301
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Serebrennikova YM, Smith JM, Huffman DE, Leparc GF, García-Rubio LH. Quantitative interpretations of Visible-NIR reflectance spectra of blood. OPTICS EXPRESS 2008; 16:18215-18229. [PMID: 18958099 DOI: 10.1364/oe.16.018215] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This paper illustrates the implementation of a new theoretical model for rapid quantitative analysis of the Vis-NIR diffuse reflectance spectra of blood cultures. This new model is based on the photon diffusion theory and Mie scattering theory that have been formulated to account for multiple scattering populations and absorptive components. This study stresses the significance of the thorough solution of the scattering and absorption problem in order to accurately resolve for optically relevant parameters of blood culture components. With advantages of being calibration-free and computationally fast, the new model has two basic requirements. First, wavelength-dependent refractive indices of the basic chemical constituents of blood culture components are needed. Second, multi-wavelength measurements or at least the measurements of characteristic wavelengths equal to the degrees of freedom, i.e. number of optically relevant parameters, of blood culture system are required. The blood culture analysis model was tested with a large number of diffuse reflectance spectra of blood culture samples characterized by an extensive range of the relevant parameters.
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302
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Abstract
Objectives The objective of this study is to review the basics of laser and established tissue response patterns to thermal injury, with specific reference to endovenous laser ablation (EVLA). This study also reviews the current theories and supporting aspects for the mechanism of action of EVLA in the treatment of superficial venous reflux. Methods The method involves the review of published literature and original investigation of histological effects of 810 nm and 980 nm wavelength EVLA on explanted blood-filled bovine saphenous vein in an in vitro system. Results The existing histological reports confirm that EVLA produces a transmural vein wall injury, typically associated with perforations and carbonization. The pattern of injury is eccentrically distributed, with maximum injury occurring along the path of laser contact. Intravenous temperature monitoring studies during EVLA have confirmed that the peak temperatures at the fibre tip exceed 1000°C, and continuous temperatures of at least 300°C are maintained in the firing zone for the majority of the procedure. Steam production during EVLA, which occurs early in the photothermolytic process when temperatures reach 100°C, accounts for only 2% of applied energy dose, and is therefore unlikely to be the primary mechanism of action of thermal injury during the procedure. Conclusion EVLA causes permanent vein closure through a high-temperature photothermolytic process at the point of contact between the vein and the laser.
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Affiliation(s)
- C-M Fan
- Division of Angiography and Interventional Radiology,
Brigham and Women's Hospital
| | - R Rox-Anderson
- Harvard Medical School, Director, Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, USA
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303
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Vasefi F, Kaminska B, Chan PKY, Chapman GH. Multi-spectral angular domain optical imaging in biological tissues using diode laser sources. OPTICS EXPRESS 2008; 16:14456-14468. [PMID: 18794982 DOI: 10.1364/oe.16.014456] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Angular Domain Imaging (ADI) employs micromachined angular filter to detect non-scattered photons that pass through the micro-scale tunnels unattenuated while scattered photons are rejected. This paper describes the construction of an ADI system utilizing diode lasers at three different wavelengths in the range of the red and near infrared spectrum. Experiments are performed to verify the feasibility of ADI at multi-wavelengths. ADI results of chicken breast as a biological scattering medium are presented for different thicknesses. A spatial resolution of <0.5 mm is achieved with 5 mm thick chicken breast using a 975 nm diode laser source.
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Affiliation(s)
- Fartash Vasefi
- Simon Fraser University, School of Engineering Science, 8888 University Drive, Burnaby, BC, Canada.
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304
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Shih WC, Bechtel KL, Feld MS. Intrinsic Raman spectroscopy for quantitative biological spectroscopy part I: theory and simulations. OPTICS EXPRESS 2008; 16:12726-36. [PMID: 18711511 PMCID: PMC2840632 DOI: 10.1364/oe.16.012726] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We present a novel technique, intrinsic Raman spectroscopy (IRS), to correct turbidity-induced Raman spectral distortions, resulting in the intrinsic Raman spectrum that would be observed in the absence of scattering and absorption. We develop an expression relating the observed and intrinsic Raman spectra through diffuse reflectance using the photon migration depiction of light transport. Numerical simulations are employed to validate the theoretical results and study the dependence of this expression on sample size and elastic scattering anisotropy.
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305
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Duncan DD, Kirkpatrick SJ. Can laser speckle flowmetry be made a quantitative tool? JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2008; 25:2088-94. [PMID: 18677371 PMCID: PMC2572153 DOI: 10.1364/josaa.25.002088] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The ultimate objective of laser speckle flowmetry (and a host of specific implementations such as laser speckle contrast analysis, LASCA or LSCA; laser speckle spatial contrast analysis, LSSCA; laser speckle temporal contrast analysis, LSTCA; etc.) is to infer flow velocity from the observed speckle contrast. Despite numerous demonstrations over the past 25 years of such a qualitative relationship, no convincing quantitative relationship has been proven. One reason is a persistent mathematical error that has been propagated by a host of workers; another is a misconception about the proper autocorrelation function for ordered flow. Still another hindrance has been uncertainty in the specific relationship between decorrelation time and local flow velocity. Herein we attempt to dispel some of these errors and misconceptions with the intent of turning laser speckle flowmetry into a quantitative tool. Specifically we review the underlying theory, explore the impact of various analytic models for relating measured intensity fluctuations to scatterer motion, and address some of the practical issues associated with the measurement and subsequent data processing.
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Affiliation(s)
- Donald D Duncan
- Department of Biomedical Engineering, Oregon Health and Science University, Portland, OR 97239, USA.
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306
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Pop CVL, Neamtu S. Aggregation of red blood cells in suspension: study by light-scattering technique at small angles. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:041308. [PMID: 19021316 DOI: 10.1117/1.2956658] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Red blood cells (RBCs) in the presence of plasma proteins or other macromolecules have a tendency to form aggregates. Light-scattering technique was used to investigate the RBC aggregation process. A highly diluted suspension of RBCs was illuminated with a 632.8-nm HeNe laser. Angular-resolved measurements of light intensity scattered by an RBC suspension from a 200-microm thick optical glass cuvette during 10 min of their aggregation process were performed at 1 to 4 off-axis deg with a very high angular resolution, at hematocrits in the range of 3.5 x 10(-2) to 10(-1). The angular spreading of forward-scattered light at small angles during the RBC aggregation process was described in terms of a new, effective phase function model that has been used for fitting the experimental data. The aggregated RBCs' optical properties, such as effective scattering anisotropy and scattering cross section, were determined. The results were compared with prediction of Mie theory for equivolumetric spherical particles. The time dependence of the aggregates mean radius and of the mean number of cells per aggregate was also calculated. Last, the potential of the proposed technique (forward-scattering light technique) as a new quantitative investigation of cellular aggregation process was estimated.
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Affiliation(s)
- Cristian V L Pop
- National Institute for Research and Development of Isotopic and Molecular Technologies, Molecular and Biomolecular Physics Department, 71-103 Donath Street, 400293 Cluj-Napoca, Romania.
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307
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Martinsen P, Charlier JL, Willcox T, Warman G, McGlone A, Künnemeyer R. Temperature dependence of near-infrared spectra of whole blood. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:034016. [PMID: 18601561 DOI: 10.1117/1.2943191] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The temperature dependence (30 to 40 degrees C) of near-infrared spectra (500 to 1100 nm) of whole human blood, including red blood cells with intact physiological function, is investigated. Previous studies have focused on hemoglobin solutions, but the operation of red blood cells is critically dependent on intact cell membranes to perform normal oxygen transport and other physiological functions. Thus measurements of whole blood are more directly related to changes that occur in vivo. In addition to the response of hemoglobin to temperature in the spectra, a temperature response from water in the plasma is also detected. The temperature response of the water absorption at 960 nm is approximately ten times smaller than the temperature response of the oxyhemoglobin component in the blood at 610 nm. However, it is the most significant temperature effect between 800 and 1000 nm. This work will aid the precision and understanding of full spectrum near-infrared measurements on blood.
