bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffractive focusing elements for signal purposes produced by e-beam lithography
Authors: Ryzi Z. , Matejka F.
Published: February 2023

There is a great number of applications of signal lights in many areas of people’s lives, for instance in industry, traffic, households, etc. All these signal lights contain, in addition to the light source, a focusing element. Such an element has several characteristics: it converts the light intensity distribution of a light source to another distribution; enlarges radiation area; and is usually specified by the major narrow angle intensity distribution, which contains most of the light energy, and the minor intensity distribution which should direct radiation to the rest of the solid angle. These focusing elements are usually produced as reflectors or refractors, and there are advanced technologies developed for their production. However, focusing elements for signal lights can also be a field for the application of diffractive optical elements.
GRIN-lens based optical interconnection systems for planes of micro emitters and detectors: Microlens arrays improve transmission efficiency
Authors: Baukens V. , Goulet A. , Thienpont H. , Veretennicoff I. , Cox W.R. , Guan C.
Published: February 2023

There has recently been significant progress in the development of arrays of fast and sensitive optoelectronic emitters, detectors and transceiver devices. If arrays of these devices are to be successfully incorporated into switching fabrics, data communication or information processing systems, then highly efficient optical systems must be developed to interconnect them. It is indeed important to minimise transmission losses, because the bandwidth of such data channels strongly depend on the amount of optical power impinging on the receivers. The highly divergent nature of some of these sources, such as Lambertian emitters and microcavity LEDs, does not facilitate this task, because of the high insertion losses at the input of the optical system. Moreover we want these systems to be compact, low cost, robust and easily assembled. In this paper we present a novel, hybrid and compact optical system, based on large diameter radial gradient refractive index (GRIN) lenses and microlenses that fulfills these requirements. We also model this system with raytracing software and evaluate its performances experimentally.
Visible testbed projector with replicated DOE
Authors: Chen C. Bill , Hegg Ronald G. , Johnson Todd , King Bill , Rock David F. , Spande Robert
Published: February 2023

This paper focuses on the need and proper application of DOE’s invisible systems and on the nature and performance of the projector optical design and test results.
Generic approach to relate surface-relief profile height and the phase function of diffractive optical element
Authors: Golub Michael A.
Published: February 2023

Phase transfer function Φ of thin surface-microrelief diffractive optical element (DOE) is usually considered proportional to its microrelief height h in accordance with relation Φ = kμ h, where k = 2π/λ, λ is the wavelength, μ is the scaling factor. Conventional approximate equations1 are μ = n-1 for transmitting and μ = 2cosθ0 for reflective elements, where n is the refractive index of the microrelief material and θ0 is the angle of incidence. This relations are approximate even within scalar diffraction approach because they do not take into consideration the local slopes of the incident and the output beam as well as the curvature of the substrate surface, orientation of microrelief with respect to incident beam. Solutions of rigorous diffraction theory2 are much more precise, but limited to the cases of regular diffraction gratings, while most of DOEs and computer generated holograms feature more complicated spatial structure. Piecewise-smooth surface considerations3,4 are related to the definite type of DOE and require numerical solutions even for simple phase functions.
Demonstration of a Monolithic Micro-Optical Bridge for Free-Space Intrachip Interconnects
Authors: Thienpont H. , Verschaffelt G. , Buczynski R. , Tuteleers P. , Vynck P. , Baukens V. , Kufner S. , Kufner M. , Hermanne A. , Genoe J. , Coppée D. , Vounckx R. , Heremans P. , Veretennicoff I.
Published: February 2023

Future advances in the application of photonic interconnects will involve the insertion of parallel-channel links into Multi-Chip Modules (MCMs) [1]. These will make use of new device-level components such as arrays of Vertical Cavity Surface Emitting Lasers (VCSEL's) [2] or arrays of Micro Cavity Light-Emitting Diodes (MCLED’s) [3] and low power photoreceiver circuits [4]. One of the challenges associated with the development of free-space intra- and inter-MCM optoelectronic interconnects is the fabrication of manufacturable, chip-compatible, and high precision monolithic micro-optical pathway blocks. These three-dimensional modules should integrate micro-optical components to optically interconnect surface-normal transmitters and receivers.
Rigorous coupled-wave diffraction analysis of stratified volume photopolymer holograms
Authors: Ishii Yukihiro , Kubota Toshihiro
Published: February 2023

Stratified volume holograms (SVHs) have been studied1,2 in the layered structures of holograms that are useful for several applications in optical communication such as an optical wavelength-selective filter. The hitherto investigation was performed by using the beam propagation method (BPM) to emulate the SVH with thin (Raman-Nath) gratings, taking into no account the reflection at the boundaries. Here we develop a rigorous coupled-wave model to analyze the TE-polarized diffraction properties of stratified volume photopolymer holograms. The numerical and experimental angular selectivities of stratified holograms are shown.
Integrated micro-optical systems fabricated by replication technology
Authors: Gale M.T. , Rossi M. , Stauffer L. , Scheidt M. , Rogers J.R.
Published: February 2023

