Photoacoustic/Optoacoustic imaging

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. 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.

One remaining challenge in photoacoustic imaging involves correcting phase and amplitude aberrations induced during propagation through complex media. In a recent project, we introduced a computational reconstruction framework tailored for imaging through thick layers, such as brain imaging through the skull, using ultrasound waves [1]. In scenarios like transcranial brain imaging, fetal ultrasound, and imaging of obese patients, a thick acoustically aberrating layer near the transducer array distorts the recorded signal. This project overcomes these limitations by employing a novel analytical wave propagation formulation and an automatic-differentiation regularized iterative optimization algorithm. The algorithm simultaneously reconstructs the aberrating layer's profile and the optically absorbing targets, demonstrating significant improvements in reconstruction fidelity compared to previous methods.

photoacoustic_imaging_results

Previous group works:

  1. Slobodkin, Yevgeny, and Ori Katz,  “Computational wave-based photoacoustic imaging through an unknown thick aberrating layer”, Photoacoustics 36 (2024), 100584
  2. 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.
  3. Chaigne, Thomas, et al. “Super-resolution photoacoustic imaging via flow-induced absorption fluctuations”. Optica 411 (2017): , 4, 11, 1297–1404.