Optical polarimetry as a method to monitor glucose levels in the aqueous humor has shown promise as a way to noninvasively ascertain blood glucose concentration. A major limiting factor to polarimetric approaches for glucose monitoring in the aqueous humor is time varying birefringence due to motion artifact. Here, we present a modulation approach for real-time polarimetry that is capable of glucose monitoring in vitro at optical modulation frequencies of tens of kHz and includes the DC-compensation in a single device. Such higher frequency modulation has the potential benefit of improving the signal-to-noise ratio of the system in the presence of motion artifacts. In this report we present a near real-time closed-loop single wavelength polarimeter capable of glucose sensing in vitro at an optical modulation frequency of 32 kHz. The single wavelength polarimetric setup and in vitro glucose measurements will be presented demonstrating the sensitivity and accuracy of the system. Our PID control system can reach stability in less than 10 ms which is fast enough to overcome motion artifact due to heart beat and respiration. The the system can predict the glucose concentration with a standard error of less than 18.5 mg/dL and a MARD of less than 6.65% over the physiologic glucose range of 0-600 mg/dL. Our results indicate that this optical modulation approach coupled with dual-wavelength polarimetry has the potential to improve the of the dual-wavelength approach for in vivo glucose detection applications.

In recent years, significant advances have been made in the development of noninvasive polarimetric glucose detection systems, salutary for the treatment of our rapidly increasing diabetic population. This area of research utilizes the aqueous humor as the detection medium for its strong correlation to blood glucose concentration and highlights three major features: the optical activity of glucose, minimal scattering of the medium, and the ability to detect sub-millidegree rotation in polarized light. However, many of the current polarimetric systems are faced with size constraints based on the paramount optical components. As a step toward developing a low cost hand-held design, our group has designed a miniaturized integrated single-crystal Faraday modulator/compensator. This device is capable of replacing the traditional two component arrangement that has been widely reported on in many Faraday-based polarimetric configurations. In this study, the newly designed prototype is compared with a theoretical model and its performance is evaluated experimentally under both noninvasive static and dynamic glucose monitoring conditions. The combined rotator can achieve modulation depths above 1°, and when operating in a compensated closed-loop configuration, it has demonstrated glucose prediction errors of 1.8 mg/dL and 5.4 mg/dL under hypoglycemic and hyperglycemic conditions, respectively. These results demonstrate that such an integrated design can perform similar if not better than its larger two-part predecessors. This technology could also be extended to facilitate the use of multispectral polarimetry by considerably reducing the required number of physical components. Such multispectral techniques have demonstrated usefulness for in vivo and multi-analyte noninvasive sensing.

Competitive binding assays based on the protein Concanavalin A (ConA) have been proposed as potential sensors for continuous glucose monitoring applications. However, ConA-based assays in the literature have primarily displayed a lack of sensitivity or a lack of repeatability in their glucose response. This work explores this apparent trade-off by separating the measured glucose response into the recognition and fluorescence transduction mechanisms. The recognition responses are modeled for typical competing ligands/assays used in the literature, and they are combined with an optimized fluorescence approach to yield expected fluorescent glucose responses. Because aggregation is known to increase the apparent affinity between multivalent ligands and multivalent receptors, preliminary models are generated for assays that were initially optimized with multivalent ligands but increase in affinity over time. These models accurately predict the low sensitivity for monovalent ligands and the lack of repeatability in the responses with multivalent ligands as seen in the literature. This subsequently explains the aforementioned trade-off no matter the optical approach.

