The purpose of this initial study was to begin development of a new, objective diagnostic instrument that will allow simultaneous quantitation of multiple proteases within a single periodontal pocket using a chemical fiber optic senor. This approach could potentially be adapted to use specific antibodies and chemiluminescence to detect and quantitate virtually any compound and compare concentrations of different compounds within the same periodontal pocket. The device could also be used to assay secretions in salivary ducts or from a variety of wounds. The applicability is, therefore, not solely limited to dentistry and the device would be important both for clinical diagnostics and as a research too.

We present a novel minimally invasive method to measure the concentration of photodynamic therapy drugs in real time. The method is based on measurements of backscattered and fluorescence light using a steady state fluorescence spectrometer. The ratio of the fluorescence to scattered light is found to be linearly proportional to the absorption coefficient of the photosensitizer. The fiber-optic probe used for the measurements has a small source-detector separation, therefore the measurements could be performed through the working channel of an endoscope.

Study of biomolecular interaction dynamics and relations between their structure and function is very important for the understanding of biological system. The laser diffractometry technique, as well as the surface plasmon resonance technique, can give information about the interaction kinetics, molecular binding stoichiometry, and the concentration of molecules in a solution. This method offers detailed and accurate determination of real-time adsorption kinetics of protein without labeling of the protein. When the polarized light is reflected on a solid surface, the reflectance has a minimum at the principal incidence angle. As the proteins are adsorbed over the surface the reflectance increases. Therefore, the temporal register of reflected intensity gives curves representing the binding kinetics of antibody in real-time. The technique is highly sensible because of the great difference in the refractive index between silicon and organic material. This method was applied to study the adhesion kinetics of monoclonal anti-AB antibodies at surface of a silicon wafer. The mathematical analysis of results would suggest that the antibody association occurs according to classical Langmuir surface adsorption. This analysis permits to obtain the adhesion and dissociation of the antibody.

Quantitative assessment of regional heart motion has significant potential for more accurate diagnosis of heart disease and/or cardiac irregularities. Local heart motion may be studied from medical imaging sequences. Using functional parametric mapping, regional myocardial motion during a cardiac cycle can be color mapped onto a deformable heart model to obtain better understanding of the structure- to-function relationships in the myocardium. In this study, 3D reconstructions were obtained from the Dynamic Spatial Reconstructor at 15 time points throughout one cardiac cycle. Deformable models were created from the 3D images for each time point of the cardiac cycle. From these polygonal models, regional excursions and velocities of each vertex representing a unit of myocardium were calculated for successive time intervals. The calculated results were visualized through model animations and/or specially formatted static images. The time point of regional maximum velocity and excursion of myocardium through the cardiac cycle was displayed using color mapping. The absolute value of regional maximum velocity and maximum excursion were displayed in a similar manner. Using animations, the local myocardial velocity changes were visualized as color changes on the cardiac surface during the cardiac cycle. Moreover, the magnitude and direction of motion for individual segments of myocardium could be displayed. These results suggest that the ability to encode quantitative functional information on dynamic cardiac anatomy enhances the diagnostic value of 4D images of the heart. Myocardial mechanics quantified this way adds a new dimension to the analysis of cardiac functional disease, including diastolic filling deficits and/or disturbances in regional electrophysiology and contraction patterns.

In the present study, the principle of synchronous luminescence (SL) is described for use in biomedical diagnostics. The SL method involves scanning simultaneously both emission and excitation wavelengths while keeping a constant wavelength interval between them. This SF procedure simplifies the emission spectrum and provides for greater selectivity and is used to detect subtle differences in the fluorescence emission of the biochemical species of cells and tissues. The SL method can be used to analyze tissue in vivo or to investigate spectral differences in normal and neoplastic cells in vitro. SL scans of skin tissues illustrate the use of the method. For in vitro diagnostics, a difference between the flourescent spectra of the normal rat liver epithelial and hepatoma cell lines were detected using synchronous fluorescence. The potential use of SF as s screening tool for cancer diagnosis is discussed.

A technique for enhancing the contrast of subcutaneous veins has been demonstrated. This techniques uses a near IR light source and one or more IR sensitive CCD TV cameras to produce a contrast enhanced image of the subcutaneous veins. This video image of the veins is projected back onto the patient's skin using a n LCD video projector. The use of an IR transmitting filter in front of the video cameras prevents any positive feedback from the visible light from the video projector from causing instabilities in the projected image. The demonstration contrast enhancing illuminator has been tested on adults and children, both Caucasian and African-American, and it enhances veins quite well in all cases. The most difficult cases are those where significant deposits of subcutaneous fat are present which make the veins invisible under normal room illumination. Recent attempts to see through fat using different IR wavelength bands and both linearly and circularly polarized light were unsuccessful. The key to seeing through fat turns out to be a very diffuse source of RI light. Results on adult and pediatric subjects are shown with this new IR light source.

