Bernie Schattka

Clinical utilization of near-infrared spectroscopy devices for burn depth assessment.

The diagnosis of burn depth is based on a visual assessment and can be subjective. Near‐infrared (NIR) spectroscopic devices were used preclinically with positive results. The purpose of this study was to test the devices in a clinical setting using easily identifiable burn wounds. Adult patients with acute superficial and full‐thickness burns were enrolled. NIR point spectroscopy and imaging devices were used to collect hemodynamic data from the burn site and an adjacent unburned control site. Oxy‐hemoglobin and deoxy‐hemoglobin concentrations were extracted from spectroscopic data and reported as oxygen saturation and total hemoglobin. Sixteen patients (n=16) were included in the study with equal numbers in both burn wound groups. Point spectroscopy data showed an increase in oxygen saturation (p<0.0095) and total hemoglobin (<0.0001) in comparison with the respective control areas for superficial burn wounds. The opposite was true for full‐thickness burns, which showed a decrease in oxygenation (p<0.0001) and total hemoglobin (p<0.0147) in comparison with control areas. NIR imaging technology provides an estimate of hemodynamic parameters and could easily distinguish superficial and full‐thickness burn wounds. These results confirm that NIR devices can successfully distinguish superficial and full‐thickness burn injuries.

Long-wavelength near-infrared spectroscopic imaging for in-vivo skin hydration measurements

A digital imaging system has been developed to collect skin hydration data. The system combines a near-infrared camera with a liquid-crystal tunable filter (LCTF) to acquire spectral images at multiple narrow wavelength bands between 960 and 1700 nm. Software has been developed to control the instrument and to process the data. Reflectance images were collected of subjects whose forearms had been treated to increase and decrease skin moisture. The infrared absorption band between 1400 and 1500 nm was used to calculate relative skin moisture, and the intensity of this band was plotted as a function of position in the form of a grayscale image. This is a rapid, non-contact and non-invasive technique to provide information on skin hydration of use to medical and cosmetic research and clinical practice.

Differentiating atherosclerotic plaque burden in arterial tissues using femtosecond CARS-based multimodal nonlinear optical imaging

A femtosecond CARS-based nonlinear optical microscope was used to simultaneously image extracellular structural proteins and lipid-rich structures within intact aortic tissue obtained from myocardial infarction-prone Watanabe heritable hyperlipidemic rabbits (WHHLMI). Clear differences in the NLO microscopic images were observed between healthy arterial tissue and regions dominated by atherosclerotic lesions. In the current ex-vivo study, we present a single parameter based on intensity changes derived from multi-channel NLO image to classify plaque burden within the vessel. Using this parameter we were able to differentiate between healthy regions of the vessel and regions with plaque, as well as distinguish plaques relative to the age of the WHHLMI rabbit.

Noninvasive Measurement of Edema in Partial Thickness Burn Wounds

A lack of noninvasive tools to quantify edema has limited our understanding of burn wound edema pathophysiology in a clinical setting. Near-infrared spectroscopy (NIR) is a new noninvasive tool able to measure water concentration/edema in tissue. The purpose of this study was to determine whether NIR could detect water concentration changes or edema formation in acute partial-thickness burn injuries. Adult burn patients within 72 hours postinjury, thermal etiology, partial-thickness burn depth, and <20% TBSA were included. Burn wounds were stratified into partial-thickness superficial or deep wounds based on histology and wound healing time. NIR devices were used to quantify edema in a burn and respective control sites. The sample population consisted of superficial (n = 12) and deep (n = 5) partial-thickness burn injuries. The patients did not differ with respect to age (40 ± 15 years), TBSA (5 ± 4%), and mean time for edema assessment (2 days). Water content increased 15% in burned tissue compared with the respective control regions. There were no differences in water content at the control sites. At 48 hours, deep partial-thickness injuries showed a 23% increase in water content compared with 18% superficial partial-thickness burns. NIR could detect differences in water content or edema formation in partial-thickness burns and unburned healthy regions. NIR holds promise as a noninvasive, portable clinical tool to quantify water content or edema in burn wounds.

Using multimodal femtosecond CARS imaging to determine plaque burden in luminal atherosclerosis

Luminal atherosclerosis imaging was demonstrated by multimodal femtosecond CARS microscopy (MM-CARS). Using a myocardial infarction-prone rabbit model of atherosclerosis, this study demonstrated the utility of multimodal CARS imaging in determining atherosclerotic plaque burden through two types of image analysis procedures. Firstly, multimodal CARS images were evaluated using a signal-intensity parameter based on intensity changes derived from the multi-channel data (e.g. TPEF, SHG and CARS) to classify plaque burden within the vessel. Secondly, the SHG images that mainly correspond to collagen fibrils were evaluated using a texture analysis model based on the first-order statistical (FOS) parameters of the image histogram. Correlation between FOS parameters of collagen images with atherosclerosis plaque burden was established. A preliminary study of using spectroscopic CARS in identifying the different lipid components within the plaque was also discussed.

