Proceedings Volume 2676

Biomedical Sensing, Imaging, and Tracking Technologies I

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Proceedings Volume 2676

Biomedical Sensing, Imaging, and Tracking Technologies I

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Volume Details

Date Published: 24 April 1996
Contents: 6 Sessions, 43 Papers, 0 Presentations
Conference: Photonics West '96 1996
Volume Number: 2676

Table of Contents

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Table of Contents

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  • Bionavigation and Tracking
  • Advanced Bioimaging Techniques and Devices
  • Advanced Biomedical Techniques for Trauma Care
  • Biomedical Sensors
  • Optical Methods in Biophysics
  • Clinical Laser and Optoelectronic Systems
  • Biomedical Sensors
  • Advanced Bioimaging Techniques and Devices
  • Clinical Laser and Optoelectronic Systems
Bionavigation and Tracking
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MINOP: development of a miniaturized endoscopic operation system for neurosurgery
Andreas E. Guber, Paul Wieneke
Within the framework of R&D activities in the field of microsystems technology, the Institute for Microstructure Technology of Karlsruhe Research Center among others has started to improve the functionality of existing medicotechnical instruments by increased integration of microtechnical components. On the basis of microsystems fabrication techniques, completely novel medical endoscope systems have become feasible. In cooperation with clinical, technical and industrial partners, a novel endoscopic operation system based on microsystems technology is being developed by the Institute for Microstructure Technology and the Aesculap AG company, Tuttlingen within the framework of the MINOP joint project. This new system shall be applied above all in the field of neurosurgery. This newly conceived endosystem is characterized by a multitude of novelties. It can perform a number of both sensor and actor functions. Due to its extremely small outer diameter, it can be applied through minute openings. As a result of the integrated microfluidic control system, the flexible endoscope can be moved to the actual site of operation on a previously specified path. This will allow future bi- and triportal neuro-endoscopic interventions for critical operations in the brain area. The different lumina of the flexible endoscope fulfill various functions. Via the optical fibers, laser radiation may be led to the distal end of the endoscope. Using microtechnical fabrication methods, special plastic microlenses have been produced. The working channel can be applied for rinsing and removal. Furthermore, the cleaning of the optics or the taking of tissue samples are possible. If required, another laser fiber can be driven forward through the working channel for selective therapy. For the first time, high-performance microinstruments have been developed on the basis of novel materials. These instruments can be applied either through the working channel or through an additional trocar.
ac magnetic trackers for biomedical application: now and in the near future
A number of ac magnetic trackers have been, and are now being, used in the medical community for varied applications from describing electronically the exact shape of a subject to tracking movement of objects. A good reason for using this technology is that the magnetic fields pass through the body without occlusions and without ionizing radiation. This paper commences with descriptions of several such tools readily available, including our 3D input stylus and 3DRAW tablet defining object dimensions to 0.01' accuracy and our close-in Short Ranger transmitter operating precisely between 2' - 12' over the subject. For the future, R&D and military electronics sponsored topics such as a metal distortion insensitive magnetic source, a high performance 240 Hz (or up to eight sensors each operating at 30 Hz) tracker with the processing power to virtually eliminate metal distortion effects and an approach for building a biologically insertible tracker are discussed to indicate the potential for new tracking tools. Discussion of needs from the medical community is encouraged in order to better guide efforts in applying our specialty technology to biomedical applications where ewe are neophytes.
Advanced Bioimaging Techniques and Devices
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Laser opto-acoustic tomography for medical diagnostics: experiments with biological tissues
Feasibility of laser optoacoustic tomography to detect turbid tissues with different optical properties was experimentally investigated using real biological tissues. The following abilities of this technique were quantitatively studied: maximal depth of optoacoustic signal detection, acoustic attenuation of laser-induced pressure waves, and limit of resolution. Two types of biological tissues were used for the experiments: chicken breast muscle as a tissue with low absorption coefficient and bovine liver as a tissue with higher absorption coefficient. Tissue samples were irradiated by Q-switched Nd:YAG-laser pulses to satisfy stress-confined irradiation conditions. Laser-induced pressure waves generated in the liver samples were detected by a wide-band acoustic transducer. Pressure wave amplitude, duration, and propagation time were analyzed after the experiments. The results and theoretical calculations have demonstrated that laser-induced optoacoustic signals from biological tissues with higher absorption coefficient are measurable at depth 5 times higher than penetration depth of radiation. Low acoustic attenuation (0.006 cm-1) for laser-induced pressure waves was detected. Feasibility of the proposed imaging to detect 3 mm3 liver sample (tumor model) placed inside 80 mm-muscle tissue is demonstrated.
Optical tomography of rat brain
Juergen Beuthan, Richard Freyer, Olaf Minet, et al.
An experimental set-up for the optical tomography using photon density waves is described. The intensity of a NIR laser diode (825 nm) is modulated with a frequency of 110 MHz (modulating degree equal to 80%). The line scan of a rat brain at 64 linear steps and 64 angular steps contains the ac attenuation and the phase shift separately. Due to the impact of scattering in the medium these data are not the basis for a backprojection and deconvolution for the tomographic reconstruction itself. The first approach for a preprocessing consists in the determination of the geometry dependent modulation transfer function (MTF). The line scan is then corrected by the filter which varies with the position. An optical tomogram of a rat brain is presented. This procedure is suitable for biological objects up to a diameter of 30 mm approximately, for example small finger joints.
Diagnosis of inflammatory rheumatic diseases with photon density waves
Juergen Beuthan, Viravuth Prapavat, Rolf-Dieter Naber, et al.
Rheumatoid arthritis (RA) is a common inflammatory disease of interphalangeal joints. The utilization of conventional imaging systems (e.g. x-rays) for non invasive diagnostics at an early stage of the disease is difficult, since pathologically induced changes do not occur at this stage in hard tissue. Use of MR and ultrasound methods are both methodically problematic and expensive. Therefore investigations for optical diagnostics using photon density waves (PDW) were carried out. The PDW was realized with an intensity modulated laser diode (825 nm, fmod: 110 MHz) and an ac- and phase detection in a 2D transillumination scanner. Measurements of optical properties of synovia and synovialis of healthy and early RA stages were performed and indicated a significant pathological increase of (mu) s. The detected PDW-pictures provided corresponding results. Further investigations regarding the object- variation of the modulation transfer function provide a sufficient spatial resolution in order to assign functional changes to anatomical structures. The results are presented using photos.