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Affiliation(s)
- Paul Martinsen
- The Food and Horticulture Research Institute of New Zealand, Hamilton, New Zealand 3240.
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308
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Xu X, Yu L, Chen Z. Optical clearing of flowing blood using dextrans with spectral domain optical coherence tomography. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:021107. [PMID: 18465956 PMCID: PMC2778029 DOI: 10.1117/1.2909673] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Spectral domain optical coherence tomography (SDOCT) images have been used to investigate the mechanism of optical clearing in flowing blood using dextrans. The depth reflectivity profiles from SDOCT indicate that dextrans become increasingly more effective in reducing scattering in flowing blood, except for 5 mgdl(-1) of Dx500, with increasing molecular weights (MW 70,000 and 500,000) and concentrations (0.6, 2, and 5 mgdl(-1)). Among the tested dextrans, Dx500 at 2 mgdl(-1) had the most significant effect on light scattering reduction with the strongest capability to induce erythrocyte aggregation. Dx500 at 5 mgdl(-1) contributes more refractive index matching but induces a decrease in aggregation that leads to the same level as 0.6 mgdl(-1) Dx500. Previous studies identified various mechanisms of light scattering reduction in stationary blood induced by optical clearing agents. Our results suggest that erythrocyte aggregation is a more important mechanism for optical clearing in flowing blood using dextrans, providing a rational design basis for effective flowing blood optical clearing, which is essential for improving OCT imaging capability through flowing blood.
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Affiliation(s)
- Xiangqun Xu
- Zhejiang Sci-Tech University, School of Science, Hangzhou 310018, China.
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309
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Vasefi F, Kaminska B, Chapman GH. Angular domain optical imaging using a micromachined tunnel array and a Keplerian lens system. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2008; 2008:3730-3734. [PMID: 19163522 DOI: 10.1109/iembs.2008.4650019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Angular Domain Imaging (ADI) is a technique that selects quasi-ballistic photons exiting from a highly scattering medium by an array of silicon micromachined micro-tunnels. Each channel has a limited acceptance angle based on its geometry therefore those photons that traverse within the acceptance angle of the micro-tunnels will be detected by the imager. In this paper, the ADI technique has been investigated by using newly micromachined tunnels with less spacing between the channels. Also, a Keplerian lens system is used to remove the diffracted light exiting from the tunnels that results due to internal reflection of scattered photons along the tunnel's walls. With these changes, improvements in the spatial resolution including sharper edges and definition were observed. The experiments show that the new setup can resolve test structure objects down to 100 mum embedded midway through a 2 cm long cuvette filled with 0.3% Intralipid solution in the 808 nm wavelength.
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Affiliation(s)
- F Vasefi
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada
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310
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Wang RK, Tuchin VV. Optical Tissue Clearing to Enhance Imaging Performance for OCT. OPTICAL COHERENCE TOMOGRAPHY 2008. [DOI: 10.1007/978-3-540-77550-8_28] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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311
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Fredriksson I, Larsson M, Strömberg T. Optical microcirculatory skin model: assessed by Monte Carlo simulations paired with in vivo laser Doppler flowmetry. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:014015. [PMID: 18315373 DOI: 10.1117/1.2854691] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
An optical microvascular skin model, valid at 780 nm, was developed. The model consisted of six layers with individual optical properties and variable thicknesses and blood concentrations at three different blood flow velocities. Monte Carlo simulations were used to evaluate the impact of various model parameters on the traditional laser Doppler flowmetry (LDF) measures. A set of reference Doppler power spectra was generated by simulating 7000 configurations, varying the thickness and blood concentrations. Simulated spectra, at two different source detector separations, were compared with in vivo recorded spectra, using a nonlinear search algorithm for minimizing the deviation between simulated and measured spectra. The model was validated by inspecting the thickness and blood concentrations that generated the best fit. These four parameters followed a priori expectations for the measurement situations, and the simulated spectra agreed well with the measured spectra for both detector separations. Average estimated dermal blood concentration was 0.08% at rest and 0.63% during heat provocation (44 degrees C) on the volar side of the forearm and 1.2% at rest on the finger pulp. The model is crucial for developing a technique for velocity-resolved absolute LDF measurements with known sampling volume and can also be useful for other bio-optical modalities.
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Affiliation(s)
- Ingemar Fredriksson
- Linköping University, Department of Biomedical Engineering, University Hospital, S-581 85 Linköping, Sweden.
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312
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Peris VA, Hu S. Validation of a Monte Carlo platform for the optical modelling of pulse oximetry. ACTA ACUST UNITED AC 2007. [DOI: 10.1088/1742-6596/85/1/012027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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313
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Zhu D, Lu W, Zeng S, Luo Q. Effect of light losses of sample between two integrating spheres on optical properties estimation. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:064004. [PMID: 18163820 DOI: 10.1117/1.2815691] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A Monte Carlo algorithm is applied to simulate the measurements of a sample with glass slides sandwiched between the double integrating sphere (DIS) setup. The effects caused by various parameters, such as the sample port of integrating sphere, thicknesses, and optical properties of the sample, on light losses and optical properties estimated by the inverse adding-doubling method (IAD) have been investigated. The results show that the light loss greatly increases the estimated error of absorption coefficient and slightly affects the estimated scattering coefficient. When the increase of apparent absorption of the sample induced by the light loss is 59%, the relative error of the scattering coefficient is less than 2% and that of the absorption coefficient reaches 28%. Enhancing the sample port diameter or decreasing the thickness of the sample can reduce the error effectively, and the effect of the former is much greater than that of the latter. In addition, the IAD method is proved to be valid for estimating the optical properties of a highly scattering or highly absorbing sample. This study can not only evaluate the error of optical properties estimation, but also provide optimal ways for the design of DIS and a scheme for acquiring accurate optical properties of tissue.
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Affiliation(s)
- Dan Zhu
- Huazhong University of Science and Technology, Britton Chance Center for Biomedical Photonics, Wuhan National Laboratory for Optoelectronics, Wuhan, 430074, China
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314
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Technical review of endovenous laser therapy for varicose veins. Eur J Vasc Endovasc Surg 2007; 35:88-95. [PMID: 17920307 DOI: 10.1016/j.ejvs.2007.08.005] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Accepted: 08/09/2007] [Indexed: 11/22/2022]
Abstract
BACKGROUND In the last decade, several new treatments of truncal varicose veins have been introduced. Of these new therapies, endovenous laser therapy (EVLT) is one of the most widely accepted and used treatment options for incompetent greater and lesser saphenous veins. OBJECTIVE The objective of this report is to inform clinicians about the EVLT procedure and to review its efficacy and safety in treatment of truncal varicose veins. Also, we discuss some of the underlying theoretical principles and laser parameters that affect EVLT. METHODS We carried out a literature review of EVLT;s efficacy and safety. We included reports that included 100 or more limbs with a follow-up of at least 3 months. The principals and procedure of EVLT are described. Of the laser parameters, mode of administration, wavelength, fluence, wattage and pullback speed are discussed. CONCLUSION EVLT appears to be a very effective and safe option in the treatment of varicose veins but large randomized comparative studies are needed.
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315
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Petrov Y, Prough D, Deyo D, Petrova I, Motamedi M, Esenaliev R. In vivo noninvasive monitoring of cerebral blood with optoacoustic technique. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2004:2052-4. [PMID: 17272123 DOI: 10.1109/iembs.2004.1403603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We present the results of blood oxygenation (oxyhemoglobin saturation) measurements using an optoacoustic system in vivo in the superior sagittal sinus of sheep. The system included a nanosecond Nd:YAG laser as a source of radiation and a specially designed optoacoustic probe for signal detection. The optoacoustic signal induced in the superior sagittal sinus by the nanosecond laser pulses correlated well with actual oxyhemoglobin saturation measured with CO-oximeter. We propose to use a two- or multi- wavelength optoacoustic system for noninvasive continuous monitoring of cerebral venous blood oxygenation. The spectra of effective attenuation coefficient were measured in the range 680-1300 nm for oxy- and deoxygenated whole blood and can be employed for calibration of the system.
