Apparatus and method for detecting a substance

• US 6,484,044 B1
• Filed: 04/28/2000
• Issued: 11/19/2002
• Est. Priority Date: 04/30/1999
• Status: Active Grant

• Current Assignee: Hermann V. Lilienfeld-Toal
• Original Assignee: Hermann V. Lilienfeld-Toal
• Inventors: Lilienfeld-Toal, Hermann v.
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): KREMER, MATTHEW J
• Application Number:
  US09/560,169
• Time in Patent Office: 935 Days
• Field of Search: 600/309-310, 600/322-324, 600/326, 600/328, 600/315-316, 600/365
• US Class Current: 600/316
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids

Abstract

An apparatus for detecting a substance in a sample, particularly for in vivo detecting and measuring glucose in body tissue or blood contains a semiconductor laser for emitting mid-infrared laser light at at least two discrete wavelengths, each at a different peak or valley in the absorption spectrum of the substance in the sample. A photoacoustic detector detects acoustic signals originating from absorption of the laser light. An indication unit evaluates the acoustic signals separately for each wavelength and calculates a detection result based on all acoustic signals from the different wavelengths.

Claims

1. An apparatus for detecting a substance in a sample, comprising:

a laser device for irradiating the sample with a light beam which penetrates into the sample,

an acoustic detector for detecting acoustic signals originating within the sample from absorption of the light beam, and

an indication unit coupled to the acoustic detector for indicating the presence of a substance from the detected acoustic signals,

wherein the laser device generates infrared light of at least two discrete wavelengths in a mid-infrared wavelength region of 2.5 to 25 μ

m, each discrete wavelength at a different peak or valley in the absorption spectrum of an substance in the sample, and wherein the indication unit indicates the presence of the substance based on acoustic signals detected for each of said discrete wavelengths.

2. An apparatus according to claim 1, wherein said discrete wavelengths include one at a peak and one at a valley in the absorption spectrum.

3. An apparatus according to claim 1, wherein said discrete wavelengths include at least three distinct wavelengths each at a peak or valley in the absorption spectrum.

4. An apparatus according to claim 1, wherein said laser device emits said at least two discrete wavelengths as individual laser beam pulses at different times to a same location of the sample.

5. An apparatus according to claim 1, wherein the laser device includes a semiconductor laser having a quantum well structure.

6. An apparatus according to claim 5, wherein the semiconductor laser is a quantum cascade laser.

7. An apparatus according to claim 1, wherein said indication unit includes calculating means for calculating the concentration of a substance from-the amplitude of the acoustic signal at each of said discrete wavelengths by a least square method based on a reference spectrum.

8. A method for detecting a substance in a sample, comprising the following steps:

irradiating the sample with a laser light beam which penetrates into the sample,

detecting acoustic signals originating within the sample from absorption of the laser light beam, and

indicating a presence of the substance from the detected acoustic signals,

wherein said laser light beam is generated at at least two discrete wavelengths in a mid-infrared wavelength region of 2.5 to 25 μ

m, each discrete wavelength at a different peak or valley in a absorption spectrum of the substance in the sample, and the presence of the substance is indicated based on the acoustic signal detected for each of said discrete wavelengths.

9. An apparatus for detecting a substance in a sample wherein the substance has an absorption spectrum, comprising:

a laser device for irradiating the sample with a light beam which penetrates into the sample, the laser device generating the light beam at a plurality of discrete bandwidths in a mid-infrared wavelength region of 2.5 to 25 μ

m, each discrete bandwidth being located at a different peak or valley bandwidth of an absorption spectrum of the substance and having a bandwidth that is smaller than its corresponding peak or valley bandwidth of the absorption spectrum of the substance;

an acoustic detector for detecting acoustic signals originating within the sample from absorption of the light beam, and

an indication unit coupled to the acoustic detector for indicating the presence of the substance from the detected acoustic signals, the indication unit indicating the presence of the substance based on acoustic signals detected for each of the discrete bandwidths.

10. The apparatus of claim 9 wherein each discrete bandwidth of the light beam does not exceed two thirds of the width of its corresponding peak or valley bandwidth of the absorption spectrum of the substance.

11. The apparatus of claim 9 wherein each discrete bandwidth of the light beam does not exceed one third of the width of its corresponding peak or valley bandwidth of the absorption spectrum of the substance.

12. The apparatus of claim 9 wherein the discrete bandwidths include at least one bandwidth at each peak or valley bandwidth of the absorption spectrum.

13. The apparatus of claim 9 wherein the laser device includes a semiconductor laser having a quantum well structure.

14. The apparatus of claim 13 wherein the semiconductor laser is a quantum cascade laser.

15. The apparatus of claim 9 wherein the indication unit includes means for calculating a concentration of the substance from the amplitude of the acoustic signal at each discrete bandwidth by a least square method based on a reference spectrum.

16. The apparatus of claim 15 wherein the calculating means discards a portion of each acoustic signal, which in accordance with a traveling time of the signal, originates from a portion of the sample where no useful information on the substance is expected.

17. A method for detecting a substance in a sample wherein the substance has an absorption spectrum, comprising the following steps:

irradiating the sample with a laser light beam which penetrates into the sample, the light beam being at a plurality of discrete bandwidths in a mid-infrared wavelength region of 2.5 to 25 μ

m, each discrete bandwidth being located at a different peak or valley bandwidth of the absorption spectrum of the substance and having a bandwidth that is smaller than its corresponding peak or valley bandwidth of the absorption spectrum of the substance;

detecting acoustic signals originating within the sample from absorption of the laser light beam, and

indicating a presence of the substance based on the acoustic signals detected for each of the discrete bandwidths.

18. The method of claim 17 wherein each discrete bandwidth of the light beam does not exceed two thirds of the width of its corresponding peak or valley bandwidth of the absorption spectrum of the substance.

19. The method of claim 17 wherein each discrete bandwidth of the light beam does not exceed one third of the width of its corresponding peak or valley bandwidth of the absorption spectrum of the substance.

20. The method of claim 17 wherein the discrete bandwidths include at least one bandwidth at each peak or valley peak or valley bandwidth of the absorption spectrum.