 2 h, and the vascular perfusion density increased by 12% after 5 h. This work helps to provide a valuable theoretical basis and research ideas for the clinical treatment of cerebral edema. Full article
(This article belongs to the Special Issue Tissue Optics)
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Communication
Comparison of the Capabilities of Spectroscopic and Quantitative Video Analysis of Fluorescence for the Diagnosis and Photodynamic Therapy Control of Cholangiocellular Cancer
Photonics 2022, 9(2), 65; https://doi.org/10.3390/photonics9020065 - 26 Jan 2022
Viewed by 688
Abstract
Cholangiocellular cancer (CCC) is a malignant neoplasm of the hepatobiliary system that is difficult to diagnose and treat. Currently, the most effective treatment of CCC is demonstrated under the control by fluorescent diagnosis. Photodynamic therapy (PDT) has also shown good results in the [...] Read more.
Cholangiocellular cancer (CCC) is a malignant neoplasm of the hepatobiliary system that is difficult to diagnose and treat. Currently, the most effective treatment of CCC is demonstrated under the control by fluorescent diagnosis. Photodynamic therapy (PDT) has also shown good results in the treatment of this disease, and fluorescence analysis of the photosensitizer is a good approach to control PDT. This article presents the results of a comparison of spectroscopic and quantitative video-fluorescent analysis of chlorin e6 photosensitizer fluorescence in vivo during cholangiocellular cancer surgery. Spectroscopic analysis provides accurate information about the concentration of the photosensitizer in the tumor, while the video-fluorescence method is convenient for visualizing tumor margins. A direct correlation is shown between these two methods when comparing the fluorescence signals before and after PDT. The applied paired Student’s t-test shows a significant difference between fluorescence signal before and after PDT in both diagnostic methods. In this regard, video-fluorescence navigation is not inferior in accuracy, sensitivity, or efficiency to spectroscopic methods. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Design and Simulation of an Ultra-Wide Field Optical Coherence Tomography Retinal Imaging System
Photonics 2021, 8(11), 476; https://doi.org/10.3390/photonics8110476 - 27 Oct 2021
Viewed by 541
Abstract
Peripheral retinal imaging is a unique approach for assessing and monitoring ocular diseases. In this paper, we proposed a design for an optical coherence tomography system to accomplish ultrawide field (>120°) retinal imaging without montages. Scanning of the sample arm was achieved via [...] Read more.
Peripheral retinal imaging is a unique approach for assessing and monitoring ocular diseases. In this paper, we proposed a design for an optical coherence tomography system to accomplish ultrawide field (>120°) retinal imaging without montages. Scanning of the sample arm was achieved via two ellipsoidal mirrors. The optical design software Zemax and an eye model were used to estimate the inherent aberrations in the system and the optical performance of retinal imaging. Simulation results of the aberrations in the designed system indicated that the designed system can achieve an unprecedented imaging field of view (FOV) while maintaining acceptable resolution without sacrificing the working distance. This work suggests that ultrawide field optical coherence tomography retinal imaging is achievable, which is highly important for the diagnosis and treatment of ocular—especially peripheral—retinopathy. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Proposal for a Skin Layer-Wise Decomposition Model of Spatially-Resolved Diffuse Reflectance Spectra Based on Maximum Depth Photon Distributions: A Numerical Study
Photonics 2021, 8(10), 444; https://doi.org/10.3390/photonics8100444 - 14 Oct 2021
Cited by 4 | Viewed by 586
Abstract
In the context of cutaneous carcinoma diagnosis based on in vivo optical biopsy, Diffuse Reflectance (DR) spectra, acquired using a Spatially Resolved (SR) sensor configuration, can be analyzed to distinguish healthy from pathological tissues. The present contribution aims at studying the depth distribution [...] Read more.