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Affiliation(s)
- Y Petrov
- Center for Biomedical Engineering, University of Texas, Galveston, TX 77555, USA
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316
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Zharov VP, Galanzha EI, Shashkov EV, Kim JW, Khlebtsov NG, Tuchin VV. Photoacoustic flow cytometry: principle and application for real-time detection of circulating single nanoparticles, pathogens, and contrast dyes in vivo. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:051503. [PMID: 17994867 DOI: 10.1117/1.2793746] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The goal of this work is to develop in vivo photoacoustic (PA) flow cytometry (PAFC) for time-resolved detection of circulating absorbing objects, either without labeling or with nanoparticles as PA labels. This study represents the first attempt, to our knowledge, to demonstrate the capability of PAFC with tunable near-infrared (NIR) pulse lasers for real-time monitoring of gold nanorods, Staphylococcus aureus and Escherichia coli labeled with carbon nanotubes (CNTs), and contrast dye Lymphazurin in the microvessels of mouse and rat ears and mesenteries. PAFC shows the unprecedented threshold sensitivity in vivo as one gold nanoparticle in the irradiated volume and as one bacterium in the background of 10(8) of normal blood cells. The CNTs are demonstrated to serve as excellent new NIR high-PA contrast agents. Fast Lymphazurin diffusion in live tissue is observed with rapid blue coloring of a whole animal body. The enhancement of the thermal and acoustic effects is obtained with clustered, multilayer, and exploded nanoparticles. This novel combination of PA microscopy/spectroscopy and flow cytometry may be considered as a new powerful tool in biological research with the potential of quick translation to humans, providing ultrasensitive diagnostics of pathogens (e.g., bacteria, viruses, fungi, protozoa, parasites, helminthes), metastatic, infected, inflamed, stem, and dendritic cells, and pharmacokinetics of drug, liposomes, and nanoparticles in deep vessels (with focused transducers) among other potential applications.
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Affiliation(s)
- Vladimir P Zharov
- University of Arkansas for Medical Sciences, Phillips Classic Laser Laboratories, Little Rock, Arkansas 72205, USA.
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317
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Nishidate I, Maeda T, Aizu Y, Niizeki K. Visualizing depth and thickness of a local blood region in skin tissue using diffuse reflectance images. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:054006. [PMID: 17994894 DOI: 10.1117/1.2798703] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A method is proposed for visualizing the depth and thickness distribution of a local blood region in skin tissue using diffuse reflectance images at three isosbestic wavelengths of hemoglobin: 420, 585, and 800 nm. Monte Carlo simulation of light transport specifies a relation among optical densities, depth, and thickness of the region under given concentrations of melanin in epidermis and blood in dermis. Experiments with tissue-like agar gel phantoms indicate that a simple circular blood region embedded in scattering media can be visualized with errors of 6% for the depth and 22% for the thickness to the given values. In-vivo measurements on human veins demonstrate that results from the proposed method agree within errors of 30 and 19% for the depth and thickness, respectively, with values obtained from the same veins by the conventional ultrasound technique. Numerical investigation with the Monte Carlo simulation of light transport in the skin tissue is also performed to discuss effects of deviation in scattering coefficients of skin tissue and absorption coefficients of the local blood region from the typical values of the results. The depth of the local blood region is over- or underestimated as the scattering coefficients of epidermis and dermis decrease or increase, respectively, while the thickness of the region agrees well with the given values below 1.2 mm. Decreases or increases of hematocrit value give over- or underestimation of the thickness, but they have almost no influence on the depth.
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Affiliation(s)
- Izumi Nishidate
- Yamagata University, Department of Bio-system Engineering, 4-3-16, Jonan, Yonezawa, Yamagata 992-8510, Japan
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318
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Friebel M, Helfmann J, Müller G, Meinke M. Influence of shear rate on the optical properties of human blood in the spectral range 250 to 1100 nm. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:054005. [PMID: 17994893 DOI: 10.1117/1.2799154] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The intrinsic optical parameters-absorption coefficient mua, scattering coefficient mus, anisotropy factor g, and effective scattering coefficient mus'--are determined for human red blood cells of hematocrit 42.1% dependent on the shear rate in the wavelength range 250 to 1100 nm. Integrating sphere measurements of light transmittance and reflectance in combination with inverse Monte-Carlo simulation are carried out for different wall shear rates between 0 and 1000 s(-1). Randomly oriented cells show maximal mua, mus, and mus' values. Cell alignment and elongation, as well as the Fahraeus effect at increasing shear rates, lead to an asymptotical decrease of these values. The anisotropy factor shows this behavior only below 600 nm, dependent on absorption; above 600 nm, g is almost independent of shear rate. The decrease of mus' is inversely correlated with the hemoglobin absorption. Compared to randomly oriented cells, aggregation reduces all parameters by a different degree, depending on the hemoglobin absorption. It is possible to evaluate the influence of collective scattering phenomena, the absorption within the cell, and the cell shape.
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Affiliation(s)
- Moritz Friebel
- Laser-und Medizin-Technologie GmbH, Berlin, Fabeckstrasse 60-62, 14195 Berlin, Germany
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319
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Mordon SR, Wassmer B, Zemmouri J. Mathematical modeling of 980-nm and 1320-nm endovenous laser treatment. Lasers Surg Med 2007; 39:256-65. [PMID: 17252577 DOI: 10.1002/lsm.20476] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND AND OBJECTIVES Endovenous laser treatment (ELT) has been proposed as an alternative in the treatment of reflux of the great saphenous vein (GSV) and small saphenous vein (SSV). Numerous studies have since demonstrated that this technique is both safe and efficacious. ELT was presented initially using diode lasers of 810 nm, 940 nm, and 980 nm. Recently, a 1,320-nm Nd:YAG laser was introduced for ELT. This study aims to provide mathematical modeling of ELT in order to compare 980 nm and 1,320 nm laser-induced damage of saphenous veins. STUDY DESIGN/MATERIALS AND METHODS The model is based on calculations describing light distribution using the diffusion approximation of the transport theory, the temperature rise using the bioheat equation, and the laser-induced injury using the Arrhenius damage model. The geometry to simulate ELT was based on a 2D model consisting of a cylindrically symmetric blood vessel including a vessel wall and surrounded by an infinite homogenous tissue. The mathematical model was implemented using the Macsyma-Pdease2D software (Macsyma, Inc., Arlington, MA). Calculations were performed so as to determine the damage induced in the intima tunica, the externa tunica and inside the peri-venous tissue for 3 mm and 5 mm vessels (considered after tumescent anesthesia) and different linear endovenous energy densities (LEED) usually reported in the literature. RESULTS Calculations were performed for two different vein diameters: 3 mm and 5 mm and with LEED typically reported in the literature. For 980 nm, LEED: 50 to 160 J/cm (CW mode, 2 mm/second pullback speed, power: 10 W to 32 W) and for 1,320 nm, LEED: 50 to 80 J/cm (pulsed mode, pulse duration 1.2 milliseconds, peak power: 135 W, repetition rate 30 Hz to 50 Hz). DISCUSSION AND CONCLUSION Numerical simulations are in agreement with LEED reported in clinical studies. Mathematical modeling shows clearly that 1,320 nm, with a better absorption by the vessel wall, requires less energy to achieve wall damage. In the 810-1,320-nm range, blood plays only a minor role. Consequently, the classification of these lasers into hemoglobin-specific laser wavelengths (810, 940, 980 nm) and water-specific laser wavelengths (1,320 nm) is inappropriate. In terms of closure rate, 980 nm and 1,320 nm can lead to similar results and, as reported by the literature, to similar side effects. This model should serve as a useful tool to simulate and better understand the mechanism of action of the ELT.