Tissue characterization with optical coherence tomography (OCT)
Alexander R. Knuettel, S. Koch, Rainer Schork, et al.
Tissue spectroscopy and high resolution imaging down to penetration depths of about 1 mm are of great interest for diagnostic purposes. In this paper we cover both disciplines by analyzing detected and simulated heterodyne signals obtained with optical coherence tomography (OCT). The detected signals are affected by photons propagating in forward direction and single-backscattering (dependent on the reflecting target). In the spectroscopic part, we retrieved scattering parameters, which are scattering coefficients (mu) s and mean scattering angles (theta) RMS. We fitted experimentally detected axial point spread functions (PSFs) to simulated curves, obtained by an analytical model described elsewhere. Ballistic photons (coherent component) and multiply forward scattered photons (incoherent component) contribute to the detected signals. In one study, (mu) s and (theta) RMS were retrieved for a slice of 0.5 mm thick tissue. Several simulations about the contrast (obtained from axial PSFs) vs. (theta) RMS and vs. numerical aperture (NA) of the focusing optics were performed for different reflecting targets. In addition, temporal signal fluctuations and the corresponding probability distribution functions (PDFs) are of interest to assess the accuracy of obtained parameters. We show that incoherent averaging provides a means for reducing detected signal fluctuations. Finally in vivo images with a mean resolution of about 20 micrometer are presented.
Quantitative analysis of trabecular microstructure by optical processing of bone radiographs
Isaac Leichter, Victor Neeman, Meir Leibergall, et al.
Bone resorption in metabolic bone diseases alters the structure of trabecular microstructure in the spongy bone and reduces its mechanical strength. Most of the methods used to diagnose bone loss are based on measuring the radiation absorbed by the bone tissue minerals and cannot evaluate the micro-structure of bone trabeculae in the examined tissue. The present study describes a method, based on optical processing of conventional radiographs for quantitative evaluation of trabecular micro-structure. The analysis is based on applying optical Fourier diffractometry methods to femoral neck radiographs. The method enables quantitative characterization of the structure of the trabecular pattern which appears on the bone radiograph. The changes in trabecular structure result in bone tissue deterioration which reflects many metabolic bone diseases. This method makes it possible to represent the bone microstructure by a quantitative bone index which depends on the light intensity distribution at the Fourier plane. A special optical correlator was constructed and unique software was developed for data processing. The optical device consists of a light source, a film positioner, optical components and an electronic device for accurate light intensity measurements. The device can process the image on a conventional x-ray film and analyze in real time image structures in preferred directions and locations. The method was tested on femoral neck radiographs of patients and showed a significant correlation between the results and the pathologic state of the bone. The advantages of this optical method as a practical tool for the early detection of bone loss are further evaluated.
Computer-assisted surgical techniques evaluated with wound-healing-impaired animal model
Lou Reinisch, Courtney West, Mike Rivas, et al.
As part of our computer assisted surgical techniques (CAST) program, we use computers to assist in the guidance of surgical lasers. The computer helps to create laser incisions with minimal widths, a reduction of collateral thermal damage, and regulates the rate of tissue ablation. Previous studies have compared laser incisions under manual control to incisions made with the CAST system. These studies were carried out with healthy animals. In this study, we compare the manual and CAST laser incisions on rats with induced diabetes. The diabetic rats have impaired wound healing and make a better model for our wound healing studies. Cutaneous incisions were made on the dorsal pelt using a carbon dioxide laser. The incisions were sutured and allowed to heal for 3, 7, 14, and 21 days. Wounds were analyzed histologically and with tensiometry. We have found definite advantages to the CAST program.
Laser optic-acoustic tomography for medical diagnostics: principles
This paper is to describe principles of laser optoacoustic tomography for medical diagnostics. Two types of imaging modes are presented. The first is the tomography in transmission mode, which utilizes detection of stress transients transmitted from the laser-excited volume toward the depth through thick layers of tissue. The second is the tomography in reflection mode which utilizes detection of stress transients generated in superficial tissue layer and reflected back toward tissue surface. To distinguish the two modes, we have abbreviated them as (1) laser optoacoustic tomography in transmission mode, LOATT, and (2) time-resolved stress detection tomography of light absorption, TRSDTLA, in reflection mode where emphasis is made on high spatial resolution of images. The basis for laser optoacoustic tomography is the time-resolved detection of laser-induced transient stress waves, selectively generated in absorbing tissues of diagnostic interest. Such a technique allows one to visualize absorbed light distribution in turbid biological tissues irradiated by short laser pulses. Laser optoacoustic tomography can be used for detection of tissue pathological changes that result in either increased concentration of various tissue chromophores such as hemoglobin or in development of enhanced microcirculation in diseased tissue. Potential areas of applications are diagnosis of cancer, brain hemorrhages, arterial atherosclerotic plaques, and other diseased tissues. In addition, it can provide feedback information during medical treatments. Both LOATT and TRSDTLA utilize laser excitation of biological tissues and sensitive detection of laser-induced stress waves. Optical selectivity is based upon differences in optical properties of pathologically different tissues. Sensitivity comes from stress generation under irradiation conditions of temporal stress confinement. The use of sensitive wide-band lithium niobate acoustic transducers expands limits of laser optoacoustic tomography. The technology allows us to determine directly temperature distributions in tissues and locate tissues volumes with different absorption. To demonstrate principles of TRSDTLA, experiments were conducted in vivo with mice-model for breast cancer using specially designed front-surface transducers- reflectometers. To present advantages and limitation of LOATT, experiments were performed in phantoms made of gel with polystyrene spheres colored with copper sulfate. Our experimental results and theoretical calculations show that TRSDTLA can be applied for non- invasive histology of layered tissues with in-depth resolution of up to 2 microns. TRSDTLA in acoustic reflection mode is promising for diagnostics of skin and ocular diseases. LOATT in acoustic transmission mode can be applied for detection of small tissue volumes with enhanced absorption located inside organs at the depth of up to 10 cm.
