Reconstructing initial pressure and speed of sound distributions simultaneously in photoacoustic tomography

TL;DR

This paper presents a method for simultaneously reconstructing initial pressure and speed of sound distributions in photoacoustic tomography, improving image accuracy by using multiple data sets to address the ill-posed inverse problem.

Contribution

It introduces a gradient-based iterative approach with multigrid techniques for joint reconstruction, leveraging multiple data sets to enhance accuracy and reduce artifacts.

Findings

Successful simultaneous reconstruction demonstrated in numerical simulations.

Using multiple initial pressure distributions improves inhomogeneity localization.

Method reduces artifacts and enhances image quality in photoacoustic tomography.

Abstract

Image reconstruction in photoacoustic tomography relies on an accurate knowledge of the speed of sound in the target. However, the speed of sound distribution is not generally known, which may result in artefacts in the reconstructed distribution of initial pressure. Therefore, reconstructing the speed of sound simultaneously with the initial pressure would be valuable for accurate imaging in photoacoustic tomography. Furthermore, the speed of sound distribution could provide additional valuable information about the imaged target. In this work, simultaneous reconstruction of initial pressure and speed of sound in photoacoustic tomography is studied. This inverse problem is known to be highly ill-posed. To overcome this, we study an approach where the ill-posedness is alleviated by utilising multiple photoacoustic data sets that are generated by different initial pressure distributions within the same imaged target. Then, these initial pressure distributions are reconstructed simultaneously with the speed of sound distribution. A methodology for solving this minimisation problem is formulated using a gradient-based iterative approach equipped with bound constraints and a multigrid approach. The methodology was evaluated with numerical simulations. Different approaches for generating multiple initial pressure distributions and their effect on the solution of the image reconstruction problem were studied. The results show that initial pressure and speed of sound can be simultaneously reconstructed from photoacoustic data. Furthermore, utilising multiple initial pressure distributions improves the reconstructions such that the locations of initial pressure and speed of sound inhomogeneities can be better distinguished and image artifacts are reduced.