Due to the increasing prevalence of diabetes, research toward painless glucose sensing continues. Oxygen sensitive phosphors with glucose oxidase (GOx) can be used to determine glucose levels indirectly by monitoring oxygen consumption. This is an attractive combination because of its speed and specificity. Packaging these molecules together in “smart materials” for implantation will enable non-invasive glucose monitoring. As glucose levels increase, oxygen levels decrease; consequently, the luminescence intensity and lifetime of the phosphor increase. Although the response of the sensor is dependent on glucose concentration, the ambient oxygen concentration also plays a key role. This could lead to inaccurate glucose readings and increase the risk of hyper- or hypoglycemia. To mitigate this risk, the dependence of hydrogel glucose sensor response on oxygen levels was investigated and compensation methods explored. Sensors were calibrated at different oxygen concentrations using a single generic logistic equation, such that trends in oxygen-dependence were determined as varying parameters in the equation. Each parameter was found to be a function of oxygen concentration, such that the correct glucose calibration equation can be calculated if the oxygen level is known. Accuracy of compensation will be determined by developing an overall calibration, using both glucose and oxygen sensors in parallel, correcting for oxygen fluctuations in real time by intentionally varying oxygen, and calculating the error in actual and predicted glucose levels. While this method was developed for compensation of enzymatic glucose sensors, in principle it can also be implemented with other kinds of sensors utilizing oxidases.

Currently, invasive methods are used to measure the hemoglobin concentration and the most hemoglobin-derivatives, whereby blood is taken from the patient and subsequently analyzed. The noninvasive method presented here allows pain free continuous on-line patient monitoring with minimum risk of infection and facilitates real time data monitoring allowing immediate clinical reaction to the measured data. Visible and near infrared (VIS-NIR) spectroscopy in combination with photo-plethysmography (PPG) is used for a detection of human tissue properties and the measurement of hemoglobin concentration in whole blood and hemoglobin derivatives. The absorption, scattering and the anisotropy of blood and tissue is a function of the irradiated wavelengths. This fact is used to calculate the optical absorbability characteristic of blood and tissue which is yielding information about blood components like hemoglobin-concentration (cHb), carboxyhemoglobin (COHb) and arterial oxygen saturation (SaO2). The ratio between the PPG peak to peak pulse amplitudes for each wavelength is used in combination with a dynamic spectrum extraction. The prediction of the bloodand tissue-parameters is based on a Principal Component Regression (PCR) method. The non-invasive sensor system is calibrated with a lab based artificial blood circulatory system and with data from clinical studies.

Trauma is the number one cause of death for people between the ages 1 and 44 years in the United States. In addition, according to the Centers of Disease Control and Prevention, injury results in over 31 million emergency department visits annually. Minimizing the resuscitation period in major abdominal injuries increases survival rates by correcting impaired tissue oxygen delivery. Optimization of resuscitation requires a monitoring method to determine sufficient tissue oxygenation. Oxygenation can be assessed by determining the adequacy of tissue perfusion. In this work, we present the design of a wireless perfusion and oxygenation sensor based on photoplethysmography. Through optical modeling, the benefit of using the visible wavelengths 470, 525 and 590nm (around the 525nm hemoglobin isobestic point) for intestinal perfusion monitoring is compared to the typical near infrared (NIR) wavelengths (805nm isobestic point) used in such sensors. Specifically, NIR wavelengths penetrate through the thin intestinal wall (~4mm) leading to high background signals. However, these visible wavelengths have two times shorter penetration depth that the NIR wavelengths. Monte-Carlo simulations show that the transmittance of the three selected wavelengths is lower by 5 orders of magnitude depending on the perfusion state. Due to the high absorbance of hemoglobin in the visible range, the perfusion signal carried by diffusely reflected light is also enhanced by an order of magnitude while oxygenation signal levels are maintained. In addition, short source-detector separations proved to be beneficial for limiting the probing depth to the thickness of the intestinal wall.

The esophageal cancer is a disease with a high mortality. In order to lead a higher survival rate five years after the cancer’s treatment, we inevitably need a method to diagnose the cancer in an early stage and support the therapy. Raman spectroscopy is one of the most powerful techniques for the purpose. In the present study, we apply Raman spectroscopy to obtain ex vivo spectra of normal and early tumor human esophageal sample. The result of principal component analysis indicates that the tumor tissue is associated with a decrease in tryptophan concentration. Furthermore, we can predict the tissue type with 80% accuracy by linear discriminant analysis which model is made by tryptophan bands.

