There is a need for technology capable of providing unique, sensitive, and rapid detection against threats posed by biological weapons, infectious diseases, and environmental pathogens. A potential solution presented herein is a photonic-based biosensor that utilizes a pair of diffractive phase gratings. This concept is merged with the ability to use surface chemistry techniques to precisely immobilize receptors at specific locations to create optical grating structures out of biological materials. The sensor is configured such that a change in the optical phase of diffracted laser light results when the refractive index profile of the 'bio-grating' is altered upon analyte binding to the molecular receptors within the grating structure. Because of the phase nature of the detection technique and the noise reduction nature of the grating geometry, the method is inherently sensitive with a potential for detecting small amounts of the unlabeled analyte. The optical transduction technique utilizing the gratings is described in detail. Data is presented addressing the analyte detection sensitivity from results generated from ideal optical glass gratings of varying etch depth. The fabrication techniques for creating gratings out of biological materials are discussed.

This work provides an overview of progress made, in our laboratory, towards the development of a practical biochipbased technology with a biofluidics system for the detection of E. coli and other pathogens. Efforts have been devoted towards efficient coupling between a compact biofluidics sample/reagent delivery system and an integrated circuit (IC) biochip, consisting of a 2-dimensional photosensor array, for on-chip monitoring of bioassays. The complementary metal-oxide semiconductor (CMOS) technology has been implemented to design and produce the IC biochip, which features a 4x4 array of independently addressable photodiodes that are integrated with amplifiers, discriminators and logic circuitry on a single platform. The CMOS-based biochip offers the advantages of compactness and low power consumption, making it better suited for field use than other array detectors, including CCDs. The biofluidics system includes a 0.4 mL hybridization chamber, which accommodates disposable sampling platforms embedded with bioreceptors for selective capture of pathogen DNA, proteins, or antibodies in discrete zones. The independently operating photodiodes of the IC biochip offer the capability of monitoring of multiple assays. Highlights of this work include highly sensitive detection of E. coli (<50 organisms) and quantitative capability with a linear dynamic range of 3-5 orders of magnitude for various assays.

In response to a broad-based need for point-of-care multiplex diagnostic capability, we have developed a novel hybrid platform to analyze optically encoded microspheres arranged on a 2-dimensional planar array. The microspheres which we have initially selected are developed by Luminex Inc. as substrates for sandwich-type fluorescent immunoassays and are typically used in conjunction with a customized flow analyzer. CCD-based optics are the essential feature which enables the development of a rugged diagnostic instrument which can be scaled for point-of-care applications. We have characterized the Multiplex Immunoassay Diagnostic System (MIDS) using a benchtop prototype built around a conventional 12-bit CCD. This system is capable of resolving up to 6 discrete classes of fluorescent microbeads, and measuring their corresponding reporter signal. The MIDS sensitivity to the phycoerythrin (PE) reporter compared favorably to that of the reference Luminex flow system, and is capable of identifying viral, bacterial, and protein simulants in laboratory samples, at concentrations less than 1μg/ml. The ability to resolve small differences in the average PE fluorescence is a direct function of CCD performance, and may be a necessary trade-off for developing a portable and economical detection system. However, we are confident that the MIDS platform can easily be scaled to meet the nominal requirements of any given point-of-care or screening application, and furthermore provide much-needed diagnostic functionality in this particular environment.

The fluorescent decay kinetics of an exogenous fluorescent dye injected or immobilized in a polymer implant can be sensitive to the biochemical environment of the tissue and can provide quantitative in vivo biochemical information of the tissue site. In this research project, we develop the rationale for NIR fluorescence spectroscopy of biologically relevant dyes for the sensing of analyte concentration, such as Ca²⁺, pH, glucose, etc. In vivo analytical sensing using fluorescence spectroscopy is complicated not only by the scattering of tissue, but also by the fact that most sensing fluorophores exhibit more than one (multi-exponential) decay lifetime. The objective of this paper is to demonstrate the concept of fluorescence lifetime spectroscopy in scattering media using a pH sensing dye, Carboxy Seminaphthofluorescein-1 (C-SNAFL-1). Work to extrapolate our results to an analyte-sensing dye construct embedded in a polymer are also presented. Supported by the National Institutes of Health (R01 CA67176).