Ultrasound-modulated optical tomography for dense turbid media
Continuous-wave ultrasonic modulation of scattered laser light has been used to image objects in tissue-simulating turbid media for the first time. We hypothesized that the ultrasound wave focused into the turbid media modulates the laser light passing through the ultrasonic focal zone. The modulated laser light collected by a photomultiplier tube reflects the local mechanical and optical properties in the focal zone. Buried objects in 5-cm thick tissue phantoms (absorption coefficient (mu) $a) equals 0.1 cm-1, reduced scattering coefficient (mu) s' equals 10 cm-1) were located with millimeter resolution by scanning and detecting alterations of the ultrasound-modulated optical signal.
Application of image analysis in the myocardial biopsies of patients with dilated cardiomyopathy
Emanuel Agapitos, Nikolaos Kavantzas, M. G. Bakouris, et al.
The aim of our study is to investigate if myocardial fibrosis measured by image analysis may be considered as an important and accurate index of dilated cardiomyopathy and its prognosis. The study group consisted of 24 patients with dilated cardiomyopathy which was diagnosed by echocardiography, radionuclide ventriculography, cardiac catheterization and left ventricular endomyocardial biopsy. The patients' overall disability was conventionally expressed with the criteria for functional capacity. Using image analysis the percentage of fibrosis in a total of 35 myocardial biopsies was measured accurately. A comparison study between the percentage of myocardial fibrosis and the clinical parameters (left ventricular ejection fraction and overall functional capacity) showing the degree of each patient's heart failure followed. A correlation was found among fibrosis, left ventricular ejection fraction and overall functional capacity. The cases with small values of fibrosis (less than 10%) have big values of ejection fraction and belong in Class I of overall functional capacity. The cases with big values of fibrosis (greater than 10%) belong in Classes III and IV of overall functional capacity and have small values of ejection fraction. The results of the comparison study were presented graphically and were considered significant. Myocardial fibrosis measured by image analysis might be considered an important prognostic index of dilated cardiomyopathy.
Reconstructed x-ray image for one-dimensional translation of an area focal plane array
Gary E. Halama, James A. McAdoo, Hong Liu
We report experimental results that further confirm the feasibility of a novel large-field digital mammography technique. This technique uses a mosaic of area array CCDs in a checker board like pattern with spacing left between the CCDs for the driver and readout electronics. To obtain a complete x-ray image, the mosaic must be repositioned four times with an x-ray exposure at each position. To reduce the patient dose, a lead shield with appropriately patterned holes is introduced between the x-ray source and the patient. A previous report with similar tests used optical sources to evaluate the fundamental system concepts. The results reported here, however, were obtained using x-ray images acquired under clinical conditions and represent a more realistic demonstration of our concept. A high precision translation stage was used to position a fiber-coupled scintillating screen/CCD sensor assembly and acquire two images per sequence. These images were then combined using a simple computer algorithm to produce a seamless composite. A systematic but relatively easy alignment of the two critical surfaces yielded consistent, repeatable alignment of the images in the composite. These results make a convincing case for the feasibility of our area-scanning large-field mammography concept.
Theoretical model for contrast-detail-detectability prediction in digital radiography
This paper reports the results of our investigation into developing a theoretical model to predict the contrast-detail detectability in digital radiography. The equations presented in this paper are a continuation of our previous study on quasi-ideal observer signal-to-noise ratio and lesion detectability. In this project, numerical calculations were performed to determine contrast-detail curves of CCD and other x-ray imaging systems under clinical mammographic conditions. A contrast-detail phantom was imaged to validate the calculations predicted by our theoretical model. The experimental measurements were well predicted by the model's calculations. The theoretical model and the experimental techniques investigated in this research will help mammographers, scientists and engineers to optimize design trade-offs for emerging digital mammographic systems. It will also leverage efforts toward the development of practical techniques that can be performed at non-academic clinical sites, to quantitatively access the performance of new or existing digital radiography systems.
New storage phosphor for x-ray microscopy for biological application
Vyacheslav I. Kochubey, Konsuella E. Gyunsburg, Yuliya G. Sedova, et al.
The new silverless radiophotoluminescence substances - a single alkaly- halide crystals (nondoped and doped by In +2 ) are proposed and tested as X-ray image detectors. Their spatial resolution is not worse than 2 pm and they allow detection of pictures in X-rays with a dynamic range of about I 0 000. A stored X-ray image can be read out many times by photoluminescence measurements under UV excitation. The image can be erased completely by heating ofphosphor at a temperature of 400 °C during a half an hour. Unique combination of the resolution and the dynamic range of lyminosity offers sample scope for x-ray microscopy under biology. Keywords: X-ray microscopy, radiophotoluminescence, alkaly- halide crystals
Advanced Biomedical Techniques for Trauma Care
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Analysis of exhaled breath by laser detection
Karla D. Thrall, James J. Toth, Steven W. Sharpe
The goal of our work is two fold: (1) to develop a portable rapid laser based breath analyzer for monitoring metabolic processes, and (2) predict these metabolic processes through physiologically based pharmacokinetic (PBPK) modeling. Small infrared active molecules such as ammonia, carbon monoxide, carbon dioxide, methane and ethane are present in exhaled breath and can be readily detected by laser absorption spectroscopy. In addition, many of the stable isotopomers of these molecules can be accurately detected, making it possible to follow specific metabolic processes. Potential areas of applications for this technology include the diagnosis of certain pathologies (e.g. Helicobacter Pylori infection), detection of trauma due to either physical or chemical causes and monitoring nutrient uptake (i.e., malnutrition). In order to understand the origin and elucidate the metabolic processes associated with these small molecules, we are employing physiologically based pharmacokinetic (PBPK) models. A PBPK model is founded on known physiological processes (i.e., blood flow rates, tissue volumes, breathing rate, etc.), chemical-specific processes (i.e., tissue solubility coefficients, molecular weight, chemical density, etc.), and on metabolic processes (tissue site and rate of metabolic biotransformation). Since many of these processes are well understood, a PBPK model can be developed and validated against the more readily available experimental animal data, and then by extrapolating the parameters to apply to man, the model can predict chemical behavior in humans.