Antibiotic resistance is a major health care problem mostly caused by the inappropriate use of antibiotics. At the root of the problem lies the current method for determination of bacterial susceptibility to antibiotics which requires overnight cultures. Physicians suspecting an infection usually prescribe an antibiotic without waiting for the results. This practice aggravates the problem of bacterial resistance. In this work, a rapid method of diagnosis and antibiogram for a bacterial infection was developed using Surface Enhanced Raman Spectroscopy (SERS) with silver nanoparticles. SERS spectra of three species of gram negative bacteria, Escherichia coli, Proteus spp., and Klebsiella spp. were obtained after 0 and 4 hour exposure to the seven different antibiotics. Even though the concentration of bacteria was low (2x10⁵ cfu/ml), species classification was achieved with 94% accuracy using spectra obtained at 0 hours. Sensitivity or resistance to antibiotics was predicted with 81%-100% accuracy from spectra obtained after 4 hours of exposure to the different antibiotics. With the enhancement provided by SERS, the technique can be applied directly to urine or blood samples, bypassing the need for overnight cultures. This technology can lead to the development of rapid methods of diagnosis and antibiogram for a variety of bacterial infections.

Analysis of the emissions from the corneas and aortas of rabbits subjected to high-cholesterol diets were performed by fluorescence microscopy using the Europium Chlortetracycline (EuCTc) complex as fluorescent probe. This complex presents absorption around 400 nm and emission around 615 nm with emission lifetime of a few microseconds, which differs from the lifetimes of biological tissues. The results show that EuCTc, present an intensified red fluorescence in the presence of LDL. Microscopic images obtained using the EuCTc probe suggests that LDL is initially deposited on the luminal surface of the blood vessel, before plaque formation. The red emission in luminal surface of the blood vessel is not observed in animals fed by 60 days with high cholesterol diet group, and the intima layer presents an increase in thickness and several red points that indicate the presence of macrophages and foam cells. Microscopic examination of 60 days high cholesterol diet rabbits corneas has shown that most red fluorescence occurred in the cornea epithelial cells or associated with the elongated profiles of keratocytes. The results showed that the EuCTc probe may be useful in fluorescence angioscopy and in clinical trials of corneal epithelial defects.

Increasing numbers of accidents caused by drivers under the influence of drugs, raise drug tests to worldwide interest. We developed a one-step extraction technique for cocaine in saliva and analyzed reference samples with laser spectroscopy employing two different schemes. The first is based on attenuated total reflection (ATR), which is applied to dried samples. The second scheme uses transmission measurements for the analysis of liquid samples. ATR spectroscopy achieved a limit of detection (LOD) of 3μg/ml. The LOD for the transmission approach in liquid samples is < 10 μg/ml. These LODs are realistic as such concentration ranges are encountered in the saliva of drug users after the administration of a single dose of cocaine. An improved stabilization of the set-up should lower the limit of detection significantly.

The application of tunable Mid-infrared laser system based on fiber-optic ATR sensor to regent-free quantification of glucose concentration was presented. The five laser emission wavelengths, including 1081, 1076, 1051, 1041 and 1037 cm^-1, were employed for glucose determination. In our experiments, absorbance at the five wavelengths correlates strongly well with glucose concentration (R²>0.99, SD<0.0004, P<0.0001), and the noise-equivalent concentration is as low as 3.8 mg/dL. Compared with the conventional FT-IR spectrometer, higher sensitivity was aquired because of the laser higher power and spectral resolution, and it is about 4 times as high as that of FT-IR spectrometer. All the results of this investigation suggested that the tunable CO₂ laser spectroscopy is a powerful method for glucose measurement. Especially, the multiple tunable wavelengths, which makes it possible for glucose determination in blood or interstitial fluide with complicated components.