In the context of cutaneous carcinoma diagnosis based on in vivo optical biopsy, Diffuse Reflectance (DR) spectra, acquired using a Spatially Resolved (SR) sensor configuration, can be analyzed to distinguish healthy from pathological tissues. The present contribution aims at studying the depth distribution of SR-DR-detected photons in skin from the perspective of analyzing how these photons contribute to acquired spectra carrying local physiological and morphological information. Simulations based on modified Cuda Monte Carlo Modeling of Light transport were performed on a five-layer human skin optical model with epidermal thickness, phototype and dermal blood content as variable parameters using (i) wavelength-resolved scattering and absorption properties and (ii) the geometrical configuration of a multi-optical fiber probe implemented on an SR-DR spectroscopic device currently used in clinics. Through histograms of the maximum probed depth and their exploitation, we provide numerical evidence linking the characteristic penetration depth of the detected photons to their wavelengths and four source–sensor distances, which made it possible to propose a decomposition of the DR signals related to skin layer contributions. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Intraoperative Control of Hemoglobin Oxygen Saturation in the Intestinal Wall during Anastomosis Surgery
Photonics 2021, 8(10), 427; https://doi.org/10.3390/photonics8100427 - 04 Oct 2021
Cited by 1 | Viewed by 487
Abstract
During surgery for colon cancer, monitoring of the oxygen saturation of hemoglobin in the tissues under study makes it possible to assess the degree of blood supply to the anastomosis areas of the colon. Adequate blood supply in this area is decisive in [...] Read more.
During surgery for colon cancer, monitoring of the oxygen saturation of hemoglobin in the tissues under study makes it possible to assess the degree of blood supply to the anastomosis areas of the colon. Adequate blood supply in this area is decisive in terms of the consistency of the anastomosis and can significantly reduce the risk leakage of anastomosis. In this work, we propose a new approach to assessing the hemoglobin oxygen saturation based on measuring both the diffuse reflectance and transmittance spectra of the colon wall tissues. The proposed method is based on the use of two fiber-optic tools for irradiation from both sides—the intestinal lumen and the outside of the intestinal wall. The spectra are recorded from the external side. To determine the degree of hemoglobin saturation, two algorithms, both based on the Taylor series expansion of the coefficient of light attenuation by tissues, are proposed. The results of a clinical study of the proposed approach on volunteers were obtained, allowing to draw a conclusion about the applicability of the approach in a clinical setting. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Multimodal and Multiview Wound Monitoring with Mobile Devices
Photonics 2021, 8(10), 424; https://doi.org/10.3390/photonics8100424 - 02 Oct 2021
Viewed by 539
Abstract
Along with geometric and color indicators, thermography is another valuable source of information for wound monitoring. The interaction of geometry with thermography can provide predictive indicators of wound evolution; however, existing processes are focused on the use of high-cost devices with a static [...] Read more.
Along with geometric and color indicators, thermography is another valuable source of information for wound monitoring. The interaction of geometry with thermography can provide predictive indicators of wound evolution; however, existing processes are focused on the use of high-cost devices with a static configuration, which restricts the scanning of large surfaces. In this study, we propose the use of commercial devices, such as mobile devices and portable thermography, to integrate information from different wavelengths onto the surface of a 3D model. A handheld acquisition is proposed in which color images are used to create a 3D model by using Structure from Motion (SfM), and thermography is incorporated into the 3D surface through a pose estimation refinement based on optimizing the temperature correlation between multiple views. Thermal and color 3D models were successfully created for six patients with multiple views from a low-cost commercial device. The results show the successful application of the proposed methodology where thermal mapping on 3D models is not limited in the scanning area and can provide consistent information between multiple thermal camera views. Further work will focus on studying the quantitative metrics obtained by the multi-view 3D models created with the proposed methodology. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Characterization of Collagen I Fiber Thickness, Density, and Orientation in the Human Skin In Vivo Using Second-Harmonic Generation Imaging
Photonics 2021, 8(9), 404; https://doi.org/10.3390/photonics8090404 - 21 Sep 2021
Cited by 2 | Viewed by 765
Abstract
The assessment of dermal alterations is necessary to monitor skin aging, cancer, and other skin diseases and alterations. The gold standard of morphologic diagnostics is still histopathology. Here, we proposed parameters to distinguish morphologically different collagen I structures in the extracellular matrix and [...] Read more.