The design of fiber-optic probes plays an important role in optical spectroscopic studies, including fluorescence spectroscopy of biological tissues. It can affect the light delivery and propagation into the tissue, the collection efficiency (total number of photons collected vs. total number of photons launched) and the origin of collected light. This in turn affects the signal to noise ratio (SNR) and the extend of tissue interrogation, thus influencing the diagnostic value of such techniques. Three specific fiber-optic probe designs were tested both experimentally and computationally via Monte Carlo simulations. In particular, the effects of probe architecture (single-fiber vs. two bifurcated multifiber probes), probe-to-target distance (PTD), and source-to-detector separation (SDS) were investigated on the collected diffuse reflectance of a Lambertian target and an agar-based tissue phantom. This study demonstrated that probe architecture, PTD, and SDS are closely intertwined and considerably affect the light collection efficiency, the extend of target illumination, and the origin of the collected reflected light. Our findings can be applied towards optimization of fiber-optic probe designs for quantitative fluorescence spectroscopy of diseased tissues.

We present a computational code capable of simulating time-resolved fluorescence emission from multi-layered biological tissues, and apply this code to model tissue fluorescence emission data acquired in vivo during clinical endoscopy. The code for multi-layered media is based on a Monte Carlo model we developed previously to simulate time-resolved fluorescence propagation in a semi-infinite turbid medium. Here, the code is applied to simulate data acquired from measurements on tissues in the lower gastrointestinal tract. Clinical data were obtained in vivo during endoscopy using a portable time-resolved fluorescence spectrometer employing a single fiber-optic probe for excitation and detection. Tissue was modeled as a two-layered medium consisting of a mucosal layer of finite thickness above a sub-mucosal layer. The emitted fluorescence was considered as arising from mucosal epithelial cells, due to the presence of nicotinamide dinucleotide as the constituent fluorophore (lifetime τ = 1.5 ns), and from sub-mucosal structural proteins (collagen, lifetime τ = 5.2 ns). Simulations modeled changes in tissue pathology as a function of independently changing the mucosal layer thickness, the fluorophore absorption coefficients and the fluorescence quantum yields. It was observed that the emanating fluorescence from the mucosal layer changes by ~50-60% with these changes resulting in appreciable differences of ~2 ns in the average lifetimes. These simulations indicate that it may be possible to quantify the fluorescence observed from tissue based on both biochemical and histological criteria. The simulations may also be used to provide a useful method for designing and testing the efficacies of different fiber-probe geometries.

In this communication, we report the design, development, calibration, and characterization of a fluorescence spectroscopy instrument capable of measuring time-resolved fluorescence spectra from 350nm to 800nm with subnanosecond resolution. The compact system can be used in a variety of clinical settings including endoscopic procedures. The instrument can accommodate various types of laser sources and fiber optic probes for different types of applications. The typical acquisition time is about 0.8 s per wavelength or 40 s for a 200 nm time-resolved fluorescence spectrum including online fluorescence lifetime analysis. The system has a variable spectral resolution from 0.1 to 10 nm and temporal resolution of 300 ps. Fluorescence spectra can be acquired with a sensitivity of 10^-9M at signal-to-noise ratio of 46. The fluorescence lifetimes of Rhodamin B and 9- cyanoanthracene were determined to be 2.92∓0.12 ns and 12.28∓0.12 ns indicating good agreement with literature values.

Laser-induced fluorescence (LIF) is used for in-vivo cancer diagnosis of the esophagus and skin cancer. For esophageal measurements a fiberoptic probe inserted through an endoscope was used. Autofluorescence of normal and malignant tissues were measured directly on patient skin without requiring an endoscope. Measurement of the fluorescence signal from the tissue was performed using laser excitation at 410 nm. The methodology was applied to differentiate normal and malignant tumors of the esophagus and malignant skin lesions. The results of this LIF approach were compared with histopathology results of the biopsy samples and indicated excellent agreement in the classification of normal and malignant tumors for the samples investigated.

To evaluate the capabilities of a calibrated autofluorescence imaging method for detecting neoplastic lesions, an imaging system that records autofluorescence images calibrated by the cross-polarized reflection images from excitation was instrumented. Cervical tissue was selected as the living tissue material. Sixteen human subjects were examined in vivo with the imaging system before the loop electrosurgical excision procedure (LEEP). It was found that neoplastic lesions can be differentiated from surrounding normal tissue based on the contrast in the calibrated autofluorescence signals, which from neoplastic lesions were generally lower than that from normal cervical tissue.

