Rebecca J. Bussjager

Effect of hemoglobin concentration variation on the accuracy and precision of glucose analysis using tissue modulated, noninvasive, in vivo Raman spectroscopy of human blood: a small clinical study

Tissue modulated Raman spectroscopy was used noninvasively to measure blood glucose concentration in people with type I and type II diabetes with HemoCue fingerstick measurements being used as reference. Including all of the 49 measurements, a Clarke error grid analysis of the noninvasive measurements showed that 72% were A range, i.e., clinically accurate, 20% were B range, i.e., clinically benign, with the remaining 8% of measurements being essentially erroneous, i.e., C, D, or E range. Rejection of 11 outliers gave a correlation coefficient of 0.80, a standard deviation of 22 mg/dL with p<0.0001 for N=38 and places all but one of the measurements in the A and B ranges. The distribution of deviations of the noninvasive glucose measurements from the fingerstick glucose measurements is consistent with the suggestion that there are at least two systematic components in addition to the random noise associated with shot noise, charge coupled device spiking, and human factors. One component is consistent with the known variation of fingerstick glucose concentration measurements from laboratory reference measurements made using plasma or whole blood. A weak but significant correlation between the deviations of noninvasive measurements from fingerstick glucose measurements and the test subjects hemoglobin concentration was also observed.

Electro-optic beam-steering device based on a lanthanum-modified lead zirconate titanate ceramic wafer

We demonstrate a lanthanum-modified lead zirconate titanate ceramic-based electro-optic beam-steering device that has a 3 mm × 3 mm working area. A series of resistors were made by evaporation of chromium onto the substrate to produce and control the required voltage distribution among the electrodes. A steering angle of 0.04° was obtained with an applied voltage of 700 V. Design considerations, computer simulations, and experimental results are presented.

Simultaneous, noninvasive observation of elastic scattering, fluorescence and inelastic scattering as a monitor of blood flow and hematocrit in human fingertip capillary beds

We report simultaneous observation of elastic scattering, fluorescence, and inelastic scattering from in vivo near-infrared probing of human skin. Careful control of the mechanical force needed to obtain reliable registration of in vivo tissue with an appropriate optical system allows reproducible observation of blood flow in capillary beds of human volar side fingertips. The time dependence of the elastically scattered light is highly correlated with that of the combined fluorescence and Raman scattered light. We interpret this in terms of turbidity (the impeding effect of red blood cells on optical propagation to and from the scattering centers) and the changes in the volume percentages of the tissues in the irradiated volume with normal homeostatic processes. By fitting to a model, these measurements may be used to determine volume fractions of plasma and RBCs.

Instrument for near infrared emission spectroscopic probing of human fingertips in vivo

We present instrumentation for probing of volar side fingertip capillary beds with free space coupled near infrared light while collecting Raman, Rayleigh, and Mie scattered light as well as fluorescence. Fingertip skin capillary beds are highly vascularized relative to other tissues and present a desirable target for noninvasive probing of blood. But human hands and fingers in particular are also highly idiosyncratic body parts requiring specific apparatus to allow careful and methodical spectroscopic probing. The apparatus includes means for precise and reproducible placement of the tissues relative to the optical aperture. Appropriate means are provided for applying and maintaining pressure to keep surface tissues immobile during experiments while obtaining the desired blood content and flow. Soft matter, e.g., skin, extrudes into the aperture in response to any applied pressure, e.g., to keep the tissue in registration with the optical system, so the position, contact area, pressure, and force are continuously measured and recorded to produce feedback for an actuator applying force and to discern the compliance of the test subject. The compliance strongly affects the reliability of the measurement and human factors must be adequately managed in the case of in vivo probing. The apparatus produces reproducible observations and measurements that allow consistent probing of the tissues of a wide range of skin types.

