Apparatuses 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. An apparatus for the non-invasive in vivo determination of the concentration of alcohol, a substance of abuse, or both, in human tissue of an individual by Raman spectroscopy, comprising:
(a) an illumination subsystem for generating excitation light,
(b) a sampling subsystem for delivering the excitation light to a portion of the in vivo tissue and detecting light from the in vivo tissue, wherein the sampling subsystem comprises:
(b1) an optical input to receive the excitation light from the illumination subsystem,
(b2) a sampling surface that forms a tissue interface to illuminate the tissue with the excitation light delivered from the optical input, and
(b3) an optical output to collect the emitted light from the tissue and output the collected light to the spectrometer subsystem, wherein at least one of the optical input and the optical output comprises one or more optical fibers, wherein the optical input and the optical output comprise the same optical fibers;
(c) a spectrometer subsystem for determining a Raman spectrum from the detected light
(d) a computing subsystem for correcting the measured Raman spectrum, and
(e) a calibration subsystem for determining the relationship between the corrected Raman spectrum and the concentration of alcohol, a substance of abuse, or both.
2. The apparatus of claim 1 , wherein the illumination subsystem comprises a light source comprising a continuous wave diode laser; a pulsed, modulated or mode-locked laser; a solid-state laser; an organic light emitting diode; a solid state light emitting diode; a gas laser; or a broad-band light source with a line filter.
3. An apparatus of claim 1 , an optical diffuser or scrambler to provide reproducible and uniform radiance at the input of the sampling subsystem.
4. The apparatus of claim 3 , wherein the optical diffuser or scrambler comprises a ground glass plate, a reflective integrating chamber, a diffuse integrating chamber, a homogenizer, or a light pipe.
5. The apparatus of claim 1 , further comprising an ergonomic apparatus to hold the sampling surface and to position the tissue at the interface.
6. The apparatus of claim 5 wherein the ergonomic apparatus mounts with the tissue of the individual.
7. The apparatus of claim 1 , further comprising a line filter between the optical input and the tissue to pass a narrow bandwidth of the excitation light from the illumination subsystem.
8. The apparatus of claim 1 , further comprising a light pipe or homogenizer between the optical output and the spectrometer subsystem.
9. The apparatus of claim 1 , further comprising a high pass filter between the sampling surface and the spectrometer subsystem.
10. The apparatus of claim 1 , wherein the optical input and the optical output comprise two or more channels, each channel comprising a specific orientation of the optical input and the optical output.
11. The apparatus of claim 10 , wherein the two or more channels are oriented to target a compartment of the tissue pertinent to the concentration of alcohol, a substance of abuse, or both.
12. The apparatus of claim 1 , wherein the input and output optical fibers are arranged in concentric rings with a cylindrical gap therebetween.
13. The apparatus of claim 1 , wherein the input and output optical fibers are arranged in a linear geometry.
14. The apparatus of claim wherein at least one of the optical input and the optical output comprises a light pipe, lens, or mirror.
15. The apparatus of claim 1 , wherein the sampling subsystem further comprises a thermostat to maintain a constant temperature of the tissue.
16. The apparatus of claim 1 , wherein the sampling subsystem further comprises an index matching fluid between the sampling surface and the tissue.
17. The apparatus of claim 1 , wherein the spectrometer subsystem comprises a dispersive spectrometer.
18. The apparatus of claim 1 , wherein the spectrometer subsystem comprises an interferometric/modulating spectrometer.
19. The apparatus of claim 18 , wherein the interferometric/modulating spectrometer comprises a Fourier Transform spectrometer.
20. The apparatus of claim 1 , wherein the computing subsystem comprises means for correcting the measured spectrum for tissue scattering and absorption of the excitation light and the emitted light to provide an intrinsic tissue Raman emission.
21. An apparatus as in claim 1 wherein the computing subsystem comprises means for subtracting an enrollment spectrum for the individual, determined at a different time than the present determination of the Raman spectrum, from the measured Raman spectrum.
22. The apparatus of claim 1 , further comprising a biometric measurement device for collecting biometric data of the individual.
23. The apparatus of claim 22 , further comprising means for identifying the individual by comparing the biometric data of the individual with enrollment data for an enrolled set of individuals.
24. The apparatus of claim 23 , wherein the identifying means comprises comparing a Raman spectrum of the detected light for the individual to enrollment spectra of the enrolled set of individuals.
25. The apparatus of claim 22 , further comprising means for verifying the individual by comparing the biometric data of the individual with enrollment data for the individual.
26. The apparatus of claim 25 , wherein the verifying means comprises comparing a Raman spectrum of the detected light for the individual to an enrollment spectrum for the individual.