Carotenoid antioxidants form an important part of the human body's anti-oxidant system and are thought to play an important role in disease prevention. Studies have shown an inverse correlation between high dietary intake of carotenoids and risk of certain cancers, heart disease and degenerative diseases. For example, the carotenoids lutein and zeaxanthin, which are present in high concentrations in the human retina, are thought to prevent age-related macular degeneration, the leading cause of blindness in the elderly in the Western world. We have developed various clinical prototype instruments, based on resonance Raman spectroscopy, that are able to measure carotenoid levels directly in the tissue of interest. At present we use the Raman technology to quantify carotenoid levels in the human retina, in skin, and in the oral cavity. We use resonant excitation of the π-conjugated molecules in the visible wavelength range and detect the molecules' carbon-carbon stretch frequencies. The spectral properties of the various carotenoids can be explored to selectively measure in some cases individual carotenoid species linked ot the prevention of cancer, in human skin. The instrumentation involves home-built, compact, high-throughput Raman systems capable of measuring physiological carotenoid concentrations in human subjects rapidly and quantitatively. The instruments have been demonstrated for field use and screening of tissue carotenoid status in large populations. In Epidemiology, the technology holds promise as a novel, noninvasive and objective biomarker of fruit and vegetable uptake.

Compressive stress on bone, cartilage and other tissues accompanies normal activity. While the biomechanical properties of many tissues are reasonably well-understood at many levels of structure, surprisingly little is known at the ultrastructural and crystal lattice levels. We show how the use of diamond anvil cell Raman microspectroscopy enables a deeper understanding of the response of tissue to mechanical stress. We discuss the reversible responses of deproteinated and intact bone powders to hydrostatic pressure and compare these responses to those of a model compound, synthetic carbonated apatite.

We describe the development of a surface-enhanced Raman scattering gene (SERGen) probe technology for rapid screening for diseases and pathogens through DNA hybridization assays. The technology combines the use of gene probes labeled with SERS-active markers, and nanostructured metallic platforms for inducing the SERS effect. As a result, SERGen-based methods can offer the spectral selectivity and sensitivity of SERS as well as the molecular specificity of DNA sequence hybridization. Furthermore, these new probe s preclude the use of radioactive labels. As illustrated herein, SERGen probes have been used as primers in polymerase chain reaction (PCR) amplifications of specific DNA sequences, hence further boosting the sensitivity of the technology. We also describe several approaches to developing SERS-active DNA assay platforms, addressing the challenges of making the SERGen technology accessible and practical for clinical settings. The usefulness of the SERGen approach has been demonstrated in the detection of HIV, BRCA1 breast cancer, and BAX genes. There is great potential for the use of numerous SERGen probes for multiplexed detection of multiple biological targets.

Optical coherence tomography (OCT) is a cross-sectional imaging modality capable of acquiring images to depths of a few millimeters at resolutions ranging from 10-15 μm. This makes OCT useful for visualizing layers and structures within the tissue, but not effective for seeing in vivo cellular level detail. Random spatially dependent speckle patterns were seen in our images due to the coherent properties of light utilized in OCT. These speckle patterns are dependent on various optical parameters of the system, including numerical aperture, as well as the size and distribution of light scattering particles within the sample. The purpose of this study is to evaluate the application of statistical and spectral texture analysis techniques for differentiating tissue types based on the structural and speckle content in OCT images. Good correct classification rates were obtained when five different bovine tissues were compared in pairs, averaging 80% correct, and reasonable rates were obtained comparing normal vs. abnormal mouse lung tissue, averaging 64.0% and 88.6%, respectively. This study has shown that texture analysis of OCT images may be capable of differentiating tissue types without reliance on visible structures.