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Affiliation(s)
- Serge R Mordon
- INSERM (French National Institute of Health and Medical Research), Lille University Hospital, Lille, France.
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320
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Hong Y, Makita S, Yamanari M, Miura M, Kim S, Yatagai T, Yasuno Y. Three-dimensional visualization of choroidal vessels by using standard and ultra-high resolution scattering optical coherence angiography. OPTICS EXPRESS 2007; 15:7538-50. [PMID: 19547079 DOI: 10.1364/oe.15.007538] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Scattering optical coherence angiography (S-OCA) is a noninvasive imaging method that is based on the high-speed standard 800nm band spectral-domain optical coherence tomography (SD-OCT) and the ultra-high-resolution SD-OCT which has the axial resolution of 6.1 mum and 2.9 mum in tissue, respectively. In this paper, we have demonstrated the use of this method for in vivo human retinal imaging. A three-dimensional view of the choroidal vasculature was obtained by segmenting the choroidal vessels; this was done using intensity threshold based binarization at each depth plane relative to the retinal pigment epithelium. A vascular projection image was obtained by integrating the segmented choroidal vasculature. In order to assess the feasibility of the proposed method, we compared these images with those obtained using existing invasive methods such as fluorescein angiography and indocyanine green angiography. Clinically worthful images are obtained from the application of S-OCA to the agerelated macular degeneration and polypoidal choroidal vasculopathy.
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321
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Yasuno Y, Hong Y, Makita S, Yamanari M, Akiba M, Miura M, Yatagai T. In vivo high-contrast imaging of deep posterior eye by 1-microm swept source optical coherence tomography and scattering optical coherence angiography. OPTICS EXPRESS 2007; 15:6121-39. [PMID: 19546917 DOI: 10.1364/oe.15.006121] [Citation(s) in RCA: 209] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Retinal, choroidal and scleral imaging by using swept-source optical coherence tomography (SS-OCT) with a 1-microm band probe light, and high-contrast and three-dimensional (3D) imaging of the choroidal vasculature are presented. This SS-OCT has a measurement speed of 28,000 A-lines/s, a depth resolution of 10.4 microm in tissue, and a sensitivity of 99.3 dB. Owing to the high penetration of the 1-microm probe light and the high sensitivity of the system, the in vivo sclera of a healthy volunteer can be observed. A software-based algorithm of scattering optical coherence angiography (S-OCA) is developed for the high-contrast and 3D imaging of the choroidal vessels. The S-OCA is used to visualize the 3D choroidal vasculature of the in vivo human macula and the optic nerve head. Comparisons of S-OCA with several other angiography techniques including Doppler OCA, Doppler OCT, fluorescein angiography, and indocyanine green angiography are also presented.
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Affiliation(s)
- Yoshiaki Yasuno
- Computational Optics Group in the University of Tsukuba, Tsukuba, Ibaraki, Japan.
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322
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Barton JK, Frangineas G, Pummer H, Black JF. Cooperative Phenomena in Two-pulse, Two-color Laser Photocoagulation of Cutaneous Blood Vessels¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2001)0730642cpitpt2.0.co2] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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323
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Black JF, Barton JK. Chemical and Structural Changes in Blood Undergoing Laser Photocoagulation¶. Photochem Photobiol 2007. [DOI: 10.1111/j.1751-1097.2004.tb00054.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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324
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Meinke M, Müller G, Helfmann J, Friebel M. Empirical model functions to calculate hematocrit-dependent optical properties of human blood. APPLIED OPTICS 2007; 46:1742-53. [PMID: 17356617 DOI: 10.1364/ao.46.001742] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The absorption coefficient, scattering coefficient, and effective scattering phase function of human red blood cells (RBCs) in saline solution were determined for eight different hematocrits (Hcts) between 0.84% and 42.1% in the wavelength range of 250-1100 nm using integrating sphere measurements and inverse Monte Carlo simulation. To allow for biological variability, averaged optical parameters were determined under flow conditions for ten different human blood samples. Based on this standard blood, empirical model functions are presented for the calculation of Hct-dependent optical properties for the RBCs. Changes in the optical properties when saline solution is replaced by blood plasma as the suspension medium were also investigated.
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Affiliation(s)
- Martina Meinke
- Institut für Medizinische Physik and Lasermedizin, Campus Benjamin Franklin, Charité-Universitätsmedizin, Berlin, Germany.
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325
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Meinke M, Müller G, Helfmann J, Friebel M. Optical properties of platelets and blood plasma and their influence on the optical behavior of whole blood in the visible to near infrared wavelength range. JOURNAL OF BIOMEDICAL OPTICS 2007; 12:014024. [PMID: 17343499 DOI: 10.1117/1.2435177] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The optical parameters absorption coefficient, scattering coefficient, and the anisotropy factor of platelets (PLTs) suspended in plasma and cell-free blood plasma are determined by measuring the diffuse reflectance, total and diffuse transmission, and subsequently by inverse Monte Carlo simulation. Furthermore, the optical behavior of PLTs and red blood cells suspended in plasma are compared with those suspended in saline solution. Cell-free plasma shows a higher scattering coefficient and anisotropy factor than expected for Rayleigh scattering by plasma proteins. The scattering coefficient of PLTs increases linearly with the PLT concentration. The existence of physiological concentrations of leukocytes has no measurable influence on the absorption and scattering properties of whole blood. In summary, red blood cells predominate over the other blood components by two to three orders of magnitude with regard to absorption and effective scattering. However, substituting saline solution for plasma leads to a significant increase in the effective scattering coefficient and therefore should be taken into consideration.
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Affiliation(s)
- Martina Meinke
- Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Institut für Medizinische Physik und Lasermedizin, Fabeckstr. 60-62, 14195 Berlin, Germany.
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326
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Phillips JP, Langford RM, Jones DP. Investigation of an optical fiber cerebral oximeter using a Monte Carlo model. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2007; 2007:1113-1116. [PMID: 18002157 DOI: 10.1109/iembs.2007.4352491] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
A new system for monitoring the oxygen saturation of blood within brain tissue has been developed for patients recovering from neurosurgery or trauma. The system is based on a two-wavelength oximeter, implemented via an optical fiber probe designed to pass through the lumen of a cranial bolt. The oximeter records the oxygen saturation of blood within a small volume of brain tissue surrounding the probe using the differential absorption of light at each wavelength. The contribution to the absorption and the degree of scatter by the brain tissue, blood and other components is difficult to quantify by analytical methods. A Monte Carlo model was developed to try to predict these contributions and thereby identify those variables which might have a significant influence on the calculation of oxygen saturation from measurements of back-scattered intensity in the brain. The model was validated for whole blood by comparing results from the model with empirical results obtained from samples of blood over a range of saturation values.
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Affiliation(s)
- Justin P Phillips
- Anaesthetic Laboratory, St Bartholomew's Hospital, London, EC1A 7BE, UK.
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327
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Meinke M, Müller G, Gersonde I, Friebel M. Determination of oxygen saturation and hematocrit of flowing human blood using two different spectrally resolving sensors. BIOMED ENG-BIOMED TE 2006; 51:347-54. [PMID: 17155871 DOI: 10.1515/bmt.2006.068] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The blood parameters oxygen saturation and hematocrit were determined by two different spectral sensors using reflectance spectra from 550 to 900 nm and partial transmission spectra centered at 660 nm. The spectra were analyzed by the method of partial least squares. One sensor consists of a miniature integrating sphere, while the other was fiber-guided. The results show that the geometry of the sensors and different blood flows do not influence the spectral analysis significantly. Independent of the sensor geometry, both hematocrit and oxygen saturation could be determined with an absolute predicted root mean square error of less than 3%. Furthermore, the analysis showed that hematocrit prediction requires eight wavelength regions and oxygen saturation prediction requires four wavelength regions using reflectance spectroscopy. This implies that if the measurement is restricted to reflectance, a spectrometer is indispensable for determining both blood parameters. Hematocrit determination could be improved using reflectance measurements in combination with transmission.