Optical microsystems formed by the planar integration of micro-optical elements on a transparent slab are of considerable interest as compact, robust microsystems for applications in sensors and optical instruments. In a typical such microsystem [1], a sequence of micro-optical elements are arranged on one surface of a slab substrate which folds the optical paths between the elements by reflection at the opposite surface (Fig. 1). A major advantage of this approach is the ability to fabricate all micro-optical elements as one block, thus avoiding subsequent positioning and alignment steps. This can readily be achieved by the use of ‘planar’ (micrometer relief) micro-optical elements. Most commonly they are fabricated in a fused silica slab either as binary optical elements, by conventional multiple resist lithography and etching steps [1], or as continuous-relief elements, by techniques such as direct laser or e-beam writing or halftone lithography followed by transfer into the slab material by proportional etching [2].
Counterfeit-Deterrents for Surface-Relief Diffractive Optical Elements
Authors: Raguin Daniel H. , McGuire Robert , Gretton Geoffrey
Published: February 2023

Surface-relief diffractive optical elements (DOEs) have a wide range of applications in present-day optical systems. DOEs have been used for the achromatization, color-correction, and athermalization of imaging systems. Diffractive phase plates are used as fanout gratings in optical interconnect and laser machining applications. Phase plates are also prevalent in display and alignment applications whereby they are used to generate arrows, company logos, and grids and lines, respectively. The ability to design and fabricate high-quality, precision, surface-relief, DOE masters requires a high level of intellectual property in addition to sophisticated manufacturing infrastructure. However, once a high-quality DOE is produced, it is an easier task to produce polymer replicas of the surface using technologies such as cast-and-cure, embossing, and injection molding.[1] The technology to perform high-quality replicas of DOE surfaces is becoming more prevalent globally. As the volume of surface-relief DOEs inserted into the marketplace increases, one must consider measures to deter unauthorized reproductions of one’s intellectual property. Counterfeiting is a $50 billion dollar a year business,[2] and although most of the items counterfeited include computer hardware and software, clothing, and perfume, DOEs, as their market-presence increases, will attract counterfeiters.
Dual Element Diffractive Element Algorithm for Beam Shaping and Phase Encryption
Authors: Johnson Eric G. , Fedor Adam
Published: February 2023

This paper illustrates a technique for phase encryption and beam shaping using two diffractive elements in a cascaded optical system. The method is based on the method of projections and can be used to form both intensity and phase distributions in the output plane.
Waveguides and Diffractive Elements for Non-contact Sensors: Analysis
Authors: Dinesen Palle G. , Lading Lars , Lynov Jens-Peter , Hesthaven Jan S.
Published: February 2023

A number of optical techniques for measuring the dynamic motions of fluids and solids are based on quasielastic light scattering and detection by light beating (dynamic interferometry). Most of the methods are used for scientific investigations. The set-ups are generally bulky and delicate to operate. A considerable reduction in size can be obtained by applying diffractive (or holographic) elements.1,2,3
Fabrication of large circular diffractive optics
Authors: Burge J. H.
Published: February 2023

Equipment and techniques were developed at the University of Arizona for fabricating large computer-generated holograms (CGH’s) for measuring aspheric telescope mirrors. A large laser writing machine was built to fabricate binary zone plates onto spherical surfaces up to 1.8 meters in diameter and with focal ratios as fast as f/1. This machine writes 6-µm to 150-µm features with radial position accuracy better than 1 µm rms over the full diameter. The problems of applying and processing photoresist are avoided by writing the patterns using a simple thermochemical technique. Numerous holograms up to 1.2 m across have been successfully written and tested.
Diffractive Optics: From Basic Research to Practical Applications
Authors: Morris G. Michael
Published: February 2023

A diffractive optical element is an optical device that utilizes interference and diffraction, rather than refraction or reflection, to shape an emerging wavefront. In this talk we will concentrate on the image-forming capabilities of diffractive optics. Traditional Fresnel zone plates are characterized by low efficiency as a result of their construction with alternating clear and opaque regions and do not find wide application. Volume holography has distinct advantages for certain applications; however, environmental and material issues preclude its use in many applications. The majority of applications today utilize surface-relief diffractive optical elements. Surface-relief diffractive optics make use of precision-engineered surface structures to provide wavefront transformations in optical phase and can be highly efficient. In the past few years, diffractive optics has received overwhelming attention and numerous commercial and government applications of the technology are being developed. A key factor for this transition from the research laboratories to practical applications is the improvements in the manufacturing processes that provide high quality (high diffraction efficiency/low scatter) diffractive optical elements.
Low-Distortion Imaging Spectrometer Designs utilizing Convex Gratings
Authors: Mouroulis Pantazis
Published: February 2023

The requirement for very low distortion in pushbroom imaging spectrometers has been recently recognized. It has been shown that the spectral response function of a pixel must be known with great accuracy.1 A small uncertainty in the location of the peak of this function can lead to significant error in the calculated pixel radiance. A maximum shift of less than 1 % of the spectral response function (e.g. 0.1nm in 10nm halfwidth) has been identified as desirable in order to produce data that are free of significant spectral calibration errors.
Three-dimensional optical diffusion tomography using iterative coordinate descent optimization
Authors: Milstein Adam B. , Oh Seungseok , Webb Kevin J. , Bouman Charles A. , Millane Rick P.
Published: February 2023