Current patient monitoring procedures in hospital intensive care units (ICUs) generate vast quantities of medical data, much of which is considered extemporaneous and not evaluated. Although sophisticated monitors to analyze individual types of patient data are routinely used in the hospital setting, this equipment lacks high order signal analysis tools for detecting long-term trends and correlations between different signals within a patient data set. Without the ability to continuously analyze disjoint sets of patient data, it is difficult to detect slow-forming complications. As a result, the early onset of conditions such as pneumonia or sepsis may not be apparent until the advanced stages. We report here on the development of a distributed software architecture test bed and software medical models to analyze both asynchronous and continuous patient data in real time. Hardware and software has been developed to support a multi-node distributed computer cluster capable of amassing data from multiple patient monitors and projecting near and long-term outcomes based upon the application of physiologic models to the incoming patient data stream. One computer acts as a central coordinating node; additional computers accommodate processing needs. A simple, non-clinical model for sepsis detection was implemented on the system for demonstration purposes. This work shows exceptional promise as a highly effective means to rapidly predict and thereby mitigate the effect of nosocomial infections.

We report on development of a new type of tissue analysis that facilitates a comprehensive method to characterize tissues and simultaneously identifies significant genes, based on the combination of different statistical approaches using co-variants such as quantitative microscopical tissue data. The introduction of tissue imaging into bioinformatics relies on a computer assisted histomorphometry, which enables tissue imaging to be executed in a fully automated, high-throughput fashion with quantitative analytical capabilities. As cells and tissues are centrally located in the biological hierarchy of function, improvements in the ability to obtain more quantitative information about tissue structure are critical to elucidate upstream functional effects of gene and protein expression. Furthermore, a detailed quantitative description of tissues may be expected to improve diagnosis and the understanding of structure and function of larger tissue constructs and organs in normal and disease states. Particular methods are described here that correlate gene expression to tissue structural data, essentially linking a bottom-up and top-down methodology important for improvement of diagnosis and discovery informatics.

We study possibilities of implementation of Surface Plasmon Resonance (SPR) sensors on purely silicon platform, in which SPR-supporting Au film is used with a silicon prism in the Kretschmann-Raether geometry. Based on theoretical and experimental analyses we have determined the conditions and parameters of SPR excitations on such a platform in the infrared light for configurations of bio- and gas sensing. The approach enables one to apply well-developed silicon microfabrication and integration methods for SPR technique, opening up the possibilities to miniaturize SPR bio- and chemical sensors.

Pathologist study tissue samples to determine the presence and nature of diseases. Morphology is a critical component to identifying cellular and tissue structures and the functional changes produced by disease. Technical advances in the field of pathology have primarily been in the areas of tissue preparation and the staining process that enhances the pathologist's identification of these structures. Pathologist's primary tool for diagnosis has remained the same for over a century--the optical microscope. Radiology has made tremendous advances with digitization and the ease of exchange and image analysis that comes with digital data and today's computer technology. Pathology is primed to enter the digital era as well. The major hurdles to wide spread acceptance of conversion to digital pathological imaging have been image resolution, scanner throughput, image file size and image display rates. InterScope Technologies, Inc. has developed a high-throughput, high-resolution microscopic slide digitization system that is well suited for pathological examination and diagnosis. This system is fully automated, captures at 0.3 μm per pixel, and can capture a slide in under 3 minutes, and has the potential to capture much faster. This paper will present the technical challenges associated with digital pathological imaging and how InterScope has addressed these challenges in the development of their digital scanner.

Slide-based cytometry (SBC) is a promising new development in clinical diagnostics. The Laser Scanning Cytometer (LSC) was the first such system that became commercially available. Over the years methods have been developed that can be applied in a broad variety of clinical diagnostic settings. The principle of SBC is that fluorochrome labeled specimens are immobilized on microscopic slides which are placed on a conventional epi-fluorescence microscope. Specimens are analyzed by one or two lasers. Data comparable to flow cytometry are generated. But in addition, the position of each individual event is recorded, a feature that allows to re-localize and to visualize each event that has been measured. The major advantage of LSC compared with other cytometric methods is the combination of two features: a) the minimal clinical sample volume needed, and b) the connection of fluorescence data and morphological information about the measured event. We have developed and will present examples of different techniques for application in clinical diagnosis: (1) Immunophenotyping using up to six different fluorochromes at a time, (2) analysis of minimal sample volumes using fine needle aspirate biopsies, and (3) analysis of cells in tissue sections. With these assays and assays developed by others, SBC has proven its wide spectrum of clinical applicability and can be introduced as a standard technology for multiple clinical settings.