The assessment of dermal alterations is necessary to monitor skin aging, cancer, and other skin diseases and alterations. The gold standard of morphologic diagnostics is still histopathology. Here, we proposed parameters to distinguish morphologically different collagen I structures in the extracellular matrix and to characterize varying collagen I structures in the skin with similar SAAID (SHG-to-AF Aging Index of Dermis, SHG—second-harmonic generation; AF—autofluorescence) values. Test datasets for the papillary and reticular extracellular matrix from images in 24 female subjects, 36 to 50 years of age, were generated. Parameters for SAAID, edge detection, and fast Fourier transformation directionality were determined. Additionally, textural analyses based on the grey level co-occurrence matrix (GLCM) were conducted. At first, changes in the GLCM parameters were determined in the native greyscale images and, furthermore, in the Hilbert-transformed images. Our results demonstrate a robust set of parameters for noninvasive in vivo classification for morphologically different collagen I structures in the skin, with similar and different SAAID values. We anticipate our method to enable an automated prevention and monitoring system with an age- and gender-specific algorithm. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Ex Vivo Determination of Broadband Absorption and Effective Scattering Coefficients of Porcine Tissue
Photonics 2021, 8(9), 365; https://doi.org/10.3390/photonics8090365 - 31 Aug 2021
Cited by 2 | Viewed by 927
Abstract
A novel approach for precise determination of the optical scattering and absorption properties of porcine tissue using an optimized integrating sphere setup was applied. Measurements on several sample types (skin, muscle, adipose tissue, bone, cartilage, brain) in the spectral range between 400 nm [...] Read more.
A novel approach for precise determination of the optical scattering and absorption properties of porcine tissue using an optimized integrating sphere setup was applied. Measurements on several sample types (skin, muscle, adipose tissue, bone, cartilage, brain) in the spectral range between 400 nm and 1400 nm were performed. Due to the heterogeneity of biological samples, measurements on different individual animals as well as on different sections for each sample type were carried out. For all samples, we used an index matching method to reduce surface roughness effects and to prevent dehydration. The derived absorption spectra were used to estimate the concentration of important tissue chromophores such as water, oxy- and deoxyhemoglobin, collagen and fat. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Evaluation of Three Iterative Algorithms for Phase Modulation Regarding Their Application in Concentrating Light Inside Biological Tissues for Laser Induced Photothermal Therapy
Photonics 2021, 8(9), 355; https://doi.org/10.3390/photonics8090355 - 27 Aug 2021
Viewed by 530
Abstract
The focusing of light through turbid media like biological tissues is strongly hindered by the scattering of light which limits its safe practice and application in medicine. In order to control this phenomenon, we shaped the incident wavefront using three algorithms including a [...] Read more.
The focusing of light through turbid media like biological tissues is strongly hindered by the scattering of light which limits its safe practice and application in medicine. In order to control this phenomenon, we shaped the incident wavefront using three algorithms including a four-element division algorithm, a partitioning algorithm, and simulated annealing to control, iteratively, a spatial light modulator (SLM). We have tested two different convergence criteria to achieve a focal point inside a turbid environment, made up of a mixture of agar and milk, set to mimic a specific depth of human skin, and provide comparison results. A camera and a lens are used to visualize the focal area and give feedback information to the algorithms. A discussion on the use of these algorithms and convergence criteria is presented, being focused on its convergence time and performance. Depending on the algorithm and operational parameters, improvements of 29% to 46% of the irradiance in the region of interest were accomplished. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Spectroscopic Approach to Correction and Visualisation of Bright-Field Light Transmission Microscopy Biological Data
Photonics 2021, 8(8), 333; https://doi.org/10.3390/photonics8080333 - 13 Aug 2021
Cited by 2 | Viewed by 635
Abstract
The most realistic information about a transparent sample such as a live cell can be obtained using bright-field light microscopy. Under high-intensity pulsing LED illumination, we captured a primary 12-bit-per-channel (bpc) response from an observed sample using a bright-field microscope equipped with a [...] Read more.