Biomedical Sensors
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Simultaneous measurement of Cy5.5-labeled capture antibodies and Cy5-labeled antigens in a fiber optic biosensor: photobleaching and resonance energy transfer effects during fiber regeneration
Randy R. Wadkins, Joel P. Golden, Frances S. Ligler
Fiber optic biosensors using evanescent wave excitation of fluorescence have proven their ability to detect antigens rapidly in a variety of environmental and clinical samples. One problem associated with these biosensors is the fiber-to-fiber variability in measured signal. We have addressed this problem by labeling an immobilized anti-trinitrotoluene ((alpha) TNT) capture antibody with the fluorescent cyanine derivative Cy5.5 (emission (lambda) max equals 696 nm). The antigen (a TNT analog) was then labeled with fluorescent Cy5 (emission (lambda) max equals 668 nm). Both fluorophores were excited by 635 nm light, and their emission was collected using a fiber optic spectrometer. The fluorescence from the Cy5.5 labeled capture antibody served as a calibration signal for each fiber and was used to correct for differences in optics, fiber defects, and varying amounts of immobilized capture antibody. The calibration process could be used repeatedly following fiber regeneration. However, when each immobilized antibody was labeled with at least one Cy5.5 fluorophore, fluorescence resonance energy transfer (FRET) was observed between the Cy5-antigen donor and the Cy5.5-labeled acceptor. The extent of FRET affected the measured antigen and calibration signal, and these signals had to be adjusted accordingly. We describe the procedures to account for fluorescently labeled antibodies during extended biosensor use.
Molecular assembly of multilayer enzyme on fiber optic surface: toward the development of chemiluminescence-based fiber optic biosensors
Zhongping Chen, Harry Hong Gao, Jayant Kumar, et al.
We report here on a technique to immobilize a multilayer enzyme assembly on an optic fiber surface. A multilayer of an enzyme, alkaline phosphatase, was successfully immobilized on an optical fiber surface. Chemiluminescence, ellipsometry, and surface plasmon resonance were used to characterize the structure and activity of the assembly. A chemiluminescence-based fiber optic biosensor utilizing this immobilization technique has been developed for the detection of organophosphorous-based pesticides. Detection of pesticide at sub-ppm level has been achieved for paraoxon.
Real-time immunoassays using fiber optic long-period grating sensors
Tuan A. Tran, Vikram Bhatia, Tiffanie D'Alberto, et al.
Photoinduced long-period gratings (LPG) in optical fibers offer a completely new approach to the fabrication of highly sensitive evanescent wave biosensors. In contrast to other types of evanescent wave sensors where a surface plasmon must be carefully constructed from a waveguide substrate that must be polished and deposited with a thin metallic film of precise thickness via a sputtering process, the proposed technique simply relies on the formation of gratings within a communication grade germanium-doped optical fiber. Using an amplitude mask that is optimized for operation at 244 nm, an incoming collimated UV beam forms a spatially periodic optical intensity pattern along the axis of the fiber. Given sufficient exposure time on the order of seconds, a refractive index grating is induced within the core of the fiber. In this method, the LPG is used to detect and monitor in real-time the interaction of a specific antigen to the immobilized antibody on the silica fiber. When the density of the bound protein changes (i.e., when the antigen binds to the antibody), the associated refractive index of the bound film will also change. If a broadband light source is injected into the optical fiber, the output spectrum of the LPG sensor will shift in response to the refractive index changes.
Diffraction method of vocal chord oscillation sensing
A method of small-amplitude biovibrations detection is presented in the paper. The method uses a dependence of properties of speckle-structures formed by focused coherent light field diffraction from rough surfaces on the statistics and movement parameters of the surface. With the help of computer modeling the different components of skin surface vibration were analyzed and their influence on speckles dynamics was studied. Human vocal chord oscillations spectrum was monitored using the developed technique.
Broadband single-mode optical fiber surface plasma wave chemical sensor
Andrew J.C. Tubb, Frank P. Payne, Roger Millington, et al.
We describe a new design of optical fiber surface plasma wave chemical sensor. The sensor consists of a tapered single mode optical fiber with a thin layer of silver evaporated on to the tapered section. The gradually changing diameter of the fiber along the taper results in a distributed coupling between the guided mode of the fiber and the surface plasma wave. As a result, and in contrast to conventional plasma wave sensors, coupling to the surface plasma wave occurs over a broad spectral range, typically several hundred nm. The device shows good sensitivity to changes in the refractive index of the external environment, with refractive index changes of 10-4 being detectable. The device is compact, simple to make, and has applications as a biochemical or immunosensor.
Mainstream sensor unit for closed-circle anesthetic gas monitoring
Stephan Junger, Norbert O. Lutter, Johannes Schwider, et al.
The use of closed circle systems in anesthesia requires accurate real-time anesthetic gas monitoring. A demonstration system was designed in order to test monitoring feasibilities for volatile anesthetics, N2O, carbon-dioxide, and water based on nondispersive infrared spectroscopy (NDIR) in the wavelength range from 3 to 13 microns. Calibration curves have been obtained using mass flow controllers. These results are compared with simulations thus representing the basis for the selection of interference filters with optimized central wavelengths and bandwidths. The paper describes the design of a miniaturized sensor unit that permits integration into the breathing circuit yielding a decrease of response time and measurement delay when compared with sidestream sampling devices. This mainstream sensor unit consists of a miniaturized infrared spectroscopic cell to detect gas concentrations, as well as a pressure and a temperature sensor. A stabilized infrared source is coupled to the spectroscopic cell using a silver halide glass fiber bundle. The radiation passes two different absorption lengths adapted to the typical concentrations and extinction coefficients and is focused onto multispectral detectors by aspheric reflective surfaces. Six signal and two reference channels are amplified by miniaturized multichannel lock-in modules and transferred to a PC for acquisition, calibration, processing and display.