In medical practice the monitoring of organ and tissue vitality is a critical need in operating rooms as well as in intensive care units (ICUs). The concept of multiparametric monitoring of tissue vitality was described in details in our previous publication. The device, called "Tissue Spectroscope" (TiSpec), contained a single light source (325nm) used as an excitation light. The emitted-reflected light from the tissue was analyzed to provide real-time information on the following three parameters: microcirculatory tissue blood flow, mitochondrial NADH redox state and tissue reflectance. Those 3 parameters represent the main components of tissue O2 balance under in vivo conditions. The 325nm He:Cd laser used was a large bulky and expensive to operate as a critical component in a modern medical device unit. The development of an ultraviolet laser diode by Nichia, Japan, enabled us to replace the light source of the TiSpec with a 390nm laser diode, stabilized by a system developed by Toptica Photonics AG. This change in light source permitted the construction of a second model of the TiSpec, having the following advantages: 1. Smaller in dimensions, 2. Safer in terms of UV radiation effects, 3. Better stabilized for long term monitoring. The new TiSpec was tested in various animal studies as well as in various clinical applications. In order to monitor the brain during neurosurgical procedures, two special fiber optic probes were developed and used. Preliminary studies have shown that the 390nm based TiSpec could be used in monitoring of various organs.

We describe a new approach for the parallel reading of the response of micromechanical sensors in array using an interferential imaging method coupled with a multichannel lock-in detection. The mechanical response of each sensor is deduced from the image of their topography. The goal is the detection of stress changes through the measurement of induced topography changes between loaded sensors and reference sensors. A measurement of the out-of-plane displacement field is a sensitive and reliable method to determine the mechanical stress in microcantilevers. In this study gold-covered SiO₂ cantilevers have been used as sensors and a displacement measurement sensitivity of 230 pm has been achieved with no averaging. Such a value is equivalent to a stress change sensitivity better than 0.001 MPa for our application. The fields of application extend from DNA biochips to environmental sensors.

An ongoing clinical study of an experimental infrared (IR) device, the Vein Contrast Enhancer (VCE) that visualizes surface veins for medical access, indicates that a commercial device with the performance of the existing VCE would have significant clinical utility for even a very skilled phlebotomist. A proof-of-principle prototype VCE device has now been designed and constructed that captures IR images of surface veins with a commercial CCD camera, transfers the images to a PC for real-time software image processing to enhance the vein contrast, and projects the enhanced images back onto the skin with a modified commercial LCD projector. The camera and projector are mounted on precision slides allowing for precise mechanical alignment of the two optical axes and for measuring the effects of axes misalignment. Precision alignment of the captured and projected images over the entire field-of-view is accomplished electronically by software adjustments of the translation, scaling, and rotation of the enhanced images before they are projected back onto the skin. This proof-of-principle prototype will be clinically tested and the experience gained will lead to the development of a commercial device, OnTarget!, that is compact, easy to use, and will visualize accessible veins in almost all subjects needing venipuncture.

Thermotherapies such as radio-frequency ablation achieve necrosis of liver tumors through thermal coagulation and are frequently employed when surgical resection is impossible. Currently, thermotherapy procedures suffer from the lack of an adequate feedback control system, making it difficult to know precisely when to terminate therapy. In vitro and in vivo studies were performed on canine liver tissue to determine the feasibility of using fluorescence and diffuse reflectance spectroscopy to provide an objective endpoint for these procedures. The fluorescence and diffuse reflectance spectra of liver tissue exhibited consistent changes over the coagulation process. In vitro results showed a shift in the primary fluorescence peak from 490 nm in the native state to 510 nm in the fully coagulated state; in addition, a three- to four-fold increase in the absolute intensity of the diffuse reflectance spectra was observed upon complete coagulation. Similar spectral alterations were obtained in vivo. Based on our results, fluorescence and diffuse reflectance spectroscopy provide a direct way to assess the biochemical and structural changes associated with tissue thermal damage; hence, they can be developed into a feedback system for thermotherapies.