We demonstrate accurate and efficient three-dimensional optical diffusion imaging using simulated noisy data from a set of measurements at a single modulation frequency. A Bayesian framework provides for prior model conditioning, and a dual-step cost function optimization allows sequential estimation of the data noise variance and the image.
Tomographic reconstruction of layered tissue structures
Authors: Hielscher Andreas H. , Azeez-Jan Mohideen , Bartel Sebastian
Published: February 2023

In recent years the interest in the determination of optical properties of layered tissue structure has resurfaced. Applications include, for example, studies on layered skin tissue and underlying muscles, imaging of the brain underneath layers of skin, skull, and meninges, and imaging of the fetal head in utero beneath the layered structures of the maternal abdomen. In this work we approach the problem of layered structures in the framework of model-based iterative image reconstruction schemes. These schemes are currently developed to determine the optical properties inside tissue from measurement on the surface. If applied to layered structure these techniques yield substantial improvements over currently available semi-analytical approaches.
The Kirchhoff Approximation in diffusive media with arbitrary geometry
Authors: Ripoll Jorge , Ntziachristos Vasilis , Culver Joe , Yodh Aijun G. , Nieto-Vesperinas Manuel
Published: February 2023

Due to the fact that the Kirchhoff Approximation (KA) does not involve matrix inversion for solving the forward problem, it is a very useful tool for quickly solving 3D geometries of arbitrary size and shape. Its potential mainly lies in the rapid generation of Green’s functions for arbitrary geometries, which is key to tomography techniques. We here apply it to light diffusion and study its Emits of validity, proving that it is a very useful approximation for diffuse optical tomography (DOT). Its use can improve the existing imaging techniques for real time diagnostics in medicine.
Internal point spread imaging of cardiac tissue to provide depth resolution for bulk tissue imaging experiments
Authors: Popp Alois K. , Pertsov Arkady M. , Weitz David A.
Published: February 2023

In order to provide depth resolution for bulk tissue imaging experiments using fluorescence or absorption signals, we have designed an internal laser point spread technique. A laser light source has been imbedded in different depths into cardiac tissue and tissue phantoms, the signal on the tissue surface detected by a CCD detector. These measurements in combination with an analytic solution of the diffusion allow us to estimate optical properties of the investigated tissue. We show how this information provides the core of depth quantification of fluorescence and absorption measurements in bulk tissue and investigate experimentally the transition from single scattering to diffuse photon transport in cardiac tissue and suspensions of microscopic spherical particles that serve as model systems.
Optical imaging of hemoglobin distribution in human skin
Authors: Kobayashi Manami , Ito Yasunobu , Sakauchi Naofumi , Oda Ichiro , Konishi Ikuo , Tsunazawa Yoshio
Published: February 2023

We have developed a new four-wavelength optical imager to evaluate the oxygen supply in human skin for peripheral circulation. It measures the reflected light from human skin by a CCD and presents the maps of hemoglobin distribution. This paper describes the principle, system configuration and performance test for human foot during and after venous and arterial occlusion. The obtained images showed distinct local difference in skin oxygenation due to blood flow.
3-D images and morphological investigation of chondrocytes obtained from a new born baby
Authors: Medina H. , Colantuoni Gladys , Quintero M. , Joshi J. , Joshi N.V.
Published: February 2023

A recently developed multiple beam interference confocal microscopy and conventional confocal microscopic techniques were employed to obtain 3-D images and morphological details of chondrocytes obtained from a postmortem of 1 day old baby for the first time. Unprecedented images clearly showed that they were circular and internal structures were noticeably visible. The nucleus shows two or three nucleoids. Peripheral nuclear organelles were also perceptible. These techniques permit to examine with precision the thickness of the organelles.
Three-dimensional optical tomographic imaging of vascular reactivity in the brain
Authors: Hielscher Andreas H. , Bluestone Avraham Y. , Abdoulaev Gassan S. , Lasker Joseph , Barbour Randall L. , Schmitz Christoph H.
Published: February 2023

We report on the first three-dimensional, volumetric, tomographic localization of changes in the concentration of oxyhemoglobin and deoxyhemoglobin in the brain. To this end we have developed a model-based iterative image reconstruction scheme that employs adjoint differentiation methods to minimize the difference between measured and predicted data. To illustrate the performance of the technique, the three-dimensional distribution of changes in the concentration of oxyhemoglobin and deoxyhemoglobin during a Valsalva maneuver are visualized. The observed results are consistent with previously reported effects concerning optical responses to hemodynamic perturbations.
Time-resolved spatial sensitivity profiles on the surface of brain cortex
Authors: Okada Eiji
Published: February 2023

The time-resolved spatial sensitivity profiles on the brain surface and in the plane perpendicular to the brain surface are predicted by Monte Carlo simulation to discuss the volume of tissue sampled by multi-channel near infrared instruments. The adult head model consists of five types of tissue. The temporal point spread function of the detected light is divided into five parts and the trajectories of photons detected during each gate are accumulated to obtain the time-resolved spatial sensitivity profiles. Early photons only graze the cortex surface around the middle of the source and detector whilst late photons tend to penetrate into white matter. The spatial sensitivity profiles for the late photons widely spread on the cortex surface. These results suggest that the detected signal mainly reflects the absorption change in the grey matter.
Second harmonic generation and random lasing after two-photon excitation
Authors: Zacharakis Giannis , Anglos Demetrios , Papazoglou Theodore G.
Published: February 2023

