Measuring and testing – Instrument proving or calibrating – Gas or liquid analyzer
Reexamination Certificate
1999-08-25
2001-03-06
Raevis, Robert (Department: 2856)
Measuring and testing
Instrument proving or calibrating
Gas or liquid analyzer
Reexamination Certificate
active
06196046
ABSTRACT:
TECHNICAL FIELD
The present invention relates to spectrometers used for the non-invasive generation and capture of thermal gradient spectra from human or animal tissue. More particularly, the present invention relates to devices and methods that calibrate spectrometers of the type that are used for the non-invasive generation and capture of thermal gradient spectra from human or animal tissue. Even more particularly, the present invention relates to calibration methods and devices that contain a base source of thermal gradient spectra associated with glucose to test and calibrate a spectrometer used for the non-invasive generation and capture of thermal gradient spectra from human or animal tissue.
BACKGROUND OF THE INVENTION
Millions of diabetics are force to draw blood daily to determine their blood sugar levels. To alleviate the constant discomfort of these individuals, substantial effort has been expanded in the search for a non-invasive apparatus and methodology to accurately determine blood glucose levels. Four patent applications, each assigned to Optiscan Biomedical Corporation of Alameda, Calif., have significantly advanced the state of the art of non-invasive blood glucose analysis The methodology taught in U.S. patent application Ser. No. 08/820,378 is performed by the apparatus taught in U.S. patent application Ser. No. 08/816,723, and each of these references is herewith incorporated by reference. While the methodology taught in the incorporated references presents a significant advance in non-invasive glucose metrology, there exists room for further improvements. One such improvement lies in the manner in which the data collected by the apparatus are manipulated. In the methodology taught in Ser. No. 08/820,378 a volts-to-watts radiometric calibration step is often required. To preclude this requirement, U.S. patent application Ser. No. 09/267,121 teaches a methodology that takes advantage of the fact that by inducing a temperature gradient, a difference parameter between the signal at a reference wavelength and the signal of an analyte absorption wavelength may be detected. The frequency or magnitude or phase difference of this parameter may be used to determine analyte concentration. A further object of the invention taught therein is to provide a method of inducing intermittent temperature modulation and using the frequency, magnitude, or phase differences caused by analyte absorbance to determine analyte concentration. This intermittent temperature may be periodic or a periodic. Another improvement concerns U.S. patent application Ser. No. 09/265,195 entitled: “Solid-state Non-invasive Infrared Absorption Spectrometer for the Generation and Capture of Thermal Gradient Spectra from Living Tissue” which teaches a method of inducing a temperature gradient and monitoring of radiation emitted from test samples. The complete teachings of U.S. patent application Ser. No. 09/267,121 and Ser. No. 09/265,195 are also herewith incorporated by reference.
As has been noted in Ser. No. 09/265,195, the non-invasive spectrometer require calibration to assure quality performance to the diabetic end user. While such calibration presents no particular difficulty in the laboratory environment, it will be appreciated that accurate calibration in the field presents some rather interesting challenges. The laboratory type standards are basically an aqueous solution of glucose, where the exact concentration of glucose is known. However, once this type of prior art standard solution leaves the laboratory it is subject to a wide variety of environment effects which can serve to degrade its accuracy. Such effects include, but are not limited to evaporation, contamination, fermentation, dilution, sundry photochemical effects, spillage, and the like. Given the need for extremely precise measurements afforded by the principles of the present invention, any degradation in accuracy is unacceptable. A further second problem lies in the fact that a prior art solution of glucose cannot properly mimic the physiology of human tissue. To applicants' knowledge there are no known standards available for use in calibrating a non-invasive spectrometer in the field that can overcome the foregoing problems associated with laboratory standards comprising aqueous solution of glucose.
Thus, a primary object of the present invention is to provide a calibration standard apparatus for use in calibrating a non-invasive spectrometer in the field.
A related object of the present invention is to provide a field calibration standard that overcomes the problems associated with prior art laboratory type of standards comprising aqueous solution of glucose.
An other object of the present invention is to provide a field calibration standard that properly mimic the physiology of human tissue.
Yet another object of the present invention is to provide a spectrometer apparatus that not only can perform non-invasive glucose level tests in humans, but that is adapted to receive the calibration standards and perform the thermal gradient calibration measurements.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the foregoing object is accomplished by providing a calibration standard for calibrating a thermal gradient spectrometer. The standard comprises a structure having a particular glucose concentration which a thermal gradient spectrometer reads for determining whether the spectrometer is in calibration. The structure of the calibration standard properly mimics the physiology of human tissue. Human tissue, and most importantly human skin, is a layered structure. Accordingly, the principles of the present invention contemplate the use of layered polymeric standard structures which closely mimic human skin. A number of such standards, each containing a difference concentration of glucose, may be used.
One structure for such a standard includes a number of polymeric layers. The first layer, that which is placed in contact with the optical window of the spectrometer is intended to mimic the stratum corneum. The second layer mimics the epidermis. Standards are provided at a variety of glucose concentrations including concentrations consisting of 0% glucose; 50 mg/dL glucose (physiological hypoglycemia); 10 mg/dL glucose (physiological normal); 500 mg/dL glucose (physiological hyperglycemia); and 1000 mg/dL glucose (outside the physiological limits). The standards are packed in a hermetic container and treated to prolong shelf life and to retard microbial growth. Sterile standards are also within the scope of the present invention. The container, and the standards themselves are provided with imprinted data about the standard, including its glucose concentration. The labeling could be machine-readable, for example, using a bar code.
In use, a spectrometer is placed in a calibration mode, manually or automatically upon presentation of the standard thereto. The spectrometer then reads the encoded information from the standard, or as manually entered. The spectrometer then scans the standard. When complete, the instrument prompts for the next standard in the series. When all standards in the series have been scanned, the spectrometer post-processes the data. The instrument may then determine that it is within specification, and so notifies the operator. The instrument could also determine that it is out of specification and may perform an automatic adjustment. It will then notify the operator that the adjustment have been successfully accomplished. The instrument may also determine that it is out of specification and that it requires manual adjustment. The operator must be notified accordingly. In each of the above cases, operator notification may additionally require a network connection to a computer or remote database. Such network connection may provide not only a repository for calibration information for a number of instruments, but may serve to automatically calibrate the instrument from the remote location. In similar fashion, the network connection may also be utilized to retain a remote database of patient information, a
Azizi Kamrava
Braig James R.
Correia David J.
Godfrey Joan C.
Goldberger Daniel S.
LaRiviere Grubman & Payne, LLP
Optiscan Biomedical Corporation
Raevis Robert
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