Label-free imaging of arterial tissues using photonic crystal fiber (PCF) based nonlinear optical microscopic system

Nonlinear optical (NLO) microscopy provides a minimally invasive optical method for fast molecular imaging at subcellular resolution with 3D sectioning capability in thick, highly scattering biological tissues. In the current study, we demonstrate the imaging of arterial tissue using a nonlinear optical microscope based on photonic crystal fiber and a single femto-second oscillator operating at 800nm. This NLO microscope system is capable of simultaneous imaging extracellular elastin/collagen structures and lipid distribution within aortic tissue obtained from coronary atherosclerosis-prone WHHLMI rabbits (Watanabe heritable hyperlipidemic rabbit-myocardial infarction) Clear pathological differences in arterial lumen surface were observed between healthy arterial tissue and atherosclerotic lesions through NLO imaging.

Near-infrared Spectroscopy, In Vivo Tissue Analysis by

In vivo near-infrared (NIR) spectroscopy has the potential of becoming an important tool in a number of areas in clinical medicine. Technological developments in photonics that have been spurred on by the communication revolution have set the stage for rapid advancement of optical and NIR spectroscopy based on noninvasive or minimally invasive medical diagnostic techniques. The goal of this article is to review the current capabilities and limitations of in vivo NIR spectroscopy and highlight the impact of these capabilities and limitations in selected areas where NIR spectroscopy is being used to address clinical problems. The optical properties of tissues are briefly reviewed, as are the instrumental methods available to the experimentalist. These properties and methods largely dictate the feasibility of an in vivo spectroscopic diagnostic approach and constrain the scope of problems that can be tackled using optical–NIR spectroscopy. Some of the more successful applications are described, including studies of tissue oxygenation, ischemia, and viability. A number of factors that can confound interpretation of in vivo NIR results are discussed. The number and magnitude of confounding influences that arise in in vivo spectroscopy can be daunting to the experimentalist and may represent the largest barrier in transforming in vivo spectroscopic measurements into clinically meaningful and reliable information. In vivo NIR spectroscopy abounds with opportunity and challenge.

A single-photon fluorescence and multi-photon spectroscopic study of atherosclerotic lesions

In this study we compare the single-photon autofluorescence and multi-photon emission spectra obtained from the luminal surface of healthy segments of artery with segments where there are early atherosclerotic lesions. Arterial tissue was harvested from atherosclerosis-prone WHHL-MI rabbits (Watanabe heritable hyperlipidemic rabbit-myocardial infarction), an animal model which mimics spontaneous myocardial infarction in humans. Single photon fluorescence emission spectra of samples were acquired using a simple spectrofluorometer set-up with 400 nm excitation. Samples were also investigated using a home built multi-photon microscope based on a Ti:sapphire femto-second oscillator. The excitation wavelength was set at 800 nm with a ~100 femto-second pulse width. Epi-multi-photon spectroscopic signals were collected through a fibre-optics coupled spectrometer. While the single-photon fluorescence spectra of atherosclerotic lesions show minimal spectroscopic difference from those of healthy arterial tissue, the multi-photon spectra collected from atherosclerotic lesions show marked changes in the relative intensity of two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) signals when compared with those from healthy arterial tissue. The observed sharp increase of the relative SHG signal intensity in a plaque is in agreement with the known pathology of early lesions which have increased collagen content.

Ex-vivo evaluation of an early caries detector based on integrated OCT and polarized Raman spectroscopy (Conference Presentation)

Early detection of incipient caries would allow dentists to provide more effective measures to delay or to reverse caries’ progression at earlier stage. Such earlier intervention could lead to improved oral health for the patients and reduced burden to the health system. Previously, we have demonstrated that the combination of morphological and biochemical information furnished by optical coherence tomography (OCT) and polarized Raman spectroscopy (PRS), respectively, provided a unique tool for dental caries management. In this study we will report the first pre-clinical caries detection system that includes a hand-held probe with a size slightly larger than a tooth brush. This probe presents a novel platform combining both OCT and PRS optics in a very tight space ideal for clinical practice. OCT cross-sectional images of near-surface enamel morphology are obtained with miniaturized MEMS scanning device and are processed in real-time to identify culprit regions. These regions are sequentially analyzed with polarized Raman spectroscopy for further confirmation. PRS is performed using 830nm laser line and four detection channels in order to obtain polarized Raman spectroscopic data, i.e. depolarization ratio of the hydroxyapatite Raman band at ~960 cm-1. A detailed description of this hand-held caries detector and ex-vivo/in-vivo test results will be presented.