Aberration correction in photoacoustic imaging using paraxial backpropagation

Photoacoustic (PA) imaging aims for the reconstruction of acoustic sources that originate in pulsed light absorption. While the speed of sound (SOS) in biological tissue is heterogeneous, standard reconstruction algorithms usually assume a constant SOS. This results in deformations of the reconstructed sources, which are referred to as aberration and can have a severe impact on the spatial resolution. If the SOS is known, aberrations can be compensated during the reconstruction at the expense of an increasing computational effort. Algorithms that account for heterogeneous SOS usually compute individual delays for each reconstructed pixel or perform an entire wave field simulation. In this contribution, we present an alternative approach by introducing a PA backpropagation based on a paraxial approximation of the wave equation that can be computed with almost the computational efficiency of a standard frequency domain reconstruction. The method accounts for refraction and neglects unwanted back-reflections during the backpropagation process. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731771, Photonics Private Public Partnership, and is supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 16.0160. Dominic Depke is supported by the Graduate School of the Cells-in-Motion Cluster of Excellence (EXC 1003 - CiM), University of Münster, Germany.