Robert B. Northrop

Noninvasive optical polarimetric glucose sensing using a true phase measurement technique

The development and testing of a noninvasive true phase optical polarimetry sensing system to monitor in vivo glucose concentrations is described. To demonstrate the applicability of this optical sensor for glucose movement, the authors calibrate the system and then test it in vitro using both a glass test cell filled with glucose solution in the physiologic range, with a path length of 0.9 cm to approximate the 1-cm path length present in the anterior chamber of the eye, and then on an excised human eye. The technique used helium neon laser light which was coupled through a rotating linear polarizer along with two stationary linear polarizers and two detectors to produce reference and signal outputs whose amplitudes varied sinusoidally with a frequency of twice the angular velocity of the rotating polarizer, and whose phase was proportional to the rotation of the linear polarization vector passing through the glucose solution.<<ETX>>

Location and characterization of partial discharge sites in shielded power cables

An instrument capable of detecting and locating partial discharge sites and faults in shielded power cables was developed on behalf of a group of US electric utilities. The instrument uses state-of-the-art electronic hardware and advanced digital signal processing techniques. The partial discharge signals are reconstructed using the cable traveling wave characteristics (transfer function), and noise is reduced both through choice of hardware and by modern signal enhancement techniques. An adjunct instrument was also developed to correlate the location of a partial discharge site along the cable to the position along the surface of the cable burial trench. The principle and the implementation of the instrumentation package are described, and results obtained in the laboratory on a 175 m, 15 kV URD cable are discussed. >

Location of partial discharges in shielded cables in the presence of high noise

Updated information on a partial discharge location system intended to pinpoint the location of defects and/or faults on a shielded buried underground cable is presented. The system is based on the principle of reflectometry. Its salient characteristics include the following two features: (a) an ability to pinpoint the location of a partial discharge source not only along the cable length, but also along the surface of the trench where it is buried; and (b) the ability to operate in a high noise environment. Recent field and laboratory data obtained on noise and techniques for its mitigation are discussed in some detail. These techniques include analog/digital notch filters for the elimination of AM broadcast noise and an adaptive digital filtering scheme which incorporates the transfer function of the cable for added accuracy. >

Noninvasive Instrumentation and Measurement in Medical Diagnosis

INTRODUCTION TO NON-INVASIVE MEASUREMENT Definition of Non-Invasive Measurement, Minimally Invasive Measurements Modalities of NI Instrumentation VISUAL INSPECTION OF TISSUES WITH ENDOSCOPES AND OTHER OPTICAL DEVICES Ophthalmoscopes, Slit Lamps, and Otoscopes Endoscopes CCD Cameras Non-Invasive Diagnosis of Skin Lesions NON-INVASIVE DIAGNOSIS USING SOUNDS FROM WITHIN THE BODY Means of Analysis for Acoustic Signals Heart Sounds Breath Sounds Otoacoustic Emissions MEASUREMENT OF ELECTRICAL POTENTIALS FROM THE BODY SURFACE Electrodes Biopotential Amplifiers The ECG The Electomyogram (EMG) The Electroencephalogram (EEG) OTHER BODY SURFACE POTENTIALS The Electroculogram (EOG) The Electroretinogram (ERG) The Electrocochleogram (EcoG) Discussion THE MAGNETOENCEPHALOGRAM (MEG) The SQUID and SQUID Arrays Other BioMagnetic Measurements NON-INVASIVE MEASUREMENT OF BLOOD PRESSURE The Cuff Sphygmomanometer Other Means of Estimating Blood Pressure Non-Invasively BODY TEMPERATURE MEASUREMENTS Conductive Heat Transfer and Thermometer Response Time The LIT Blackbody Thermometer NON-INVASIVE BLOOD GAS SENSING WITH ELECTRODES Transcutaneous O2 Sensing Transcutaneous CO2 Sensing TESTS ON NATURALLY-VOIDED BODY FLUIDS Instrumental Methods What Can Be Learned from Urine What Can Be Learned from Feces What Can Be Learned from Saliva What Can Be Learned from the Breath PLETHYSMOGRAPH Volume Displacement Plethysmography Impedance Plethysmography Photo-Plethysmography PULMONARY FUNCTION TESTS Spirometers and Related Equipment Tests with Spirometers MEASUREMENT OF BASAL METABOLISM The BMR Test Procedures OCULAR TONOMETRY The No-Touch, Air Puff Tonometer Contact Tonometers NI TESTS INVOLVING THE INPUT OF AUDIBLE SOUND ENERGY Zac Measurements of the Respiratory System (RAIMS) Zac Measurements of the Eardrum (Tympanometry) Trans-Thoracic Acoustic Transfer Function: a Possible Measure of Lung Condition NI TESTS USING ULTRASOUND (Excluding Imaging) The Doppler Effect Reflected Doppler Ultrasound for Blood and Tissue Velocity Measurements A No Touch Ocular Pulse Measurement System (NOTOPM) The Constant-Phase, Closed-Loop, Type-1, Ranging System Measurement of Tissue Glucose Concentration by Closed-Loop, Constant-Phase, CW Ultrasound (A Prototype System) NI APPLICATIONS OF PHOTON RADIATION (EXCLUDING IMAGING) Bone Densitometry Non-Invasive Diagnosis by Tissue Fluorescence Optical Interferometric Measurement of Nanometer Displacements of Biological Surfaces Laser Doppler Velocimetry Transcutaneous IR Spectroscopy Estimation of Blood Glucose for NI Measurement of Optical Rotation of the Aqueous Humor: A Prototype Instrument Pulse Oximetry Non-Invasive Measurement of Certain Biomolecules by Raman Spectroscopy A SURVEY OF MEDICAL IMAGING SYSTEMS X-Rays Tomography Positron Emission Tomography (PET) Magnetic Resonance Imaging (MRI) Single Photon Emission Tomography (SPECT) Optical Coherence Tomography (OCT) Ultrasound Imaging Other Imaging Modalities FUTURE TRENDS IN NI MEASUREMENTS AND DIAGNOSIS NI Chemical Tests for Cancer not Involving DNA Fluorescence Tests for Biomolecules: FISH and SKY The SpectraCube(R) System The DNA Microarray BIBLIOGRAPHY AND REFERENCES Each section also includes an introduction and a chapter summary.