We observed a difference in the thermal response of localized reflectance signal of human skin between type-2 diabetic and non-diabetic volunteers. We investigated the use of this thermo-optical behavior as a basis for a non-invasive method for the determination of the diabetic status of a subject. We used a two-site temperature differential method, which is predicated upon the measurement of localized reflectance from two areas on the surface of the skin, each of these areas is subjected to a different thermal perturbation. The response of skin localized reflectance to temperature was measured and used in a classification algorithm. We used a discriminant function to classify subjects as diabetics or non-diabetics. In a prediction set of 24 non-invasive tests collected from 6 diabetics and 6 non-diabetics, the sensitivity ranged between 73% and 100%, and the specificity ranged between 75% and 100%, depending on the thermal conditions and probe-skin contact time. The difference in thermo-optical response of the skin of the two groups may be explained in terms of difference in response of cutaneous microcirculation to temperature, which is manifested as a difference in the near infrared light absorption and scattering. Another factor is the difference in the temperature response of the scattering coefficient between the two groups, which may be caused by cutaneous structural differences induced by non-enzymatic glycation of skin protein fibers, and/or by the difference in blood cell aggregation.

Radio frequency (RF) lesioning in the human brain is a common surgical therapy for relieving severe pain as well as for movement disorders such as Parkinsonia. During the procedure a small electrode is introduced by stereotactic means towards a target area localized by CT or MRI. An RF-current is applied through the electrode tip when positioned in the target area. The tissue in the proximity of the tip is heated by the current and finally coagulated. The overall aim of this study was to improve the RF-technique and its ability to estimate lesion size by means of optical methods. Therefore, the optical differences between white and gray matter, as well as lesioned and unlesioned tissue were investigated. Reflection spectroscopy measurements in the range of 450-800 nm were conducted on fully anesthetized pigs during stereotactic RF-lesioning (n=6). Light from a tungsten lamp was guided to the electrode tip through optical fibers, inserted along a 2 mm in diameter monopolar RF-electrode. Measurements were performed in steps of 0-10 mm from the target in each hemisphere towards the entry point of the skull. In the central gray of the porcine brain measurements were performed both before and after the creation of a lesion. A total of 55 spectra were collected during this study. Correlation to tissue type was done using post-operative MR-images. The spectral signature for white and gray matter differs significantly for the entire spectral range of 450-800 nm. Pre- and post-lesioning reflection spectroscopy showed the largest differences below 600 and above 620 nm, which implies that lasers within this wavelength range may be useful for in-vivo measurements of tissue optical changes during RF-lesioning.

A customized dual CCD based optical mapping system is designed and constructed for the purpose of applying ratiometry to the study of cardiac arrhythmia mechanisms. The system offers 490 frames per second data acquisition speed, 128 by 128 detector elements and 12 bits digitization. Each CCD camera is dedicated to imaging a specific region of the di-4-ANEPPS emission spectrum, through the use of appropriate filtering, the red region (635 ∓ 27.5nm) and the green region (532nm ∓ 19nm). The resulting two dimensional images collected from each spectrum region behaved consistently with the spectrum shift characteristics of di-4-ANEPPS, with the fluorescence intensity of the red region decreasing during action potential and the fluorescence intensity of the green region increasing during action potential. By taking the ratio of the two images, a ratiometric signal is constructed that offered improved uniformity in fluorescence intensity distribution, compared to the individual regional images.

Our objective is to develop a 3D endoscopic system which can be used to evaluate physical characteristics, such as perimeter and depth of objects. We describe here our dual-channel endoscopic system which relies on the structured light (SL) technology to project structured light and generate feature points on the imaged object for the measurement of surface profile. Using a modified pin-hole camera model the imaging and projection channels of the endoscope were calibrated and the distortions of both channels were corrected. Analysis of the imaged object gives the 3D surface points after establishing correspondence and triangulation. We report on the initial performance of this system on objects of known geometries. The results demonstrate the potential of the technology in clinical applications.

An integrated 3D medical image processing and analysis system we developed can provide powerful functions such as image preprocessing, virtual cutting, surface rendering, volume rendering, and manipulation. The system description, the method adopted and the application examples are presented. The system can be widely applied to processing and analysis of CT and MR images.

