Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2003-02-13
2004-12-28
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S365000, C600S310000
Reexamination Certificate
active
06836678
ABSTRACT:
FIELD OF THE INVENTION
This invention is generally related to a non-invasive blood glucose monitor, and more particularly to a non-invasive blood glucose monitor based on micro-optical-mechanical-electro-system (MOMES).
BACKGROUND OF THE INVENTION
Non-invasive measurement of blood glucose concentration offers many advantages over invasive measurements, since the intermittent tests, which are widely practiced by diabetic patients, involve pain and discomfort from frequent finger-pricking.
Non-invasive measurement approaches of blood glucose concentration based on absorption measurements in the infrared region have been explored more than 20 years.
An early U.S. Pat. No. 4,169,676 (October, 1979) to Kaiser shows a method for the use of attenuated total reflection glucose measurement by placing the attenuated total reflection plate directly against the skin and especially against the tongue. The procedure and device shown there uses a laser and determines the content of glucose in a specific living tissue sample by comparing the infrared absorption of the measured material against the absorption of infrared in a control solution by use of a reference prism.
Another early U.S. Pat. No. 4,655,225 (April, 1987) to Dahne, et al. describes an apparatus for non-invasively measuring the level of glucose in a blood stream or tissues. The method is photometric and uses light in the near-infrared region. Dahner's device is jointly made up to two main sections, a light source and a detector section. They may be situated about a body part such as a finger. The desired near-infrared light is achieved by use of filters. The detector section is made up of a light-collecting integrating sphere or half-sphere leading to a means for detecting wavelengths in the near-infrared region.
In recent years more methods and apparatus have been proposed. U.S. Pat. No. 5,974,337 (Oct. 26, 1999) describes an instrument for non-invasive glucose measurement. The described instrument irradiates the distal phalanx of a subject's finger with light in the near infrared. The transmitted or reflected radiation is detected and analyzed and an estimate of blood glucose level made. The signal is coupled with a fiber optic probe by means of a conventional arrangement of lenses and mirrors. Illumination fibers and collection fibers are provided in separate structures.
U.S. Pat. No. 5,424,545 (Jun. 13, 1995) describes an instrument for non-invasive blood analyte determination that relies on calorimetric analysis to arrive at a blood analyte determination. A light beam is coupled with an illumination fiber by means of lenses and mirrors.
U.S. Pat. No. 6,064,898 (May 16, 2000) describes a non-invasive blood component analyzer that provides built-in path length monitoring to allow use in subjects of varying finger size. It provides a light source either from LED's or from a lamp. The light is simply emitted in the vicinity of the sampling site and coupled through the atmosphere.
U.S. Pat. No. 5,782,755 (Jul. 21, 1998) discloses a method of spatial resolved diffused reflectance for measurement of glucose in a biological system. It uses multiple spot sources, such as flash bulbs, and a single detector. The light sources are spaced different distances along a single line from a detector and are sequenced at different time intervals to derive the spatial reflectance profiles.
All above-mentioned methods and apparatus are impossible to detect on the spectrum the relative heights of the waveform (peak and trough), which are finely varied by the coupling of glucose and protein, resulting in insufficiency in the accuracy and reproducibility of the blood glucose measurement.
U.S. Pat. No. 6,031,233 (Feb. 29, 2000) describes an apparatus based on an infrared spectrometer. Light is emitted from a lamp and passed through an acousto-optical tuning filter for wavelength selection. The acoustic-optical tuning filter is composed of a high frequency electric power source, a high frequency vibrator, and an acousto-optic variable oscillator. The filtered light is focused through one or more lenses and directed toward the measurement site through a window. The use of the acousto-optical tuning filter for wavelength selection requires a wavelength synthesizer and an RF amplifier.
This apparatus is not only complicated and expensive but also leaves several problems to be solved.
Problem 1, the light absorbed by the tissue subjected to analysis constitutes, together with other losses due to scattered stray radiations and RF interference, signals inherent to the practice of the method and the apparatus components, the background response noise from which the useful signals must be separated.
Problem 2, skin tissue is composed of various compositions of fat and protein, as well as veins, arteries, and bones. Such heterogeneous structure can contribute to local variation of the light absorption and scattering.
Problem 3, a temporal variation in glucose concentration is associated with blood flow changes during a heartbeat process of the blood subject of measurement. Data received at individual points of the heartbeat process are not the same.
Problem 4, portable and handheld non-invasive blood glucose instruments are demanded for point of care and in home use. Such instruments in which light is coupled by means of an arrangement of conventional lenses and mirrors have high space requirements and they are highly vulnerable to mechanical shock.
SUMMARY OF THE INVENTION
Accordingly, it is intended to provide a non-invasive blood glucose monitor of solving the aforementioned problems, excelling in accuracy and reproducibility.
It is an object of the present invention to provide a non-invasive blood glucose monitor with main components being MOMES devices so that it is small enough to fit the palm of your hand.
Furthermore, it is an object of the present invention to provide a non-invasive blood glucose monitor that enables to use a combination of modulated monochromatic infrared light and synchronous detection technology for maximizing the electronic single-to-noise ratio.
It is yet another object of the present invention to provide a non-invasive blood glucose monitor that enables the use of a tunable filter to eliminate stray infrared radiation so that the optical signal to noise ratio can be maximized.
It is yet another object of the present invention to provide a non-invasive blood glucose monitor that enables selecting and switching of the illumination infrared light in an infrared wavelength range so that an infrared absorbance spectrum of the blood subject of measurement can be obtained.
It is yet another object of the present invention to provide a non-invasive blood glucose monitor that enables scanning over a large area of measurement so that the poor reproducibility caused by non-homogeneity of the subject of measurement can be overcome.
It is yet another object of the present invention to provide a non-invasive blood glucose monitor that enables the measurement of blood glucose in a period of a heartbeat and an average can be made to eliminate the blood flow changes due to heartbeat.
In order to realize the above-mentioned objects, the present invention provides a MOMES-based non-invasive blood glucose monitor consisting primarily of a micromachined infrared interferometer array, a micromachined infrared mechanical modulator array, a micromachined infrared tunable filter, and needed driver and signal processing integrated circuits.
The micromachined infrared interferometer array, micromachined infrared mechanical modulator array, and micromachined infrared tunable filter are an adaptation of Fabry-Perot devices that employ the principle of optic interference. The basic unit is a Fabry-Perot cavity consisting of two parallel planar reflectors separated by an air gap. At least two flexible beams support one of the two reflectors. Applying a voltage to the two reflectors can change the length of the air gap.
Infrared light passes through one of the two reflectors and is multiply reflected within the cavity. The multiply transmitte
Johnsonbaugh Bruce H.
Kremer Matthew
Winakur Eric F.
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