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Affiliation(s)
- Martina Meinke
- Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, CC6, Institut für Medizinische Physik und Lasermedizin, Berlin, Germany.
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328
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Salomatina E, Jiang B, Novak J, Yaroslavsky AN. Optical properties of normal and cancerous human skin in the visible and near-infrared spectral range. JOURNAL OF BIOMEDICAL OPTICS 2006; 11:064026. [PMID: 17212549 DOI: 10.1117/1.2398928] [Citation(s) in RCA: 240] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Differences in absorption and/or scattering of cancerous and normal skin have the potential to provide a basis for noninvasive cancer detection. In this study, we have determined and compared the in vitro optical properties of human epidermis, dermis, and subcutaneous fat with those of nonmelanoma skin cancers in the spectral range from 370 to 1600 nm. Fresh specimens of normal and cancerous human skin were obtained from surgeries. The samples were rinsed in saline solution and sectioned. Diffuse reflectance and total transmittance were measured using an integrating sphere spectrophotometer. Absorption and reduced scattering coefficients were calculated from the measured quantities using an inverse Monte Carlo technique. The differences between optical properties of each normal tissue-cancer pair were statistically analyzed. The results indicate that there are significant differences in the scattering of cancerous and healthy tissues in the spectral range from 1050 to 1400 nm. In this spectral region, the scattering of cancerous lesions is consistently lower than that of normal tissues, whereas absorption does not differ significantly, with the exception of nodular basal cell carcinomas (BCC). Nodular BCCs exhibit significantly lower absorption as compared to normal skin. Therefore, the spectral range between 1050 and 1400 nm appears to be optimal for nonmelanoma skin cancer detection.
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Affiliation(s)
- Elena Salomatina
- Massachusetts General Hospital, Wellman Center for Photomedicine, Boston, Massachusetts 02114, USA
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329
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Tomita M, Ohtomo M, Suzuki N. Contribution of the flow effect caused by shear-dependent RBC aggregation to NIR spectroscopic signals. Neuroimage 2006; 33:1-10. [PMID: 16877009 DOI: 10.1016/j.neuroimage.2006.05.042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Revised: 03/02/2006] [Accepted: 05/23/2006] [Indexed: 11/28/2022] Open
Abstract
Near-infrared spectroscopy (NIRS) is widely used to record activation-related blood oxygenation changes in human brain tissue. However, the changes in the NIRS signal upon increased flow are influenced not only by the hemoglobin and oxyhemoglobin concentrations but also by changes in light scattering by various brain constituents. This paper points out the large contribution of flow-dependent red blood cell (RBC) aggregation as a cause of this altered light scattering, a phenomenon which has not previously been considered in the theoretical analysis of NIRS signals. Here, we show that RBCs, which constitute a major chromophore in the tissue, not only absorb light at hemoglobin molecules but also scatter it strongly at the cell membranes of aggregated RBCs, and that the blood optical density per se changes greatly with the size of the plasma gap, which varies according to flow. When local blood flow increases by 50%, the amount of the optical attenuation due to RBC dispersion/disaggregation (the flow effect) can reach 90% of the NIRS signal change for venous blood. The reasons why the optical signal due to blood oxygenation alone can be amount to less than 10% of the total are because the near-infrared lies in the most unfavorable range in the hemoglobin absorption spectrum for determining blood oxygenation, while the flow effect in the NIR range is large. We conclude that reported activation-related changes in brain blood oxygenation, at least in the peripheral region around the activation focus, based on NIRS can be mainly ascribed to the flow effect arising from RBC dispersion/disaggregation with increased flow in the venous system.
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Affiliation(s)
- Minoru Tomita
- Department of Neurology, School of Medicine, Keio University, 35 Shinanomachi, Tokyo 160-8582, Japan.
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330
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Lagali N, Burns K, Zimmerman D, Munger R. Hemodialysis monitoring in whole blood using transmission and diffuse reflection spectroscopy: A pilot study. JOURNAL OF BIOMEDICAL OPTICS 2006; 11:054003. [PMID: 17092152 DOI: 10.1117/1.2357611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Visible and near infrared transmission and diffuse reflection spectroscopy were used to monitor changes in whole blood resulting from hemodialysis treatment for end-stage renal disease. Blood samples from 8 patients on chronic hemodialysis therapy were measured in the 500- to 1700-nm wavelength range immediately before and after a single treatment. Principal component scores characteristic of each spectrum were derived, and mean pre- and posttreatment scores of the first principal component indicated a significant treatment-dependent change in both optical transmission (P = 0.004) and diffuse reflection (P < 0.001). Significant treatment-induced change persisted (P < 0.05) when the first four principal components were used to account for >97% of the treatment-dependent spectral variation. Some blood spectral changes expressed in terms of difference spectra (posttreatment - pretreatment) were consistent with standard clinical indicators of weight reduction, urea reduction, and potassium change, with probable origins at a molecular level. The results indicate the feasibility of using optical transmission and diffuse reflection spectroscopy to characterize clinically relevant blood changes for the future development of more comprehensive indicators of hemodialysis efficacy and long-term clinical outcomes. Moreover, the optical techniques employed are adaptable for potential online monitoring of blood changes during the hemodialysis treatment.
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Affiliation(s)
- Neil Lagali
- University of Ottawa Eye Institute, Ottawa Health Research Institute, Ottawa, Ontario K1H 8L6, Canada.
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331
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Skirtach AG, Muñoz Javier A, Kreft O, Köhler K, Piera Alberola A, Möhwald H, Parak WJ, Sukhorukov GB. Laser-Induced Release of Encapsulated Materials inside Living Cells. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200504599] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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332
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Skirtach AG, Muñoz Javier A, Kreft O, Köhler K, Piera Alberola A, Möhwald H, Parak WJ, Sukhorukov GB. Laser-Induced Release of Encapsulated Materials inside Living Cells. Angew Chem Int Ed Engl 2006; 45:4612-7. [PMID: 16791887 DOI: 10.1002/anie.200504599] [Citation(s) in RCA: 329] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Andre G Skirtach
- Institut für Grenzflächen, Max-Planck-Institut für Kolloid- und Grenzflächenforschung, Am Mühlenberg 1, 14424 Golm/Potsdam, Germany.
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333
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McCain ST, Gehm ME, Wang Y, Pitsianis NP, Brady DJ. Coded aperture Raman spectroscopy for quantitative measurements of ethanol in a tissue phantom. APPLIED SPECTROSCOPY 2006; 60:663-71. [PMID: 16808868 DOI: 10.1366/000370206777670693] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Coded aperture spectroscopy allows for sources of large étendue to be efficiently coupled into dispersive spectrometers by replacing the traditional input slit with a patterned mask. We describe a coded aperture spectrometer optimized for Raman spectroscopy of diffuse sources, (e.g., tissue). We provide design details of the Raman system, along with quantitative estimation results for ethanol at non-toxic levels in a lipid tissue phantom. With 60 mW of excitation power at 808 nm, leave-one-out and blind cross-validation of partial least squares (PLS) regression models achieve r(2) > 0.98. Leave-one-out cross-validation demonstrates prediction errors of <15% at the common legal limit for intoxication (17.4 mmol/L = 0.08% by vol) and the best blind cross-validation achieves <12% error at this concentration.
