Confocal photoacoustic microscopy with optical lateral resolution

• US 9,226,666 B2
• Filed: 05/01/2013
• Issued: 01/05/2016
• Est. Priority Date: 10/25/2007
• Status: Active Grant

• Current Assignee: Washington University In St Louis
• Original Assignee: Washington University In St Louis
• Inventors: Wang, Lihong, Maslov, Konstantin
• Primary Examiner(s): Cattungal, Sanjay
• Application Number:
  US13/874,653
• Publication Number:
  US 20130245406A1
• Time in Patent Office: 979 Days
• Field of Search: 600437-480
• US Class Current: 1/1
• CPC Class Codes: A61B 2090/306 using optical fibres
• 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 5/0068 Confocal scanning
• CPC Class Codes: A61B 5/0082 adapted for particular medical purposes
• 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 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/444 Evaluating skin marks, e.g. mole, nevi, tumour, scar
• CPC Class Codes: A61B 5/4848 Monitoring or testing the effects of treatment, e.g. of medication
• CPC Class Codes: A61B 8/485 involving measuring strain or elastic properties
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01N 2291/02872 Pressure
• CPC Class Codes: G01N 29/0681 by acoustic microscopy, e.g. scanning acoustic microscopy
• CPC Class Codes: G01N 29/2418 using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics photoacoustic cells G01N21/1702; measuring characteristics of vibrations by using radiation-sensitive means G01H9/00; acousto-optical conversion techniques for short-range imaging G01S15/8965; sound-producing devices using laser bundle G10K15/046
• CPC Class Codes: G02B 21/0028 specially adapted for specific applications, e.g. for endoscopes, ophthalmoscopes, attachments to conventional microscopes
• CPC Class Codes: G02B 21/008 Details of detection or image processing, including general computer control

Abstract

A method for determining a ratio of hemoglobin absorption within a biological tissue using a handheld device is provided. The method includes focusing at least one light pulse into a predetermined area inside an object using at least one excitation wavelength, wherein a fluorescence signal is based on at least a local excitation optical fluence and properties of fluorophores in the predetermined area. The method further includes receiving a photoacoustic signal emitted by the object in response to the at least one light pulse, the photoacoustic signal being a product of the local excitation optical fluence, an optical absorption coefficient of hemoglobin, and an acoustic detection sensitivity. The method further includes determining the ratio of hemoglobin absorption based on a hemoglobin absorption coefficient that is based at least partially on the fluorescence signal and the photoacoustic signal.

Claims

1. A method for determining a ratio of hemoglobin absorption within a biological tissue using a handheld device, said method comprising:

focusing at least one first light pulse comprising a first excitation wavelength into the predetermined area;

detecting a first fluorescence signal emitted by at least one fluorophore within the predetermined area in response to the at least one first light pulse;

detecting a first photoacoustic signal emitted by hemoglobin within the predetermined area in response to the at least one first light pulse;

focusing at least one second light pulse comprising a second excitation wavelength into the predetermined area;

detecting a second fluorescence signal emitted by the at least one fluorophore within the predetermined area in response to the at least one second light pulse;

detecting a second photoacoustic signal emitted by the hemoglobin within the predetermined area in response to the at least one second light pulse; and

determining the ratio of hemoglobin absorption based at least partially on the first and second fluorescence signals and the first and second photoacoustic signals.

2. A method according to claim 1, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly that includes an optical assembly of lenses and mirrors.

3. A method according to claim 1, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly positioned on an XYZ translation stage.

4. A method according to claim 3, further comprising performing raster scanning along a surface of the object with simultaneous adjustment of an axial position of the focusing assembly to compensate for a curvature of the surface of the object.

5. A method according to claim 1, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse into a nearly diffraction-limited point using a focusing assembly that includes an optical microscope objective lens.

6. A method according to claim 1, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly that includes an objective lens configured to form an image of a small pinhole on the predetermined area inside the object.

7. A method according to claim 1, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly that includes a single-mode optical fiber configured to emit the at least one first and the at least one second light pulse.

8. A method according to claim 1, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly that includes an oscillating mirror.

9. A method according to claim 1, further comprising creating an image of the predetermined area inside the object based on the received photoacoustic signal.

10. A method for determining an oxygen metabolic rate (MRO2) within a biological tissue using a handheld multi-wavelength photoacoustic device, said method comprising:

obtaining an incoming oxygen saturation, an outgoing oxygen saturation, and a total hemoglobin concentration in a vessel within the biological tissue using a handheld multi-wavelength photoacoustic device;

determining the MRO2 based on the incoming oxygen saturation, the outgoing oxygen saturation, the total hemoglobin concentration, an area of the vessel, and a mean flow velocity of blood of the vessel, wherein the area of the incoming vessel and the mean flow velocity are based on measurements obtained by one of ultrasound imaging, optical coherence tomography, and flow imaging technologies.

11. A method according to claim 10, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly that includes an optical assembly of lenses and mirrors.

12. A method according to claim 10, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly positioned on an XYZ translation stage.

13. A method according to claim 10, further comprising performing raster scanning along a surface of the object with simultaneous adjustment of an axial position of the focusing assembly to compensate for a curvature of the surface of the object.

14. A method according to claim 10, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse into a nearly diffraction-limited point using a focusing assembly that includes an optical microscope objective lens.

15. A method according to claim 10, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly that includes an objective lens configured to form an image of a small pinhole on the predetermined area inside the object.

16. A method according to claim 10, wherein the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly that includes a single-mode optical fiber configured to emit the at least one light pulse.

17. A method according to claim 10, wherein focusing the at least one first and the at least one second light pulse comprises focusing at least one light pulse using a focusing assembly that includes an oscillating mirror.

18. A method according to claim 10, further comprising creating an image of the predetermined area inside the object based on the received acoustic waves.

19. An apparatus for determining a ratio of hemoglobin absorption within a predetermined area inside an object, said apparatus comprising:

a focusing assembly configured to focus at least two light pulses comprising a first light pulse at a first excitation wavelength and a second light pulse at a second excitation wavelength into the predetermined area;

a photo-detector configured to detect at least two fluorescence signals emitted in response to the at least two light pulses;

an ultrasonic transducer configured to receive at least two photoacoustic signals emitted in response to the at least two light pulses; and

a processor configured to determine the ratio of hemoglobin absorption based at least partially on the at least two fluorescence signals and the at least two photoacoustic signals.

20. An apparatus according to claim 19, wherein said focusing assembly comprises an optical assembly of lenses and mirrors configured to focus the at least one first and the at least one second light pulse in such a way that a focal point of said focusing assembly coincides with a focal point of said ultrasonic transducer.