Analyzing near infrared scattering from human skin to monitor changes in hematocrit

The leading preventable cause of death, world-wide, civilian or military, for all people between the ages of 18-45 is undetected internal hemorrhage. Autonomic compensation mechanisms mask changes such as e.g. hematocrit fluctuations that could give early warning if only they could be monitored continuously with reasonable degrees of precision and relative accuracy. Probing tissue with near infrared radiation (NIR) simultaneously produces remitted fluorescence and Raman scattering (IE) plus Rayleigh/Mie light scattering (EE) that noninvasively give chemical and physical information about the materials and objects within. We model tissue as a three-phase system: plasma and red blood cell (RBC) phases that are mobile and a static tissue phase. In vivo, any volume of tissue naturally experiences spatial and temporal fluctuations of blood plasma and RBC content. Plasma and RBC fractions may be discriminated from each other on the basis of their physical, chemical and optical properties. Thus IE and EE from NIR probing yield information about these fractions. Assuming there is no void volume in viable tissue, or that void volume is constant, changes in plasma and RBC volume fractions may be calculated from simultaneous measurements of the two observables, EE and IE. In a previously published analysis we showed the underlying phenomenology but did not provide an algorithm for calculating volume fractions from experimental data. Here we present a simple analysis that allows continuous monitoring of fluid fraction and hematocrit (Hct) changes by measuring IE and EE, and apply it to some experimental in vivo measurements.

Analyzing near-infrared scattering from human skin to monitor changes in hematocrit

Probing tissue with near-infrared radiation (NIR) simultaneously produces remitted fluorescence and Raman scattering (IE) plus Rayleigh∕Mie light scattering (EE) that noninvasively give chemical and physical information about the materials and objects within. We model tissue as a three-phase system: plasma and red blood cell (RBC) phases that are mobile and a static tissue phase. In vivo, any volume of tissue naturally experiences spatial and temporal fluctuations of blood plasma and RBC content. Plasma and RBC fractions may be discriminated from each other on the basis of their physical, chemical, and optical properties. Thus, IE and EE from NIR probing yield information about these fractions. Assuming there is no void volume in viable tissue, or that void volume is constant, changes in plasma and RBC volume fractions may be calculated from simultaneous measurements of the two observables, EE and IE. In a previously published analysis we showed the underlying phenomenology but did not provide an algorithm for calculating volume fractions from experimental data. Now, we present a simple analysis that allows monitoring of fluid fraction and hematocrit (Hct) changes by measuring IE and EE, and apply it to some experimental in vivo measurements.

Reversible photoredox processing of transition metal oxides

The authors describe a novel laser chemical process having potential for optical data storage and processing applications. Reversible oxygen exchange involving WO{sub 3}, using readily available laser sources offers improved durability and versatility over existing erasable optical data storage media. Being interconvertible using heat and blue-green laser sources, the well known yellow WO{sub 3} and blue W{sub 2}O{sub 5} can function as erased and written states.

Diamond shaped ring laser characterization, package design and performance

A semiconductor diamond-shaped ring laser was fabricated and packaged for further test and analysis as an element in digital photonic logic. The optical characteristics of the ring laser were quantified in order to design a prototype package. The mode field was found to be quasi-circular. Based on the mode field of the laser, coupling curves were calculated and Corning OptiFocustrade lensed fiber was chosen to use for the four fiber outputs. Each fiber placement was actively optimized. Output power measurements were made for each facet before and after fiber coupling. Reflections from fiber tips were found to affect the final output power distribution of the device even though the fibers were anti-reflection (AR) coated, and additional effort was put into minimizing its variance. The packaged devices were tested for performance in digital photonic logic applications. Tests conducted to this point indicate that the packaging enabled a multiple port device of this type to be sufficiently portable for field testing

Glucose and Other Measurements

Simultaneous measurement of elastic and inelastic remitted light from tissues being irradiated with a single near infrared laser wavelength can be used to calculate the plasma and red blood cell volumes of the included blood.

Evaluation of an extension of a nonlinear interface optical switch structure for dual mode switching

There is a need for devices which will allow integration of photonic/optical computing subsystems into electronic computing architectures. This effort reviews the nonlinear interface optical switch (NIOS) concept and then describes a new effect, the erasable optical memory (EOM) effect. We evaluate an extension of the NIOS device to allow simultaneous optical/electronic, i.e. dual mode, switching of light utilizing the EOM effect. Specific devices involve the fabrication of thin film tungsten (VI) oxide (WO/sub 3/) and tungsten (V) oxide (W/sub 2/O/sub 5/) on the hypotenuse of glass (BK-7), fused silica (SiO/sub 2/) and zinc selenide (ZnSe) right angle prisms. The extent to which the chemical state of the film can also be manipulated electrically, in a purely gas-solid context, is discussed. Temporal response, spatial density of packing the switches and clarifying considerations regarding choices of materials are also presented.