Methods for noninvasive determination of in vivo alcohol concentration using Raman spectroscopy
Methods and apparatuses for the determination of an attribute of the tissue of an individual use non-invasive Raman spectroscopy. For example, the alcohol concentration in the blood or tissue of an individual can be determined non-invasively. A portion of the tissue is illuminated with light, the light propagates into the tissue where it is Raman scattered within the tissue. The Raman scattered light is then detected and can be combined with a model relating Raman spectra to alcohol concentration in order to determine the alcohol concentration in the blood or tissue of the individual. Correction techniques can be used to reduce determination errors due to detection of light other than that from Raman scattering from the alcohol in the tissue. Other biologic information can be used in combination with the Raman spectral properties to aid in the determination of alcohol concentration, for example age of the individual, height of the individual, weight of the individual, medical history of the individual and his/her family, ethnicity, skin melanin content, or a combination thereof. The method and apparatus can be highly optimized to provide reproducible and, preferably, uniform radiance of the tissue, low tissue sampling error, depth targeting of the tissue layers or sample locations that contain the attribute of interest, efficient collection of Raman spectra from the tissue, high optical throughput, high photometric accuracy, large dynamic range, excellent thermal stability, effective calibration maintenance, effective calibration transfer, built-in quality control, and ease-of-use.
1. A method for the non-invasive determination of an attribute of a human tissue of an individual by Raman spectroscopy using a single spectrometer, wherein the spectrometer comprises a detector configured to detect light incident thereon, the method comprising:
(a) illuminating a portion the tissue with excitation light, where the tissue is not the eye;
(b) collecting light from the tissue and generating a spectroscopic signal using the single spectrometer subsystem, wherein the spectroscopic signal includes information from at least one of: a steady state Raman measurement, a time-resolved Raman measurement, a spontaneous Raman measurement, a surface-enhanced Raman scattering (SERS) measurement, an anti-Stokes Raman scattering measurement, and a coherent anti-Stokes Raman spectroscopy (CARS) measurement, and wherein wavelength information obtained from a reference beam in connection with the spectroscopic signal is obtained with the detector, and wherein wavelength information obtained from the tissue in connection with the spectroscopic signal is obtained with the same detector; and
(c) determining the attribute from the spectroscopic signal and a multivariate model relating spectroscopic signals from Raman scattering and the attribute.
2. The method of claim 1 , further comprising determining at least one additional attribute from the spectroscopic signal using a model relating spectroscopic signals from Raman scattering to the at least one additional attribute.
3. The method of claim 1 , further comprising combining biologic information of the individual with the model to determine the attribute.
4. The method of claim 1 , wherein the attribute comprises analyte presence, analyte concentration, rate or direction of change of analyte concentration, or combinations and subsets thereof.
5. The method of claim 4 , wherein the analyte comprises alcohol.
6. The method of claim 4 , wherein the analyte comprises a substance of abuse.
7. The method of claim 4 , wherein the analyte comprises an alcohol byproduct.
8. The method of claim 1 , wherein the tissue comprises tissue containing a plurality of constituents that display Raman scattering at one or more wavelengths in common with the wavelengths at which the analyte exhibits electronic absorption.
9. The method of claim 1 , wherein the tissue comprises skin of the forearm, finger, palm, hand, or wrist.
10. The method of claim 1 , wherein the attribute comprises biometric data.
11. The method of claim 10 , further comprising determining the identity of the individual from the biometric data.
12. The method of claim 11 , wherein determining the identity of the individual comprises determining whether the individual is among an enrolled set of individuals.
13. The method of claim 12 , wherein determining the identity of the individual comprises comparing a Raman spectrum of the detected light for the individual to enrollment spectra of the enrolled set of individuals.
14. The method of claim 10 , further comprising verifying the identity of the individual from the biometric data.
15. The method of claim 14 , wherein the identity verifying step comprises comparing a Raman spectrum of the detected light for the individual to an enrollment spectrum for the individual.
16. The method of claim 1 , wherein the illuminating step comprises illuminating the tissue with excitation light delivered from an optical input and the detecting step comprises collecting the emitted light with an optical output and the method further comprises orienting the optical input and the optical output to target a compartment of the tissue pertinent to the attribute.
17. The method of claim 1 , wherein the determining step comprises spectrally separating the detected light to provide a measured Raman spectrum and the method further comprises correcting the measured Raman spectrum.
18. The method of claim 17 , wherein the correcting step comprises correcting the measured Raman spectrum for tissue scattering and absorption of the excitation light and the emitted light to provide an intrinsic tissue Raman emission.
19. The method of claim 1 , wherein a Raman spectrum from an individual is adjusted by an enrollment spectrum from the individual.
20. The method of claim 19 , wherein the enrollment spectrum of an individual is mathematically adjusted by a Raman spectrum upon successful identity determination or verification.
21. The method of claim 1 , wherein the determining step comprises collecting calibration or training data and establishing a mathematical relationship between the training data and the attribute represented in the training data.
22. The method of claim 1 , further comprising mitigating the presence of a topical interferent on the attribute determination.
23. The method of claim 22 , wherein the topical interferent mitigating step comprises removing the topical interferent from the tissue prior to the detecting step.
24. The method of claim 22 , wherein the topical interferent mitigating step comprises removing outlier measurements from the attribute determining step.
25. The method of claim 22 , wherein the topical interferent mitigating step comprises adapting the model in the attribute determining step to include a spectral signature of the topical interferent.