Digital image interpretation is the basis of medical diagnoses. Through extensive review of patient data, an algorithm was developed to identify features of diagnostic importance in radiological images. The algorithm is generally applicable. Results from cardiac, lung, and military imagery are reported. The algorithm uses a pulse coupled neural network. It is this neural network that is fabricated on a custom CMOS chip. Each neuron of the pulse coupled neural network accepts an external optical input. The optical input is accomplished by a photo-detector. The neurons communicate laterally through a voltage grid. The communication strength, light sensitivity and other global parameters are under external control. A programmable logic array is on the camera board. Data for a specific neuron is accessed by an addressing scheme typically used for a CCD array. The individual neuron speed ranges from 10 to 50 Mhertz, and is fixed by a digital clock. The current chip is configured to operate at 300 Hertz. The chip logic is a hybrid of analog and digital circuitry to minimize the neuron size, maximize the number of neurons at a fixed cost. The hybrid circuitry also minimized the noise level in the chip.

The study of coronary arteries has evolved from examining gross anatomy and morphology to scrutinizing micro-anatomy and cellular composition. Technological advances such as high-powered digital microscopes and high precision cutting devices have allowed clinicians to examine coronary artery morphology and pathology at micron resolution. Our work explores the composition of normal coronary arteries in order to provide the foundation for further study of remodeled tissue. The first of two coronary arteries was sliced into 442 sections with 4 micron inter-slice spacing. Each slice was stained for elastin and collagen. The second coronary artery was sectioned into 283 slices, also with 4 micron resolution. These slices were stained for cellular nuclei and smooth muscle. High sectioned into 283 slices, also with 4 micron resolution. These slices were stained for cellular nuclei and smooth muscle. High resolution light microscopy was used to image the sections. The data was analyzed for collagen/elastin content and nuclei density, respectively. Processing of this type of data is challenging in the areas of segmentation, visualization and quantification. Segmentation was confounded by variation in image quality as well as complexity of the coronary tissue. These problems were overcome by the development of 'smart' thresholding algorithms for segmentation. In addition, morphology and image statistics were used to further refine the result of the segmentation. Specificity/sensitivity analysis suggests that automatic segmentation can be very effective. 3D visualization of coronary arteries is challenging due to multiple tissue layers. Method such as summed voxel projection and maximum intensity projection appear to be effective. Shading methods also provide adequate visualization, however it is important to incorporate combined 2D and 3D displays. Surface rendering techniques are useful tools for visualizing parametric data. Quantification in 3D is simple in practice but appropriate descriptions of these results must be displayed to clinicians in a clear way. Preliminary results are promising, but continued development of algorithms for processing histological data is needed.

Craniofacial analysis is a very important and widely used procedure in orthodontic caphalometry, which plays a key role in diagnosis and treatment planning. This involves establishing reference standards and specification of landmarks and variables. The manual approach takes up a tremendous amount of the orthodontist's time. In this paper, we developed a web-based approach for the craniofacial and dentition analyses. A digital computed radiography (CR) system is utilized for obtaining the craniofacial image, which is stored as a bitmap file. The system comprises of two components - a server and a client. The server component is a program that runs on a remote machine. To use the system, the user has to connect to the website. The client component is now activated, which uploads the image from the PC and displays it on the canvas area. The landmarks are identified using a mouse interface. The reference lines are generated. The resulting image is then sent to the server which performs all measurement and calculates the mean, standard deviation, etc. of the variables. The results generated are sent immediately to the client where it is displayed on a separate frame along with the standard values for comparison. This system eliminates the need for every user to load other expensive programs on his machine.

A new fiber optic sensor integrating dielectric diffraction gratings and thin films on optical fiber endfaces is prosed for biomedical sensing applications. This device utilizes a resonant dielectric waveguide grating structure fabricated on an optical fiber endface to probe reactions occurring in a sensing layer deposited on its surface. The operation of this sensor is based upon a fundamental resonance effect that occurs in waveguide gratings. An incident broad- spectrum signal is guided within an optical fiber and is filtered to reflect or transmit a desired spectral band by the diffractive thin film structure on its endface. Slight changes in one or more parameters of the waveguide grating, such as refractive index or thickness, can result in a responsive shift of the reflected or transmitted spectral peak that can be detected with spectroscopic instruments. This new sensor concept combines improved sensitivity and accuracy with attractive features found separately in currently available fiber optic sensors, such as large dynamic range, small sensing proximity, real time operation, and remote sensing. Diffractive elements of this type consisting of a photoresist grating on a Si₃N₄ waveguide have been fabricated on multimode optical fiber endfaces with 100 micrometers cores. Preliminary experimental tests using a tunable Ti:sapphire laser indicate notches of 18 percent in the transmission spectrum of the fiber endface guided-mode resonance devices. A theoretical analysis of the device performance capabilities is presented and applied to evaluate the feasibility and potential advantages of this bioprobe.

In the present paper, recent experimental advances obtained with a laser Doppler self-mixing velocimeter are reported. The self-mixing effect in a semiconductor laser is used to realize the velocimeter. The velocity is calculated measuring the frequency peak of the frequency spectrum of the intensity signal generated by the laser diode when modulated by feedback light coming from the moving scattering particles. A special optical fiber version of this velocimeter to be used specifically for intra-arterial blood velocity measurement has been realized and a solution for reducing temperature influence on the semiconductor performances is proposed. The results of the in vivo tests carried out with the proposed sensor are presented.

