Data processing: measuring – calibrating – or testing – Calibration or correction system
Reexamination Certificate
2001-08-28
2003-09-02
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
C250S573000, C702S090000, C703S002000
Reexamination Certificate
active
06615151
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the fields of spectroscopy, spectrophotometry, and chemometrics. In particular, the present invention relates to a method of building instrument variation tolerance into calibration algorithms for spectroscopic devices for chemical composition analysis with spectroscopic methods. The method of the present invention is particularly suitable for blood glucose, cholesterol and other chemical components prediction based on near-infrared spectrophotometry measurements.
BACKGROUND OF THE INVENTION
Spectroscopy is a well established method, which has extremely wide applications for chemical analysis of plasma, gases, liquids and solids practically in all field of modern science and technology as well in everyday life including food production, food processing, healthcare and medicine. The role of spectroscopy is to identify and to perform quantitative analysis of chemical composition of various bodies and substances or to recognize and measure concentration one or more selected chemical components (analytes) in the bodies and substances. One of such applications is a non-invasive measurement of different substances like glucose, cholesterol water, fat, protein, hemoglobin, melanin and other in human body, therefore a non-invasive glucose concentration measurement has been selected here as an illustrative example only and cannot be considered as an exclusive area of patent application.
Biotechnological analysis and examination are often based on the measurement of various chemical analytes in the composition of a biological matrix such as blood, interstitial fluid, or living tissue. Such measurements may be used to evaluate a patient's state of health and to determine what, if any, treatment is necessary. For example, the frequent monitoring of blood glucose levels in diabetic persons with glucometers is often necessary to allow such persons to manage the diabetes mellitus disease, by taking insulin injections or oral drugs to lower blood glucose when required. Intensive treatment based on frequent blood glucose measurements can significantly reduce the incidence of blindness, kidney loss, and other complications associated with diabetes.
Most home-based glucose measurement systems require the patient to invasively collect a blood sample, by pricking his or her finger, placing the sample on an appropriate test strip, and then testing the sample in an optical glucometer. For millions of diabetics around the world, the use of lancets or other sharp instruments to draw blood for monitoring their insulin levels is a painful process, and one that often builds up calluses on fingers, making the collection of blood even more difficult. This invasive procedure may be especially difficult to perform on children and therefore particularly trying on parents. Furthermore, the test strips required for each blood sample are generally not reusable, and when multiple measurements are taken each day, amount to significant costs from the patient's point of view. Thus, despite the fact that a large number of diabetics should take several measurements throughout each day (for some individuals, physicians recommend testing glucose levels from 4 to 7 times daily), due to the pain, cost, and inconvenience involved, many diabetics do not monitor their glucose levels frequently enough. A non-invasive means of measuring blood glucose levels is needed to eliminate the pain and risk of infection associated with drawing blood and thus increase the likelihood that diabetics will perform the recommended number of measurements.
For example, spectroscopy of samples containing molecules of various chemical substances is based on the analysis of how incident radiation interacts with the vibrational and rotational states of molecules, which are of analytical interest. Spectroscopic measurement techniques have gained increased popularity because of the ability to provide fast and non-invasive measurements of concentrations of different chemicals or analytes. For the reasons indicated above, this is particularly desirable for home based glucometers. Spectrophotometry is a type of spectroscopy commonly used to quantitatively measure concentrations of analytes based on spectral energy distribution in the absorption spectrum of a sample solution or medium. In spectrophotometry, the spectral power (or energy) distribution is typically analyzed within a selected part of a range of the ultraviolet, visible, or infrared spectra.
For example, near-infrared radiation (NIR) is electromagnetic radiation having a wavelength of between about 0.75 and 2.5 micrometers (i.e. from 120 to 400 THz). Near-infrared spectrophotometry generally uses instruments, which spatially disperse radiation of different wavelengths within this range, and whose spectral power density (or integrated over certain time period spectral energy density) is measured with a suitable radiation detector. The NIR spectrophotometry is increasingly being used to measure in vivo analytes such as glucose, fructose, glycerol, and ethanol.
Non-invasive, spectrophotometric measurement of glucose in human beings is performed by illumination of the selected part of human body with radiation of a known spectral composition and detecting changes in the spectral composition of the radiation interacting with (affected by) the selected body part or sample, in general. Following the Beer's law, most often these changes are expressed in the form of a function which presents a negative logarithm of the ratio of spectral power (or energy) densities of radiation flux affected by the sample to that of incident. Usually this function is referred to as absorbance. For non-absorbing samples, in absence of losses other than radiation absorption in the sample, this function is a constant equal to zero. If absorption of radiation in the sample is spectrally dependent, this function takes different values for different wavelengths (or frequencies) of the radiation and is usually called a spectral absorption (or absorbance) of the sample. Practically all known substances demonstrate absorption of electromagnetic radiation in certain spectral ranges, hence they modify spectral composition of light affected. The relative changes in spectral composition of radiation, caused by different molecules create different patterns spectral absorption pattern, specific for molecules. Therefore, recognition of this pattern can be used for identification of molecules creating the pattern. This is relatively easy when the pattern is created by a single or a very small number of sorts of molecules, with distinctively different absorption spectra. The problem becomes more complex when either the sample contains a large number of sorts of molecules or their spectra are very similar. In particular, the absorbance of the incident radiation by human body is due to presence of the various chemical components within that body as: water, fat, protein, hemoglobin, melanin, glucose and many other components. One difficulty with glucose measurement using spectral analysis, is the spectral overlap between glucose and other chemicals found in blood, often in much greater quantities than glucose. In addition, the thickness, color, and structure of the skin, bones, and blood through which the incident radiation passes affects the spectral changes in light interaction (transmitted, reflected or absorbed. Furthermore, the concentration of analytes can vary with changes in activity level, diet, hormone fluctuations, and other factors. Glucose concentration measurements are also particularly susceptible to variations in physical and chemical conditions including temperature, pressure, humidity, and skin hydration. As a result, to perform a reliable non-invasive glucose prediction, NIR spectral measurements should be performed through a vascular equilibrated region of the body, and a NIR glucose spectrophotometer must be carefully designed so that the quality of raw spectral information from an NIR glucometer is high. See generally Waynant and Chenault, “Overv
Cadell Theodore E.
Pawluczyk Romuald
Scecina Thomas
Barlow John
CME Telemetrix Inc.
Foley & Lardner
Le John
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