Simultaneous Reconstruction of Optical and Acoustical Properties in Photo-Acoustic Imaging using plasmonics

Abstract

We propose an approach for the simultaneous reconstruction of the electromagnetic and acoustic material parameters, in the given medium $Ω$ where to image, using the photo-acoustic pressure, measured on a single point of the boundary of $Ω$, generated by plasmonic nanoparticles. We prove that the generated pressure, that we denote by $p^{\star}\left(x, s, ω\right)$, depending on only one fixed point $x \in \partial Ω$, the time variable $s$, in a large enough interval, and the incidence frequency $ω$, in a large enough band, is enough to reconstruct both the sound speed, the mass density and the permittivity inside $Ω$. Indeed, from the behavior of the measured pressure in terms of time, we can estimate the travel time of the pressure, for arriving points inside $Ω$, then using the eikonal equation we reconstruct the acoustic speed of propagation. In addition, we reconstruct the internal values of the acoustic Green's function. From the singularity analysis of this Green's function, we extract the integrals along the geodesics, for internal arriving points, of the logarithmic-gradient of the mass density. Solving this (internal) integral geometric problem provides us with the values of the mass density function inside $Ω$. Finally, from the behavior of $p^{\star}\left(x, s, ω\right)$ with respect to the frequency $ω$, we detect the generated plasmonic resonances from which we reconstruct the permittivity inside $Ω$.