A sensor device for noninvasive detection and analysis of the pulsating blood flow waveforms by means of the reflective single-period photoplethysmorgraphy (SPPPG) technique has been designed and clinically tested. The sensor is operated jointly with any standard PC, by connecting the sensor head to the AD-card and using a separate hard disc with the signal processing software; all circuits are fed by the PC power supply. After processing, normalized shape of the mean SPPPG signal and its parameters are calculated and displayed; the measurement/processing time does not exceed 2 minutes. The clinically detected SPPPG signal shapes and corresponding parameters are presented and discussed. The preliminary results confirm good potential of this sensing approach for fast and patient-friendly early cardiovascular diagnostics.

A novel system incorporating optical fiber extrinsic Fabry- Perot interferometric (EFPI)-based sensors for rapid detection of biological targets is presented. With the appropriate configuration, the EFPI senor is able to measure key environmental parameters by monitoring the interferometric fringes resulting from an optical path differences of reflected signals. The optical fiber EFPI sensor has been demonstrated for strain, pressure, and temperature measurements and can be readily modified for refractive index measurements by allowing solutions to flow into an open cavity. The sensor allows for highly sensitive, real-time, refractive index measurements and by applying affinity coatings containing ligands within this cavity, specific binding of target molecules can be accomplished. As target molecules bind to the coating, there is an increased density within the film, causing a measurable refractive index change that correlates to the concentration of detected target molecules. This sensor platform offers enhanced sensing capabilities for clinical diagnostics, pharmaceutical screening, environmental monitoring, food pathogen detection, biological warfare agent detection, and industrial bioprocessing. Promising applications also exist for process monitoring within the food/beverage, petroleum, and chemical industry.

A novel optical fiber sensor is prosed for use in chemical analysis. The sensor probe is made of a gold coated multimode optical fiber, configured to exhibit surface plasmon resonance (SPR) when immersed on a set environment. The proposed detection strategy comprises measurement of the image pattern irradiated by the fiber under monochromatic illumination. A theoretical model is prosed to determine device performance. From computer simulations it is shown that the proposed configuration and detection strategy allows reaching a 30-fold enhancement in sensitivity relative to that obtained in previous SPR-based versions of the device.

A simple calibration technique for monoplane stereo x-ray imaging system in stereotactic breast biopsy was developed. According to the principle of perspective projection, a monoplane stereo imaging model was established, the geometric parameters for the purpose of 3D point reconstruction were described. The parameters are source- imager-distance and the x-ray tube positions with respect to the imaging receptor. These parameters are calculated using a phantom consisting of three radio-opaque calibration lines of known length and orientation in 3D space and applying the concepts of similar triangles. Two line segments are parallel to the image detector and another one is perpendicular to the image detector. The computer simulations and experiments were carried out which determines these parameters for our CCD based monoplane stereotactic prototype. The results were in agreement with the theoretical prediction. This calibration technique is applied to the stereo imaging system where the final calibration error is within 1.5 percent. The method is simple and reliable. One promising application of this technique for the calibration lies in digital mammography imaging guidance, but applications in other forms of radiographic imaging are possible also.

Videokeratography is a common method used by clinicians and researchers to estimate the surface topography of the human cornea. It is based on the object-to-image relationship of concentric rings reflected off the surface of the cornea. This technique works reliably in most cases for central cornea. However, the accuracy of corneal topography is reduced for peripheral cornea because of shadows caused by brows and nose and occlusions caused by eyelids. To achieve a broader coverage of the peripheral cornea, images of off- centered gaze in four directions could be combined. One of the difficulties associated with this approach is that the shape of image rings in the peripheral cornea become very irregular, z-shaped, due to abrupt change sin surface topography near the limbus. These irregularities cause complications for current algorithms for estimating the location of edges along each image ring. Many current algorithms make assumptions about he shape and relative positions of image rings to distinguish between different rings. These assumptions no longer hold with off-centered images since the image rings can deviate dramatically from an ellipsoid. Our algorithm overcomes this problem by using fewer assumptions combined with a robust segmentation algorithm to distinguish between image rings.

A pilot in vivo study was conducted to investigate the feasibility of using optical spectroscopy for brain tumor margin detection. Fluorescence and diffuse reflectance spectra were acquired using a portable clinical spectroscopic system from normal brain tissues, tumors, and tumor margins in 21 brain tumor patients undergoing craniotomy. Results form this study show the potential of optical spectroscopy in detecting infiltrating tumor margins of primary brain tumors.

A system for robotically assisted retinal surgery has been developed to rapidly and safely place lesions on the retina for photocoagulation therapy. This system provides real- time, motion stabilized lesion placement for typical irradiation times of 100 ms. The system consists of three main subsystems: a global, digital-based tracking subsystem; a fast, local analog tracking subsystem in previous SPIE presentations. This paper concentrates on the development of the confocal reflectance subsystem and its integration into the overall photocoagulation system. Specifically, our goal was to use measurable lesion reflectance growth curve parameters to develop a noninvasive method to infer lesion depth. This method will allow dynamic control of laser dosimetry to provide similar lesions across the non-uniform retinal surface.