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Affiliation(s)
- S T McCain
- Department of Electrical and Computer Engineering, and Fitzpatrick Institute for Photonics, Duke University, Durham, NC 27708, USA
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334
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Nishimura G, Kida I, Tamura M. Characterization of optical parameters with a human forearm at the region from 1.15 to 1.52 microm using diffuse reflectance measurements. Phys Med Biol 2006; 51:2997-3011. [PMID: 16723780 DOI: 10.1088/0031-9155/51/11/021] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Time- and space-resolved diffuse reflectance measurements were used to identify the optical parameters, the reduced scattering and absorption coefficients, of bulk living tissue in the region from 1.15 to 1.52 microm. Although in this region the detector was limited in its temporal resolution, we applied a peak-time shift analysis successfully to determine these coefficients in a human forearm, and then determined the absorption spectrum by space-resolved diffuse reflectance measurements. The absorption spectrum of a water content of 52% determined by magnetic resonance imaging experiments is in good agreement with the absorption coefficient obtained by optical measurements. Moreover, magnetic resonance imaging measurements suggest that the deviation of the absorption coefficients from the water spectrum in the strong water absorption band is caused by the heterogeneity of water distribution in tissue: the low content of water in the skin. These findings indicate that this optical method is potentially applicable to the non-invasive measurement of water in tissue, especially in a region lower than about 1.3-1.35 microm, which may be useful in monitoring oedema and tissue swelling.
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Affiliation(s)
- Goro Nishimura
- Biophysics Laboratory, Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812, Japan.
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335
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Friebel M, Roggan A, Müller G, Meinke M. Determination of optical properties of human blood in the spectral range 250 to 1100 nm using Monte Carlo simulations with hematocrit-dependent effective scattering phase functions. JOURNAL OF BIOMEDICAL OPTICS 2006; 11:34021. [PMID: 16822070 DOI: 10.1117/1.2203659] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The absorption coefficient mu(a), scattering coefficient mu(s), and anisotropy factor g of diluted and undiluted human blood (hematocrit 0.84 and 42.1%) are determined under flow conditions in the wavelength range 250 to 1100 nm, covering the absorption bands of hemoglobin. These values are obtained by high precision integrating sphere measurements in combination with an optimized inverse Monte Carlo simulation (IMCS). With a new algorithm, appropriate effective phase functions could be evaluated for both blood concentrations using the IMCS. The best results are obtained using the Reynolds-McCormick phase function with the variation factor alpha = 1.2 for hematocrit 0.84%, and alpha = 1.7 for hematocrit 42.1%. The obtained data are compared with the parameters given by the Mie theory. The use of IMCS in combination with selected appropriate effective phase functions make it possible to take into account the nonspherical shape of erythrocytes, the phenomenon of coupled absorption and scattering, and multiple scattering and interference phenomena. It is therefore possible for the first time to obtain reasonable results for the optical behavior of human blood, even at high hematocrit and in high hemoglobin absorption areas. Moreover, the limitations of the Mie theory describing the optical properties of blood can be shown.
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336
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Friebel M, Meinke M. Model function to calculate the refractive index of native hemoglobin in the wavelength range of 250-1100 nm dependent on concentration. APPLIED OPTICS 2006; 45:2838-42. [PMID: 16633438 DOI: 10.1364/ao.45.002838] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The real part of the complex refractive index of oxygenated native hemoglobin solutions dependent on concentration was determined in the wavelength range 250 to 1100 nm by Fresnel reflectance measurements. The hemoglobin solution was produced by physical hemolysis of human erythrocytes followed by ultracentrifugation and filtration. A model function is presented for calculating the refractive index of hemoglobin solutions depending on concentration in the wavelength range 250 to 1100 nm.
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337
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Trelles MA, Allones I, Alvarez J, Vélez M, Martín-Vázquez M, Trelles OR, Luna R, Buil C, Mordon SR. The 800-nm diode laser in the treatment of leg veins: assessment at 6 months. J Am Acad Dermatol 2006; 54:282-9. [PMID: 16443059 DOI: 10.1016/j.jaad.2005.09.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Revised: 08/29/2005] [Accepted: 09/03/2005] [Indexed: 11/29/2022]
Abstract
BACKGROUND The efficacy of the 800-nm diode laser system in clearing leg veins was analyzed subjectively and objectively in a variety of leg veins. METHODS A total of 10 women (age 25-55 years, skin types II-IV) with a variety of leg vein types were treated with an 800-nm diode laser. A sequence of pulses (5-8 stacked pulses, pulse duration 50 milliseconds, delay 50 milliseconds) was applied on a 3-mm spot (210-336 J/cm2 fluence, depending on vessel size). Treatment on the same vein was performed at intervals of 2 months until complete clearance was achieved (maximum: 3 treatments). The results were assessed at 6 months from the last treatment. Patients evaluated their subjective improvement by means of a questionnaire to elicit the satisfaction index. In an independent objective assessment, the clearance index was based on the pretreatment and posttreatment clinical photography, also analyzed by a computer program. RESULTS All patients completed the trial with mild but transient side effects. The patient 6-month assessments for very good, good, fair, poor, and worse were 1, 5, 3, 1, and 0, respectively. For the clinician-assessed clearance index, the numbers for the same grades were 2, 6, 2, 0, and 0, and for the computer assessment they were 1, 6, 2, 1, and 0. No patient scored worse in any assessment. The overall satisfaction index and clinician and computer clearance indexes were 60%, 80%, and 70%, respectively. LIMITATIONS No control group could be obtained in this study. CONCLUSIONS The 800-nm diode laser as used in the study may well offer an effective treatment method for leg veins that is comparatively pain and side-effect free. Best results were obtained in vessels of 3 to 4 mm in diameter located on the thigh, and in patients with phototype III skin. No correlation was seen between results and patient age.
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Affiliation(s)
- Mario A Trelles
- Instituto Médico Vilafortuny/Fundación Antoni de Gimbernat, Cambrils, Spain.
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338
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Subramanian H, Ibey BL, Xu W, Wilson MA, Ericson MN, Coté GL. Real-time separation of perfusion and oxygenation signals for an implantable sensor using adaptive filtering. IEEE Trans Biomed Eng 2006; 52:2016-23. [PMID: 16366225 DOI: 10.1109/tbme.2005.857667] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this paper, an adaptive filtering algorithm to separate signals due to perfusion and oxygenation has been developed using an 810-nm source, in addition to 660-nm and 940-nm sources, as an internal reference due to its limited oxygen sensitivity. The newly developed algorithm was tested using Monte Carlo simulated data to prove the effectiveness of the 810-nm reference and adaptive algorithm. Following the simulation, an in vitro model was developed to test the algorithm that used a blood flow through system wrapped with tissue. The system had the ability to isolate the effects of perfusion and oxygenation and the algorithm accurately captured the changes in these signals with reliable consistency. Using the serosal surface of the swine jejunum, in vivo data was also taken to analyze the algorithms response to fluctuating perfusion levels like that seen in hemorrhaging or failing transplants. The algorithm was able to extract the perfusion information from the oxygenation information in this in vivo study. Overall, it was shown that an adaptive filtering algorithm using an 810-nm reference has provided a means to separate oxygenation and perfusion.
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Affiliation(s)
- Hariharan Subramanian
- Department of Biomedical Engineering, Texas A&M University, College Station, TX 77843-3120, USA.
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339
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Matiukas A, Mitrea BG, Pertsov AM, Wuskell JP, Wei MD, Watras J, Millard AC, Loew LM. New near-infrared optical probes of cardiac electrical activity. Am J Physiol Heart Circ Physiol 2006; 290:H2633-43. [PMID: 16399869 DOI: 10.1152/ajpheart.00884.2005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Styryl voltage-sensitive dyes (e.g., di-4-ANEPPS) have been widely and successfully used as probes for mapping membrane potential changes in cardiac cells and tissues. However, their utility has been somewhat limited because their excitation wavelengths have been restricted to the 450- to 550-nm range. Longer excitation/emission wavelength probes can minimize interference from endogenous chromophores and, because of decreased light scattering and lower absorption by endogenous chromophores, improve recording from deeper tissue layers. In this article, we report efforts to develop new potentiometric styryl dyes that have excitation wavelengths ranging above 700 nm and emission spectra extending to 900 nm. Three dyes for cardiac optical mapping were investigated in depth from several hundred dyes containing 47 variants of the styryl chromophores. Absorbance and emission spectra in ethanol and multilamellar vesicles, as well as voltage-dependent spectral changes in a model lipid bilayer, have been recorded for these dyes. Optical action potentials were recorded in typical cardiac tissues (rat, guinea pig, pig) and compared with those of di-4-ANEPPS. The voltage sensitivities of the fluorescence of these new potentiometric indicators are as good as those of the widely used ANEP series of probes. In addition, because of molecular engineering of the chromophore, the new dyes provide a wide range of dye loading and washout time constants. These dyes will enable a series of new experiments requiring the optical probing of thick and/or blood-perfused cardiac tissues.