The most realistic information about a transparent sample such as a live cell can be obtained using bright-field light microscopy. Under high-intensity pulsing LED illumination, we captured a primary 12-bit-per-channel (bpc) response from an observed sample using a bright-field microscope equipped with a high-resolution (4872 × 3248) image sensor. In order to suppress data distortions originating from the light interactions with elements in the optical path, poor sensor reproduction (geometrical defects of the camera sensor and some peculiarities of sensor sensitivity), we propose a spectroscopic approach for the correction of these uncompressed 12 bpc data by simultaneous calibration of all parts of the experimental arrangement. Moreover, the final intensities of the corrected images are proportional to the photon fluxes detected by a camera sensor. It can be visualized in 8 bpc intensity depth after the Least Information Loss compression. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
A Pixel-Dependent Finite Element Model for Spatial Frequency Domain Imaging Using NIRFAST
Photonics 2021, 8(8), 310; https://doi.org/10.3390/photonics8080310 - 02 Aug 2021
Viewed by 617
Abstract
Spatial frequency domain imaging (SFDI) utilizes the projection of spatially modulated light patterns upon biological tissues to obtain optical property maps for absorption and reduced scattering. Conventionally, both forward modeling and optical property recovery are performed using pixel-independent models, calculated via analytical solutions [...] Read more.
Spatial frequency domain imaging (SFDI) utilizes the projection of spatially modulated light patterns upon biological tissues to obtain optical property maps for absorption and reduced scattering. Conventionally, both forward modeling and optical property recovery are performed using pixel-independent models, calculated via analytical solutions or Monte-Carlo-based look-up tables, both assuming a homogenous medium. The resulting recovered maps are limited for samples of high heterogeneity, where the homogenous assumption is not valid. NIRFAST, a FEM-based image modeling and reconstruction tool, simulates complex heterogeneous tissue optical interactions for single and multiwavelength systems. Based on the diffusion equation, NIRFAST has been adapted to perform pixel-dependent forward modeling for SFDI. Validation is performed within the spatially resolved domain, along with homogenous structured illumination simulations, with a recovery error of <2%. Heterogeneity is introduced through cylindrical anomalies, varying size, depth and optical property values, with recovery errors of <10%, as observed across a variety of simulations. This work demonstrates the importance of pixel-dependent light interaction modeling for SFDI and its role in quantitative accuracy. Here, a full raw image SFDI modeling tool is presented for heterogeneous samples, providing a mechanism towards a pixel-dependent SFDI image modeling and parameter recovery system. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Spectroscopic Measurement of Methylene Blue Distribution in Organs and Tissues of Hamadryas Baboons during Oral Administration
Photonics 2021, 8(8), 294; https://doi.org/10.3390/photonics8080294 - 24 Jul 2021
Cited by 2 | Viewed by 950
Abstract
New research on Methylene Blue (MB), carried out in 2020, shows that it can be an effective antiviral drug as part of COVID-19 treatment. According to the research findings, MB has potential as a direct antiviral drug for the prevention and treatment of [...] Read more.
New research on Methylene Blue (MB), carried out in 2020, shows that it can be an effective antiviral drug as part of COVID-19 treatment. According to the research findings, MB has potential as a direct antiviral drug for the prevention and treatment of COVID-19 in the first stages of the disease. However, the MB accumulation by various types of tissues, as well as by immune cells, has not been previously studied. Therefore, the objective of this study was to obtain spectral data on the interstitial distribution of the administered drug in endothelial tissues in primates. The data on interstitial MB distribution obtained by spectroscopic measurement at both macro- and microlevels during oral administration to Hamadryas baboon individuals demonstrate that MB accumulates in mucous membranes of gastrointestinal tract and the tissues of the respiratory, cardiovascular, immune, and nervous systems. Additionally, it was found that MB was present in lung and brain myeloid cells in significant concentrations, which makes it potentially useful for protection from autoimmune response (cytokine storm) and as a tool for the correction of immunocompetent cells’ functional state during laser irradiation. Since the cytokine storm starts from monocytic cells during SARS-CoV-2 cellular damage and since tumor-associated macrophages can significantly alter tumor metabolism, accumulation of MB in these cells provides a reason to conclude that the immune response correction in COVID-19 patients and change in macrophages phenotype can be achieved by deactivation of inflammatory macrophages in tissues with MB using laser radiation of red spectral range. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Characterization of Ex Vivo Nonmelanoma Skin Tissue Using Raman Spectroscopy
Photonics 2021, 8(7), 282; https://doi.org/10.3390/photonics8070282 - 16 Jul 2021
Cited by 2 | Viewed by 733
Abstract
Raman spectroscopy has shown great potential in detecting nonmelanoma skin cancer accurately and quickly; however, little direct evidence exists on the sensitivity of measurements to the underlying anatomy. Here, we aimed to correlate Raman measurements directly to the underlying tissue anatomy. We acquired [...] Read more.