Based on the human circulatory system, an artificial blood circulatory system was developed to allow the controlled variation of the following blood parameters: total hemoglobin concentration (ctHb), oxyhemoglobin (O₂Hb) methemoglobin (MetHb) and carboxyhemoglobin (COHb). The optical properties of the blood were observed by online spectrometer measurements. The purpose of this was to observe and quantify the absorption, transmission and scattering properties of human whole blood in the wavelength range of 400 to 1700 nm. All the non-invasive measurements of the whole blood transmission-spectra were compared with sample results obtained by a Blood Gas Analyzer (BGA) to validate the results. For all measurements, donor erythrocyte concentrates were used. The concentration of hemoglobin was changed by adding fixed amounts of blood plasma to the erythrocyte concentrate. Oxygen saturation and COHb were adjusted by a continuous flow of N₂, N₂-CO and compressed air through a hollow fibre membrane oxygenator. Different methemoglobin concentrations were adjusted by using natrium nitrite. The blood temperature was kept constant at 37 °C via a tube heating mechanism, with a separate circulation of water passing through the membrane Oxygenator. The Temperature and pressure of the system were automatically controlled and monitored. The model was also used to test new non-invasive measurement systems, and for this reason special cuvettes were designed to imitate human tissue and generate plethysmographical signals. In the future, the blood circulatory system has the potential to be used for testing, validating and also to calibrate newly developed optical prototype devices. It can also be used to further investigate blood components of interest.

Minimal invasive surgery methods have received growing attention in recent years. In vital important areas, it is crucial for the surgeon to have a precise knowledge of the tissue structure. Especially the visualization of arteries is desirable, as the destruction of the same can be lethal to the patient. In order to meet this requirement, the study presents a novel assistance system for endoscopic surgery. While state-of-the art systems rely on pre-operational data like computer-tomographic maps and require the use of radiation, the goal of the presented approach is to provide the clarification of subjacent blood vessels on live images of the endoscope camera system. Based on the transmission and reflection spectra of various human tissues, a prototype system with a NIR illumination unit working at 808 nm was established. Several image filtering, processing and enhancement techniques have been investigated and evaluated on the raw pictures in order to obtain high quality results. The most important were increasing contrast and thresholding by difference of Gaussian method. Based on that, it is possible to rectify a fragmented artery pattern and extract geometrical information about the structure in terms of position and orientation. By superposing the original image and the extracted segment, the surgeon is assisted with valuable live pictures of the region of interest. The whole system has been tested on a laboratory scale. An outlook on the integration of such a system in a clinical environment and obvious benefits are discussed.

We demonstrated that the use of thin wetting film focusing allows detection of single micrometer-size objects with 24 mm² lensfree imaging. In order to refine the technique and push the detection limit down to the nanometer scale, a deep insight in the imaging mechanisms is necessary. We constructed a model based on wetting film microfluidics and Fresnel diffraction of light. This model properly fits the intensity measurements acquired on micro-particles with our lensfree imaging setup. When the particle diameter is 1 µm, a microlens is formed by a liquid surface deformation of about 100 nm in height over few microns radial distance. The measured point spread function of the light deflected by such microlens presents a constant beam intensity over a long range, between 50 µm and 250 µm from the object plane. This is very similar to what is obtained by illuminating an axicon with a Gaussian beam, i.e. the central beam propagates for several Rayleigh ranges without appreciable divergences. In the lensfree imaging setup, the detector plane is far apart from the object (≈500 µm). Thus, it is a true advantage to form axicon lens that can propagate strong intensity beams up to the detector plane. Most important, our model predicts that the detection of smaller objetcs needs thinner films. These results are important for further detecting viruses with lensfree imaging techniques.

The non-invasive blood sugar sensor by using imaging-type 2-dimensional Fourier spectroscopy is to be realized in this work. The spectroscopic imaging, that observes the biological tissue by the dark-field image, can measure the biogenic substance quantitatively such as the glucose concentration. For the quantitative analysis with high accuracy, the correction of the background such as the light-source fluctuation and the phase-shift uncertainty is inevitable issue. Thus, the quantitative band-pass plate on which the grating is locally formed has been already proposed by [1]. In that paper, the diffractive light, whose diffraction angle depends on the wavelength, has been used as the reference light. Object lens is used to narrow down the reference light and narrowed band pass diffraction light is obtained. The changes of imaging intensities with interference phenomenon on whole area of the observation image can be confirmed using the quantitative band pass filter. This paper proposed background correction method of the interferogram in spectroscopic tomography. Correction algorithm mainly contained two parts as light source fluctuation error correction and phase shift error correction.