Stereotactic neuronavigational systems have demonstrated significant clinical influence during the past decade, and are being used in an increasing number of neurosurgical procedures. Pre-operatively acquired 3D images are used for planning purposes, and also are employed in intraoperative navigations to help localize and resect brain lesions. However, as the operation progresses, multiple factors contribute the changes that limit the accuracy of the navigation based on pore-operative images alone. The opening of the dura with the associated loss of CSF and cortical swelling, the effect of gravity relative to the craniotomy location, tumor decompression, and collapse of neural tissue around the operative site are some of the factors that contribute to errors in navigation, particularly navigation based solely on pre-operatively acquired images. Neuronavigational system assume a one-to-one correlation between patient anatomy in the operating room and the pre- operatively acquired MRI images. Since the brain deforms in a non-linear manner, intraoperative brain shift can really only be corrected via intraoperative sensing methods that effectively update the pre-operatively acquired image data during surgery.

Successful extended contact lens wear requires lens motion that provides adequate tear mixing to remove ocular debris. Proper lens motion of rigid contact lenses is also important for proper fitting. Moreover, a factor in final lens comfort and optical quality for contact lens fitting is lens centration. Calculation of the post lens volume of rigid contact lenses at different corneal surface locations can be used to produce a volume map. Such maps often reveal channels of minimum volume in which lenses may be expected to move, or local minima, where lenses may be expected to settle. To evaluate the utility of our volume map technology and evaluate other models of contact lens performance we have developed an automated video-based lens tracking system that provides detailed information about lens translation and rotation. The system uses standard video capture technology with a CCD camera attached to an ophthalmic slit lamp biomicroscope. The subject wears a specially marked contact lens for tracking purposes. Several seconds of video data are collected in real-time as the patient blinks naturally. The data are processed off-line, with the experimenter providing initial location estimates of the pupil and lens marks. The technique provides a fast and accurate method of quantifying lens motion. With better contact lens motion information we will gain a better understanding of the relationships between corneal shapes, lens design parameters, tear mixing, and patient comfort.

Minimally invasive techniques often require special biomedical monitoring schemes. In the case of laser coagulation of tumors accurate temperature mapping is desirable for therapy control. While magnetic resonance (MR)-based thermometry can easily yield qualitative results it is still difficult to calibrate this technique with independent temperature probes for the entire 2D field of view. Calculated temperature maps derived from Monte-Carlo simulations (MCS), on the other hand, are suitable for therapy planning and dosimetry but typically can not account for the extract individual tissue parameters and physiological changes upon heating. In this work, online thermometry was combined with MCS techniques to explore the feasibility and potential of such a biomodal approach for surgical assist systems. For the first time, the result of a 3D simulation were evaluated with MR techniques. An MR thermometry system was used to monitor the temperature evolution during laser-induced thermal treatment of bovine liver using a commercially available water-cooled applicator. A systematic comparison between MR-derived 2D temperature maps in different orientations and corresponding snapshots of a 3D MCS of the laser-induced processes is presented. The MCS is capable of resolving the complex temperature patterns observed in the MR-derived images and yields a good agreement with respect to absolute temperatures and damage volume dimensions. The observed quantitative agreement is around 10 degrees C and on the order of 10 percent, respectively. The integrated simulation-and-monitoring approach has the potential to improve surgical assistance during thermal interventions.

In this work, we present a novel method for the simultaneous acquisition of ultrasonic attenuation and optical absorption using photoacoustically-generated ultrasound. We discuss the theory behind the technique and apply the method to measurements in mammalian tissue samples. We show that the frequency dependence of ultrasonic attenuation measured with this technique is consistent with conventionally determined values and thus holds promise for future work.

Recently the demand for hyperpolarized noble gases is arising to improve NMR spectroscopy resolution for imaging. Hyperpolarization of noble gases is achieved by spin- exchange with alkali metal. atoms that undergo optical pumping by circularly polarized radiation. Optical pumping is usually achieved by high power semiconductor lasers. These sources have a bandwidth very large when compared with the transition bandwidth of the optically active species. This has two serious consequences: (i) the request of high power lasers, (ii) the losses that the unemployed energy delivered to the Rb vapor can provide in the efficiency of the energy transfer. Object of our investigation will be the comparison of two experimental set ups for optical pumping of Rb vapor where pumping is given in one case by a dye laser pumped by a UV nitrogen laser built in our laboratory according to the Blumlein scheme and in the other case by a semiconductor laser. Major elements that will be discussed are (1) the role of stimulated emission of Rb vapor to increase the pumping efficiency, (2) the fate of resonant photons that are emitted during Rb decays, (3) the role of applied magnetic fields in the efficiency of pumping processes.

In endoscopic ophthalmic procedures care has to be exercised that the retina is protected from overexposure. Accordingly, it is advantageous if the endoscope is equipped with a stable and reliable automatic illumination control. To this end, an illumination control system has been devised, which consists of a mechanical iris and a digital control algorithm. The iris is designed such that it influences neither the spectral composition of the lightsource nor its aperture. It is furthermore linear with respect to the light intensity such that a fast control algorithm based on the data of a digital video camera used for observation purposes can be implemented. In order that no false signals are induced from specular reflections caused, e.g., by operating tools held in front of the camera, the control algorithm is designed such that reflections and true overexposure are distinguished from each other. For this purpose, the field of view is subdivided into small sectors and a statistical evaluation is made. The application under realistic conditions shows that the unit provides the user with a well illuminated image while the retina is reliably protected from overexposure.