Random lasing and second harmonic generation after two-photon excitation was observed for the first time, in both scattering and amplifying polymer samples. Pumping was performed with sub-picosecond laser pulses at 830 nm and the emission, was observed with a spectrograph streak camera detection system for simultaneous recording of spectral and temporal features. SHG was detected at 415 nm and random lasing at 470 nm. The advantages of two photons absorption are discussed because of its enhanced detection efficiency and minimized effects on the irradiated sample (e.g. healthy tissue surrounding tumors).
Ultrahigh resolution OCT using continuum generation in an air-silica microstructure optical fiber
Authors: Hartl I. , Li X.D. , Chudoba C. , Ko T. H. , Fujimoto J.G. , Windeler R.S.
Published: February 2023

We demonstrate ultrahigh resolution optical coherence tomography using the continuum generation in an air-silica microstructure fiber. A broadband OCT system was developed, supporting a bandwidth of 370 nm at 1.3 μm center wavelength. We achieved longitudinal resolutions of 2.5 pm in air, or ~2 μm in tissue. This is to our knowledge the highest longitudinal OCT resolution demonstrated at this wavelength range and the first application of this new light source for OCT. We will also describe the application of this technique for imaging biological tissue in vivo.
Time-domain transmittance imaging in turbid media using an intensified CCD camera
Authors: D’Andrea C. , Comelli D. , Valentini G. , Cubeddu R.
Published: February 2023

A new instrumentation based on an intensified CCD camera with picosecond time resolution has been developed for optical imaging in turbid media. Scattering inclusions in a homogeneous sample have been detected by fitting the experimental data with a theoretical expression derived from the random walk theory, while absorption inclusions have been localized using time-gated images taken at suitable delays with respect to the expected arrival time of non-scattered photons.
Portable 8-channel time-resolved optical imager for functional studies of biological tissues
Authors: Cubeddu Rinaldo , Giambattistelli Eleonora , Pifferi Antonio , Taroni Paola , Torricelli Alessandro
Published: February 2023

We developed a portable dual-wavelength 8-channel system for time-resolved reflectance measurements based on pulsed laser diodes, a multianode photomultiplier and a time-correlated single-photon counting board. The performances of the system were tested on phantoms in terms of stability, reproducibility among channels, and accuracy in the determination of absolute values of the absorption and transport scattering coefficients. Preliminary in vivo measurements (cuff occlusion protocols) were performed on healthy volunteers to monitor spatial changes in tissue oxygenation and blood volume.
Wide-field Optical Coherence Tomography: Imaging of Biological Tissues at 1220 nm
Authors: Bordenave E. , Abraham E. , Jonusauskas G. , Tsurumachi N. , Oberlé J. , Rullière C. , Minot P.E. , Lassègues M. , Bazeille J.E. Surlève
Published: February 2023

A two-dimensional optical coherence tomography technique has been developed in order to obtain multiple longitudinal slices of a biological sample directly, in a single Z-scan. The system is based on a femtosecond Cr4+:Forsterite laser and an infrared camera for wide-field imaging of the sample with a depth resolution of 9 μm. With this imaging apparatus, we investigated biological tissues such as human skin, human tooth and a mouse ear to observe the different constitutive tissues of the samples.
Non-contact measurement of the optical imaging quality of an eye
Authors: Hellmuth T. , Tan C.
Published: February 2023

The optical imaging properties of the eye are both determined by optical aberrations and deviations of the eye length. We report on a device for simultaneous measurement of aberrations and eye length combining a Shack Hartmann sensor and a short coherence interferometer. The short measurement duration minimizes disturbing influences like tear film or eye length changes. The low irradiance of the patient’s eye minimizes exposure time.
PSF identification applied to 3-D fluorescence microscopy quantification
Authors: Dieterlen A. , Gramain M.P. , Xu C. , Guillemin F. , Jacquey S.
Published: February 2023

3-D optical fluorescence microscopy becomes now an efficient tool for volumic investigation of living biological samples. However, acquired raw data suffer from different distortions. In order to carry out biological analysis, restoration of raw data by deconvolution is mandatory. The system identification is useful to obtain the knowledge of the actual system and to quantify the influence of experimental parameters. High order centered moments are used as PSF descriptors. Oil immersion index, numerical aperture and specimen thickness are critical parameters for data quality. Furthermore, PSF identification is helpful to precise the experimental protocol. Application to 3-D anthracycline distribution in breast cancer cells is presented.
Characterization of the diffusion of fluorophores within microbial biofilms by fluorescence correlation microscopy under two-photon excitation
Authors: Guiot E. , Fontaine-Aupart M.P. , Briandet R. , Bellon-Fontaine M.N. , Georges P. , Brun A. , Merola F. , Arrio B.
Published: February 2023

The penetration and diffusion capabilities of fluorophores inside microbial biofilms of heterogeneous three-dimensional structure were studied by fluorescence correlation microscopy under two-photon excitation. The influence of the size and the surface charge of the fluorophores were investigated in order to understand the mechanisms involved in molecular diffusion inhibition occuring in biofilms such as electrostatic and steric interactions.
‘5-D’ fluorescence microscopy
Authors: Webb S.E.D. , Elson D.S. , Siegel J. , Lévêque-Fort S. , Gu Y. , Parsons-Karavassilis D. , Cole M.J. , French P.M.W. , Lever M. J. , Sueharov L. O. , Neil M. A. A. , Juškaitis R. , Wilson T.
Published: February 2023