Sensor materials for an intravascular fiber optic nitric oxide sensor
Babs R. Soller, Bhairavi R. Parikh, Russell F. Stahl
Nitric oxide (NO) is an important regulatory molecule in physiological processes including neurotransmission and the control of blood pressure. It is produced in excess during septic shock, the profound hypotensive state which accompanies severe infections. In-vivo measurement of NO would enhance the understanding of its varied biological roles. Our goal is the development of an intravascular fiber-optic sensor for the continuous measurement of NO. This study evaluated nitric oxide sensitive compounds as potential sensing materials in the presence and absence of oxygen. Using absorption spectroscopy we studied both the Fe II and Fe III forms of three biologically active hemes known to rapidly react with NO: hemoglobin, myoglobin, and cytochrome-c. The Fe II forms of hemoglobin and myoglobin and the Fe III form of cytochrome-c were found to have the highest sensitivity to NO. Cytochrome c (Fe III) is selective for NO even at high oxygen levels, while myoglobin is selective only under normal oxygen levels. NO concentrations as low as 1 (mu) M can be detected with our fiber-optic spectrometer using cytochrome c, and as low as 300 nM using myoglobin. Either of these materials would be adequate to monitor the increase in nitric oxide production during the onset of septic shock.
Potential for a silicon probe in a Raman spectroscopic general-nesthetic sensor
Julie R. Parnell, Paul Yager
Currently there is no direct method for measuring anesthetic levels in blood or tissue. Efforts are underway to develop a Raman spectroscopy-based sensor for general anesthetics using a polymeric probe. Signal enhancement, needed because of the inherently weak Raman signal, can be obtained by absorption of anesthetics into and recirculation of photons within the probe. Commercially available photopolymerizable silicones might have potential in the development of such probes since they are conducive to ring formation. Before attempting this, however, it is necessary to understand how the interfering silicone peaks will affect the signal-to-noise ratio of the anesthetic peaks and, ultimately, the sensor's detection limit. To this end, studies were performed on liquid anesthetics in silicon oil. The anesthetic C-H stretch peaks near 3000 cm-1 were obscured by those of the silicone. However, detection limits of 1.2, 1.5, and 1.2 MAC were observed for halothane, isoflurane, and enflurane, respectively, by monitoring a lower wavenumber region (900 - 1300 cm-1). In addition, 0 - 5 MAC mixtures of anesthetics were studied. PLS predictive models generated from MSC- corrected validation spectra predicted anesthetic levels relatively well for these mixtures (R2 equals 0.969, 0.984, and 0.979 for halothane, isoflurane, and enflurane, respectively); differences of 1 MAC were discernable.
Detection of triglycerides using immobilized enzymes in food and biological samples
Ashish Raichur, Abiodun Lesi, Henrik Pedersen
A scheme for the determination of total triglyceride (fat) content in biomedical and food samples is being developed. The primary emphasis is to minimize the reagents used, simplify sample preparation and develop a robust system that would facilitate on-line monitoring. The new detection scheme developed thus far involves extracting triglycerides into an organic solvent (cyclohexane) and performing partial least squares (PLS) analysis on the NIR (1100 - 2500 nm) absorbance spectra of the solution. A training set using 132 spectra of known triglyceride mixtures was complied. Eight PLS calibrations were generated and were used to predict the total fat extracted from commercial samples such as mayonnaise, butter, corn oil and coconut oil. The results typically gave a correlation coefficient (r) of 0.99 or better. Predictions were typically within 90% and better at higher concentrations. Experiments were also performed using an immobilized lipase reactor to hydrolyze the fat extracted into the organic solvent. Performing PLS analysis on the difference spectra of the substrate and product could enhance specificity. This is being verified experimentally. Further work with biomedical samples is to be performed. This scheme may be developed into a feasible detection method for triglycerides in the biomedical and food industries.
Development of a genosensor for Mycobacterium tuberculosis
Narayana R. Isola, Jean Pierre Alarie, Guy D. Griffin, et al.
This work involves the development of a fiberoptic genosensor for the detection of Mycobacterium tuberculosis. A rapid and sensitive non-radioactive method for the detection of Mycobacterium is described. This method involves polymerase chain reaction (PCR) amplification of the target DNA utilizing gene specific primers labelled with fluorescein at the 5' end and hybridization of the amplified product to a species specific oligonucleotide probe sequence covalently linked to the end of a fiber. The fluorescent hybridization products are detected by laser induced fluorescence using an argon laser (488 nm).
Differential NIR technique for tissue diagnosis
Liu Zheng, Hyo Sang Lee
A new NIR technique based on pseudo-random modulation/correlation method is being developed for non-invasive tissue diagnosis applications. Simulation study and preliminary experiment demonstrate the feasibility of the technique applied to tissue oxygenation measurement. Using this technique, two diode lasers emitting at different wavelengths are modulated with orthogonal pseudo-random codes. The output power from these lasers is combined and delivered by an optical fiber to the tissue phantom to be studied. Simultaneous dual-wavelength detection is achieved by using only one detector due to the unique mathematical properties of the pseudo-random code. The system is further capable of rejecting common mode noise and reducing the tissue dependent effect. Preliminary experiments demonstrate 50 ps time resolution with a 200 to 400 MHZ modulation frequency. Prototype sensor performances are demonstrated in tissue phantom experiment and fluorescence lifetime measurement. In tissue phantom experiments, overall tissue deoxygenation is simulated by changing the phantom's optical property globally and a tumor tissue is simulated by a strong absorber embedded in the uniform background phantom. The depth of the absorber was measured up to 6 cm with an accuracy of 5 mm. In the fluorescence lifetime measurement experiment, a dye with a lifetime of 1.25 ns is excited by the 670 nm light and its fluorescence is detected at 760 nm.