Recent studies have indicated that polarized light may be useful in the discrimination between benign and malignant moles. In fact, imaging polarimetry could provide noninvasive diagnosis of a range of dermatological disease states. However, in order to design an efficacious sensor for clinical use, the complete polarization-altering properties of a particular disease must be well understood. We present Mueller matrix imaging polarimetry as a technique for characterizing various dermatological diseases. Preliminary Mueller matrix imagery at 633 nm suggests that both malignant moles and lupus lesions may be identified through polarimetric measurements. Malignant moles are found to be less depolarizing than the surrounding tissue, and lupus lesions are found to have rapidly varying retardance orientation.

A new four channel continuous wave near IR spectroscopy instrument for regional cerebral oxygenation monitoring has been developed. The instrument uses laser diodes to transmit pulses of near IR light at wavelengths of 775, 845 and 904 nm. The instrument incorporates an optical switching mechanism that switches transmitted and received light in turn to monitor four regions in a time period of 4 seconds. The stability and linearity of the instrument have been measured and indicate satisfactory performance of the system. Initial tissue phantom experiments with a scattering solution of (mu) _s' estimated at 0.5mm^-1 and black absorbing spheres of varying diameter embedded in the solution, were conducted to assess the capability of the instrument to differentiate between regional changes. These experiments involved moving the position of the transmitting and receiving fibers with respect to the spheres and observing the change in attenuation of the light intensity of the four regions. The results showed that the location of the absorber could be detected regionally. Results were also obtained form adult human forearm venous and arterial occlusions for 8 subjects. The forearm was chosen because the presence of two bones, the radius and the ulna, should create differences in regional measurements. Good correlation for percentage of venous oxygen saturation was observed in 7 of the subjects. Expected decreases in oxygenated hemoglobin and increases in deoxygenated hemoglobin were observed in 7 subjects after the application of arterial occlusions.

The liver has been identified as an ideal site to spectroscopically monitor for changes in oxygen saturation during liver transplantation and shock because it is susceptible to reduced blood flow and oxygen transport. Near-IR spectroscopy, combined with multivariate calibration techniques, has been shown to be a viable technique for monitoring oxygen saturation changes in various organs in a minimally invasive manner. The liver has a dual system circulation. Blood enters the liver through the portal vein and hepatic artery, and leaves through the hepatic vein. Therefore, it is of utmost importance to determine how the liver NIR spectroscopic information correlates with the different regions of the hepatic lobule as the dual circulation flows from the presinusoidal space into the post sinusoidal region of the central vein. For NIR spectroscopic information to reliably represent the status of liver oxygenation, the NIR oxygen saturation should best correlate with the post-sinusoidal region. In a series of six pigs undergoing induced hemorrhagic chock, NIR spectra collected from the liver were used together with oxygen saturation reference data from the hepatic and portal veins, and an average of the two to build partial least-squares regression models. Results obtained from these models show that the hepatic vein and an average of the hepatic and portal veins provide information that is best correlate with NIR spectral information, while the portal vein reference measurement provides poorer correlation and accuracy. These results indicate that NIR determination of oxygen saturation in the liver can provide an assessment of liver oxygen utilization.

The US Army Medical Research and Material Command together with the US Marine Corps Combat Development Command sponsored the design and production of a far-forward, lightweight, small footprint, reconfigurable, highly mobile Advanced Surgical Suite for Trauma Casualties (ASSTC) to reduce combat casualties and morbidity. The KIA fraction has remained relatively constant over major wars and conflicts since the early 1900s. One third of the KIA perish after 10 minutes. ASSTC has the potential to dramatically lower this fraction by providing resuscitative care within a short period of wound infliction and not requiring long transport times to the caregivers. ASSTC is also unique in its capability to serve in multiple missions including humanitarian aid, infectious disease control, and disaster relief. Adding field sensor to ASSTC greatly enhances the capability of this highly mobile system to operate in many areas.

Tissue pH electrodes have been used in research and in humans to evaluate various myocardial protection methods during heart surgery. Near IR spectroscopic measurement of myocardial tissue pH is a feasible, minimally invasive method that can be used to identify regional areas of ischemia and provide the surgeon with information continuously and postoperatively. Inhomogeneous, depth dependent tissue pH levels in ischemic myocardium make a robust in-vivo optical measurement challenging. Tissue heterogeneity requires a well-defined optical probe geometry capable of detecting light with adequate localization. Monte Carlo modeling of light propagation for purely scattering and relevant absorbing and scattering media were use4d to identify possible source-detector fiber separations for a matched boundary. In the region approximately 0.3 to 0.8 mm away from the source, the models demonstrated that minimization of the wavelength dependence of scattering is possible. Wavelength dependence is apparent at separations greater than approximately 1.2 mm. Adequate localization of NIR light is tissue is feasible within this source-detector separation range based on the simulations with hemoglobin as the only absorber. The application to a small fiber sensor's fabrication is discussed.

