Abstract
Almost all known image reconstruction algorithms for photoacoustic and thermoacoustic tomography assume that the acoustic waves leave the region of interest after a finite time. This assumption is reasonable if the reflections from the detectors and surrounding surfaces can be neglected or filtered out (for example, by time-gating). However, when the object is surrounded by acoustically hard detector arrays, and/or by additional acoustic mirrors, the acoustic waves will undergo multiple reflections. (In the absence of absorption, they would bounce around in such a reverberant cavity forever.) This disallows the use of the existing free-space reconstruction techniques. This paper proposes a fast iterative reconstruction algorithm for measurements made at the walls of a rectangular reverberant cavity. We prove the convergence of the iterations under a certain sufficient condition, and demonstrate the effectiveness and efficiency of the algorithm in numerical simulations.
Highlights
Photoacoustic tomography (PAT) and the closely related modality thermoacoustic tomography (TAT) [3, 14, 15, 26, 28] are based on the photoacoustic effect, in which an acoustic wave is generated by the absorption of an electromagnetic (EM) pulse
There are several endogenous chromophores which absorb in these wavelength ranges, the most important of which are oxy- and deoxy-hemoglobin, and externally administered, molecularly-targeted, chromophores can be used as contrast agents
Since acoustic waves propagate through soft tissues with little absorption or scattering, PAT and TAT yield high-resolution images related to the EM properties of the tissue
Summary
Photoacoustic tomography (PAT) and the closely related modality thermoacoustic tomography (TAT) [3, 14, 15, 26, 28] are based on the photoacoustic effect, in which an acoustic wave is generated by the absorption of an electromagnetic (EM) pulse. Since acoustic waves propagate through soft tissues with little absorption or scattering, PAT and TAT yield high-resolution images related to the EM properties of the tissue. Such images cannot be obtained by purely optical or electrical (or EM) techniques, such as, diffuse optical tomography or electrical impedance tomography. It is not possible to obtain exact reconstructions from data measured on a finite section of a plane To overcome this limitation, more advanced measuring systems will have the object surrounded by the detector arrays Reconstruction time was comparable with that of known fast algorithms for various free-space problems (e.g. [19, 21])
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