Surgery – Diagnostic testing – Measuring or detecting nonradioactive constituent of body...
Reexamination Certificate
2000-05-15
2003-05-20
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
Measuring or detecting nonradioactive constituent of body...
C600S310000, C356S364000
Reexamination Certificate
active
06567678
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to devices and methods for measuring the concentration of one or more analytes in a biological sample. More specifically, this invention relates to devices and methods for the noninvasive determination of analyte concentrations in vivo, e. g., glucose concentrations in blood.
2. Discussion of the Art
Diabetes: Incidence, Effects and Treatment
Diabetes mellitus is a chronic disorder of carbohydrate, fat, and protein metabolism characterized by an absolute or relative insulin deficiency, hyperglycemia, and glycosuria. At least two major variants of the disease have been identified. “Type I” accounts for about 10% of diabetics and is characterized by a severe insulin deficiency resulting from a loss of insulin-secreting beta cells in the pancreas. The remainder of diabetic patients suffer from “Type II”, which is characterized by an impaired insulin response in the peripheral tissues (Robbins, S. L. et al.,
Pathologic Basis of Disease,
3rd Edition, W. B. Saunders Company, Philadelphia, 1984, p. 972). If uncontrolled, diabetes can result in a variety of adverse clinical manifestations, including retinopathy, atherosclerosis, microangiopathy, nephropathy, and neuropathy. In its advanced stages, diabetes can cause blindness, coma, and ultimately death.
The principal treatment for Type I diabetes is periodic insulin injection. Appropriate insulin administration can prevent, and even reverse, some of the adverse clinical outcomes for Type I diabetics. Frequent adjustments of the blood glucose level can be achieved either by discrete injections or, in severe cases, via an implanted insulin pump or artificial pancreas. The amount and frequency of insulin administration is determined by frequent or, preferably, continuous testing of the blood glucose level.
Tight control of blood glucose in the “normal range”, 60-120 mg/dL, is necessary for diabetics to avoid or reduce complications resulting from hypoglycemia and hyperglycemia. To achieve this level of control, the American Diabetes Association recommends that diabetics test their blood glucose 5 times per day. Thus, there is a need for accurate and frequent or, preferably, continuous glucose monitoring to combat the effects of diabetes.
Invasive Glucose Measurement
Conventional blood glucose measurements in a hospital or physician's office rely on the withdrawal of a 5-10 ml blood sample for analysis. This method is slow and painful and cannot be used for continuous glucose monitoring. An additional problem for hospitals and physician offices is the disposal of testing elements that are contaminated by blood.
Implantable biosensors have also been proposed for glucose measurement. (G. S. Wilson, Y. Zhang, G. Reach, D. Moatti-Sirat, V. Poitout, D. R. Thevenot, F. Lemonnier, and J.-C. Klein, Clin. Chem. 38, 1613 (1992)). Biosensors are electrochemical devices with enzymes immobilized at the surface of an electrochemical transducer.
Minimally Invasive Glucose Measurement
Portable, “minimally-invasive” testing systems are now commercially available. These systems require the patient to stick themselves to obtain a drop of blood which is then applied to a disposable test strip containing coated reagents or an electrochemical test element.
Although the portable instruments that read the strips are relatively inexpensive ($100-$200), the cumulative cost to diabetics for the disposable strips is considerable. Compliance is another major problem for minimally invasive techniques. Frequent finger sticks are painful and can result in infections, scarring, and nerve damage in the finger. Disposal of potentially biohazardous test strips is yet another problem with this method.
Noninvasive Glucose Measurement
“Noninvasive” (NI) glucose sensing techniques measure in-vivo glucose concentrations without collecting a blood sample. As defined herein, a “noninvasive” apparatus or method is one which can be used without removing a sample from, or without inserting any instrumentation into, the tissues. The concept involves irradiating a vascular region of the body with electromagnetic radiation and measuring the spectral information that results from one of four primary processes: reflection, absorption, scattering, or emission. The extent to which each of these processes occurs is dependent upon a variety of factors, including the wavelength and polarization state of the incident radiation and the glucose concentration in the body part. Glucose concentrations are determined from the spectral information by comparing the measured spectra to a calibration curve or by reference to a physical model of the tissue under examination. A brief description of noninvasive glucose measurements in the prior art is provided below.
Description of the Art
Infrared
NI techniques that utilize the absorption of infrared radiation can be divided into three distinct wavelength regimes: Near-infrared (NIR), Mid-infrared (MIR) and Far-infrared (FIR). As defined herein, NIR involves the wavelength range of from about 600 nm to about 1200 nm, MIR involves the wavelength range of from about 1200 nm to about 3000 nm, and FIR involves the wavelength range of from about 3000 nm to about 25000 nm. As defined herein, “Infrared” (or IR) is taken to mean a range of wavelengths from about 600 nm to about 25000 nm.
NIR
U.S. Pat. Nos. 5,086,229, 5,324,979, 5,237,178 describe a number of noninvasive NIR instruments and methods for measuring blood glucose. In general, a blood-containing body part (e. g., a finger) is illuminated by one or more light sources and the light that is transmitted through the body part is detected by one or more detectors. A glucose level is derived from a comparison to reference spectra for glucose and background interferants.
MIR
The use of MIR radiation for NI glucose measurement has been described in U.S. Pat. Nos. 5,362,966, 5,237,178, 5,533,509, 4,655,225. The principles of operation are similar to those described for the NIR, except that the penetration depth of the MIR light is less than that for NIR. As a consequence, most measurements in this region have been performed using a backscattering geometry. As defined herein, a “backscattering geometry” describes a configuration wherein scattered radiation is collected on the same side of the sample as the entry point of the incident radiation. A “transmission geometry” describes a configuration wherein light is transmitted through the sample and collected on the opposite side of the sample as the entry point of the incident radiation.
FIR
FIR measurements have been described in U.S. Pat. Nos. 5,313,941, 5,115,133, 5,481,113, 5,452,716, 5,515,847, 5,348,003, and DE 4242083.
Photoacoustic Spectroscopy
As will be described more thoroughly below, the photoacoustic (PA) effect results from the absorption of a pulse of optical energy, which is rapidly converted into thermal energy. The subsequent thermal expansion generates an acoustic pressure wave, which is measured by an acoustic transducer. In addition to the absorption of light, the measured PA signal depends upon the speed of sound in the medium, the thermal expansion coefficient of the analyte, and the specific heat of the medium.
Glucose measurements employing the photoacoustic effect have been described by Quan et al. (K. M. Quan, G. B. Christison, H. A. MacKenzie, P. Hodgson, Phys. Med. Biol., 38 (1993), pp. 1911-1922) and U.S. Pat. No. 5,348,002.
Caro et al. (U.S. Pat. No. 5,348,002) provides a PA detector and an optical detector; however, the device and method of Caro require that a relationship be drawn between the “photoacoustic response and the degree of absorption” of the sample. As will be described more fully below, the present invention requires no such a priori information. Rather, it is based solely upon a correlation between the measured PA signal and the analyte concentration. Further, the present invention employs focusing optics in order to generate a more concentrated PA signal than the apparatus of Caro et al., which employs the diverging output of an
Jeng Tayy-Wen
Lindberg John M.
McGlashen Michael L.
Oosta Gary M.
Pezzaniti Joseph L.
Abbott Laboratories
Weinstein David L.
Winakur Eric F.
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