One of the most popular level set algorithms is the so-called fast marching method. In this paper, a medical image segmentation algorithm is proposed based on the combination of fast marching method and watershed transformation. First, the original image is smoothed using nonlinear diffusion filter, then the smoothed image is over-segmented by the watershed algorithm. Last, the image is segmented automatically using the modified fast marching method. Due to introducing over-segmentation, the arrival time the seeded point to the boundary of region should be calculated. For other pixels inside the region of the seeded point, the arrival time is not calculated because of the region homogeneity. So the algorithm’s speed improves greatly. Moreover, the speed function is redefined based on the statistical similarity degree of the nearby regions. We also extend our algorithm to 3D circumstance and segment medical image series. Experiments show that the algorithm can fast and accurately obtain segmentation results of medical images.

In the recent past, optical polarimetry has been shown as a potential method for noninvasive physiologic glucose sensing in the eye. Although the necessary sensitivity and accuracy have been demonstrated experimentally through in vitro studies using a range of media from simplistic glucose doped-water to more complex media such as aqueous humor, the main problem currently hindering long-term in vivo measurements is corneal birefringence coupled with motion artifact. This is due to the inability to distinguish E-field rotation due to glucose from the effects of time varying corneal birefringence. In this investigation, the effect of corneal birefringence will be discussed and a potential method to overcome this problem will be presented with supporting results.

The Transmissible Venereal Tumor (TVT) is a very common neoplasic disease in a free-roaming dogs which affects the extern genital and presenting resistance to conventional drugs that promote high toxicity. Photodynamic Therapy (PDT) is based in tumor cells irradiation after absorption of photosensitizer substance. At present, the protoporphirin IX (PP IX) has been explored in PDT due to be endogen, then it does not present toxicity effect. This substance can be obtained by exogenous way through aminolevulinic acid (5-ALA) administration in patient. The aim of this work was establish the optimal conditions for PDD (Phodynamic Diagnosis) to irradiate the tumor after ALA administration through fluorescence spectroscopy to improve the results with PDT. In this research was studied the 5-ALA 20% absorption in TVT of vaginal and penial mucous of a female and a male dog, respectivaly. This drug was administrated topically and after 30 minutes the fluorescence spectra were collected in intervals of 15 minutes during 120 minutes. The results showed that the maximum peak of PP IX in the tumor was between 60 and 105 minutes after the ALA application. In conclusion, the optimum effect will be achieved irradiating the tumor tissue into this period.

We have developed an optical probe for local determination of tissue optical properties using a small source-detector separation (<1mm). A 1310nm LED (25 μW) coupled to a fiber with 62.5 μm diameter was used as the light source and multiple detector fibers were employed to achieve spatially resolved reflectance measurement. Each detector fiber has a diameter of 62.5 μm and apart away 125 μm from each other. Pin detectors and continuous wave detection scheme were performed to obtain a sensitivity of 4x10⁹V/W and 82dB dynamic range. Applied to the normal human skin in the forearm, 63dB signal to noise ration can be achieved with a time resolution less than 1 second. The absorption and scattering coefficientions of tissue can be calculated by generalized diffusion approximation with measured reflective intensity. In this paper, we discussed the design of the system in general, and then described our instrument, along with the technique issues that influenced its design. Phantom experimental was performed to analyze the relationship between the reflectance light and the optical properties (μ_a, μ_s). The results showed that this optical probe could be used for local determination of tissue optical properties.

When light interacts with tissue, it can be absorbed, scattered or reflected. Such quantitative information can be used to characterize the optical properties of tissue, differentiate tissue types in vivo, and identify normal versus diseased tissue. The purpose of this research is to develop an algorithm that determines the reduced scattering coefficient (μ_s’) of tissues from a single optical reflectance spectrum with a small source-detector separation. The basic relationship between μ_s’ and optical reflectance was developed using Monte Carlo simulations. This produced an analytical equation containing μ_s’ as a function of reflectance. To experimentally validate this relationship, a 1.3-mm diameter fiber optic probe containing two 400-micron diameter fibers was used to deliver light to and collect light from Intralipid solutions of various concentrations. Simultaneous measurements from optical reflectance and an ISS oximeter were performed to validate the calculated μ_s’ values determined by the reflectance measurement against the 'gold standard’ ISS readings. The calculated μ_s’ values deviate from the expected values by approximately ∓ 5% with Intralipid concentrations between 0.5 − 2.5%. The scattering properties within this concentration range are similar to those of in vivo tissues. Additional calculations are performed to determine the scattering properties of rat brain tissues and to discuss accuracy of the algorithm for measured samples with a broad range of the absorption coefficient (μ_a).

