This document summarizes a presentation on photoacoustic imaging with coherent light. It discusses how photoacoustics can be used to image in optically scattering media by coupling light and ultrasound. Two approaches for photoacoustic image formation are described: reconstruction-free imaging using time-resolved signals and reconstruction-based tomography. Enhanced imaging techniques using speckle illumination and wavefront shaping are presented, including a photoacoustic transmission matrix approach that allows focusing light through scattering samples. Challenges and potential solutions for deep tissue imaging are also outlined.

1. emmanuel.bossy@espci.fr , IHP, 12 février2014emmanuel.bossy@espci.fr , IHP, 12 février2014
Photoacoustic imaging
with coherent light
Emmanuel Bossy
Institut Langevin, ESPCI ParisTech
CNRS UMR 7587, INSERM U979
Workshop Inverse Problems and Imaging
Institut Henri Poincaré, 12 February 2014

2. emmanuel.bossy@espci.fr , IHP, 12 février2014
Background: waves and images in complex media
Incident wave
Incident wave

3. emmanuel.bossy@espci.fr , IHP, 12 février2014
Ultrasound
Visible light
Optics and acoustics in biological tissue

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Resolution = optics ∩ ultrasound
Ultrasound
Visible light
Coupling optics and acoustics in biological tissue

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Photoacoustics in optically scattering media

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Heat confinement regime
X

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X
Heat confinement regime

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Heat AND stress confinement regime

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Heat AND stress confinement regime: initial value problem

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time
pressure
2
s
R
T
c
 
0
.
2
P R
P
r
 
Heat AND stress confinement regime: initial value problem

11. emmanuel.bossy@espci.fr , IHP, 12 février2014
Manohar S. et al, Optics Express 15(19), 2007
Manohar S. et al, Physics in Medicine & Biology 50(11), 2005
• 2D PVDF array
• Light wavelength : 1064 nm
• Ultrasound frequency : 1 MHz
• Imaging depth : ~ 2 cm
• Resolution : ~ 2 mm
• Acquisition time : ~ 30 min
Examples of applications: breast tumor imaging

12. emmanuel.bossy@espci.fr , IHP, 12 février2014
Zhang E. et al, Physics in Medicine and Biology 54(4), 2009
• Optical detection with a Fabry-Perot
• Light wavelength : 670 nm
• Ultrasound frequency : 0 ─ 20 MHz
• Imaging depth : ~ 6 mm
• Resolution : ~ 100 µm
• Acquisition time : ~ 15 min
Examples of applications: vascularization imaging

13. emmanuel.bossy@espci.fr , IHP, 12 février2014
Hu S. et al, Optics Letters 36(7), 2011
• Focused single element transducer
• dual light wavelength : 561&570 nm
• Ultrasound frequency : 30 ─ 70 MHz
• Imaging depth : < 1 mm
• Resolution : ~ 10 µm
• Acquisition time : ~ 80 min
Hu S. et al, Optics Letters 36(7), 2011
Examples of applications: functional imaging

14. emmanuel.bossy@espci.fr , IHP, 12 février2014
Principles of photoacoustic image formation ?
Two different configurations:
• Reconstruction-free imaging
• Reconstruction-based imaging

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time ( “=“ distance)
Reconstruction-free imaging

16. emmanuel.bossy@espci.fr , IHP, 12 février2014
Hu S. et al, Optics Letters 36(7), 2011
time ( “=“ distance)
Reconstruction-free imaging

17. emmanuel.bossy@espci.fr , IHP, 12 février2014A. Funke, JFA, MF, ACB and E. Bossy, Applied Physics Letters 94(5), 2009
Set of raw photoacoustic signals
"reconstruction-based" : images are obtained by some reconstruction algorithm. Each point
of the final image is computed from multiple signals.
Reconstruction-based imaging (also tomography)

18. emmanuel.bossy@espci.fr , IHP, 12 février2014
Reconstruction-based imaging (also tomography)
Reconstructed image
"reconstruction-based" : images are obtained by some reconstruction algorithm. Each point
of the final image is computed from multiple signals.
A. Funke, JFA, MF, ACB and E. Bossy, Applied Physics Letters 94(5), 2009

19. emmanuel.bossy@espci.fr , IHP, 12 février2014
Photoacoustic imaging
with coherent light ?

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Photoacoustics in optically scattering media

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Enhanced photoacoustic imaging with speckle illumination
speckle illumination
J. Gâteau, T. Chaigne, O. Katz, S. Gigan and E. Bossy, Optics Letters 38(23), 2013

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speckle illumination
fluctuations (N = 2) fluctuations (N = 50)
uniform illuminationphotograph
Enhanced photoacoustic imaging with speckle illumination
J. Gâteau, T. Chaigne, O. Katz, S. Gigan and E. Bossy, Optics Letters 38(23), 2013

23. emmanuel.bossy@espci.fr , IHP, 12 février2014
speckle
illum.
Fluct.
(N = 50)
Fluct.
(N = 2)
uniform
illum.
Enhanced photoacoustic imaging with speckle illumination
J. Gâteau, T. Chaigne, O. Katz, S. Gigan and E. Bossy, Optics Letters 38(23), 2013
photograph

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Wavefront shaping
for photoacoustic imaging?

