Optical Spectroscopy System Research Articles

Time-Resolved Diffuse Optical Spectroscopy up to 1700 nm by Means of a Time-Gated InGaAs/InP Single-Photon Avalanche Diode

We present a new compact system for time-domain diffuse optical spectroscopy of highly scattering media operating in the wavelength range from 1100 nm to 1700 nm. So far, this technique has been exploited mostly up to 1100 nm: we extended the spectral range by means of a pulsed supercontinuum light source at a high repetition rate, a prism to spectrally disperse the radiation, and a time-gated InGaAs/InP single-photon avalanche diode working up to 1700 nm. A time-correlated single-photon counting board was used as processing electronics. The system is characterized by linear behavior up to absorption values of about 3.4 cm(-1) where the relative error is 17%. A first measurement performed on lipids is presented: the absorption spectrum shows three major peaks at 1200 nm, 1400 nm, and 1700 nm.

SU-E-J-197: A Novel Optical Interstitial Fiber Spectroscopic System for Real-Time Tissue Micro-Vascular Hemodynamics Monitoring.

To demonstrate a novel interstitial optical fiber spectroscopic system, based on diffuse optical spectroscopies with spectral fitting, for the simultaneous monitoring of tumor blood volume and oxygen tension. The technique provides real-time, minimally-invasive and quantification of tissue micro-vascular hemodynamics. An optical fiber prototype probe characterizesthe optical transport in tissue between two large Numerical Aperture (NA) fibers of 200μm core diameter (BFH37-200, ThorLabs) spaced 3-mm apart. Two 21-Ga medical needles are used to protect fiber ends and to facilitate tissue penetration with minimum local blunt trauma in nude mice with xenografts. A 20W white light source (HL-2000-HP, Ocean Optics) is coupled to one fiber with SMA adapter. The other fiber is used to collect light, which is coupled into the spectrometer (QE65000 with Spectrasuite Operating software and OmniDriver, Ocean Optics). The wavelength response of the probe depends on the wavelength dependence of the light source, and of the light signal collection that includes considerable scatter, modeled with Monte-Carlo techniques (S. Jacques 2010 J. of Innov. Opt. Health Sci. 2 123-9). Measured spectra of tissue are normalized by a measured spectrum of a white standard, yielding the transmission spectrum. A head-and-neck xenograft on the flank of a live mouse is used for development. The optical fiber probe delivers and collects light at an arbitrary depth in the tumor. By spectral fitting of the measured transmission spectrum, an analysis of blood volume and oxygen tension is obtained from the fitting parameters in real time. A newly developed optical fiber spectroscopic system with an optical fiber probe takes spectroscopic techniques to a much deeper level in a tumor, which has potential applications for real-time monitoring hypoxic cell population dynamics for an eventual adaptive therapy metric of particular use in hypofractionated radiotherapy.

Reversal of Age‐Related Mitochondrial Dysfunction In Vivo by Treatment with the Mitochondrially Targeted Therapeutic SS‐ 31

In vivo mitochondrial function and energy homeostasis in skeletal muscle declines with age. The ability to reverse this dysfunction with an acute treatment would represent a new paradigm for improving skeletal muscle function in the elderly. Here we test whether the novel, mitochondrially‐targeted peptide SS‐31 restores mitochondrial energetics in aged mouse skeletal muscle in vivo. We treated young and old mice with an acute 3mg/kg dose of SS‐31 and assessed in vivo mitochondrial function and energetic state after one hour using a unique combined magnetic resonance and optical spectroscopy system. In vivo mitochondrial coupling (P/O), phosphorylation capacity, and energy state (PCr/ATP) significantly declined with age. SS‐31 significantly improved all three measures of mitochondrial energetics in skeletal muscle of aged mice, but had no observed effect in young mice. Reversal of the age‐related decline in capacity and energy state may be due to both SS‐31's antioxidant activity and a more direct facilitation of mitochondrial respiratory activity in aged muscle. These results suggest that short‐term treatment with mitochondrially targeted therapeutics may represent a new approach to reverse the effects of aging on skeletal muscle energetics. This was supported by NIH grants AG001751 and AG028455.

