Photoacoustic computed tomography (PACT), also known as optoacoustic tomography, is an emerging imaging technique that holds great promise for biomedical imaging. PACT is a hybrid imaging method that can exploit the strong endogenous contrast of optical methods along with the high spatial resolution of ultrasound methods. In its canonical form that is addressed in this article, PACT seeks to estimate the photoacoustically-induced initial pressure distribution within the object. Image reconstruction methods are employed to solve the acoustic inverse problem associated with the image formation process. When an idealized imaging scenario is considered, analytic solutions to the PACT inverse problem are available; however, in practice, numerous challenges exist that are more readily addressed within an optimization-based, or iterative, image reconstruction framework. In this article, the PACT image reconstruction problem is reviewed within the context of modern optimization-based image reconstruction methodologies. Imaging models that relate the measured photoacoustic wavefields to the sought-after object function are described in their continuous and discrete forms. The basic principles of optimization-based image reconstruction from discrete PACT measurement data are presented, which includes a review of methods for modeling the PACT measurement system response and other important physical factors. Non-conventional formulations of the PACT image reconstruction problem, in which acoustic parameters of the medium are concurrently estimated along with the PACT image, are also introduced and reviewed.
Photoacoustic computed tomography (PACT) is an emerging computed imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the photoacoustically induced initial pressure distribution within tissue. The PACT reconstruction problem corresponds to a time-domain inverse source problem, where the initial pressure distribution is recovered from the measurements recorded on an aperture outside the support of the source. A major challenge in transcranial PACT brain imaging is to compensate for aberrations in the measured acoustic data that are induced by propagation of the photoacoustic wavefields through the skull. To properly account for these effects, previously proposed image reconstruction methods for transcranial PACT require knowledge of the spatial distribution of the elastic parameters of the skull. However, estimating the spatial distribution of these parameters prior to the PACT experiment remains challenging. To circumvent this issue, in this work a method to jointly reconstruct the initial pressure distribution and a low-dimensional representation of the elastic parameters of the skull is developed and investigated. The joint reconstruction (JR) problem is solved by use of a proximal optimization method that allows constraints and non-smooth regularization terms. The proposed method is evaluated by use of large-scale three-dimensional (3D) computer-simulation studies that mimic transcranial PACT experiments.
more » « less- NSF-PAR ID:
- 10204253
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Inverse Problems
- Volume:
- 36
- Issue:
- 12
- ISSN:
- 0266-5611
- Page Range / eLocation ID:
- Article No. 124007
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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