Method for selecting wavelengths for optical data acquisition
There is provided a method for optimizing wavelength selection for multiwavelength optical data acquisition of chromophores in a turbid medium. The optimization is based on the minimization of a criterion based on the variance matrix of chromophores estimate features. The method can advantageously be used to obtain physiological information from biological tissue.
1 . A method for acquiring optical information from a turbid medium containing chromophores, the method comprising the steps of:
a) defining parameters of an optical system including at least a number N of said wavelengths, a value of each of said wavelengths, source power and detector aperture for each of said wavelengths, source/detector geometries, a choice of source and detector and noise characteristics;
b) fixing a value for all of said parameters except for said value for each of the wavelengths;
c) determining a chromophore estimate feature to minimize;
d) selecting a statistical distribution of errors for absorption coefficients of said chromophores;
e) determining an optimal set of N wavelengths by minimizing a criterion, wherein said criterion is based on said absorption coefficients as a function of wavelength, extinction coefficients of said chromophores and on a predetermined concentration value of said chromophores;
f) using said optimal set of N wavelengths for obtaining said optical information.
2 . The method as claimed in claim 1 wherein said chromophore estimate feature is selected from the group consisting of error on each chromophore, linear combination of errors on several chromophores, non-linear combinations of errors on one or several chromophores, correlation (cross-talk) between two chromophores, linear combination of correlations between chromophores, non-linear combination of correlations between chromophores and combination of errors and correlations between chromophores.
3 . The method as claimed in claim 2 wherein said step of selecting a statistical distribution of errors comprises providing a predetermined distribution.
4 . The method as claimed in claim 2 wherein said selection of statistical distribution of errors is determined based on empirical data.
5 . The method as claimed in claim 3 or 4 wherein said statistical distribution of errors is a mutlivariate statistic.
6 . The method as claimed in claim 5 wherein said multivariate statistic is selected from normal distribution, Poisson distribution, Gaussian distribution and binomial distribution.
7 . The method as claimed in claim 1 wherein said optical information is used to generate an optical image and wherein said optical system is an imaging optical system.
8 . The method as claimed in claim 1 wherein said optimal set of N wavelengths is used for determining concentration of said chromophores.
9 . The method of claim 5 wherein said statistical distribution of errors is a multivariate normal of zero mean and variance and wherein said criterion is (tr(C −1 A −1 λ Σ(A −1 λ ) T C −1 )).
10 . The method as claimed in claim 1 wherein said turbid medium is a biological tissue.
11 . The method as claimed in claim 10 wherein said biological tissue is selected from breast tissue and brain tissue.
12 . The method as claimed in claim 11 wherein said chromophores are selected based on physiological characteristics of said tissue.
13 . The method as claimed in claim 12 wherein said chromophores are selected from oxy-hemoglobin, deoxy-hemoglobin, water, lipids and combination thereof.
14 . The method as claimed in claim 1 wherein said chromophores comprise at least one fluorophore.
15 . The method as claimed in claim 14 wherein said fluorophore exhibits different spectral characteristics that differ in its free and bound state.
16 . The method as claimed in claim 15 said optical information is used to generate pharmacological data.
17 . The method as claimed in claim 1 wherein said optical information is acquired with a modality selected from Time-Domain, Frequency-Domain and Continuous wave.