An improved analytical performance of magnetically boosted radiofrequency glow discharge

A magnetically boosted radiofrequency glow discharge optical emission spectroscopy (rf-GD-OES) system has been evaluated using an electromagnet setup that allows the application of transverse magnetic fields up to 70 mT. Such a configuration provides a magnetic field that is independent of the sample thickness. In particular, Cu emission lines, with different upper energy levels, are investigated using GD analysis of a pure copper sample. It is observed that their emission signals are significantly increased when applying magnetic field intensities above a threshold value (∼30 mT). Moreover, it is noticed that the GD pressure conditions as well as the upper energy levels of emission lines are the dominant parameters affecting the enhancement factor of the magnetically boosted Cu emission signals. On the other hand, aluminum matrix samples, with different copper mass contents, have been analyzed using the rf-GD-OES system, both in the normal mode and in the magnetically boosted mode. Linear calibration curves are obtained in both cases, but the slope of the calibration curves (sensitivity) is almost an order of magnitude higher when using the magnetic field. Furthermore, background levels and background noise are not affected by the presence of the external magnetic field; therefore, limits of detection are significantly improved.

Medical Utility of near Infrared Spectroscopy in Low Back Musculoskeletal Health and Disorders

The potential application of near infrared (NIR) spectroscopy has opened doors for many research investigations related to occupational health, specifically in low back muscle research. This review addressed haemodynamic measurements of paraspinal muscles within the context of low back musculoskeletal health and disorders. Systematic online English language searches were conducted using MEDLINE, EMBASE, Science Direct and Scopus. A study was included if it was focused on NIR spectroscopy application to the back region and was also published in the English language. A study was excluded if the main focus was either on upper/lower extremity specific investigations, or the experimental protocol was ambiguous, or the measures utilised were other than spectroscopy-derived haemodynamics. In total, 37 low back studies were included in the review. Studies were mainly classified into five categories: (i) postural variation, (ii) occupational exposure, (iii) aetiology of low back disorders, (iv) analysis of adipose tissue thickness on spectroscopy-derived measurements and (v) reliability of optical spectroscopy measurements. Seventeen studies were focused on the basic (patho) physiology of the low back musculature during a variety of postural variations. Thirteen studies were specific to occupational activities, whereas 10 investigations were related to low back musculoskeletal disorders. Nine studies examined the influence of adipose tissue thickness measured at the erector spinae region on haemodynamic responses. Reliability of spectroscopy-derived responses was reported in 10 studies. This systematic review supports the need for more spectroscopy-related investigations relevant to work-related activities and specific to low back musculoskeletal disorders. Rigorous statistical analysis is needed in examining the influence of adipose tissue thickness on haemodynamic responses. Although high reliability of spectroscopy-derived responses was found in the majority of studies, to date there are no investigations that have established their reliability in the low back pain patient population. More importantly, a proper calibration technique to identify the physiological minimum in the paraspinal muscle region is still elusive. Overall, understanding injury mechanisms for low back pain and other associated musculoskeletal disorders with NIR oximeters is still in its infancy. However, with the advent of advanced optical spectroscopy systems in the last decade, the potential for innovative use of NIR oximeters in low back musculoskeletal health-related research is promising.

Differential optical absorption spectroscopy measurement of CO_2 using a nanosecond white light continuum

We built a differential optical absorption spectroscopy system to measure near-surface CO2 absorption in the atmosphere using a nanosecond white light continuum. The white light laser can cover wavelengths ranging from 420 to 2400 nm, where the CO2 and H2O absorption lines are located. At an optical path length of 568 m, it was possible to evaluate atmospheric CO2 concentration from absorption bands of CO2 and H2O in the vicinity of 2000 nm detected by broadband white light simultaneously.