Near IR Spectroscopy (NIRS) can be employed to noninvasively and continuously measure in-vivo local changes in haemodynamics and oxygenation of human tissues. In particular, the technique can be particularly useful for muscular functional monitoring. We present a portable NIRS research-grade acquisition system prototype, strictly dedicate to low-noise measurements during muscular exercise. The prototype is able to control four LED sources and a detector. Such a number of sources allows for multipoint measurements or for multi-wavelength spectroscopy of tissue constituents other than oxygen, such as cytochrome aa₃ oxidation. The LEDs and the detector are mounted on separate probes, which carry also the relevant drivers and preamplifiers. By employing surface-mount technologies, probe size and weight are kept to a minimum. A single-chip mixed-signal RISC microcontroller performs source-to- detector multiplexing with a digital correlation technique. The acquired data are stored on an on-board 64 K EEPROM bank, and can be subsequently uploaded to a personal computer via serial port for further analysis. The resulting instrument is compact and lightweight. Preliminary test of the prototype on oxygen consumption during tourniquet- induced forearm ischaemia show adequate detectivity and time response.

The inhomogeneity of tissue structure greatly affects the sensitivity of tissue oxygenation measurement by near-IR spectroscopy (NIRS). We have proposed a method for correcting the influence of a subcutaneous fat layer on muscle oxygenation measurements. In this study, we validated our correction method by measuring oxygen consumption rates of the forearm muscle and comparing the measurements with those obtained by other techniques. ³¹P-magnetic resonance spectroscopy and positron emission tomography (PET). In NIRS, Vo₂mus was obtained from the falling rate of oxygenation in ischaemia tests. The values of Vo₂mos were corrected using a curve of measurement sensitivity against fat layer thicknesses, which were measured by ultrasonography. The corrected Vo₂mus showed greater values and less variation between individuals than did the uncorrected one. In the ³¹P-NMR measurements on 10 subjects, Vo₂mus was estimated from changes in phosphocreatine. The corrected Vo₂mus in NIRS correlated well with the measurements by ³¹P-NMR compared to the uncorrected Vo₂mus. This result suggested that our correction method is valid. Vo₂mus was also measured using PET in one of the authors. The measured values by NIRS. ³¹P-NMR and PET were 0.22, 0.17, 0.24 ml 100g^-1 min^-1, respectively. The measurement by NIRS using our correction method was in an acceptable range.

Hollow fibers for medical IR lasers are fabricated by silver-mirror plating and liquid-phase polymer coating method. The coating thicknesses of the inner polymer layer of the fibers are designed so that the fibers show low-loss property for medical IR lasers with various wavelengths, such as Nd:YAG at 1.06 micrometers , Er:YAG at 2.94 micrometers and CO₂ at 10.6 micrometers . Transmission characteristics of the fibers are shown. Small-bore fibers with inner diameters of 320 and 250 micrometers for low-loss Er:YAG laser transmission are successfully fabricated. These fibers show better flexibility and small additional loss when bent. A new fabrication procedure without curing-process is also proposed. By considering that end sealing is always an important task for hollow fibers in medical applications, various sealing materials, such as polyimide, cyclic olefin polymer, and fluorocarbon polymer are introduced and transmission properties are summarized.

The flexible hollow waveguides - a cyclic olefin polymer- coated silver hollow glass waveguides with various inner diameters - specially prepared for the delivery of high power 1.06 micrometers radiation were investigated using an oscillator-3 amplifiers Nd:YAG laser system. The length of a single pulse was equal to 50 psec. In dependence to a diameter of the waveguide, transmission/attenuation as a function of the input laser energy were measured together with the input/output time radiation characteristics and the spatial distribution of the output beam. The input energy up to 80 mJ, 70 mJ, and 30 mJ was transmitted with an efficiency higher that 90 percent for the COP/Ag hollow waveguides with a diameter of 1000 micrometers , 700 micrometers , and 540 micrometers , respectively. The picosecond temporal measurements show that the delivered pulse duration was not changed within a resolution of 5 picosecond. Therefore the maximum transmitted power reached was 1.5 GW. The characteristics obtained make all these waveguides very promising for the delivery of high-power laser pulse in special medical and other applications.

Hollow glass waveguides are an increasingly popular fiber- based delivery system for IR laser power. They are low loss and can be bent to radii less than 3 cm while maintaining an excellent modal distribution. The additional loss due to bending has been shown to scale linearly with the inverse of bending radius. For small bending radii however, this bending loss has bene shown to increase beyond this trend due to mode mixing. Oscillating modes have been observed by varying the radius of curvature for a waveguide bent into a single compete loop. Curved HGW distal tip prototypes of bore sizes 530 and 320 micrometers , were made and exhibited a 0.56 and a 0.17 dB increase in loss respectively over the straight waveguides.

