Capabilities of Layered Ultrasound Tomography
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Capabilities of Layered Ultrasound Tomography A. V. Goncharsky1* and S. Y. Seryozhnikov1** (Submitted by Vl. V. Voevodin) 1
Moscow Center of Fundamental and Applied Mathematics, Moscow, 119991 Russia Received May 14, 2020; revised May 20, 2020; accepted May 24, 2020
Abstract—This article discusses the capabilities of layered “2.5D” schemes in ultrasound tomography, in which the emitters and detectors are located in the same plane. The primary application of this method is medical imaging technology for early-stage breast cancer diagnosis. The inverse problem of tomographic image reconstruction is posed as a coefficient inverse problem for the wave equation, where the wave propagation velocity is an unknown function of two coordinates. In this formulation, the problem has much less computational complexity than in a 3D formulation, in which the wave velocity is reconstructed as a function of three coordinates. Nevertheless, the inverse problem in the layered “2.5D” formulation is non-linear and requires the use of supercomputers. A practically feasible parallel implementation of the image reconstruction algorithms on a GPU cluster is proposed. This study shows that the layered model is applicable if the imaged objects are close to cylindrical. Refraction of ultrasound waves in the vertical direction cannot be taken into account by the layered model. The more significant is the refraction, the more the reconstructed image differs from reality. The experiments were carried out using the test bench developed at the Scientific Research Computing Centre of Lomonosov Moscow State University. DOI: 10.1134/S1995080220080065 Keywords and phrases: ultrasound tomography, coefficient inverse problem, GPU cluster, medical imaging.
1. INTRODUCTION This paper is concerned with developing parallel algorithms for solving inverse problems of ultrasound tomography. Soft tissue imaging technologies for early-stage breast cancer diagnosis are the primary field of application of ultrasound tomography. X-Ray, MRI and PET technologies can also be used for soft tissue imaging, positron-emission tomography being the most informative for breast cancer diagnosis. However, these technologies employ either harmful radiation or chemical contrast agents that are unsafe if used for regular medical checkups. Conventional ultrasound imaging equipment is not informative for breast cancer diagnosis due to the poor image quality. In order to develop a technology for early-stage breast cancer diagnosis that is both safe and informative, the works on ultrasound diagnostic methods based on the principles of wave tomography are currently underway in the United States, Germany, and Russia [1–3]. Ultrasound tomography is absolutely safe and can be used for regular examinations. These projects are currently at the stage of experiments and prototypes. Vast majority of existing projects on ultrasound tomography [4–6] employ a layered (“2.5D”) model in which the tomographic image is reconstructed independently for each of the cross-sections of the object under study. In
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