Abstract
This paper comprehensively reviews the emerging topic of optoacoustic imaging from the image reconstruction and quantification perspective. Optoacoustic imaging combines highly attractive features, including rich contrast and high versatility in sensing diverse biological targets, excellent spatial resolution not compromised by light scattering, and relatively low cost of implementation. Yet, living objects present a complex target for optoacoustic imaging due to the presence of a highly heterogeneous tissue background in the form of strong spatial variations of scattering and absorption. Extracting quantified information on the actual distribution of tissue chromophores and other biomarkers constitutes therefore a challenging problem. Image quantification is further compromised by some frequently-used approximated inversion formulae. In this review, the currently available optoacoustic image reconstruction and quantification approaches are assessed, including back-projection and model-based inversion algorithms, sparse signal representation, wavelet-based approaches, methods for reduction of acoustic artifacts as well as multi-spectral methods for visualization of tissue bio-markers. Applicability of the different methodologies is further analyzed in the context of real-life performance in small animal and clinical in-vivo imaging scenarios.
Highlights
Nowadays, the terms optoacoustic and photoacoustic are used to describe the effect of acoustic wave generation by transient light absorption
Despite multiple early attempts to put the photophone into practical use, mainly for military communications [6], it was not until 1938 that Veingerov developed the first widely accepted implementation of the phenomenon, which he called method for gas analysis based on Tyndall-Röntgen optic-acoustic effect [7,8]
Optoacoustic biosensing and imaging provides an excellent platform for multi-scale investigations using the same contrast, from microscopic observations at the single capillary and cell level to whole body imaging of small animals and deep tissue imaging of humans
Summary
The terms optoacoustic and photoacoustic are used to describe the effect of acoustic wave generation by transient light absorption. Despite multiple early attempts to put the photophone into practical use, mainly for military communications [6], it was not until 1938 that Veingerov developed the first widely accepted implementation of the phenomenon, which he called method for gas analysis based on Tyndall-Röntgen optic-acoustic effect [7,8]. Its in-vivo use puts forth a number of challenging problems demanding intensive investigations, from imaging instrumentation, quantified reconstruction algorithms, spectral processing schemes, detection sensitivity, and other technical issues, to biology-related topics, such as effectiveness of imaging contrast approaches or animal handling. While some focused reviews address the mathematical inverse acoustic problem [23] and quantification challenges of multispectral optoacoustic reconstruction methods [24], the current paper attempts to comprehensively cover the most recent experimentally-driven algorithmic developments in the optoacoustic field and review some newly introduced image acquisition methodologies and selected practical in vivo imaging approaches
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