Hollow fibers for transmitting high-power ArF-excimer laser light are fabricated by Metal Organic Chemical Vapor Deposition method. The hollow fibers with the inner diameter of 1 mm are fabricated by depositing an aluminum film on the inside of silica glass capillary by employing dimethylethylamine alane as the precursor. The fibers shows low-loss property, high durability, and high-energy threshold with the radiation of excimer lasers.

To suppress the laser-induced air breakdown which limited the transmission of 1064-nm Q-switched Nd:YAG laser pulses through hollow waveguide, a vacuum cell was attached to the waveguide ends, where the air was expelled for the cells as well as from the waveguide core region. With this scheme, the laser-induced air breakdown was completely suppressed, and in addition, the laser-induced damage threshold of the waveguide coating materials was significantly increased. Wit a 1-mm inner diameter, 1-m long, cyclic-olefin-polymer- coated silver hollow waveguide, a maximum transmitted laser energy reached approximately 200 mJ/pulse at 10 Hz in a straight waveguide condition. In a 90 degree-bent waveguide condition the laser-induced damage to the waveguide inner coating was observed, but a maximum transmitted energy in excess of 150 mJ/pulse at 10 Hz was obtained without any damage. With the transmitted laser pulses, sharp ablation in porcine myocardium tissues was demonstrated in vitro.

Mainly due to the unexpected progress in manufacturing of solarization-reduced all-silica fibers, new fiber-optic applications in the UV-region are feasible. However, the other components like the UV-sources and the detector- systems have to be improved, too. Especially, the miniaturization is very important fitting to the small-sized fiber-optic assemblies leading to compact and mobile UV- analytical systems. Based on independent improvements in the preform and fiber processing, UV-improved fibers with different properties have been developed. The best UV-fiber for the prosed applications is selectable by its short and long-term spectral behavior, especially in the region from 190 to 350 nm. The spectrum of the UV-source and the power density in the fiber have an influence on the nonlinear transmission and the damaging level; however, hydrogen can reduce the UV-defect concentration. After determining the diffusion processes in the fiber, the UV-lifetime in commercially available all-silica fibers can be predicted. Newest results with light from deuterium-lamps, excimer- lasers and 5th harmonics of Nd:YAG laser will be shown. Many activities are in the field of UV-sources. In addition to new UV-lasers like the Nd:YAG laser at 213 nm, a new low- power deuterium-lamp with smaller dimensions has been introduced last year. Properties of this lamp will be discussed, taking into account some of the application requirements. Finally, some new applications with UV-fiber optics will be shown; especially the TLC-method can be improved significantly, combining a 2-row fiber-array with a diode-array spectrometer optimized for fiber-optics.

Accurate cardiac modeling is challenging due to the intricate structure and complex contraction patterns of myocardial tissues. Fast imaging techniques can provide 4D structural information acquired as a sequence of 3D images throughout the cardiac cycle. To mode. The beating heart, we created a physics-based surface model that deforms between successive time point in the cardiac cycle. 3D images of canine hearts were acquired during one complete cardiac cycle using the DSR and the EBCT. The left ventricle of the first time point is reconstructed as a triangular mesh. A mass-spring physics-based deformable mode,, which can expand and shrink with local contraction and stretching forces distributed in an anatomically accurate simulation of cardiac motion, is applied to the initial mesh and allows the initial mesh to deform to fit the left ventricle in successive time increments of the sequence. The resulting 4D model can be interactively transformed and displayed with associated regional electrical activity mapped onto anatomic surfaces, producing a 5D model, which faithfully exhibits regional cardiac contraction and relaxation patterns over the entire heart. The model faithfully represents structural changes throughout the cardiac cycle. Such models provide the framework for minimizing the number of time points required to usefully depict regional motion of myocardium and allow quantitative assessment of regional myocardial motion. The electrical activation mapping provides spatial and temporal correlation within the cardiac cycle. In procedures which as intra-cardiac catheter ablation, visualization of the dynamic model can be used to accurately localize the foci of myocardial arrhythmias and guide positioning of catheters for optimal ablation.

Tissue oxygenation instruments which rely on phase sensitive detection suffer form phase-amplitude crosstalk, i.e. the phase of the detected signal with respect to a reference signal is dependent on the average intensity of the light entering the photomultiplier tube (PMT). If an instrument that detects the phase of the scattered signal is to yield the phase accuracy required in order to provide useful clinical parameters, quantitative haemoglobin and oxy- haemoglobin concentrations (Hb), and (HbO₂) and mixed arterial-venous saturation all sources of phase-amplitude effects must be understood. The phase-amplitude effect has in the past been attributed to the fact that the rise time of the detector decreases with increasing light intensity. In this work an additional phase-amplitude effect in intensity modulated near IR spectroscopy (IMNIRS) instrumentation is studied. The presence of a coherent interfering signal due to low level RF coupling at the detector output will corrupt the phase of the signal of interest and cause a phase-amplitude effect. Under certain conditions a relatively low level interfering RF signal can introduce a significant error in the slope of the phase per unit distance plot. A comparison between measured and modeled phase distortion is presented and ways to reduce the effect discussed. In addition to phase-amplitude effects, the final accuracy of the quantitative measurements made by an IMNIRS instrument depends heavily on the calibration. Calibration of the measured phase and the AC and DC components of the detected light must take into account distortions due to, (a) phase-amplitude crosstalk and system phase offset, (b) detector non-linearities, (c) variation in laser source intensity and phase with time and temperature, (d) optical probe light loss and (e) variations in detector sensitivity. Current instrument performance will be presented and discussed.