Raman spectroscopy has shown great potential in detecting nonmelanoma skin cancer accurately and quickly; however, little direct evidence exists on the sensitivity of measurements to the underlying anatomy. Here, we aimed to correlate Raman measurements directly to the underlying tissue anatomy. We acquired Raman spectra of ex vivo skin tissue from 25 patients undergoing Mohs surgery with a fiber probe. We utilized a previously developed biophysical model to extract key biomarkers in the skin from the Raman spectra. We then examined the correlations between the biomarkers and the major skin structures (including the dermis, sebaceous glands, hair follicles, fat, and two types of nonmelanoma skin cancer—basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)). SCC had a significantly different concentration of keratin, collagen, and nucleic acid than normal structures, while ceramide differentiated BCC from normal structures. Our findings identified the key proteins, lipids, and nucleic acids that discriminate nonmelanoma tumors and healthy skin using Raman spectroscopy. These markers may be promising surgical guidance tools for detecting tumors in resection margins. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Elasticity Changes in the Crystalline Lens during Oxidative Damage and the Antioxidant Effect of Alpha-Lipoic Acid Measured by Optical Coherence Elastography
Photonics 2021, 8(6), 207; https://doi.org/10.3390/photonics8060207 - 08 Jun 2021
Cited by 2 | Viewed by 946
Abstract
Age-related cataracts are one of the most prevalent causes of visual impairment around the world. Understanding the mechanisms of cataract development and progression is essential to enable early clinical diagnosis and treatment to preserve visual acuity. Reductive chemicals are potential medicines effective on [...] Read more.
Age-related cataracts are one of the most prevalent causes of visual impairment around the world. Understanding the mechanisms of cataract development and progression is essential to enable early clinical diagnosis and treatment to preserve visual acuity. Reductive chemicals are potential medicines effective on cataract treatment. In this work, we investigated the cataract-induced oxidative damage in the crystalline lens and a kind of reductant, α-lipoic acid (ALA), ability to reduce the damage. We created oxidative environment to investigate the relationship between the progression of oxidative cataract and lenticular biomechanical properties measured by dynamic optical coherence elastography in porcine crystalline lenses ex vivo. The efficacy of ALA to minimize the stiffening of the lens was also quantified. The results showed a significant increase in Young’s modulus of the lens due to the formation of the oxidative cataract. We found a statistically significant difference between Young’s modulus of the lenses stored in phosphate-buffered saline and ALA solution after incubation in H2O2 solution for 3 h (43.0 ± 9.0 kPa versus 20.7 ± 3.5 kPa, respectively). These results show that the lens stiffness increases during oxidative cataract formation, and ALA has the potential to reverse stiffening of the lens caused by oxidative damage. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Three-Dimensional Mapping of Retrograde Multi-Labeled Motor Neuron Columns in the Spinal Cord
Photonics 2021, 8(5), 145; https://doi.org/10.3390/photonics8050145 - 28 Apr 2021
Viewed by 773
Abstract
The quantification and distribution characteristics of spinal motor neurons play important roles in the study of spinal cord and peripheral nerve injury and repair. In most research, the sole retrograde labeling of each nerve or muscle could not simultaneously obtain the distributions of [...] Read more.