Design and characterization of a fiber optic respiratory plethysmograph (FORP)
Andreas T. Augousti, Ali Raza, Martin Graves
Invasive techniques used in the measurement of respiration are often regarded as cumbersome, distressing to the subject and in some cases impractical for prolonged use. A current non- invasive alternative is the respiratory inductive plethysmograph (RIP), widely used in the clinical environment. The RIP, however, is expensive and prone to electromagnetic interference (EMI) and is therefore unsuitable in such environments as the interior of a magnetic resonance imaging (MRI) scanner. This research focuses on the development and construction of an all-optical analogue of the RIP, the fiber optic respiratory plethysmograph (FORP). A number of calibration techniques, both linear and non-linear, have been investigated to determine the relationship between the ribcage and abdomen during breathing. An evaluation of these techniques has provided an efficient method of respiratory volume monitoring. The results of testing the device using the various calibration methods are presented.
Novel method and system for anesthetization monitoring
Mingwei Shu, Xuedong Chi, Zhicheng Luo
Conventional monitoring of the anesthetization process relies on the measurement of the blood pressure and heart rate, and on human observations. Such measures and observations do not provide specific assessment of the depth and other aspects of anesthesia, and the overall monitoring process, which is largely based on human experience, is subjective and qualitative at best. We have developed a novel method for anesthetization monitoring which provides quantitative assessment of anesthesia by way of monitoring and on-line analyzing the dynamic processes of anesthesia, muscle relaxation, and pain reaction. Specifically, we have developed a microcomputer-based system that can simultaneously measure the EMG signals from the diaphragm muscle and soleus musculus, the contraction signals of both the striated and smooth muscles of the esophagus, and the ECG. Statistical and other characteristics of these signals in relation to the anesthetization process are analyzed in real-time, and the results are stored and printed out in an on-going process. Clinical trials with this system demonstrate the feasibility of the new monitoring method and the potential clinical applications of the system. Actual tests with the system show strong correlations between the statistical characteristics produced by the monitoring system and the various aspects of anesthesia, muscle relaxation, and pain reaction. These findings suggest that our system provides a more complete set of real-time quantitative measures of the biomedical processes relevant to anesthesia that can be used to provide objective assessment of the anesthetization process.
Optical Methods in Biophysics
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Special investigation of somatotropin for different pH
Virginia Otero de Joshi, Herminia Gil, Silvia Contreras, et al.
Spectral investigations of absorbance in deep ultra-violet region (from 200 nm to 350 nm) of (STM) was carried out for different pH values. On the high energy side the peak is located at 195 nm which is generally attributed to peptide bonds. This peak, as expected, does not show any shift with pH value (4.3 to 10.8). A rather broad peak is spread in the region from 200 nm to 240 nm which could be the superposition of the peaks corresponding to the absorption due to (alpha) helix and (beta) structure. This peak shows a red shift as pH value increases. The same hormone was glycated by a conventional method and the process was estimated with the absorption spectra. The results are discussed in the light of nonenzymatic glycation. It was found that glycation mucus somatotropin resistant towards the denaturation process.
Surface second-harmonic generation (SSHG): a new scheme for immunoassay
Liqun Yang, Daniel McStay, Peter J. Quinn
A new optical immunoassay scheme based on surface second harmonic generation (SHG) is proposed. The utility of the technique has been investigated by deposition of sample antigen and antibody (bovine serum albumin & mouse anti-bovine serum albumin IgG antibody) on glass surfaces. The laser-induced second harmonic signals generated from these sample surfaces were monitored using a photomultiplier tube (Thorn EMI, 9524A). The surface second harmonic generation characteristics of an enzyme-linked immunoassay process were investigated, which is parallely monitored by a conventional ELISA method. The SSHG immunoassay experiment was performed using a conventional sandwich immunoassay scheme on ELISA immunoassay plates. The laser-induced surface-second harmonic signals generated from sample wells of different populations of the antigen-antibody complex were subsequently measured using the photomultiplier tube. To verify the new SSHG immunoassay results, a conventional ELISA sandwich immunoassay was performed, and their results compared. The new SSHG immunoassay results showed a virtually identical conclusion as that of conventional ELISA sandwich immunoassay. The SSHG readings are promotional to that of the ELISA data. However, the readings from the new SSHG immunoassay were found much larger, which is in agreement with the theoretical expectation. In this paper, detailed experimental results of the new SSHG immunoassay are described, and subsequently compared with those of a conventional ELISA immunoassay. The feasibility and advantages of the SSHG as a new immunoassay technique also are discussed.
Unbiased feature selection through successive elimination of poor performers for EEG classification
Electroencephalogram (EEG) pattern recognition problem is considered as a composite of three subproblems: feature extraction, feature selection, and pattern classification. Focusing particularly on the feature selection issue, each subproblem is reviewed briefly and a new method for feature selection is proposed. The method suggests that first one shall extract as much information (features) as conveniently possible in several pattern information domains and then apply the proposed unbiased successive feature elimination process to remove redundant and poor features. From this set select a significantly smaller, yet useful, feature subset that enhances the performance of the classifier. The successive feature elimination process is formally described. The method is successfully applied to an EEG signal classification problem. The features selected by the algorithm are used to classify three signal classes. The classes identified were eye artifacts, muscle artifacts, and clean (subject in stationary state). Two hundred samples for each of the three classes were selected and the data set was arbitrarily divided into two subsets: design subset, and testing subset. A proximity index classifier using Mahalanobis distance as the proximity criterion was developed using the smaller feature subset. The system was trained on the design set. The recognition performance on the design set was 92.33%. The recognition performance on the testing set was 88.67% by successfully identifying the samples in eye-blinks, muscle response, and clean classes, respectively, with 80%, 97%, and 89%. This performance is very encouraging. In addition, the method is computationally inexpensive and particularly useful for large data set problems. The method further reduces the need for a careful feature determination problem that a system designer usually encounters during the initial design phase of a pattern classifier.
Optical arrays and pattern recognition in the design of an artificial nose
Todd A. Dickinson, Suneet Chadha, David R. Walt, et al.
