Imaging through scattering media with high signal to noise ratio and resolution

• US 10,036,735 B2
• Filed: 08/26/2014
• Issued: 07/31/2018
• Est. Priority Date: 08/26/2013
• Status: Active Grant

• Current Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Original Assignee: The Board of Regents of the University of Colorado (University of Colorado System)
• Inventors: Piestun, Rafael, Ju, Hengyi, Dove, Jacob, Caravaca-Aguirre, Antonio Miguel, Murray, Todd, Conkey, Donald
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US14/913,958
• Publication Number:
  US 20160356746A1
• Time in Patent Office: 1,435 Days
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: G01N 2021/1706 in solids
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 2201/0675 SLM
• CPC Class Codes: G01N 29/0654 Imaging
• 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

Abstract

Systems and methods are disclosed to enhance three-dimensional photoacoustic imaging behind, through, or inside a scattering material. Some embodiments can increase the optical fluence in an ultrasound transducer focus and/or enhance the optical intensity using wavefront shaping before the scatterer. The photoacoustic signal induced by an object placed behind the scattering medium can serve as feedback to optimize the wavefront, enabling one order of magnitude enhancement of the photoacoustic amplitude. Using the enhanced optical intensity, the object can be scanned in two dimensions and/or a spot can be scanned by re-optimizing the wavefront before post-processing of the data to reconstruct the image. The temporal photoacoustic signal provides information to reconstruct the third-dimensional information.

Claims

1. A method for sub-acoustic focusing, the method comprising:

illuminating a sample through a scatterer using a light source and at least one spatial light modulator;

receiving a photoacoustic signal from a transducer;

determining an optimized wavefront from the photoacoustic signal;

modifying a configuration of the spatial light modulator based on the optimized wavefront; and

illuminating the sample through the scatterer using the light source and the spatial light modulator with the modified configuration, wherein the modified configuration produces an optical focus that is smaller than an acoustic focus of the transducer.

2. The method according to claim 1, wherein the spatial light modulator is an optical element selected from the group consisting of one or more spatial light modulators, phase-only spatial light modulators, intensity-only spatial light modulators, prism arrays, diffractive elements, diffusers, holograms, Dammann gratings, liquid crystal spatial light modulators, phase masks, amplitude masks, acousto-optic modulator, acousto-optic deflector, and phase/amplitude masks.

3. The method according to claim 1, wherein the determining the optimized wavefront includes using an optimization algorithm to determine the optimized wavefront.

4. The method according to claim 1, further comprising scanning the sample, moving the sample with fluid, scanning a focus of the transducer, and/or scanning a focus of the light source.

5. A sub-acoustic resolution imaging system comprising:

a pulsed light source;

an optical system configured to direct light from the light source toward a sample through a scatterer;

one or more acoustic transducers configured to record acoustic signals from the sample; and

a controller coupled with at least a portion of the optical system and the one or more acoustic transducers, wherein the controller is configured to modify a phase and/or amplitude of the light directed by the optical system through the scatterer using data from the one or more acoustic transducers.

6. The imaging system according to claim 5, wherein the one or more acoustic transducers is disposed outside the scatterer such that the acoustic signals pass through the scatterer.

7. The imaging system according to claim 5, wherein the optical system comprises a spatial light modulator, one or more lenses and/or an objective lens.

8. The imaging system according to claim 5, wherein the optical system includes an optical element selected from the group consisting of one or more spatial light modulators, phase-only spatial light modulators, intensity-only spatial light modulators, prism arrays, diffractive elements, diffusers, holograms, Dammann gratings, liquid crystal spatial light modulators, phase masks, amplitude masks, acousto-optic modulator, acousto-optic deflector, and phase/amplitude masks.

9. The imaging system according to claim 5, wherein the controller is configured to use an optimization algorithm based on the data from the one or more acoustic transducers to modify the phase and/or amplitude of the light.

10. The imaging system according to claim 5, wherein the controller is configured to use spatially varying feedback to optimize an optical wavefront from the optical system such that the light is enhanced and focused to a single speckle behind the scatterer.

11. The imaging system according to claim 5, wherein the controller is configured to increase a depth of optical resolution photoacoustic microscopy by providing high intensity optical focus.

12. The imaging system according to claim 5, wherein the controller is configured to scan the sample, scan a focus of the one or more transducers, and/or scan a focus of the light source.

13. A method for focusing with sub-acoustic resolution, the method comprising:

illuminating a sample inside a scatterer with a plurality of optical wavefronts modulated by a spatial light modulator, each of the plurality of optical wavefronts produced modulated by the spatial light modulator using one of a plurality of SLM matrices selected from a population of SLM matrices;

receiving a plurality of electric signals from a transducer, wherein each of the plurality of electric signals correspond with a photoacoustic signal received at the transducer for each of the plurality of optical wavefronts such that the transducer receives a plurality of photoacoustic signals; and

determining an optimum SLM matrix from the population of SLM matrices based on the plurality of electric signals, wherein the optimum SLM matrix produces an optical focus at or near the sample that is smaller than an acoustic focus of the transducer.

14. The method according to claim 13, wherein the determining an optimum SLM matrix from the population of SLM matrices comprises determining an optimum SLM matrix from the population of SLM matrices using a genetic algorithm.

15. The method according to claim 13, wherein the determining an optimum SLM matrix from the population of SLM matrices based on the plurality of electric signals comprises determining an optimum SLM matrix from the population of SLM matrices based on a peak-to-peak voltage of the plurality of electric signals.

16. The method according to claim 13, further comprising returning an image of the sample corresponding with illumination of the sample with the optimum SLM matrix.

17. The method according to claim 13, further comprising:

scanning the sample in a x-y plane; and

repeating the method.

18. The method according to claim 13, further comprising:

moving the acoustic focus of the one or more transducers; and

repeating the method.

19. The method according to claim 13, wherein the image is a three-dimensional image of the sample.

20. The method according to claim 13, wherein the plurality of photoacoustic signals are enhanced by nonlinear effects in the sample.