Photoacoustic/Optoacoustic imaging

The photoacoustic effect, discovered by Alexander Graham Bell over 140 years ago, describes the generation of sound by exposing substances of all kinds to a variable intensity source of electromagnetic radiation. Based on the photoacoustic effect, photoacoustic imaging is a technique which typically uses short-pulsed lasers as probing energy, while detecting ultrasound generated by photon absorption and thermoelastic expansion.

Photoacoustic imaging is arguably the most exciting biomedical imaging technique of the decade, with major use in biomedical imaging ex vivo, in vitro, and in vivo. Since sound undergoes significantly less scattering and attenuation in biological tissues compared to light, the photoacoustic effect allows imaging the spatial distribution of optical absorption at much greater penetration depths than achievable with purely optical imaging methods.

Aberration correction
One remaining challenge in photoacoustic imaging consists in the correction of phase and amplitude aberrations induced during propagation through complex layers. The assumption of a spatially constant speed-of-sound is typically used to calculate delays for image reconstruction. As speed-of-sound may vary relatively largely in many practical imaging scenarios (such as in biological tissue), this assumption may cause wavefront aberrations, thus degrading effective imaging resolution.

Super resolution
Since the detected energy in photoacoustics is ultrasound, and not light, the resolution of the reconstructed images is limited by the acoustic diffraction limit. Nonlinear imaging techniques can be implemented to go beyond the acoustic diffraction limit. Imaging with resolutions beyond the diffraction limit of the imaging system are referred to as super-resolution imaging.

Photoacoustic_Imaging
Vision

  • Performing photoacoustic imaging with aberration-correction in real time.
  • Preforming photoacoustic imaging beyond the acoustic diffraction limit.
  • Preforming volumetric (3D) photoacoustic imaging.

Previous group works:
Hojman, Eliel, et al. “Photoacoustic imaging beyond the acoustic diffraction-limit with dynamic speckle illumination and sparse joint support recovery”. Optics Express 25.5 (2017): , 25, 5, 4875–4886.
Chaigne, Thomas, et al. “Super-resolution photoacoustic imaging via flow-induced absorption fluctuations”. Optica 411 (2017): , 4, 11, 1297–1404.