We report a whole-field fluorescence imaging microscope that combines 3-D spatial resolution by optical sectioning, using structured illumination, with fluorescence lifetime imaging and spectrally-resolved imaging. We show the potential of this technique in the elimination of common artefacts in fluorescence lifetime imaging and apply it to study the dependence of the lifetime on the emission wavelength in biological tissue.
FRET Measurements by TCSPC Laser Scanning Microscopy
Authors: Becker Wolfgang , Benndorf Klaus , Bergmann Axel , Biskup Christoph , König Karsten , Tirplapur Uday , Zimmer Thomas
Published: February 2023

We use a two-photon laser scanning microscope with a new Time-Correlated Single Photon Counting (TCSPC) imaging technique to obtain combined intensity-lifetime images for FRET measurements in living cells. Single photon pulses from a photomultiplier and signals from the scanning head are used to record the three-dimensional photon density over the time- and image coordinates. Double exponential decay analysis delivers the lifetime components of the quenched and the unquenched molecules in all pixels of the image. We use the ratio of the intensity coefficients of the fast and slow decay component to create images that show the size of the FRET effects in different parts of the cell.
Application of the stretched exponential function to fluorescence lifetime imaging of biological tissue
Authors: Siegel J. , Lee K.C. Benny , Webb S.E.D. , Lévêque-Fort S. , Cole M.J. , Jones R. , Dowling K. , French P.M.W. , Lever M.J.
Published: February 2023

The fluorescence decay in fluorescence lifetime imaging (FLIM) is typically fitted to a multi-exponential model with discrete lifetimes. The interaction between fluorophores in heterogeneous samples (e.g. biological tissue) can, however, produce complex decay characteristics that do not correspond to such models. Although they appear to provide a better fit to fluorescence decay data than the assumption of a mono-exponential decay, the assumption of multiple discrete components is essentially arbitrary and often erroneous. The stretched exponential function (StrEF) describes fluorescence decay profiles using a continuous lifetime distribution as has been reported for tryptophan, being one of the main fluorophores in tissue. We have demonstrated that this model represents our time-domain FLIM data better than multi-exponential discrete decay components, yielding excellent contrast in tissue discrimination without compromising the goodness of fit, and it significantly decreases the required processing time. In addition, the stretched exponential decay model can provide a direct measure of the sample heterogeneity and the resulting heterogeneity map can reveal subtle tissue differences that other models fail to show.
FT-IR Spectroscopic Imaging of Tissue Thin Sections
Authors: Lasch Peter , Boese Matthias , Diem Max
Published: February 2023

FT-IR microspectroscopy in combination with digital image reassembling methodologies have been used to characterize distinct tissue structures within thin sections from the human prostate. The spatially resolved microspectroscopic data were collected with a resolution near the diffraction limit (about 8 μm) by using a HgCdTe focal plane array detector-based infrared imaging instrument. While IR imaging based on distinct spectral parameters such as intensities, frequency values, or half-widths (the univariate imaging technique of chemical mapping) often gives unsatisfactory results, multivariate data analysis techniques (e.g. hierarchical clustering or principal component analysis) confirmed standard histopathological techniques and turned out to be helpful to discriminate reliably between different tissues structures.
Changes in in-vivo autofluorescence spectra at different periods in rat colorectal tumor progression
Authors: Fu S. , Chia C.T. , Tang C.L. , Diong C.H. , Seow C.
Published: February 2023

The study focuses on the Laser-Induced Autofluorescence (LIAF) diagnosis technique for identifying early tumor tissue. 442nm light from a Helium-Cadmium Laser is excited to investigate the spectra of the in vivo normal and tumor rat colorectal tissues. The experiment results show that the LIAF spectra of the normal and tumor colorectal tissues exhibit the significant differences. The results are potentially useful for the development of a clinical study for early colorectal cancer diagnosis.
Optical Biopsy for the Diagnosis of Breast Tumours
Authors: Pickard David C. O. , Bigio Irving J. , Bown Stephen G. , Briggs Gavin M. , Lee Andrew C. , Ripley Paul M. , Lakhani Sunil
Published: February 2023

Elastic scattering or spectroscopy offers the possibility of distinguishing between cancerous and noncancerous tissue in suspicious breast lumps with a relatively simple optical measurement. The measurement of the relative reflection of light has previously been shown to be sensitive to both the size and distribution of intra and intercellular structures as well as absorption from chromophores present in the tissue. Coupling a white tight source and spectrometer to optic fibres makes it possible to construct probes that can be inserted through the skin or used during the operation or on excised tissue such as the sentinel node. This ‘optical biopsy' is correlated with a conventional histopathological specimen obtained at the same point. Spectra have been obtained from a large number of patients with benign and malignant lesions. Some of the differences that appear in these spectra have been identified and these are discussed. To a relatively high degree of sensitivity and specificity it is shown to be possible to distinguish between malignant tumours, benign lesions and normal tissue.
Fluorescence Spectroscopy and Imaging for Detection of Colonic Dysplasia
Authors: Marcon Norman E.
Published: February 2023

Cancer of the colon is the second leading cause of cancer related death in North America and Europe. Colonoscopy is currently the gold standard for the detection and removal of polyps and the diagnosis of cancer. Although a field of intense research, there are currently no surrogate serum or stool markers that accurately identify patients at risk who may have adenomatous colon polyps or curable cancer.