Advancers in Optical Imaging in Cancer Research — Part 2

TCRT continues to offer to its readers the current advances in OPTICAL BIOPSY. This special section’s focus is presented in four articles in optical imaging area. The salient features of the articles touch upon the use of time and frequency domain in imaging, the use of different wavelengths of several of possible fingerprint molecules in cancer, the role of hypoxia in cancer, the use of key topical contrast agent with confocal micro-endoscope, and the use of ultrasound guided hybrid system with optical diffusive tomography for minima invasive cancer detection. Several key methods are discussed in these articles. Ueda’s group (1) presents clinical results on breast cancer screening using multi-channel Time Resolved optical spectroscopy system in the development of optical mammography. Time-correlated single photon counting and Ti Sapphire laser beam irradiated the breasts. 3D images of breast were reconstructed using the time-resolved paths and algorithms. More than 200 breast cancer patients participated in the study. Piao’s group (2) present imaging using frequency domain methods; in particular, DC approach with several wavelengths in optical diffusive optical tomography probing key finger print molecules of hemoglobin, oxyhemoglobin and water for imaging cancer regions. Zhu’s group (3) combined ultrasound with diffusive optical tomography commonly called DOT by Britton Chance for mapping hypoxia region of tumors. The fingerprints molecules are hemoglobin and oxyhemoglobin concentration in blood phantoms and in vivo cancer patients. The article from Kortum’s group (4) discussed on the use and efficacy of topical fluorescent contrast agent and miroenedoscopy for detection of Barrett’s neoplastic regions in 26 patients at 206 sites .The morphologic and metabolic features of gastrointestinal neoplastic lesions were delineated. The next issue of TCRT will be a continuation of articles in Optical Imaging Advances in cancer area – part 2.

Advances in Optical Imaging in Cancer Research – Part 1

TCRT continues to offer to its readers the current advances in OPTICAL BIOPSY. This special section’s focus is presented in four articles in optical imaging area. The salient features of the articles touch upon the use of time and frequency domain in imaging, the use of different wavelengths of several of possible fingerprint molecules in cancer, the role of hypoxia in cancer, the use of key topical contrast agent with confocal micro-endoscope, and the use of ultrasound guided hybrid system with optical diffusive tomography for minima invasive cancer detection. Several key methods are discussed in these articles. Ueda’s group (1) presents clinical results on breast cancer screening using multi-channel Time Resolved optical spectroscopy system in the development of optical mammography. Time-correlated single photon counting and Ti Sapphire laser beam irradiated the breasts. 3D images of breast were reconstructed using the time-resolved paths and algorithms. More than 200 breast cancer patients participated in the study. Piao’s group (2) present imaging using frequency domain methods; in particular, DC approach with several wavelengths in optical diffusive optical tomography probing key finger print molecules of hemoglobin, oxyhemoglobin and water for imaging cancer regions. Zhu’s group (3) combined ultrasound with diffusive optical tomography commonly called DOT by Britton Chance for mapping hypoxia region of tumors. The fingerprints molecules are hemoglobin and oxyhemoglobin concentration in blood phantoms and in vivo cancer patients. The article from Kortum’s group (4) discussed on the use and efficacy of topical fluorescent contrast agent and miroenedoscopy for detection of Barrett’s neoplastic regions in 26 patients at 206 sites .The morphologic and metabolic features of gastrointestinal neoplastic lesions were delineated. The next issue of TCRT will be a continuation of articles in Optical Imaging Advances in cancer area – part 2.

Optical fiber-coupled InGaAs-based terahertz time–domain spectroscopy system

The successful demonstration of an optical fiber-coupled terahertz time-domain spectroscopy (THz-TDS) system is described in this study. The terahertz output power of the emitter with two optical band rejection filters was 132 nW, which is an improvement of 70% over the output power without any filters. This improvement is due to the suppression of an optical modulated signal that is reverse-generated when an alternating current bias exceeding a certain threshold is applied to the emitter. Under the optimal alignment conditions, the terahertz detector in a fiber-coupled THz-TDS system clearly measured water vapor dips in the free space.

Spectroscopic Measurements of Silicon Wafer Thickness for Backgrinding Process

The optical microgauge system by means of near-infrared spectroscopic measurements was proposed as the thickness monitoring tool in the silicon wafer thinning process. The Fabry-Pelot interferometry and Beer’s law were employed as the principles of the system for extracting the wafer thickness from optical spectroscopic system prototyped in this study. The specifications of the system such as the thickness range and resolution were examined on the prototyped system. The filed test verified the developed system available of monitoring Si wafer as thin as 5 mm.