The quantification and distribution characteristics of spinal motor neurons play important roles in the study of spinal cord and peripheral nerve injury and repair. In most research, the sole retrograde labeling of each nerve or muscle could not simultaneously obtain the distributions of different motor neuron subpopulations. Therefore, it did not allow mapping of spatial relationships of different motor neuron columns for disclosing the functional relationship of different nerve branches. Here, we combined the multiple retrograde labeling, optical clearing, and imaging for three-dimensional (3D) visualization of motor neurons of multiple brachial plexus branches. After screening fluorescent tracers by the labeling feasibility of motor neurons and fluorescence compatibility with optical clearing, we performed mapping and quantification of the motor neurons of ulnar, median, and radial nerves in the spinal cord, then disclosed the relative spatial distribution among different neuronal subpopulations. This work will provide valuable mapping data for the understanding of the functional relationships among brachial plexus branches, hopefully facilitating the study of regeneration of axons and remodeling of motor neurons in peripheral nerve repair. Full article
(This article belongs to the Special Issue Tissue Optics)
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Article
Compressional Optical Coherence Elastography of the Cornea
Photonics 2021, 8(4), 111; https://doi.org/10.3390/photonics8040111 - 07 Apr 2021
Cited by 8 | Viewed by 982
Abstract
Assessing the biomechanical properties of the cornea is crucial for detecting the onset and progression of eye diseases. In this work, we demonstrate the application of compression-based optical coherence elastography (OCE) to measure the biomechanical properties of the cornea under various conditions, including [...] Read more.
Assessing the biomechanical properties of the cornea is crucial for detecting the onset and progression of eye diseases. In this work, we demonstrate the application of compression-based optical coherence elastography (OCE) to measure the biomechanical properties of the cornea under various conditions, including validation in an in situ rabbit model and a demonstration of feasibility for in vivo measurements. Our results show a stark increase in the stiffness of the corneas as IOP was increased. Moreover, UV-A/riboflavin corneal collagen crosslinking (CXL) also dramatically increased the stiffness of the corneas. The results were consistent across 4 different scenarios (whole CXL in situ, partial CXL in situ, whole CXL in vivo, and partial CXL in vivo), emphasizing the reliability of compression OCE to measure corneal biomechanical properties and its potential for clinical applications. Full article
(This article belongs to the Special Issue Tissue Optics)
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Review

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Review
Challenges in 3D Live Cell Imaging
Photonics 2021, 8(7), 275; https://doi.org/10.3390/photonics8070275 - 13 Jul 2021
Cited by 2 | Viewed by 940
Abstract
A short overview on 3D live cell imaging is given. Relevant samples are described and various problems and challenges—including 3D imaging by optical sectioning, light scattering and phototoxicity—are addressed. Furthermore, enhanced methods of wide-field or laser scanning microscopy together with some relevant examples [...] Read more.
A short overview on 3D live cell imaging is given. Relevant samples are described and various problems and challenges—including 3D imaging by optical sectioning, light scattering and phototoxicity—are addressed. Furthermore, enhanced methods of wide-field or laser scanning microscopy together with some relevant examples and applications are summarized. In the future one may profit from a continuous increase in microscopic resolution, but also from molecular sensing techniques in the nanometer range using e.g., non-radiative energy transfer (FRET). Full article
(This article belongs to the Special Issue Tissue Optics)
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Review
Spatial-Frequency Domain Imaging: An Emerging Depth-Varying and Wide-Field Technique for Optical Property Measurement of Biological Tissues
Photonics 2021, 8(5), 162; https://doi.org/10.3390/photonics8050162 - 12 May 2021
Cited by 3 | Viewed by 961
Abstract
Measurement of optical properties is critical for understanding light-tissue interaction, properly interpreting measurement data, and gaining better knowledge of tissue physicochemical properties. However, conventional optical measuring techniques are limited in point measurement, which partly hinders the applications on characterizing spatial distribution and inhomogeneity [...] Read more.
Measurement of optical properties is critical for understanding light-tissue interaction, properly interpreting measurement data, and gaining better knowledge of tissue physicochemical properties. However, conventional optical measuring techniques are limited in point measurement, which partly hinders the applications on characterizing spatial distribution and inhomogeneity of optical properties of biological tissues. Spatial-frequency domain imaging (SFDI), as an emerging non-contact, depth-varying and wide-field optical imaging technique, is capable of measuring the optical properties in a wide field-of-view on a pixel-by-pixel basis. This review first describes the typical SFDI system and the principle for estimating optical properties using the SFDI technique. Then, the applications of SFDI in the fields of biomedicine, as well as food and agriculture, are reviewed, including burn assessment, skin tissue evaluation, tumor tissue detection, brain tissue monitoring, and quality evaluation of agro-products. Finally, a discussion on the challenges and future perspectives of SFDI for optical property estimation is presented. Full article
(This article belongs to the Special Issue Tissue Optics)
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