Information processing in the optic lobes of the lubber grasshopper

Abstract Single unit responses in the optic lobes of the grasshopper, Romalea microptera , have been examined using a variety of simple, patterned visual stimuli. Five classes of unit response have been defined: multimodal, vector contrasting edge, light units (L-units) (tonic and ON types), net dimming units, and unmodulatable and weakly sensitive units. Multimodal and vector edge fibres have the properties of true, spatiotemporal operators, i.e. they are able to discriminate certain spatiotemporal characteristics of objects. Romalea multimodal units responded to small, contrasting objects given novel motion in a total, binocular receptive field (RF). Vector units responded selectively to long, contrasting boundaries moved in the preferred direction (anteriodorsally). They had total monocular RFs and responded over a wide range of edge speeds with an approximately cosine directional characteristic. The general morphology of the optic lobes of Romalea has been described. Recording sites were marked by radio-frequency lesioning, and trends in the location of unit types have been established with reference to the anatomical features of the lobe. The ON-gated mechano-response (i.e. following light ON) of some tonic L-units, and the general mechano- and acoustic responses of multimodal operators, underline the importance of addressing further study to uncovering the role of efferent non-visual sensory information in the operation of the arthropod visual system.

Signal processing techniques for partial discharge site location in shielded cables

An instrumentation package capable of locating partial discharge sites in cables has been developed. The digitized partial discharge (PD) signals recorded from one cable end consist of a sequence of pulses whose separations contain information on the relative location of the PD site. The signals are often contaminated by noise and undergo substantial attenuation and phase change as they travel though the cable and the detection system. Moreover, overlap of two successive pulses is possible if the PD site is close to a cable end. The authors describe and illustrate two techniques-maximum likelihood (ML) estimation and deconvolution-for extracting pulse separation from such a time series of noisy and ambiguous signals. Both real and simulated measurements are used to demonstrate the potential of these methods. A procedure whereby knowledge of the combined cable-instrumentation transfer function can be incorporated into the maximum likelihood technique is also discussed. The ML method appears to be much more effective in the presence of cable noise. The main disadvantage of the ML method is that the approximate width of the wavelet or basic PD pulse should be known to give the best compromise between noise smoothing and peak resolution. This width can be determined by an impulse response test or by knowledge of cable length and parameters. >

A No-Touch Ocular Pulse Measurement System for the Diagnosis of Carotid Occlusions

The ocular pulse (OP) is the minute, radial displacement of the corneal surface caused by arterial pressure pulsations in the ocular circulation acting on the compliance of the cornea. Features of the OP waveform have been shown by several workers to be important diagnostic indicators of cerebrovascular disease (CVD) in which the common carotid and/or lower internal carotid arteries are significantly occluded. Early diagnosis of CVD is held to be important in predicting strokes and in implementing procedures to lower their likelihood.

Correction to "Closed-Loop Regulation of a Physiological Parameter by an IPFM/SDC (Integral Pulse Frequency Modulated/Smith Delay Compensator) Controller"

This theoretical paper discusses the realization of a discrete, closed-loop control system which uses an integral pulse frequency modulated/Smith delay compensator (IPFM/SDC) controller to regulate an in vivo physiological parameter to the prescribed quantity in real time. The pharmacokinetic (PK) plant considered is the sodium nitroprusside (SNP) blood-pressure plant. The simulated plant is appropriately time-and amplitude-scaled using op-amps and RC active filter elements.

Microdegree polarimetry using a diode laser for glucose detection

The authors point out that current techniques for the quantification of blood glucose, particularly in the home environment, have lacked precision. In their investigations into the rotary effects of glucose upon the polarization vector of light, the authors have developed a polarimeter capable of microdegree precision. At the present sensitivity, normal physiological levels of blood glucose could be measured within 0.1%. A linear regression of output voltage corresponding to optical rotation yielded a standard of deviation of 4.4 microdegrees and a coefficient of linear correlation of 0.99991. Current and future research is focusing on the elimination of confounding factors such as other optically active substances.<<ETX>>

Optical polarimetric sensor for blood glucose measurement

Preliminary results for an optical polarimetry system which could be used as a sensor to monitor in vivo glucose concentrations are presented. Polarization retaining optical fibers make it feasible to transport coherent light to and from the sensing site. A bidirectional technique increases the sensitivity of the system for a given path length. Preliminary in vitro results show the ability of the system to monitor glucose levels. The first result shows the linearity of the polarization rotation of light with blood glucose levels. In a second experiment, it was verified that the polarization preserving fiber allows for the transference of linear polarized light with enough intensity, after coupling, to be detected at the output. The bidirectional technique for increasing the sensitivity is verified.<<ETX>>