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
Background: waves and images in complex media Incident wave Incident wave
Optics and acoustics in biological tissue Ultrasound Visible light
Coupling optics and acoustics in biological tissue Ultrasound Resolution = optics ultrasound Visible light
Photoacoustics in optically scattering media
Heat confinement regime X
Heat confinement regime X
Heat AND stress confinement regime
Heat AND stress confinement regime: initial value problem
pressure Heat AND stress confinement regime: initial value problem T 2R c s P P 0 R. 2 r time
Examples of applications: breast tumor imaging 2D PVDF array Light wavelength Ultrasound frequency Imaging depth Resolution Acquisition time : 1064 nm : 1 MHz : ~ 2 cm : ~ 2 mm : ~ 30 min Manohar S. et al, Physics in Medicine & Biology 50(11), 2005 Manohar S. et al, Optics Express 15(19), 2007
Examples of applications: vascularization imaging 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 Zhang E. et al, Physics in Medicine and Biology 54(4), 2009
Examples of applications: functional imaging 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 Hu S. et al, Optics Letters 36(7), 2011
Principles of photoacoustic image formation? Two different configurations: Reconstruction-free imaging Reconstruction-based imaging
Reconstruction-free imaging time ( = distance)
Reconstruction-free imaging time ( = distance) Hu S. et al, Optics Letters 36(7), 2011
Reconstruction-based imaging (also tomography) "reconstruction-based" : images are obtained by some reconstruction algorithm. Each point of the final image is computed from multiple signals. Set of raw photoacoustic signals A. Funke, JFA, MF, ACB and E. Bossy, Applied Physics Letters 94(5), 2009
Reconstruction-based imaging (also tomography) "reconstruction-based" : images are obtained by some reconstruction algorithm. Each point of the final image is computed from multiple signals. Reconstructed image A. Funke, JFA, MF, ACB and E. Bossy, Applied Physics Letters 94(5), 2009
Photoacoustic imaging with coherent light?
Photoacoustics in optically scattering media
Enhanced photoacoustic imaging with speckle illumination speckle illumination J. Gâteau, T. Chaigne, O. Katz, S. Gigan and E. Bossy, Optics Letters 38(23), 2013
Enhanced photoacoustic imaging with speckle illumination photograph uniform illumination speckle illumination fluctuations (N = 2) fluctuations (N = 50) J. Gâteau, T. Chaigne, O. Katz, S. Gigan and E. Bossy, Optics Letters 38(23), 2013
Enhanced photoacoustic imaging with speckle illumination photograph uniform illum. speckle illum. Fluct. (N = 2) Fluct. (N = 50) J. Gâteau, T. Chaigne, O. Katz, S. Gigan and E. Bossy, Optics Letters 38(23), 2013
Wavefront shaping for photoacoustic imaging?
Enhanced photoacoustic imaging with controlled illumination? Deformable mirrors (piezo, magnetics ) 10-100 actuators (typ.) course : 10-20 microns Speed > khz Adaptive optics Spatial light modulator (SLM) (mostly liquid crystals) Segmented, >1 million pixel course : 1 microns speed: 50Hz Diffractive optics, displays.
Optimization approach
Background: controlling light through scattering media Optimization
Photoacoustic-guided optimization Signal to optimize Signal to optimize (monochromatic, long coherence length) X 10 See also Kong, F. et al., Opt. Lett. 36, 2053-2055 (2011)
Photoacoustic-guided optimization with spectral filtering Chaigne et al. arxiv preprint arxiv:1310.7535 (2013). 29
Transmission-matrix approach
An alternative approach: the transmission matrix (S. Gigan) SLM : array of N pixels Linear system camera CCD : arrays of M pixels =
SLM SLM SLM An alternative approach: the transmission matrix (S. Gigan) CCD sample CCD sample Plane wave input CCD sample S. Popoff, GL, RC, MF, ACB and S. Gigan. Phys. Rev. Lett. 104,100601 (2010)
The photoacoustic transmission-matrix approach 140 pixels phase-only (532nm, 10Hz, 10ns ) spherically focused 30MHz central freq f-number=2 absorbing wires (diameter= 30µm) T. Chaigne, O. Katz, ACB, MF, E. Bossy and S. Gigan, Nature Photonics, 8, 58-64 (2014)
The photoacoustic transmission-matrix approach SLM T. Chaigne, O. Katz, ACB, MF, E. Bossy and S. Gigan, Nature Photonics, 8, 58-64 (2014)
(arb.u.) The photoacoustic transmission-matrix approach T. Chaigne, O. Katz, ACB, MF, E. Bossy and S. Gigan, Nature Photonics, 8, 58-64 (2014)
The photoacoustic transmission-matrix approach Focusing through 0.5mm thick chicken breast tissue T. Chaigne, O. Katz, ACB, MF, E. Bossy and S. Gigan, Nature Photonics, 8, 58-64 (2014)
The 2-D photoacoustic transmission-matrix approach 1D photoacoustic imaging 2D photoacoustic imaging Mono-element ultrasonic transducer Ultrasonic Array
The 2-D photoacoustic transmission-matrix approach (140 pixels, phase-only) (ultrasonic linear array) Black leaf skeleton (532nm, 10Hz, 10ns ) Submitted (arxiv:1402.0279)
The 2-D photoacoustic transmission-matrix approach The photoacoustic transmission matrix Input modes= SLM pixels Output modes = Photoacoustic pixels SLM: array of pixels SLM : array of pixels Photoacoustic image: array of pixels Submitted (arxiv:1402.0279)
The 2-D photoacoustic transmission-matrix approach uniform illumination SLM-shaped illumination Submitted (arxiv:1402.0279)
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)
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)
The 2-D photoacoustic transmission-matrix approach Standard PA image PA image when displaying focusing pattern on SLM The transmission matrix allows Identifying the targets Modulation map Submitted (arxiv:1402.0279) 43
Conclusions
Challenges with deep-tissue experiments Challenges Small speckle grains N N SLM pixels speckle grains α λ 1 μm Low enhancement Solutions Increase Decrease N SLM pixels high resolution SLM N speckle grains small absorbers high frequency transducer Decorrelation of the sample Fast instrumentation and measurements 45
Acknowledgements T. Chaigne Dr. J. Gâteau Dr. O. Katz Pr. S. Gigan A. Prost O. Simandoux F. Poisson F. Mézière Dr. M. Varna Funding ESPCI ParisTech, CNRS INCA Grant Gold Fever PEPS PSL-CNRS Fondation Pierre-Gilles de Gennes