Array sensors capable of multi-vapor discrimination have been developed that employ fiber optic bundles, CCD cameras, and artificial neural network processing. Sensors have been constructed both through spatial deposition of dye-containing photopolymers on an imaging fiber, and via individual polymer/dye coatings placed on individual single-core fibers and then bundled. Cross-reactive sensing regions are created by using a variety of polymers. The resulting array is then challenged with a variety of analytes. Vapor pulses give rise to temporal response patterns which are used to train a neural network. The final sensor array system can identify subsequent challenges with the analyte over extended periods of time with up to 100% accuracy. The sensor can also characterize analytes on the basis of functional groups and molecular weight, and is capable of identifying components of mixtures.
Electronic speckle pattern interferometry: new applications in biophysics
Electronic speckle pattern interferometry (ESPI) provides full field interferometric mapping of deformations, vibrations and density fluctuations in test objects. The interference fringes can be followed in real-time while phase-stepping techniques provide quantitative information. Interferometric measurement of biological objects by standard holography has so far been limited by fringe decorrelation due to microstructure changes. ESPI is based on video recording which allows us to monitor relatively rapid changes in biological objects. To illustrate the potentials of the technique, the gravitropical response of oat coleoptiles (seedlings) was studied. A coleoptile represents a fast growing, partly translucent biological object which is difficult to record interferometrically. However, growth and bending of the specimen were measured even on the tip of the coleoptile where the microstructure changes very rapidly. We also show how small temperature changes in transparent objects can be measured. In water, the sensitivity to temperature change is 0.7 multiplied by 10-3 K per meter. Due to a small difference in temperature between the bulk liquid and its droplet, it was possible to follow and measure movement of droplets in liquids.
Evaluation methods for retrieving information from interferograms of biomedical objects
Halina Podbielska M.D., Matthias Rottenkolber
Interferograms in the form of fringe patterns can be produced in two-beam interferometers, holographic or speckle interferometers, in setups realizing moire techniques or in deflectometers. Optical metrology based on the principle of interference can be applied as a testing tool in biomedical research. By analyzing of the fringe pattern images, information about the shape or mechanical behavior of the object under study can be retrieved. Here, some of the techniques for creating fringe pattern images were presented along with methods of analysis. Intensity based analysis as well as methods of phase measurements, are mentioned. Applications of inteferometric methods, especially in the field of experimental orthopedics, endoscopy and ophthalmology are pointed out.
Clinical Laser and Optoelectronic Systems
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Multiwavelength pulse oximetry in the measurement of hemoglobin fractions
Bernd Manzke, Johannes Schwider, Norbert O. Lutter, et al.
The two wavelength design of the majority of pulse oximeters assumes only two absorbing hemoglobin fractions, oxyhemoglobin (O2Hb), and reduced hemoglobin (HHb) irrespective of the presence of methemoglobin (MetHb) and carboxyhemoglobin (COHb). If MetHb or COHb is present, it contributes to the pulse-added absorbance signal and will be interpreted as either HHb or O2Hb or some combination of the two. In this paper we describe a noninvasive multi-wavelength pulse oximeter measuring O2Hb, HHb, MetHb, and COHb at a specified accuracy of 1.0%. The system was designed with respect to the results of numerical simulations. It consists of 9 laserdiodes (LDs) and 7 light emitting diodes (LEDs), a 16-bit analog-digital converter (ADC) and has a sampling rate of 16 kHz. The laser didoes and LEDs were coupled into multi-mode fibers and led with a liquid lightguide to the finger clip and then the photodiode. It also presents the results of a clinical study, including a setup with a quartz tungsten halogen lamp (with fiber output) and a diode array spectrometer, a standard pulse oximeter and two in-vitro oximeters (radiometer OSM3 and radiometer ABL 520) as references.
New laser system for highly sensitive clinical pulse oximetry
Mostafa Hamza, Mohammad Hamza
This paper describes the theory and design of a new pulse oximeter in which laser diodes and other compact laser sources are used for the measurement of oxygen saturation in patients who are at risk of developing hypoxemia. The technique depends upon illuminating special sites of the skin of the patient with radiation from modulated laser sources at selected wavelengths. The specific laser wavelengths are chosen based on the absorption characteristics of oxyhemoglobin, reduced hemoglobin and other interfering sources for obtaining more accurate measurements. The laser radiation transmitted through the tissue is detected and signal processing based on differential absorption laser spectroscopy is done in such a way to overcome the primary performance limitations of the conventionally used pulse oximetry. The new laser pulse oximeter can detect weak signals and is not affected by other light sources such as surgical lamps, phototherapy units, etc. The detailed description and operating characteristics of this system are presented.
System for fast measurement of in-vivo tissue fluorescence spectra under multiple wavelength excitations
Haishan Zeng, Calum E. MacAulay, Branko Palcic
Tissue autofluorescence properties are excitation wavelength dependent. In this work, we developed a nitrogen dye laser -- OMA system capable of quickly measuring tissue autofluorescence spectra in vivo under multiple wavelength excitation. The system consists of a nitrogen dye laser with stepper motor for wavelength selection, an OMA with gated intensified detector, and a PC computer. A bifurcated fiber optic bundle is used to conduct the excitation laser light and to collect the fluorescence light. Gating electronics are used to achieve a high signal to noise ratio, allowing fluorescence measurements to be performed with ambient light on or under white light illumination during endoscopy. Excitation wavelength changes are performed automatically and quickly by the stepper motor which is controlled by the OMA PIA port. The system has been tested with a tissue phantom. The time needed to switch from one excitation wavelength to the next excitation wavelength is about one second.
Nd:YAG/Er:YAG dual heads with three-wavelength laser system for dentistry
Gilwon Yoon, Hong Sig Kim, Taemin Hong, et al.
A prototype pulsed laser of dual heads of Nd:YAG and Er:YAG has been developed. Nd:YAG laser emits 1.06 micrometers and 1.3 micrometers. Er:YAG laser generates 2.94 micrometers. This laser system is designed for treating both soft and hard tissues in dentistry. Nd:YAG laser has about 100 microseconds pulse duration and repetition rates are up to 100 Hz at 1.06 micrometer and up to 30 Hz at 1.3 micrometer. The average power at 50 Hz is up to 30 W at 1.06 micrometer. Up to 10 W at 30 Hz can be obtained at 1.3 micrometer. Er:YAG laser has about 100 microsecond pulse duration, repetition rates up to 5 Hz and the average power up to 5 W. Current 1.06 micrometer Nd:YAG dental lasers show some difficulties in treating soft tissue due to low absorption and higher penetration. Dye as absorbing medium is often applied on targets to enhance absorption. A 1.3 micrometer wavelength is expected to be valuable for soft tissue treatment since absorption at this wavelength is more than ten times higher than at 1.06 micrometer. A 2.94 micrometer wavelength is available for hard tissue surgery.
