Quantitative photoacoustic tomography using illuminations from a single direction.

Aki Pulkkinen,Ben T Cox,Simon R Arridge,Jari P Kaipio,Tanja Tarvainen

doi:10.1117/1.jbo.20.3.036015

Abstract

Quantitative photoacoustic tomography is an emerging imaging technique aimed at estimating optical parameters inside tissues from photoacoustic images, which are formed by combining optical information and ultrasonic propagation. This optical parameter estimation problem is ill-posed and needs to be approached within the framework of inverse problems. It has been shown that, in general, estimating the spatial distribution of more than one optical parameter is a nonunique problem unless more than one illumination pattern is used. Generally, this is overcome by illuminating the target from various directions. However, in some cases, for example when thick samples are investigated, illuminating the target from different directions may not be possible. In this work, the use of spatially modulated illumination patterns at one side of the target is investigated with simulations. The results show that the spatially modulated illumination patterns from a single direction could be used to provide multiple illuminations for quantitative photoacoustic tomography. Furthermore, the results show that the approach can be used to distinguish absorption and scattering inclusions located near the surface of the target. However, when compared to a full multidirection illumination setup, the approach cannot be used to image as deep inside tissues.

Highlights

Photoacoustic tomography (PAT) is an emerging imaging modality developed over the last two decades, which combines the benefits of optical contrast and ultrasound propagation
Two single-direction illumination patterns were created according to Eq (6)
The image reconstruction in Quantitative photoacoustic tomography (QPAT) is an ill-posed problem, and it needs to be approached in the framework of inverse problems

Summary

Introduction

Photoacoustic tomography (PAT) is an emerging imaging modality developed over the last two decades, which combines the benefits of optical contrast and ultrasound propagation. The optical aspect provides information on the distribution of chromophores, which are light-absorbing molecules within the tissue. PAT can be used to provide images of soft biological tissues with high spatial resolution. It has successfully been applied to the visualization of different structures in biological tissues, such as human blood vessels, microvasculature of tumors, and the cerebral cortex in small animals. This information is only a qualitative image and it does not include quantitative information on the concentrations of the chromophores. For more information about PAT, see, for example, Refs. 1–5 and the references therein

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Conclusion