The photoacoustic effect, discovered by Alexander Graham Bell over 140 years ago, describes the generation of sound when substances of all kinds are exposed to a variable intensity source of electromagnetic radiation. Photoacoustic imaging, based on this effect, typically employs short-pulsed lasers as the probing energy source while detecting ultrasound generated by photon absorption and thermoelastic expansion.

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

Aberration correction

One remaining challenge in photoacoustic imaging involves correcting 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. However, in many practical imaging scenarios, such as in biological tissue, the speed-of-sound may vary significantly, potentially causing wavefront aberrations and degrading effective imaging resolution.

Super resolution
Since the detected energy in photoacoustics is ultrasound rather than light, the resolution of reconstructed images is limited by the acoustic diffraction limit. Nonlinear imaging techniques can be implemented to surpass the acoustic diffraction limit. Images with resolutions beyond the diffraction limit of the imaging system are referred to as super-resolution imaging.

Vision

• Performing photoacoustic imaging with aberration-correction in real time.
• Performing photoacoustic imaging beyond the acoustic diffraction limit.
• Performing 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.