Abstract:
A low cost means for increasing measurement sensitivity in LED/IRED near-infrared instruments is disclosed which utilizes a current modification means (27) for modifying the driving current supplied to each IRED (5) as a function of the opacity of the particular sample being measured. The current modification means is part of the processing means and comprises means for measuring a signal level (8) for each IRED at an analog-to-digital converter (10). Based upon the signal level detected for each IRED, the current modification means modifies the current to each IRED to a value that is as high as possible without saturating the analog-to-digital converter. Thus, by modifying the driving current of each IRED to such a maximal value, the analytical instrument of the present invention provides high resolution without the use of expensive electronic circuitry. Also provided is a system for generating and storing an optical signature of a particular user, thus further insuring the accuracy of measurements taken by the instrument.
Abstract:
An instrument (10) for near infrared interactance quantitative analysis measurements to improve accuracy and repeatability of the measured results. These objectives are achieved by placing a narrow bandpass optical filter (23) between near infrared emitting diode radiation sources (16, 16', 17, 17', 18 and 18') and a radiation transmission tube (12). The filter (23) allows for more distinct isolation of the desired wavelengths in the measurement to achieve improved accuracy and repeatability. The filters (23) also eliminate the time consuming task of sorting through several diodes in search of a particular diode (16, 16', 17, 17', 18 and 18') whose output wavelength band is centered at the desired wavelength.
Abstract:
A method and apparatus for performing quantitative noninvasive measurement of blood analytes, includes correction for measurement interference caused by pulse beat and changing body chemistry associated with blood circulation through the part of the body being measured as a function of time. A hypoglycemia monitor and alarm is provided which takes advantage of the methods described for separating pulse beat information from the measurement signals.
Abstract:
An improved near-infrared quantitative analysis instrument (1) includes a number of removable finger inserts (30) each dimensioned for a different finger size, which facilitates properly aligning and fitting an individual user's finger into the optical system of the analysis instrument (1) taking into account the size of the individual's finger. The inserts (30) according to the present invention can be also designed to accommodate samples of various substances for quantitative analyte measurement.
Abstract:
In a near infrared quantitative analysis instrument an initial sample (10) is measured (18, 24) for a plurality of characteristics which include the ambient temperature of the analysis instrument at the time of the reading, the temperature of the sample itself, the optical energy level of the sample, the moisture content of the sample, and the percent protein of the sample. These characteristics are stored in a computer (14, 22) to provide a series of comparison criteria. A subsequent sample (10) is then measured (18, 24) for the same characteristics as the initial sample. The initial and subsequent characteristics are compared (26). The subsequent sample is determined to be substantially identical to the initial sample for a given criterion if the subsequent sample's measurement for the corresponding characteristic is within a tolerance for that criterion. If the subsequent sample is judged to be substantially identical to the initial sample for all criteria, it is determined to be substantially identical to the initial sample.
Abstract:
Method and apparatus for determining percent fat in a body wherein near-infrared radiation (16, 16') is transmitted into the body to achieve optical interactance between the body and the near-infrared radiation. Optical absorption by the body at one or more wavelengths of the near-infrared radiation is measured (28, 29). The measured absorption of near-infrared radiation is utilized to quantitatively determine the fat content of the body. Data on a plurality of physical parameters of the body, such as height, weight, exercise level, sex, race, waste-to-hip measurement and arm circumference, can be utilized along with the measured near-infrared absorption in the quantitative determination of body fat content.
Abstract:
A procedure for verifying the accuracy of a non-invasive blood glucose measurement instrument (10) utilizes in vitro or invasive measurement instruments (100), the accuracy of which is independently verifiable. Several glucose readings are taken with each instrument at approximately the same times. The measurement data from the in vitro instrument (100) is transferred to the non-invasive instrument (10) where it is compared to the data regarding the non-invasive measurements. If the difference between the measurements of the respective instruments is within a preset range, the non-invasive instrument is permitted to be used for an additional period of time. However, if the difference is beyond an acceptable limit, then the non-invasive instrument is prevented from taking any additional measurements and must be serviced or repaired.
Abstract:
A near-infrared quantitative analysis instrument for measuring blood anlytes in a finger of a subject includes a temperature-sensing thermistor-type ring instrument (42) via a cable (41). A light shield glove (51) may be provided with the thermistor-type ring attached thereto.