Photons Plus Ultrasound: Imaging and Sensing

Imaging and sensing based on fusing the compelling features of optical and ultrasonic waves is the fastest growing area of research in biomedical optics. The annual SPIE conference on this topic, co-chaired by both of us, has been doubling in size approximately every three years since 2003 (Fig. 1). As of 2009, this conference has become the largest at SPIE Photonics West. Hybrid modalities such as photoacoustic or optoacoustic tomography can provide deep tissue penetration, high ultrasonic resolution, and speckle-free optical contrast. Applications include in vivo functional and molecular imaging of cancer, neurophysiology, and vascular disease in both animals and humans. Major challenges include development of quantitative imaging, improvement of contrast and resolution, and commercialization of the technology. We look forward to seeing significant preclinical and clinical impact from this emerging technology

Discrete Imaging Models for Three-Dimensional Optoacoustic Tomography using Radially Symmetric Expansion Functions

Optoacoustic tomography (OAT), also known as photoacoustic tomography, is an emerging computed biomedical imaging modality that exploits optical contrast and ultrasonic detection principles. Iterative image reconstruction algorithms that are based on discrete imaging models are actively being developed for OAT due to their ability to improve image quality by incorporating accurate models of the imaging physics, instrument response, and measurement noise. In this work, we investigate the use of discrete imaging models based on Kaiser-Bessel window functions for iterative image reconstruction in OAT. A closed-form expression for the pressure produced by a Kaiser-Bessel function is calculated, which facilitates accurate computation of the system matrix. Computer-simulation and experimental studies are employed to demonstrate the potential advantages of Kaiser-Bessel function-based iterative image reconstruction in OAT

Ring-based ultrasonic virtual point detector with applications to photoacoustic tomography

This is the published version. Copyright © 2007 American Institute of PhysicsAn ultrasonic virtual point detector is constructed using the center of a ring transducer. The virtual point detector provides ideal omnidirectional detection free of any aperture effect. Compared with a real point detector, the virtual one has lower thermal noise and can be scanned with its center inside a physically inaccessible medium. When applied to photoacoustictomography, the virtual point detector provides both high spatial resolution and high signal-to-noise ratio. It can also be potentially applied to other ultrasound-related technologies

A mathematical model and inversion procedure for Magneto-Acousto-Electric Tomography (MAET)

Magneto-Acousto-Electric Tomography (MAET), also known as the Lorentz force or Hall effect tomography, is a novel hybrid modality designed to be a high-resolution alternative to the unstable Electrical Impedance Tomography. In the present paper we analyze existing mathematical models of this method, and propose a general procedure for solving the inverse problem associated with MAET. It consists in applying to the data one of the algorithms of Thermo-Acoustic tomography, followed by solving the Neumann problem for the Laplace equation and the Poisson equation. For the particular case when the region of interest is a cube, we present an explicit series solution resulting in a fast reconstruction algorithm. As we show, both analytically and numerically, MAET is a stable technique yilelding high-resolution images even in the presence of significant noise in the data

Special Section Guest Editorial: Celebrating the Exponential Growth of Optoacoustic/Photoacoustic Imaging

Guest editors introduce contributors to the Special Section Celebrating the Exponential Growth of Optoacoustic/Photoacoustic Imaging. We are pleased to introduce the contributions to this JBO Special Section entitled “Celebrating the Exponential Growth of Biomedical Optoacoustic/Photoacoustic Imaging.” This title was chosen to reflect the strong growth of the field over the last two and a half decades. The diversity of papers in this special section bears witness to this, with contributions that encompass numerical modelling, advanced instrumentation, functional imaging, clinical translation, and novel biomedical applications

Investigation of iterative image reconstruction in three-dimensional optoacoustic tomography

Iterative image reconstruction algorithms for optoacoustic tomography (OAT), also known as photoacoustic tomography, have the ability to improve image quality over analytic algorithms due to their ability to incorporate accurate models of the imaging physics, instrument response, and measurement noise. However, to date, there have been few reported attempts to employ advanced iterative image reconstruction algorithms for improving image quality in three-dimensional (3D) OAT. In this work, we implement and investigate two iterative image reconstruction methods for use with a 3D OAT small animal imager: namely, a penalized least-squares (PLS) method employing a quadratic smoothness penalty and a PLS method employing a total variation norm penalty. The reconstruction algorithms employ accurate models of the ultrasonic transducer impulse responses. Experimental data sets are employed to compare the performances of the iterative reconstruction algorithms to that of a 3D filtered backprojection (FBP) algorithm. By use of quantitative measures of image quality, we demonstrate that the iterative reconstruction algorithms can mitigate image artifacts and preserve spatial resolution more effectively than FBP algorithms. These features suggest that the use of advanced image reconstruction algorithms can improve the effectiveness of 3D OAT while reducing the amount of data required for biomedical applications

Reconstruction of a function from its spherical (circular) means with the centers lying on the surface of certain polygons and polyhedra

We present explicit filtration/backprojection-type formulae for the inversion of the spherical (circular) mean transform with the centers lying on the boundary of some polyhedra (or polygons, in 2D). The formulae are derived using the double layer potentials for the wave equation, for the domains with certain symmetries. The formulae are valid for a rectangle and certain triangles in 2D, and for a cuboid, certain right prisms and a certain pyramid in 3D. All the present inversion formulae yield exact reconstruction within the domain surrounded by the acquisition surface even in the presence of exterior sources.Comment: 9 figure

Photons Plus Ultrasound: Imaging and Sensing

Imaging and sensing based on fusing the compelling features of optical and ultrasonic waves is the fastest growing area of research in biomedical optics. The annual SPIE conference on this topic, co-chaired by both of us, has been doubling in size approximately every three years since 2003 (Fig. 1). As of 2009, this conference has become the largest at SPIE Photonics West. Hybrid modalities such as photoacoustic or optoacoustic tomography can provide deep tissue penetration, high ultrasonic resolution, and speckle-free optical contrast. Applications include in vivo functional and molecular imaging of cancer, neurophysiology, and vascular disease in both animals and humans. Major challenges include development of quantitative imaging, improvement of contrast and resolution, and commercialization of the technology. We look forward to seeing significant preclinical and clinical impact from this emerging technology