Clinicians therefore rely on white light colonoscopy to survey colonic mucosa in their search for polyps. White light endoscopy has some limitations. It cannot detect flat, non-raised lesions. It cannot distinguish easily between hyperplastic and adenomatous polyps. Subtle, flat lesions may be missed. Scars at the sites of previous sessile polyps are difficult to evaluate for recurrence.

Endoscopies utilizing fluorescence techniques either on the basis of intrinsic fluorescence or exogenous (prodrug) compounds, have the potential to compliment white light endoscopy by improving detection of mucosal dysplasia and ultimately improve outcomes for cancer detection before the date of escape from cure.
Optical Biopsy for the Diagnosis of Dysplasia in Barrett’s Oesophagus
Authors: Pickard David C. O. , Bigio Irving J. , Bown Stephen G. , Lovat Laurence B. , Ripley Paul M. , Novelli Marco
Published: February 2023

Barrett’s oesophagus is an increasingly common pre-cancerous condition, which occurs in patients suffering from acid reflux into their gullet. Biopsies must be taken from patients diagnosed with this condition regularly to pick up signs of pre-cancerous changes. Elastic scattering spectroscopy offers the possibility of distinguishing between benign and pre-cancerous changes in the lower oesophagus with a relatively simple optical measurement. This ‘optical biopsy’ is correlated with a conventional histopathological specimen obtained at the same point. It is shown that to a relatively high degree of sensitivity and specificity it is possible to distinguish between pre-malignant patches, benign lesions and normal tissue.
Light Induced Autofluorescence for Detection of Nasopharyngeal Carcinoma in vivo
Authors: Chang Hanpeng , Wen Yue , Lee Siu Lung , Yuen Powing , Wei William I. , Sham Jonathan , Qu Jianan Y.
Published: February 2023

To improve the accuracy of conventional white light endoscopy in detecting the small lesion and identifying the margin of observable tumors, in vivo, the potential of light-induced fluorescence (LIF) spectroscopic imaging, using a genera multivariate spectral classification algorithm, was evaluated. A conventional endoscopic system with a multiple channel spectrometer was used to measure the autofluorescence of nasopharyngeal tissue in vivo. Classification was based on the spectral difference between the carcinoma and normal tissue. A sophisticated algorithm based on Principal Component Analysis (PCA) was developed to differentiate between the nasopharyngeal carcinoma (NPC) from the normal tissue. Firstly, preprocessing was done to reduce noise and to calibrate the different measurement distances an geometry. Secondly, processing by PCA was done to effectively reduce the variable dimensions while maintaining useful information for analysis. Thirdly, various post-processing techniques were investigated and the classification performance was compared. Algorithms based on ratio of autofluorescence at two-wavelength and three-wavelength bands were used for comparison. The PCA based method shows a significant improvement over the two-wavelength and three-wavelength algorithm. Based on the entire spectra, the sensitivity of 92% and specificity of 96% were achieved using the PCA based algorithm for the detection of nasopharyngeal carcinomas. In conclusion, the PCA based statistical algorithm is efficient to achieve high spectral classification performance of NPC.
Spectral Characteristic Analysis of Lung Cancer Serum
Authors: Li Xiaozhou , Jin Huiqiang , Liu Huasheng , Ding Jianhua , Lin Junxiu
Published: February 2023

Spectral changes of lung cancer serum in the process of tumor evolution were investigated in this study. We kept close watch on the tumor progression of a group of patients, and measured their serum spectra using 488.0nm and 514.5nm excitation of an Ar-ion laser once a week. There was no apparent change observed in fluorescence spectrum in different period. However, the relative intensity of three Raman peaks (mode A, B and C) decreased every week later. For quantitative analysis of such changes, a parameter Ir (relative intensity of C Raman peak) was introduced and Ir-value was calculated. Calculation showed that Ir-value was degressive with tumor evolution, but β (Ir5145/Ir4880) varied irregularly. To the end, no Raman peak was observed. We assumed that three Raman peaks were derived from beta carotene. It indicated that the content of beta carotene decreased with the aggravation of lung cancer.
Measurement of subcutaneous adipose tissue development in children by the optical device LIPOMETER
Authors: Möller Reinhard , Horejsi Renate , Sudi Karl , Berg Aloys , Reibnegger Gilbert , Tafeit Erwin
Published: February 2023

The new optical device LIPOMETER enables the non-invasive, quick and save determination of the thickness of subcutaneous adipose tissue (SAT) layers (in nun) at any site of the human body. The topographic specification of 15 evenly distributed body sites allows the precise measurement of subcutaneous body fat distribution, socalled subcutaneous adipose tissue topography (SAT-Top).

SAT-Top was determined in more than 1000 children, aging from 7 to 21 yr. We describe the SAT-Top development of these subjects through different age groups and the differences between male and female SAT-Top development in each age group.