High rate deposition of mixed oxides by controlled reactive magnetron-sputtering from metallic targets

Mixed optical materials open new possibilities for the design and optimization of thin film properties. For example the refractive index may be tuned between the refractive indices of the pure materials. Low film stress of mixed optical materials can lead to high mechanical and optical capability. Therefore such materials are of great interest for optical applications, especially if the dielectric properties can be tailored during film deposition.A reactive pulsed magnetron deposition using two different pure metallic targets is proposed to alleviate the unfavorable performance of existing mixed optical film deposition methods. Co-sputtering of different materials in such a dual magnetron setup leads to separate hysteresis for each target. Each target is individually controlled using an optical emission spectroscopy system with separated optical fibers integrated in a closed-loop control. Embedded proportional-integral controllers modify a digital pulse pattern used for pulsed discharge power control to stabilize the emission intensity at the set point for pre-selected wavelengths. In this way the composition of the resulting films can be adjusted while the process is controlled in the high-rate transition mode. It was shown that the proposed deposition method is capable to provide continuous tuning of the refractive index of the mixed optical materials throughout the whole range defined by the single-material films.After discussing the process control system, deposition results of hafnium–aluminum–oxide and zirconium–aluminum–oxide films prepared with this technique are presented. Optical and mechanical film properties of the mixtures are compared to the properties of single homogeneous films.

Recent advances in ground-based ultraviolet remote sensing of volcanic SO2 fluxes

Measurements of volcanic SO2 emission rates have been the mainstay of remote-sensing volcanic gas geochemistry for almost four decades, and they have contributed significantly to our understanding of volcanic systems and their impact upon the atmosphere. The last ten years have brought step-change improvements in the instrumentation applied to these observations, which began with the application of miniature ultraviolet spectrometers that were deployed in scanning and traverse configurations, with differential optical absorption spectroscopy evaluation routines. This study catalogs the more recent empirical developments, including: ultraviolet cameras; wide-angle field-of-view differential optical absorption spectroscopy systems; advances in scanning operations, including tomography; and improved understanding of errors, in particular concerning radiative transfer. Furthermore, the outcomes of field deployments of sensors during the last decade are documented, with respect to improving our understanding of volcanic dynamics and degassing into the atmosphere.

Temperature Dependence of Atmospheric NO3 Loss Frequency

A new indicator with temperature dependence of the NO3 loss frequency, was developed to study the contribution of NO3 to the oxidation of monoterpenes and NOx removal in the atmosphere. The new indicator arises from the temperature dependence of kinetic constant. The new indicator was applied to data of observation based on differential optical absorption spectroscopy system on the outskirts of Hefei, China. According to the findings, the contribution of monoterpenes to the loss of NO3 was 70%–80%.

LED标准具结构对差分吸收光谱系统探测NO2的影响及去除方法研究

LED标准具结构对差分吸收光谱系统探测NO₂的影响及去除方法研究

心肌梗死患者红细胞的光镊拉曼光谱

Making use of optical tweezers Raman spectroscopy system to study the differences between normal human red blood cells and the red blood cell RBC in patients with myocardial infarction.We also investigate the changes of the contents in RBC and its variation mechanism.It is hopeful to provide a new,quick and easy method to diagnosis this disease,and may provide reliable experimental evidence for clinical diagnosis.

Observation on the spatial distribution of air pollutants by active multi-axis differential optical absorption spectroscopy

An active 4-axis differential optical absorption spectroscopy system is developed in the project. The system has 4 telescopes integrated together that can simultaneously project and receive 4 independent light beams for measurement. The 4 beams share one xenon short-arc lamp as the light source. Each telescope can be adjusted individually to point to different reflectors. The angle between different beams can be adjusted up to 28°. A test is conducted on the system with four beams setting to measure the concentration of NO2 in the same area. The comparison shows good consistency between measurement data from different beams: the correlation coefficient (R2) between the data from any two beams is no less than 0.97 and the average difference between different beams is below 1×10-9. The long-term observations on the vertical distributions of NO2 and SO2 around Fudan University reveal the average feature of its daily variation: the concentration of NO2 shows a variation of double-peak in a day, the 2 peaks occur in the early morning and the evening respectively, while the valleys occur in the afternoon and the wee hours; the layer of 44—66 m has the highest NO2 concentration, while the layer of 66—88 m the lowest; during the nighttime, inter-layer difference of NO2 concentration is higher than that during the daytime and can be as high as 17×10-9; the concentration of SO2 shows a variation of single-peak in a day, the peak occurs in the forenoon; the vertical distribution of SO2 is relatively even, with the inter-layer difference below 3×10-9.