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Affiliation(s)
- Arvydas Matiukas
- Department of Pharmacology, State University of New York-Upstate Medical University, 750 E Adams St., Syracuse, NY 13210, USA.
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340
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Larsson M, Strömberg T. Toward a velocity-resolved microvascular blood flow measure by decomposition of the laser Doppler spectrum. JOURNAL OF BIOMEDICAL OPTICS 2006; 11:014024. [PMID: 16526901 DOI: 10.1117/1.2166378] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Tissue microcirculation, as measured by laser Doppler flowmetry (LDF), comprises capillary, arterial, and venous blood flow. With the classical LDF approach, it has been impossible to differentiate between different vascular compartments. We suggest an alternative LDF algorithm that estimates at least three concentration measures of flowing red blood cells (RBCs), each associated with a predefined, physiologically relevant, absolute velocity in millimeters per second. As the RBC flow velocity depends on the dimension of the blood vessel, this approach might enable a microcirculatory flow differentiation. The LDF concentration estimates are derived by fitting predefined Monte Carlo simulated, single-velocity spectra to a measured, multiple-velocity LDF spectrum. Validation measurements, using both single- and double-tube flow phantoms perfused with a microsphere solution, show that it is possible to estimate velocity and concentration changes, and to differentiate between flows with different velocities. Our theory is also applied to RBC flow measurements. A Gegenbauer kernel phase function (alpha(gk)=1.05; g(gk)=0.93), with an anisotropy factor of 0.987 at 786 nm, is found suitable for modeling Doppler scattering by RBCs diluted in physiological saline. The method is developed for low concentrations of RBCs, but can in theory be extended to cover multiple Doppler scattering.
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Affiliation(s)
- Marcus Larsson
- Linköpings Universitet, Department of Biomedical Engineering, University Hospital, S-581 85 Linköping, Sweden.
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341
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Friebel M, Meinke M. Determination of the complex refractive index of highly concentrated hemoglobin solutions using transmittance and reflectance measurements. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:064019. [PMID: 16409084 DOI: 10.1117/1.2138027] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The complex refractive index of highly concentrated hemoglobin solutions as they appear in red blood cells are determined in the wavelength range of 250 to 1100 nm using transmittance and Fresnel reflectance measurements. The determined real parts of the refractive indices are on average 0.02 units higher than the values found in the literature. The wavelength dependence of the measured data in the UV region differs from the calculated data using the Kramers-Kronig relation.
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Affiliation(s)
- Moritz Friebel
- Laser- und Medizin-Technologie GmbH, Berlin, Fabeckstr. 60-62, 14195 Berlin, Germany
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342
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Laufer J, Elwell C, Delpy D, Beard P. In vitro measurements of absolute blood oxygen saturation using pulsed near-infrared photoacoustic spectroscopy: accuracy and resolution. Phys Med Biol 2005; 50:4409-28. [PMID: 16148401 DOI: 10.1088/0031-9155/50/18/011] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Pulsed photoacoustic spectroscopy was used to measure blood oxygen saturation in vitro. An optical parametric oscillator laser system provided nanosecond excitation pulses over the wavelength range 740-1040 nm which were used to generate photoacoustic signals in a cuvette through which a saline suspension of red blood cells was circulated. The signal amplitude and the effective attenuation coefficient were extracted from the photoacoustic signals as a function of wavelength to provide photoacoustic spectra of the blood. From these, the relative concentrations of oxy- and deoxyhaemoglobin, and therefore blood oxygen saturation (SO2), were determined using forward models of the absorbed energy distribution based on diffusion theory. A standard linear model of the dependence of absorbance on the concentration of chromophores was also used to calculate the blood oxygen saturation from the signal amplitude spectra. The diffusion approximation model was shown to produce the highest accuracy in blood SO2. The photoacoustically determined oxygen saturation was found to have an accuracy of +/-4% SO2 for signal amplitude data and +/-2.5% SO2 for effective attenuation spectra. The smallest change in oxygen saturation that can be measured using this technique was +/-1% SO2.
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Affiliation(s)
- Jan Laufer
- Department of Medical Physics and Bioengineering, University College London, Malet Place Engineering Building, London WC1E 6BT, UK
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343
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Nazarian S, Knight BP, Dickfeld TL, Zviman MM, Jayanti VB, Amundson D, Hanlin J, Castleberry J, Smith MF, Blankenship L, Halperin HR, Ferguson TB, Berger RD. Direct visualization of coronary sinus ostium and branches with a flexible steerable fiberoptic infrared endoscope. Heart Rhythm 2005; 2:844-8. [PMID: 16051122 DOI: 10.1016/j.hrthm.2005.04.020] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Accepted: 04/18/2005] [Indexed: 12/22/2022]
Abstract
BACKGROUND Placement of electrophysiology catheters and pacing leads in the coronary sinus is challenging in some patients, particularly those with dilated cardiomyopathy. We hypothesized that cannulation of the coronary sinus and its branches can be facilitated by direct visualization. This study reports our experience with navigation into and within the coronary sinus in a closed-chest animal preparation, using a flexible steerable fiberoptic infrared endoscope that allows visualization through flowing blood. OBJECTIVES The purpose of this study was to assess the feasibility of direct visualization of endocardial structures through infrared endoscopy. METHODS Internal jugular venous access was obtained in 10 healthy mongrel dogs (weight 35-45 kg). The infrared endoscope (2900 fiber imaging bundle, wavelength 1,620 nm, frame rate 10-30/s, 320 x 256 pixels) was advanced to the coronary sinus ostium and branches by direct visualization of anatomic landmarks, such as the tricuspid valve and inferior vena cava. Localization was confirmed by fluoroscopy, contrast injection, and pathologic examination. RESULTS Structures such as the tricuspid valve and inferior vena cava were visualized at distances of 1 to 2 cm, allowing successful coronary sinus identification and engagement in all 10 dogs. Coronary sinus branch images closely resembled pathologic findings. CONCLUSION Direct visualization of the coronary sinus ostium and branches is possible through infrared endoscopy. This technique likely will facilitate coronary sinus engagement and navigation for pacing lead and catheter placement.
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Affiliation(s)
- Saman Nazarian
- Division of Cardiology, Johns Hopkins Hospital, Baltimore, Maryland 21287, USA.
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344
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Dam JS, Yavari N, Sørensen S, Andersson-Engels S. Real-time absorption and scattering characterization of slab-shaped turbid samples obtained by a combination of angular and spatially resolved measurements. APPLIED OPTICS 2005; 44:4281-90. [PMID: 16045216 DOI: 10.1364/ao.44.004281] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We present a fast and accurate method for real-time determination of the absorption coefficient, the scattering coefficient, and the anisotropy factor of thin turbid samples by using simple continuous-wave noncoherent light sources. The three optical properties are extracted from recordings of angularly resolved transmittance in addition to spatially resolved diffuse reflectance and transmittance. The applied multivariate calibration and prediction techniques are based on multiple polynomial regression in combination with a Newton--Raphson algorithm. The numerical test results based on Monte Carlo simulations showed mean prediction errors of approximately 0.5% for all three optical properties within ranges typical for biological media. Preliminary experimental results are also presented yielding errors of approximately 5%. Thus the presented methods show a substantial potential for simultaneous absorption and scattering characterization of turbid media.
