Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Determining biological unknowns
Keywords Spectral analysis, Electromagnetics
Applicant: Sandia Corp. (US)
Patent number: US5857462
Publication date: 12 January 1999
Title: Systematic wavelength selection for improved multivariate spectral analysis
The invention presents methods and apparatus for determining in a biological material one or more unknown values of at least one known characteristic, for example the concentration of an analyte such as glucose in blood or the concentration of one or more blood gas parameters, with a model based on a set of samples with known values of the known characteristics and a multivariate algorithm using several wavelength subsets. The method includes selecting multiple wavelength subsets, from the electromagnetic spectral region appropriate for determining the known characteristic, for use by an algorithm wherein the selection of wavelength subsets improves the model's fitness of the determination for the unknown values of the known characteristic.
The selection process utilises multivariate search methods that select both predictive and synergistic wavelengths within the range of wavelengths utilized.
The fitness of the wavelength subsets is determined by the fitness function F=f(cost, performance). The method includes the steps of:
using one or more applications of a genetic algorithm to produce one or more count spectra, with multiple count spectra then combined to produce a combined count spectrum;
smoothing the count spectrum;
selecting a threshold count from a count spectrum to select these wavelength subsets which optimize the fitness function; and
eliminating a portion of the selected wavelength subsets.
The determination of the unknown values can be made: noninvasively and in vivo; invasively and in vivo; or in vitro.