Radiant energy – Luminophor irradiation – With ultraviolet source
Reexamination Certificate
1995-12-01
2001-05-15
Westin, Edward P. (Department: 2878)
Radiant energy
Luminophor irradiation
With ultraviolet source
C250S459100
Reexamination Certificate
active
06232609
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to glucose monitoring, and more particularly, to glucose level monitoring using laser-induced emission spectroscopy.
Millions of people, afflicted with diabetes, must periodically monitor their blood glucose level because their bodies are unable to maintain a constant blood glucose level without diet adjustments and periodic insulin injections. Most popular methods for monitoring blood glucose levels require a small blood sample that is periodically drawn from the body for analysis.
Recently, noninvasive optical techniques have been developed to monitor the blood's glucose level using infrared absorption through a portion of the body. However, infrared absorption techniques are susceptible to accuracy problems, in part because glucose has more than 20 infrared absorption peaks, many of which overlap with the absorption peaks of other constituents in the body.
Fluorescence spectroscopy using ultraviolet (UV) excitation light has been introduced for monitoring glucose levels. This technique requires, among other things, the monitoring of a spectral peak within the induced fluorescence spectrum. Accurately locating the peak may be difficult for a low-level fluorescence signal in the presence of noise. Increasing the intensity of the excitation light may not be a desirable option because of concerns of UV exposure to the body. Also, known fluorescence spectroscopic techniques generally fail to take full advantage of information contained in the fluorescence spectrum at wavelengths other than the peak wavelength and fail to account for certain nonlinear relationships between the glucose level and the resulting emission spectra.
From the discussion above, it should be apparent that there is a need for an apparatus, and related method, for monitoring glucose that is simple and rapid to use, and that provides good accuracy in spite of nonlinearities or low signal-to-noise levels. The present invention fulfills these needs.
SUMMARY OF THE INVENTION
The present invention is embodied in an apparatus, and related method, that determines the concentration of glucose in a sample that includes water, by directly monitoring induced glucose ultraviolet and visible (UV-visible) emission light from the sample. The apparatus compensates for nonlinearities between these parameters and the glucose.
The apparatus includes a light source, a sensor, and a processor. The light source emits ultraviolet excitation light of at least one predetermined energy level. The excitation light is directed at a sample to produce return light from the sample. The return light includes induced emissions of light produced as a result of interactions between the excitation light and any glucose with water present in the sample. The sensor monitors the return light and generates at least three electrical signals indicative of the intensity of return light associated with glucose concentration distinguishing characteristics of the emission light. The processor processes the electrical signals, using a predictive model, to determine the concentration of glucose in the sample. In one feature of the invention, the predictive model is defined using six latent variables. The latent variables are used to derive prediction coefficients that are associated with the glucose concentration distinguishing characteristics.
In a more detailed feature of the invention, the intensity of the excitation light remains relatively constant while the sensor generates the electrical signals. Further, the at least three electrical signals indicate the intensity of return light within a respective number of predetermined wavelength bands within the wavelength band of the emission light. In another feature, the sensor may includes a first detector adapted to detect the return light within a first wavelength band and generate a first electrical signal, a second detector adapted to detect the return light within a second wavelength band and generate a second electrical signal, and a third detector adapted to detect the return light within a third wavelength band and generate a third electrical signal.
In yet another more detailed feature of the invention, the sensor monitors the intensity of return light within eight different wavelength bands and generates eight electrical signals, each indicative of the intensity of return light within a respective wavelength band. More particularly, using an excitation light having a wavelength of about 308 nanometers, the eight wavelength bands may be centered at about 342, 344, 347, 352, 360, 370, 385 and 400 nanometers, respectively. Alternatively, the sensor may generate a plurality of electrical signals that indicate the intensity of return light substantially continuously across an extended wavelength spectrum associated with the emission light.
In another more detailed feature of the invention, the energy of the excitation light is varied over several predetermined energy levels, and the sensor generates, at each intensity level, a first electrical signal based on the intensity of return light within a wavelength of the emission light associated with raman scattering, and a second electrical signal based on the intensity of return light within a wavelength band of the emission light associated with a peak of a broad glucose emission band. Further, the apparatus may include one or more waveguides for transmitting the excitation light from the light source to the sample and for transmitting the return light from the sample to the sensor.
In a related method of the invention, a regression model is provided that accounts for a nonlinear relationship between the concentration of glucose in a sample and an electrical signal based on certain glucose concentration distinguishing characteristics of a light emission spectrum that includes UV-visible emission light produced by glucose related interactions with the excitation light. Further, a sample is caused to produce a light emission spectrum that includes emission light produced by any glucose related interaction or direct fluorescence, and a plurality of electrical signals are generated that represent the glucose concentration distinguishing characteristics. Finally, the plurality of electrical signals are processed, using the regression model, to determine the glucose concentration and an electrical signal generated based on the glucose concentration determined using the regression model.
Other features and advantages of the present invention should become apparent from the following description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.
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Grundfest Warren S.
Snyder Wendy J.
Cedars-Sinai Medical Center
Hanig Richard
Pretty, Schroeder & Poplawski, P.C.
Westin Edward P.
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