SAT layer profiles (medians of the 15 body sites) for boys and girls in age group 1 (7-9 yr) show a very similar pattern for both sexes, followed by slightly decreasing SAT layer thicknesses in boys and increasing values in girls in the subsequent age groups. Between age group 3 (11-13 yr) and age group 7 (19-21 yr) male and female SAT-Top is significantly different in (almost) all body sites.

We present a precise description of SAT-Top development in boys and girls, providing a basis for further investigations hi different fields such as obesity, sport sciences or metabolic disorders, and suggesting the LIPOMETER technique as an appropriate measurement tool.
Improvement of resolution in detection of 3D-functional structures m isolated perfused pig heart
Authors: Rauh Robert , Hiller Michael , Trinks Tobias , Kessler Manfred
Published: February 2023

Subcellular structures play a decisive role in light scattering properties of tissue. Our recent efforts aimed at monitoring these structures by use of micro lightguides and scanning tissue spectroscopy technique (EMPHO II SSK) at isolated perfused organs. With application of 70μm lightguides at an isolated perfused pig heart model we were able to improve the resolution to a step size of 20μm.
Autofluorescence lifetime measurements in images of the human ocular fundus
Authors: Schweitzer D. , Kolb A. , Hammer M.
Published: February 2023

Measurements of the autofluorescence at the fundus prove to be an important tool in early diagnosis and in discovering the pathomechanism, e. g., in age-related macular degeneration. In addition to the action of lipofuscin in the ageing process, flavines play an important role as prosthetic groups. As metabolic changes occur at cellular level, patient–specific optimized therapy should be possible according to endogenous fluorophores, before morphological alterations are manifest. As a first tool for the detection of dynamic autofluorescence, a laser scanner ophthalmoscope will be presented permitting lifetime measurements at the living human eye-ground under extremely weak detectable light.

Considering histograms of lifetimes after excitation at 457.8 nm and determined at the living human eye ground in parapapillary region, a lifetime τ ≅ 1.38 ns was calculated most frequently in the long-wave emission range (λ>550 nm). This points to the main contribution of lipofuscin. If the emission range is extended down to 515 nm, components with longer lifetimes are additionally detectable. Lifetime measurements at a human fundus specimen confirmed the lifetime of 1.38 ns in lipofuscin-rich pigment epithelium, whereas the mean lifetime of an intact fundus was 2.04 ns. A comparison of lifetimes before, during, and after breathing of 100% oxygen results in a quenching of the mean lifetime of 0.15 ns by oxygen.
Time-resolved fluorescence studies of porphycene and tetrasulfonated phthalocyanine dyes in varying solvents
Authors: Gundy Sarah , Van der Putten Wil , Shearer Andy , Ryder Alan G. , Ball Michael
Published: February 2023

Various chemicals used for photodynamic therapy, a promising treatment for cancer, exhibit high fluorescence yields which can be used for tumour detection. For a chosen few such compounds fluorescence lifetimes, absorption, and steady state fluorescence spectra were measured at different concentrations (ranging from 10-5 M to 10-8 M) in a variety of solvents The lifetimes were repeated at three different concentrations (ranging from 10-5 M to 10-6 M) in suspensions of 3T3 fibroblast cells.
Near-Infrared Spectroscopy as a diagnostic tool in patients with suspected stroke or traumatic brain injury
Authors: Goldberg S. , Lott C. , Ostermeyer M. , Hennes H.-J.
Published: February 2023

The factor time for identifying intracranial bleeding is very important, especially superficial hematoma can be asymptomatic in the beginning, but needs rapid intervention before structural or functional brain defects occur Superficial bleeding can be located between the dura mater, a hard skin tissue and the brain (subdural hematoma) between the dura mater and the skull (epidural hematoma). Superficial intracranial hematoma causes compression and displacement of the healthy brain structure. In these cases the pressure needs to be released by draining t e blood through a drill hole in the skull. In case of an accident or stroke m a prehospital setting, minimal diagnostic equipment is available. In addition to the clinical symptoms NIRS can corroborate the suspection of superficial intracranial bleeding. It may be helpful for the rescue-team to guide the decision either to take the patient to the next local hospital or accept the longer distance to a medical center, offering a cranial computensed tomography (CCT)-scan or even neurosurgery.
Influence of the phase function on the determination of the optical properties of biological media
Authors: Kienle Alwin , Forster Florian K , Hibst Raimund
Published: February 2023

We investigated the influence of the phase function on the determination of the optical properties of turbid media by measuring the spatially resolved reflectance, R(ρ). Monte Carlo simulations of R(ρ) using different experimental and theoretical phase functions served as ‘experimental data’. We show that the errors in the optical properties are as high as 100%, if these data are fitted with a standard solution of the diffusion In addition, Monte Carlo simulations are applied to fit the ‘experimental data’ using the scattering coefficient, the absorption coefficient and an additional parameter, that characterizes the phase function, as fitting parameters. It is shown that the errors in the optical parameters are ≤ 20%.
Optical properties of tissue simulators based on laser induced spectroscopy and scattering measurements
Authors: Drakaki Helen , Makropoulou Myrsini , Serafetinides Alexander A.
Published: February 2023