Near IR Spectroscopy (NIRS) can be employed to noninvasively and continuously measure in-vivo local changes in haemodynamics and oxygenation of human tissues. Monitoring of these parameters is particularly useful both for basic research and during surgery, when a continuous and real-time measurement can help to avoid permanent damage to the tissues. We present a modular acquisition system in which each subsystem, from the case to the single acquisition front-end is designed to meet all the requirements of a research-grade instrument, dedicated to intraoperatory measurements. Part of the modules of the acquisition system has been dedicated to multipoint NIRS. A module prototype has been developed, which is able to control four LED sources and two detectors. On each front-end a RISC microcontroller performs source and detector multiplexing with a digital correlation technique. A number of such modules can be independently addressed through a bus by a PC-based workstation for data collection, processing and visualization. Preliminary test of the prototype on tourniquet-induced forearm ischemia show adequate detectivity and time response. The operating parameters derived from the prototype will be employed in the design of a high channel count module, which will exploit the capabilities of a digital signal processor, for spatially mapped brain oxygenation monitoring.

The interaction of light with tissue has ben used to recognize disease since the mid-1800s. The recent developments of light sources, detectors, and fiber optic probes provide opportunities to measure these interactions, which yield information for tissue diagnosis at the biochemical, structural, or physiological level. In this paper, we describe a bioimaging system designed for biomedical applications and show laser-indued fluorescence (LIF) images mammalian brain tissue. The LIF imaging of tissue was carried out in vitro using two laser excitations: 488 nm and 514 nm. Images were recorded through an acousto- optic tunable filter over the range 500 nm-650 nm with a charged coupled device camera. Background subtracted images were generated across the fluorescent wavelength. Subtraction allowed a safe comparison to be made with well- contrasted images. Of the two tested excitation wavelengths, 488 nm excitation gave the more distinctive contrast.

Potentialities of a double-position CW laser sensing technique with an optimal base are studied to detect absorbing inhomogeneities in turbid media at large optical depths. In the frame of the diffusion approximation, we have found the cross-section of an absorbing inhomogeneity in a turbid medium and derived approximate expressions for irradiance distribution, the spatial profile and contrast of the object and the optimal base length. 2D-images of the object were constructed. A system with rotated base is presented. It enables to extract useful component from detected signal by measuring modulation amplitude. We have performed laboratory experiments on laser sensing of a black object in a model turbid medium in the reflective and transilluminative regimes and proved the validity of our theory. The results of this work demonstrate feasibility of the double-position CW laser sensing technique with the optimal source-receiver separation to detect and characterize absorbing inhomogeneities in biotissues at a depth of several photon transport mean free paths. We expect that this technique can be effectively applied to bioimaging to monitor in vivo the internal structure of the human tissue.

In this research a new way of express diagnostics of microbiocenosis and its disturbances is suggested. The express diagnostics of anaerobic infection allows to perform quick assessment of the injury microbiocenosis, the state of gastoenteric tract, the disbacteriosis presence and the degree of its development, to follow up dynamics of microflora variations in the process of medication treatment. The research were performed with optical PNC- method. The basic of the method is in registration of stimulated radiations and registration of their space fields, which occur in the process of probing radiation interaction with biological tissues and their active elements. The process is called Photon-undulatory Nonlinear Conversion or in short PNC-process. The optical diagnostic PNC-method developed here allows detecting the presence of anaerobic microflora directly at the bed of a patient. It makes possible to control the dynamic of patient rehabilitation process, providing strictly individual assessments.

The physical principles of building isotherms of enzyme adsorption on latexes by analysis of light dissipation are considered. The method of obtaining hydroperoxide latexes is described. The result of the reaction of adsorption of protacrine enzyme on hydroperoxide latexes are shown.

Profuse bleeding due to retinal tearing represents a common problem when working in the posterior chamber of the diabetic eye. If the traction and vibration associated with traditional vitrectomy tools could be eliminated, then many of their associated problems could also be removed. By investigating the tuning of laser energy in order to target the protein in the vitreous, rather than the bulk fluid, it is proposed that such a cutting device could be manufactured. A series of scans were performed on swine vitreous in order to determine its optical properties. A scanning spectrometer covering the region between 2.5 and 25 micrometers was used to scan both the vitreous and pure water samples. For each collagen scan, the water samples from either side were subtracted to give the absorption due to vitreous alone. It was found that there were several peaks of potential interest in the vitreous samples. As well as the water peak at around 3 micrometers, there was also a series of peaks between 6.2 and 6.5 micrometers. These latter bands represent absorption that is due to the proteins in the vitreous. Targeting these Amide bands could represent a possible method of targeting the laser energy without causing the collateral damage associated with high cutting or liquefaction rates. This could thus allow either higher aspiration rates while working in the center of the eye, or more precise removal of membranes in more delicate regions of the eye without any traction on the retina begin caused.