Changes in morphology and optical properties of sclera and choroidal layers due to hyperosmotic agent

Light scattering in the normally white sclera prevents diagnostic imaging or delivery of a focused laser beam to a target in the underlying choroid layer. In this study, we examine optical clearing of the sclera and changes in blood flow resulting from the application of glycerol to the sclera of rabbits. Recovery dynamics are monitored after the application of saline. The speed of clearing for injection delivery is compared to the direct application of glycerol through an incision in the conjunctiva. Although, the same volume of glycerol was applied, the sclera cleared much faster (5 to 10 s) with the topical application of glycerol compared to the injection method (3 min). In addition, the direct topical application of glycerol spreads over a larger area in the sclera than the latter method. A diffuse optical spectroscopy system provided spectral analysis of the remitted light every two minutes during clearing and rehydration. Comparison of measurements to those obtained from phantoms with various absorption and scattering properties provided estimates of the absorption coefficient and reduced scattering coefficient of rabbit eye tissue.

Specialty Fiber Coupler: Fabrications and Applications

We review the research on specialty fiber couplers with emphasis placed on the characteristics that make them attractive for biomedical imaging, optical communications, and sensing applications. The fabrication of fiber couplers has been carried out with, in addition to conventional single mode fiber, various specialty fibers such as photonic crystal fiber, double clad fiber, and hole-assisted fiber with a Ge-doped core. For the fiber coupler fabrication, the side polishing and the fused biconical tapered methods have been developed. These specialty fiber couplers have been applied to optical coherence tomography, fluorescence spectroscopy, fiber sensors, and optical communication systems. This review aims to provide a detailed statement on the recent progress and novel applications of specialty fiber couplers.

Estimation of the efficiency of the hybrid LIDAR-DOAS system of lidar sensing of the polluted atmosphere using pulsed excilamps

Results of a closed numerical experiment on laser sensing of minor gas impurity concentrations in the tropospheric layer of the atmosphere based on new hybrid LIDAR-DOAS technique with a XeCl* excilamp used for a pulsed wideband radiation source are discussed. Quantitative estimates obtained using a new stochastic genetic search algorithm confirm that the suggested approach, expanding the possibilities of the classical Differential Optical Absorption Spectroscopy (DOAS) system to remote monitoring and localization of dangerous anthropogenic emissions of toxic gases up to the tropopause height, is promising. The necessity of estimating backscattered signals with high spectral resolution by solving the nonstationary radiative transfer equation calls for a significant modification of the statistical simulation algorithms. A combination of the Monte Carlo method with a genetic algorithm of solving inverse problems of reconstructing profiles of gaseous components in the troposphere enables exact quantitative prediction of the efficiency of new promising lidar systems of environmental monitoring to be provided.

Visible light optical spectroscopy is sensitive to neovascularization in the dysplastic cervix

Neovascularization in cervical intraepithelial neoplasia (CIN) is studied because it is the precursor to the third most common female cancer worldwide. Diffuse reflectance from 450-600 nm was collected from 46 patients (76 sites) undergoing colposcopy at Duke University Medical Center. Total hemoglobin, derived using an inverse Monte Carlo model, significantly increased in CIN 2+ (N=12) versus CIN 1 (N=16) and normal tissues (N=48) combined with P<0.004. Immunohistochemistry using monoclonal anti-CD34 was used to quantify microvessel density to validate the increased hemoglobin content. Biopsies from 51 sites were stained, and up to three hot spots per slide were selected for microvessel quantification by two observers. Similar to the optical study results, microvessel density was significantly increased in CIN 2+ (N=16) versus CIN 1 (N=21) and normal tissue (N=14) combined with P<0.007. Total vessel density, however, was not significantly associated with dysplastic grade. Hence, our quantitative optical spectroscopy system is primarily sensitive to dysplastic neovascularization immediately beneath the basement membrane, with minimal confounding from vascularity inherent in the normal stromal environment. This tool could have potential for in vivo applications in screening for cervical cancer, prognostics, and monitoring of antiangiogenic effects in chemoprevention therapies.