Measurements of the tissue optical parameters and the theoretical modeling of the light propagation in biological tissues is very important for real time laser treatment dosimetry and noninvasive diagnosis. An integrating sphere based technique was used to determine the tissue optical properties. Soft tissue – like phantoms were irradiated with visible lasers and the optical parameters were compared with results calculated from the Beer’s law model of light propagation and the Kubelka - Munk simulation.
Simultaneous Near-IR Spectroscopy and Magnetic Resonance Imaging to Assess Cerebral Oxygenation and Brain Water during Hypoxia-Ischemia in 2-week-old Rats
Authors: Shaw R.A. , Tuor U.I. , Foniok T. , Bascaramurty S. , Ringland K. , McKenzie E. , Qiao M. , Tomanek B. , Mantsch H.H.
Published: February 2023

Cerebral near-infrared spectroscopy can potentially probe several parameters related to the onset of stroke and the ensuing tissue damage. One obvious marker of ischemia is cerebral oxygenation, which can be lowered sharply in stroke-affected tissue. Also commonly assessed, though less straightforward to recover, is the redox state of the cytochrome aa3 copper center. Finally, parameters that are in principle available but seldom recovered from in vivo near-IR spectra are changes in water concentration and scattering properties of the tissue. We have evaluated the potential for near-IR spectroscopy to detect relevant changes in cerebral oxygenation, blood volume, water content, and scattering properties in an infant rat stroke model that is well characterized by magnetic resonance imaging methods. The specific aim was to acquire near-IR spectra simultaneously with MR images and to correlate stroke-associated changes detected via these two modalities prior to, during and after a hypoxia-ischemia episode within this stroke model. Presented here are results from the design and testing of a near-IR illumination/detection system that is compatible with an MR imaging system, and the recovery of trends in the near-IR spectra that complement the hypoxic-ischemic changes observed in the MR images. Unexpectedly large intensity changes observed for the in vivo near-IR water absorptions are ascribed to hypoxia-induced variations in effective optical pathlength, suggesting that the water absorptions may prove generally useful as a means to track such changes.
Detection of optical inhomogeneity by Monte Carlo simulation
Authors: Kumar D. , Singh Megha
Published: February 2023

Light propagation in simulated tissue models was analyzed by Monte Carlo method. For this purpose three tissue models were considered. Heart tissue without abnormality was considered as control. For other two models small spherical size tissues of different optical parameters inside the control tissue, at different depths, were introduced. Depending on the optical properties of the abnormalities the photon distributions within and on the surface of the tissues were altered. These results showed that the variation in the backscattered fraction of photons on the tissue surface helps in identifying and characterizing the abnormality.
Real time inversion using Monte Carlo results for the determination of absorption coefficients in multilayered tissues: application to non invasive muscle oxymetry (Part 2)
Authors: Avrillier Sigrid , Tinet Eric , Tualle Jean Michel , Costes Frederic , Revel Frank , Offivier Jean-Pierre.
Published: February 2023

A clinical study of the evolution of the space resolved near infrared reflectance with the subcutaneous layers thickness, at rest, on the vastus lateralis, is used to determine convenient sets of muscle and fat optical coefficients at 850 nm and 780 nm. These coefficients are then used to establish pre-calculated 3 layers MC simulations tables of the reflectance as a function of the fat thickness. Real time inversion during effort is then performed to determine the absolute muscle oxygenation.
In vitro study of the conventional and laser apicoectomy effects on dentin permeability
Authors: Paradella Thaís C. , Mello Guilherme P. S. , Munin Egberto , Redígolo Marcela L. , Pacheco Marcos T.T.
Published: February 2023

In the past years, lasers have become a special tool in dentistry. To study the effects of laser apicoectomy compared to the conventional surgical treatment, freshly-extracted single-root teeth were used, submitted to traditional endodontic treatment and divided into four groups: Group I, conventional apicoectomy using diamond burs; Group II, the same treatment as Group I, however, with a 15 second orthophosphoric acid application; Group III Er:YAG laser cut (10 Hz - 400 mJ); and finally, Group IV Er:YAG laser cut (10 Hz - 400 mJ) and surface treatment with Nd:YAG laser (10 Hz - 2 W). The samples were submitted to 2,5% blue methylene dye solution, at 25° C and 37° C for 36 h and 18 h, respectively, and analyzed under optical microscope. The results show that Group II had the higher permeability of all the groups and Group IV had the lower one, due to the successful Nd:YAG laser surface treatment.
Photodynamic diagnostics and therapy of premalignant lesions and cancer – own three year clinical experience
Authors: Sieron Aleksander , Adamek Mariusz , Biniszkiewicz Tomasz , Cebula Wojciech , Cieslar Grzegorz , Krupka Aleksandra Kawczyk - , Niepsuj Grzegorz , Szygula Michał , Wojciechowski Boguslaw , Zieleznik Witold
Published: February 2023

The results of application of photodynamic diagnostics (PDD) and photodynamic therapy (PDT) for diagnosis and treatment of premalignant lesions and malignant tumours of different tissues were presented. In the period 1998-2000 a total of 314 patients were diagnosed with use of different methods of PDD and a total of 78 patients were treated with use of PDD. On the basis of obtained result we consider PDD and PDT to be sensitive, efficient and non-invasive methods of diagnostics and therapy of malignant lesions.