A photon pair density wave (PPDW) is initiated and compared with the conventional defused photon density wave (DPDW) to verify its optical properties generated by correlated parallel polarized pair photons propagating in a scattering medium. An optical heterodyne signal is generated by the scattered correlated pair photons in the scattering medium. However, the phase delay of the signal depends upon the beat frequency and the distance between source and detector. This is similar to DPDW at the lower modulated frequency of laser source in frequency domain. Spherical wave fronts of constant attenuated intensity and the phase delay of PPDW are observed in a homogenous scattering medium by using a lock-in amplifier. The assumption that polarized photon pairs propagating as photon density wave in a multiple scattering medium is verified experimentally. Optical properties of PPDW in the scattering medium are demonstrated successfully.

An experimental and numerical study is performed to analyze short pulse laser propagation through tissue phantoms without and with inhomogeneities / tumors imbedded in it. Short pulse laser probing techniques has distinct advantages over conventional very large pulse width or cw lasers primarily due to the additional information conveyed about the tissue interior by the temporal variation of the observed signal. Both the scattered temporal transmitted and reflected optical signals are measured experimentally using a streak camera for samples irradiated with a short pulse laser source. Parametric study involving different scattering and absorption coefficients of tissue phantoms and inhomogeneities as well as the detector position and orientation is performed. The temporal and spatial profiles of the scattered optical signals are compared with the numerical modeling results obtained by solving the transient radiative transport equation using discrete ordinates technique.

The primary treatment for brain tumors with infiltrating margins is surgical resection. However at the present time this method is limited by visual discrimination between normal and neoplastic marginal tissues during surgery. Imaging modalities such as CT, MRI, PET, and optical imaging techniques can accurately localize tumor margins. We hypothesize that coupling the fine resolution of current imaging techniques with the precise cutting of mid-infrared lasers through image-guided neurosurgery has the potential to enhance tumor margin resection. This paper describes a feasibility study designed to optically track in three-dimensional space the articulated arm delivery of a non-contact ablative laser beam. Infrared-emitting diodes (IRED's) were attached to the handheld probe of an articulated arm to enable optical tracking of the laser beam focus in the operating room. Crosstalk between the infrared laser beam and the tracking diodes was measured. The geometry of the adapted laser probe was characterized to allow tracking the laser beam focus projected in front of the articulated arm. The target localization accuracy was assessed. Stray laser light did not affect optical tracking accuracy. The mean target registration errors while optically tracking the laser beam focus was 3.16 ∓ 1.04 mm. Analysis of target localization errors indicated that precise optical tracking of a laser beam focus in three-dimensional space is feasible. However, since the projected beam focus is spatially defined relative to the tracking diodes, tracking accuracy is highly sensitive to laser beam delivery geometry and beam trajectory/alignment out of the articulated arm.

This paper discusses a potential solution by mounting micro sensors on the tip of a 0.0018" catheter guidewire that can measure local fluid properties, such as pressure, pressure gradient, temperature, and species concentration levels. A design for mounting the sensors on the guidewire tip is proposed. The technique involves etching of picket shaped cavities on the silicon chip carrier. The MEMS sensor is then flip-chip bonded on to the silicon carrier. The design is biologically compatible, minimizing the exposure of potentially hazardous materials to the arterial system. Further, electrical and mechanical connections are robust, while the profile remains within the 0.018" outside diameter of the guide-wire. Basic design for manufacturability issues such as, materials constraints, minimization of parts and working surfaces, providing nesting features, and modular design have been addressed while arriving at the final design. The focus of the current paper is on pressure sensors but the design is generic and should be applicable for the other types of sensors also.

Array biosensors provide the capability of immobilizing multiple capture biomolecules onto a single surface and therefore offer the exciting prospect of multi-analyte detection. A miniaturized, fully automated, stand-alone biosensor is reported which can simultaneously test multiple samples for multiple analytes. This portable system (< 10 lbs) is particularly appropriate for on-site monitoring for food safety, infectious disease detection, and biological warfare defense. The surface-selective nature of this technology allows determination of binding constants and tracking of both specific and non-specific binding events as they occur. Thus, it provides an exciting new research tool for characterizing the interactions of biomolecules with surfaces or immobilized receptors in real time. This capability has important implications for development of new materials and sensors.