Biomedical Sensors
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Tissue viability assessment via laser-based fluorescence monitor
Craig H. Curtis, Nasser Peyghambarian, Eustace L. Dereniak, et al.
A preliminary study of the degree to which recently introduced inhalation anesthetics influence the intracellular energetic metabolism of isolated perfused rat livers is undertaken via NADH fluorometry. During liver transplantation, anesthesiologists desire to maintain a high level of metabolic energy status in newly transplanted liver tissue. Ischemic storage of donor liver tissue prior to transplantation is known to inhibit mitochondrial electron transfer, which results in decreased levels of ATP and increased levels of NADH in the stored tissue. The ability of transplanted liver tissue to regenerate ATP at normal levels is desirable for early post- operative recovery of liver function. Previous studies have examined the differential effects inhalation anesthetics have on the energetic metabolism of tissue at the cellular level; the trend of such agents is to induce a dose-dependent increase in NADH fluorescence in accordance with their strengths as general anesthetics. The present study evaluates the differential effects exhibited by new inhalation anesthetics on the return of function of energetic metabolism in liver tissue. The third-harmonic (355 nm) output of a Nd:YAG laser is spatially filtered and used as the excitation source for surface fluorometric measurements of isolated buffer-perfused rat livers. Lastly, maximum fluorescence emission versus spot-size are measured.
Applications of tunable diode laser spectroscopy for the detection of exhaled endogenous gases: CO, NH3, CH4, N20, and CO2
Andrian I. Kouznetsov, Eugene V. Stepanov
Tunable diode laser spectroscopy (TDLS) is proposed for content measurements of trace gases like CO, carbon-dioxide, NH3, CH4, NO, NO2 in human and animal's exhalation. High sensitivity and wide dynamic range of the method ensure fast detection of these gases at ppb level and within the accuracy better than 10%. One-expiration sample is enough to reach these parameters. There is no need for any preliminary preparations of tested samples. Some pairs of the gases, for instance, CO and carbon-dioxide, NH3 and carbon- dioxide, or CO and nitrous oxide, can be measured simultaneously by one laser providing complex studies. The high sensitive gas analysis could provide necessary background to the noninvasive diagnostics in a wide variety of medical problems. Perspectives of the TDLS methods in application to medicine diagnostics are demonstrated by the first results of exhalation tests.
Advanced Bioimaging Techniques and Devices
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Quantitative analysis of coherent detection in a turbid medium
Charles A. DiMarzio, Scott C. Lindberg
Coherent detection is a promising technique for medical imaging, because it offers high spectral and temporal resolution, high spatial and angular resolution, and higher signal-to- noise ratio than direct detection. Analysis techniques developed for coherent lidars used in remote sensing of clouds are applicable to coherent medical imaging. Single-scattering models, in which analysis is normally performed using the irradiance of the transmitter and of the 'back-propagated local oscillator' (BPLO), have been used for a variety of beam profiles, but are not applicable to medical imaging in highly-scattering tissue. However, recent work has extended the BPLO technique to model lidar returns from dense, highly-scattering clouds. The computation is based on fluence rates determined using a Monte-Carlo model. Results are equally applicable to various coherent imaging systems, as well as vibration measurement, and holography. The equations are described and sample results are presented for reflection from tissue and transillumination. Variations in signal behavior with different layered structures in the tissue are considered.
Clinical Laser and Optoelectronic Systems
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Optical parametric oscillators for medical applications
Lawrie A. W. Gloster, Paul S. Golding, Terence A. King
In recent years optical parametric oscillators (OPOs) have undergone a renaissance largely due to the discovery of new nonlinear materials capable of wide continuous tuning ranges spanning from the UV to the near-infrared spectral regions. To date, however, OPOs have not been exploited in the medical field despite their advantages over the dye laser in terms of tuning range and solid state structure. We consider the development of an OPO based on barium borate (BBO) which can be tailored to suit applications in medicine. Converting the maximum number of pump photons to tunable signal and idler photons is of great importance to secure high-fluence radiation necessary for many treatments. With this in mind, we report on an all- solid-state system using BBO which has been optimized by computer modeling with the potential of delivering amplification factors of typically up to 20 over a continuous tuning range of 700 nm to 1000 nm. As an example of its biomedical application, we describe the selective excitation of biomolecules and chromophores for cell destruction using malachite green isothiocyanate labelled bacteria. The potential for development is reviewed towards other medical applications such as diagnostic sensing and phototherapy.
Modeling of 2-um Tm:Ho:ZBLAN diode-pumped cw double-clad fiber lasers
Stuart D. Jackson, Terence A. King
Theoretical modeling of high-power thulium-sensitized holmium fluorozirconate (Tm:Ho:ZBLAN) glass fiber lasers operating on the 2 micrometer transition in holmium is presented. High output power in single-mode can be achieved by pumping the inner cladding of the double clad fiber with a single-mode core with high-power multimode cw diode lasers. The possibility of higher output powers with the double-clad fiber laser (or DCFL) arrangement over the core-pumped fiber laser means that these particular lasers are well suited to a number of medical applications which require output of high power and good beam quality. In a preliminary step to characterize and optimize these devices, a computer model has been developed to analyze the performance of the device when the power coupling coefficients and doping concentrations are varied. It is shown that the form and hence values of the power coupling coefficients which relate to the transfer of power to and from the ensemble of nonabsorbing modes to the ensemble absorbing modes which propagate within the inner cladding and core of the fiber respectively are paramount to the operation of the DCFL. In addition, for a specific doping level the choice of pump wavelength can be made on the grounds of existing core-pumped fiber laser technology.