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Enhanced photoacoustic imaging with controlled illumination?
Spatial light modulator (SLM)
(mostly liquid crystals)
Segmented, >1 million pixel
course : 1 microns
speed: 50Hz
Deformable mirrors
(piezo, magnetics…)
10-100 actuators (typ.)
course : 10-20 microns
Speed > kHz
Adaptive optics Diffractive optics, displays ….

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Optimization approach

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Optimization
Background: controlling light through scattering media

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Signal to optimizeSignal to optimize
See also Kong, F. et al., Opt. Lett. 36, 2053-2055 (2011)
(monochromatic,
long coherence
length)
X 10
Photoacoustic-guided optimization

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29Chaigne et al. arXiv preprint arXiv:1310.7535 (2013).
Photoacoustic-guided optimization with spectral filtering

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Transmission-matrix approach

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SLM : array of N pixels Linear system camera CCD : arrays of M pixels
=
An alternative approach: the transmission matrix (S. Gigan)

32. emmanuel.bossy@espci.fr , IHP, 12 février2014
Plane wave input
SLM
CCD
sample
SLM
CCD
sample
SLM
CCD
sample
S. Popoff, GL, RC, MF, ACB and S. Gigan. Phys. Rev. Lett. 104,100601 (2010)
An alternative approach: the transmission matrix (S. Gigan)

33. emmanuel.bossy@espci.fr , IHP, 12 février2014T. Chaigne, O. Katz, ACB, MF, E. Bossy and S. Gigan, Nature Photonics, 8, 58-64 (2014)
(532nm, 10Hz, 10ns )
absorbing wires (diameter= 30µm)
• 140 pixels
• phase-only
• spherically focused
• 30MHz central freq
• f-number=2
The photoacoustic transmission-matrix approach

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SLM
The photoacoustic transmission-matrix approach
T. Chaigne, O. Katz, ACB, MF, E. Bossy and S. Gigan, Nature Photonics, 8, 58-64 (2014)

35. emmanuel.bossy@espci.fr , IHP, 12 février2014
(arb.u.)
The photoacoustic transmission-matrix approach
T. Chaigne, O. Katz, ACB, MF, E. Bossy and S. Gigan, Nature Photonics, 8, 58-64 (2014)

36. emmanuel.bossy@espci.fr , IHP, 12 février2014
Focusing through 0.5mm thick
chicken breast tissue
The photoacoustic transmission-matrix approach
T. Chaigne, O. Katz, ACB, MF, E. Bossy and S. Gigan, Nature Photonics, 8, 58-64 (2014)

37. emmanuel.bossy@espci.fr , IHP, 12 février2014
2D photoacoustic imaging1D photoacoustic imaging
Mono-element ultrasonic transducer
Ultrasonic Array
The 2-D photoacoustic transmission-matrix approach

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(532nm, 10Hz, 10ns )
Black leaf skeleton
(140 pixels, phase-only)
(ultrasonic linear array)
The 2-D photoacoustic transmission-matrix approach
Submitted (arXiv:1402.0279)

39. emmanuel.bossy@espci.fr , IHP, 12 février2014
SLM : array of pixels
Photoacoustic
image: array of pixels
SLM: array of pixels
The photoacoustic transmission matrix
• Input modes= SLM pixels
• Output modes = Photoacoustic pixels
The 2-D photoacoustic transmission-matrix approach
Submitted (arXiv:1402.0279)

40. emmanuel.bossy@espci.fr , IHP, 12 février2014
The 2-D photoacoustic transmission-matrix approach
uniform
illumination
SLM-shaped
illumination
Submitted (arXiv:1402.0279)

41. emmanuel.bossy@espci.fr , IHP, 12 février2014
The 2-D photoacoustic transmission-matrix approach
The photoacoustic transmission-matrix contains information on multiple
random illuminations : equivalent to several speckle illumination
Submitted (arXiv:1402.0279)

42. emmanuel.bossy@espci.fr , IHP, 12 février2014
The 2-D photoacoustic transmission-matrix approach
The photoacoustic transmission-matrix contains information on multiple
random illumination : equivalent to several speckle illumination
Submitted (arXiv:1402.0279)

43. emmanuel.bossy@espci.fr , IHP, 12 février2014
43
Standard PA image
Modulation map
PA image when displaying
focusing pattern on SLM
The transmission matrix allows
Identifying the targets
The 2-D photoacoustic transmission-matrix approach
Submitted (arXiv:1402.0279)

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Conclusions …

45. emmanuel.bossy@espci.fr , IHP, 12 février2014
• Increase
 high resolution SLM
• Decrease
 small absorbers
 high frequency transducer
• Fast instrumentation
and measurements
grainsspeckle
pixelsSLM
N
N

pixelsSLMN
grainsspeckleN
45
Challenges Solutions
• Small speckle grains
α λ ≈ 1 μm
 Low enhancement
• Decorrelation of the sample
Challenges with deep-tissue experiments

46. emmanuel.bossy@espci.fr , IHP, 12 février2014
Acknowledgements
O. SimandouxA. Prost F. Poisson F. Mézière
T. Chaigne Dr. J. Gâteau Dr. O. Katz Pr. S. Gigan
Funding
ESPCI ParisTech, CNRS
INCA Grant Gold Fever
PEPS PSL-CNRS
Fondation Pierre-Gilles de Gennes
Dr. M. Varna