Minimally-invasive human blood glucose detection can be realized by measuring the glucose concentration of interstitial fluid to predict the blood glucose level. As the amount of transdermally extracted interstitial fluid was minimal and its composition was complex, a glucose measurement method by surface plasmon resonance (SPR) based on PAA-ran-PAAPBA polymer binding was proposed. The polymer was immobilized on the gold film of SPR sensor using layer-by-layer self-assembly technique to capture the glucose molecules in interstitial fluid to realize the detection of glucose concentration with high precision. 2~1000mg/dL glucose solutions were measured utilizing the SPR sensor by polymer binding. The fitting degrees were 0.90177 and 0.99509 in the range of 2~10mg/dL and 25~1000mg/dL respectively. The dynamic dissociation process of glucose molecules from PAA-ran-PAAPBA was verified to be able to satisfy the requirements of the human blood glucose continuous monitoring in clinics.

Resonance Raman spectroscopy is an emerging spectroscopy tool capable of highly specific and highly sensitive analysis of biological molecules in solutions. The complexity of experimental set-up and reliance on laser sources with very short life-time and very high maintenance requirement were always considered the major bottle-neck problem on the way of wide spread of applications of deep-UV Raman spectroscopy in biology and medicine. In this report, we present the design of a very inexpensive system based on a diode-pumped solid-state laser system capable of performing Raman analysis in the deep UV.

Oxidative stress (OS), which increases during retinal degenerative disorders, contributes to photoreceptor cell loss. The objective of this study was to investigate the changes in the metabolic state of the eye tissue in rodent models of retinitis pigmentosa by using the cryofluorescence imaging technique. The mitochondrial metabolic coenzymes NADH and FADH₂ are autofluorescent and can be monitored without exogenous labels using optical techniques. The NADH redox ratio (RR), which is the ratio of the fluorescence intensity of these fluorophores (NADH/FAD), was used as a quantitative diagnostic marker. The NADH RR was examined in an established rodent model of retinitis pigmentosa (RP), the P23H rat, and compared to that of control Sprague-Dawley (SD) rats and P23H NIR treated rats. Our results demonstrated 24% decrease in the mean NADH RR of the eyes from P23H transgenic rats compared to normal rats and 20% increase in the mean NADH RR of the eyes from the P23H NIR treated rats compared to P23H non-treated rats.

Diabetes mellitus and hypertension diseases are frequently found in the same patient, which if untreated predispose to atherosclerotic and kidney diseases. The objective of this study was to identify potential biomarkers in the urine of diabetic and hypertensive patients through dispersive near-infrared Raman spectroscopy. Urine samples were collected from patients with diabetes and hypertension but no complications (LG), high degree of complications (HG), and control ones: one fraction was submitted to biochemical tests and another one was stored frozen (-20°C) until spectral analysis. Samples were warmed up and placed in an aluminum sample holder for Raman spectra collection using a dispersive spectrometer (830 nm wavelength, 300 mW laser power and 20 s exposure time). Spectra were then submitted to Principal Components Analysis. The PCA loading vectors 1 and 3 revealed spectral features of urea/creatinine and glucose, respectively; the PCA scores showed that patients with diabetes/hypertension (LG and HG) had higher amount of glucose in the urine compared to the normal group (p < 0.05), which can bring serious consequences to patients. Also, the PCA scores showed that the amount of urea decreased in the groups with diabetes/hypertension (p < 0.05), which generates the same concern as it is a marker that has a strong importance in the metabolic changes induced by such diseases. These results, applied to the analysis of urine of patients with diabetes/hypertension, can lead to early diagnostic information of complications and a possible disease prognosis in the patients where no complications from diabetes and hypertension were found.

Breast cancer-related lymphedema (BCRL) can be irreversible with profound negative impact on patients' quality of life. Programs that provide screening and active surveillance for BCRL are essential to determine whether early detection and intervention influences the course of lymphedema development. Established methods of quantitatively assessing lymphedema at early stages include "volume" methods such as perometry and bioimpedance spectroscopy. Here we demonstrate 1) Use of topographical techniques analogous to those used in corneal topography 2) Development of point-of-care lymphedema detection and characterization based on off-the-shelf hardward 3) The role of subsurface imaging 4) Multimodal diagnostics and integration yielding higher sensitivity/ specificity.

This PDF file contains the front matter associated with SPIE Proceedings Volume 8591, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.