Continous Light Emission Photoacoustic Spectroscopy

• US 20110190612A1
• Filed: 02/02/2011
• Published: 08/04/2011
• Est. Priority Date: 02/02/2010
• Status: Abandoned Application

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: McKenna, Edward M., Li, Youzhi
• Application Number:
  US13/019,742
• Publication Number:
  US 20110190612A1
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/412 Detecting or monitoring sepsis
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: G01N 2021/1706 in solids
• CPC Class Codes: G01N 2021/3144 for oxymetry
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 21/4795 spatially resolved investigating of object in scattering medium in vivo A61B

Abstract

Methods and systems are provided for analyzing microcirculation using photoacoustic spectroscopy by emitting continuous light at one or more frequencies. A photoacoustic spectroscopy monitor may utilize a slow modulation method to vary the wavelength of light emitted, such that different absorbers may be measured in a patient'"'"'s tissue. The photoacoustic spectroscopy sensor may emit a lower power continuous light towards a patient'"'"'s tissue. The acoustic response generated by the tissue may be sensed by a thin polymer sensing film at the detector of the sensor. Based on the amplitude and phase information of the acoustic response sensed by the detector, the monitor may determine a concentration of an absorber, as well as a location of the absorbers, in the patient'"'"'s tissue.

Claims

1. A method, comprising:

modulating a continuous light source in a photoacoustic spectroscopy sensor to emit a light having a wavelength absorbable by an absorber in a patient'"'"'s tissue;

emitting the modulated light towards the patient'"'"'s tissue; and

determining an amplitude component and a phase component of an acoustic wave generated in response to the emitted modulated light.

2. The method, as set forth in claim 1, wherein modulating the continuous light source comprises modulating the continuous light source at two or more frequencies.

3. The method, as set forth in claim 2, wherein the two or more frequencies are based on one or more of a physiological condition of the patient, one or more absorbers in the patient'"'"'s tissue, or a configuration of the photoacoustic spectroscopy sensor.

4. The method, as set forth in claim 1, wherein the continuous light source emits light continuously, at approximately 50 mW to 1 W.

5. The method, as set forth in claim 1, wherein the amplitude component and the phase component of the acoustic wave are determined based on a comparison of the acoustic wave with a waveform of the emitted modulated light.

6. The method, as set forth in claim 1, wherein the amplitude component of the acoustic wave indicates a concentration of the absorber.

7. The method, as set forth in claim 1, wherein the phase component of the acoustic wave indicates a location of the absorber in the patient'"'"'s tissue.

8. A photoacoustic spectroscopy system, comprising:

a continuous wave light source configured to be modulated to emit one or more wavelengths of light into a patient'"'"'s tissue;

a detector configured to receive a response wave generated in the patient'"'"'s tissue in response to the light emitted by the continuous wave light source, wherein the response wave is non-optical; and

a processor configured to determine a concentration of an absorber in the patient'"'"'s tissue based on the response wave and the one or more wavelengths of light.

9. The system, as set forth in claim 8, comprising a modulator configured to modulate the continuous wave light source through a range of frequencies.

10. The system, as set forth in claim 8, wherein the response wave is one or more of a pressure wave, an acoustic wave, or a thermal wave.

11. The system, as set forth in claim 8, wherein the detector comprises a Fabry-Perot polymer film transducer.

12. The system, as set forth in claim 8, wherein the detector comprises a film between about 1 μ

m to about 50 μ

m in thickness.

13. The system, as set forth in claim 8, comprising a lock-in amplifier configured to determine a frequency of the response wave based on the light emitted into the patient'"'"'s tissue.

14. The system, as set forth in claim 13, wherein the lock-in amplifier is configured to output a voltage signal comprising one or more of amplitude information or phase information of the response wave.

15. The system, as set forth in claim 8, comprising a photoacoustic spectroscopy sensor configured to continuously emit the one or more wavelengths of light, and further configured to receive the response wave.

16. The system, as set forth in claim 8, further comprising a pulse oximetry sensor configured to emit one or more wavelengths of light to the patient'"'"'s tissue and receive the light that has been transmitted through or scattered by the patient'"'"'s tissue.

17. The system, as set forth in claim 8, comprising memory storing algorithms directed to calculating the concentration of the absorber and the depth of the absorber, wherein the processor is capable of accessing the memory to execute the algorithms.

18. A photoacoustic spectroscopy monitor, comprising:

a modulator configured to modulate a continuous light source;

data processing circuitry configured to receive a response to an emission of the continuous light source and determine an amplitude and a phase of the response, wherein the response comprises non-optical data; and

a processor configured to utilize one or more of the amplitude or the phase to calculate one or more of a concentration of an absorber in a patient'"'"'s tissue or a location of the absorber.

19. The monitor of claim 18, wherein the response is on or more of a pressure wave, an acoustic wave, or a thermal wave.

20. The monitor of claim 18, wherein the data processing circuitry is configured to lock in a response frequency based on an emission frequency of the continuous light source.

21. The monitor of claim 18, wherein the data processing circuitry is configured to process a signal comprising the amplitude and the phase of the response.

22. The monitor of claim 18, wherein the location of the absorber is a depth in the patient'"'"'s tissue of where the concentration of the absorber is determined.

23. The monitor of claim 18, wherein the absorber comprises one or more of blood, other fluids, a tissue, or any other component in the patient capable of absorbing light energy and generating a kinetic response.