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Affiliation(s)
- Jan S Dam
- Department of Physics, Lund Institute of Technology, P.O. Box 118, SE-22100 Lund, Sweden
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345
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Benaron DA, Parachikov IH, Cheong WF, Friedland S, Rubinsky BE, Otten DM, Liu FWH, Levinson CJ, Murphy AL, Price JW, Talmi Y, Weersing JP, Duckworth JL, Hörchner UB, Kermit EL. Design of a visible-light spectroscopy clinical tissue oximeter. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:44005. [PMID: 16178639 DOI: 10.1117/1.1979504] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We develop a clinical visible-light spectroscopy (VLS) tissue oximeter. Unlike currently approved near-infrared spectroscopy (NIRS) or pulse oximetry (SpO2%), VLS relies on locally absorbed, shallow-penetrating visible light (475 to 625 nm) for the monitoring of microvascular hemoglobin oxygen saturation (StO2%), allowing incorporation into therapeutic catheters and probes. A range of probes is developed, including noncontact wands, invasive catheters, and penetrating needles with injection ports. Data are collected from: 1. probes, standards, and reference solutions to optimize each component; 2. ex vivo hemoglobin solutions analyzed for StO2% and pO2 during deoxygenation; and 3. human subject skin and mucosal tissue surfaces. Results show that differential VLS allows extraction of features and minimization of scattering effects, in vitro VLS oximetry reproduces the expected sigmoid hemoglobin binding curve, and in vivo VLS spectroscopy of human tissue allows for real-time monitoring (e.g., gastrointestinal mucosal saturation 69+/-4%, n=804; gastrointestinal tumor saturation 45+/-23%, n=14; and p<0.0001), with reproducible values and small standard deviations (SDs) in normal tissues. FDA approved VLS systems began shipping earlier this year. We conclude that VLS is suitable for the real-time collection of spectroscopic and oximetric data from human tissues, and that a VLS oximeter has application to the monitoring of localized subsurface hemoglobin oxygen saturation in the microvascular tissue spaces of human subjects.
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Affiliation(s)
- David A Benaron
- Stanford University School of Medicine, Department of Pediatrics, Division of Neonatal and Developmental Medicine, Palo Alto, California 94305, USA
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346
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Li J, Dietsche G, Iftime D, Skipetrov SE, Maret G, Elbert T, Rockstroh B, Gisler T. Noninvasive detection of functional brain activity with near-infrared diffusing-wave spectroscopy. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:44002. [PMID: 16178636 DOI: 10.1117/1.2007987] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
We use near-infrared dynamic multiple scattering of light [diffusing-wave spectroscopy (DWS)] to detect the activation of the somato-motor cortex in 11 right-handed volunteers performing a finger opposition task separately with their right and left hands. Temporal autocorrelation functions g(1)(r,tau) of the scattered light field are measured during 100-s periods of motor task alternating with 100-s resting baseline periods. From an analysis of the experimental data with an analytical theory for g(1)(r,tau) from a three-layer geometry with optical and dynamical heterogeneity representing scalp, skull, and cortex, we obtain quantitative estimates of the diffusion coefficient in cortical regions. Consistent with earlier results, the measured cortical diffusion coefficient is found to be increased during the motor task, with a strong contralateral and a weaker ipsilateral increase consistent with the known brain hemispheric asymmetry for right-handed subjects. Our results support the interpretation of the increase of the cortical diffusion coefficient during finger opposition being due to the functional increase in cortical blood flow rate related to vasodilation.
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Affiliation(s)
- Jun Li
- Universität Konstanz, Fachbereich Physik and Fachbereich Psychologie, Universitätsstr. 10, 78457 Konstanz, Germany
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347
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Sorg BS, Moeller BJ, Donovan O, Cao Y, Dewhirst MW. Hyperspectral imaging of hemoglobin saturation in tumor microvasculature and tumor hypoxia development. JOURNAL OF BIOMEDICAL OPTICS 2005; 10:44004. [PMID: 16178638 DOI: 10.1117/1.2003369] [Citation(s) in RCA: 172] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Tumor hypoxia has been shown to have prognostic value in clinical trials involving radiation, chemotherapy, and surgery. Tumor oxygenation studies at microvascular levels can provide understanding of oxygen transport on scales at which oxygen transfer to tissue occurs. To fully grasp the significance of blood oxygen delivery and hypoxia at microvascular levels during tumor growth and angiogenesis, the spatial and temporal relationship of the data must be preserved and mapped. Using tumors grown in window chamber models, hyperspectral imaging can provide serial spatial maps of blood oxygenation in terms of hemoglobin saturation at the microvascular level. We describe our application of hyperspectral imaging for in vivo microvascular tumor oxygen transport studies using red fluorescent protein (RFP) to identify all tumor cells, and hypoxia-driven green fluorescent protein (GFP) to identify the hypoxic fraction. 4T1 mouse mammary carcinoma cells, stably transfected with both reporter genes, are grown in dorsal skin-fold window chambers. Hyperspectral imaging is used to create image maps of hemoglobin saturation, and classify image pixels where RFP alone is present (tumor cells), or both RFP and GFP are present (hypoxic tumor cells). In this work, in vivo calibration of the imaging system is described and in vivo results are shown.
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Affiliation(s)
- Brian S Sorg
- Duke University Medical Center, Department of Radiation Oncology, Durham, North Carolina, USA
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348
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Meinke M, Gersonde I, Friebel M, Helfmann J, Müller G. Chemometric determination of blood parameters using visible-near-infrared spectra. APPLIED SPECTROSCOPY 2005; 59:826-35. [PMID: 16053549 DOI: 10.1366/0003702054280603] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Visible and near-infrared (NIR) integrating sphere spectroscopy and chemometric multivariate linear regression were applied to determine hematocrit (HCT) and oxygen saturation (SatO2) of circulating human blood. Diffuse transmission, total transmission, and diffuse reflectance were measured and the partial least squares method (PLS) was used for calibration considering different wavelength ranges and selected optical measurement parameters. HCT and SatO2 were changed independently. Each parameter was adjusted to different levels and four designs with blood from different donors were carried out for the calibration with PLS. The calibration included the changes in hemolysis as well as inter-individual differences in cell dimensions and hemoglobin content. At a sample thickness of 0.1 mm the HCT and SatO2 were predicted with a root mean square error (PRMSE) of 1.4% and 2.5%, respectively, using transmission and reflectance spectra and the full Vis-NIR range. Using only diffuse NIR reflectance spectroscopy and a sample thickness of 1 mm, HCT and SatO2 could be predicted with a PRMSE of 1.9% and 2.8%, respectively. Prediction of hemolysis was also possible for one blood sample with a PRMSE of 0.8% and keeping HCT and SatO2 stable with a PRMSE of 0.03%.
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Affiliation(s)
- M Meinke
- Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Institut für Medizinische Physik und Lasermedizin, Germany
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349
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Kraitl J, Ewald H, Gehring H. An optical device to measure blood components by a photoplethysmographic method. ACTA ACUST UNITED AC 2005. [DOI: 10.1088/1464-4258/7/6/010] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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350
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Faber DJ, Mik EG, Aalders MCG, van Leeuwen TG. Toward assessment of blood oxygen saturation by spectroscopic optical coherence tomography. OPTICS LETTERS 2005; 30:1015-7. [PMID: 15906988 DOI: 10.1364/ol.30.001015] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The use of spectroscopic optical coherence tomography to assess hemoglobin oxygen saturation of whole blood is investigated. We propose to use the differential attenuation coefficient to determine the degree of saturation. Our data show qualitative agreement between the measured differential attenuation coefficients as a function of saturation and predictions based on the oxygen-saturation-dependent absorption and scattering properties of blood.
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Affiliation(s)
- Dirk J Faber
- Laser Center, Academic Medical Center, University of Amsterdam, PO. Box 22700, 1100 DE Amsterdam, The Netherlands.
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