D. I. Zotov

Simulation of a functional solution to the acoustic tomography problem for data from quasi-point transducers

Two variants of a functional-analytical algorithm intended for solving inverse tomography problems are discussed and numerically carried out. The acoustic fields that are transmitted and received by transducers, which are equivalent to point ones, serve as experimental data. These data are used to calculate the classical or generalized scattering amplitude, and the scatterer characteristics are then reconstructed. The algorithm requires neither model linearization, no iterations for refining the estimates of scatterers, thus making it attractive for solving acoustic-tomography problems in different applications. The results of the numerical reconstruction of inhomogeneities in the sound velocity and absorption in a medium are presented.

Reconstruction of the sound velocity and absorption spatial distributions in soft biological tissue phantoms from experimental ultrasound tomography data

The paper is devoted to implementing in a specific tomographic device a two-step algorithm designed to reconstruct the spatial distributions of the sound velocity and absorption coefficient, primarily in soft biological tissues. To generate the input data of the first and second steps, a correlation algorithm is used based on determination of the time shift in the signal propagation time in the presence of an object. The results of reconstruction are presented, which are based on data measured for objects-phantoms using a developed experimental ultrasound tomograph model. We discuss problems that arise during reconstruction with a low resolution at the first step of the algorithm, and we demonstrate the high spatial resolving power achieved at the second step.

Reconstruction of spatial distributions of sound velocity and absorption in soft biological tissues using model ultrasonic tomographic data

A two-step algorithm is used to reconstruct the spatial distributions of the acoustic characteristics of soft biological tissues-the sound velocity and absorption coefficient. Knowing these distributions is urgent for early detection of benign and malignant neoplasms in biological tissues, primarily in the breast. At the first stage, large-scale distributions are estimated; at the second step, they are refined with a high resolution. Results of reconstruction on the base of model initial data are presented. The principal necessity of preliminary reconstruction of large-scale distributions followed by their being taken into account at the second step is illustrated. The use of CUDA technology for processing makes it possible to obtain final images of 1024 × 1024 samples in only a few minutes.

Ultrasound tomography of soft biological tissues containing strong inhomogeneities

Applied aspects concerning experimental data processing have been discussed. The data are obtained on a prototype of ultrasound medical acoustic tomograph, designed for early diagnostics of benign and malignant tumors in soft biological tissues. The result of the study is the reconstructed distribution patterns of speed of sound and absorption in an organ under test.

A prototype for a tomography system using third-order acoustic nonlinear effects

A prototype of a tomography system for reconstructing the distributions of acoustic nonlinear parameters is developed and manufactured on the basis of the effect of nonlinear noncollinear interaction of three primary waves. Application of coded primary signals with further correlation processing of a detected combination signal makes it possible to reconstruct the complete image of an object as a result of a single experiment using a small number of transducers, i.e., three radiators and one receiver. A mirror system is proposed, consisting of two coaxial conical acoustic mirrors that make it possible to transform the front of a wave from a cylindrical transducer into a homogeneous quasi-plane beam with a large width close to the real medical diagnostics requirements. Results of physical experiments are given.

Reconstruction of the blood flow velocity vector as an additional mode of ultrasonic tomograph

The possibility of simultaneous reconstruction of the blood flow velocity vector and spatial distributions of the speed of sound and absorption coefficient in a medical ultrasonic tomograph is discussed. The operating capacity of the proposed spatial-correlation method for determining the blood flow velocity vector is confirmed by experiments on a tomograph prototype.

Vector field reconstruction of flows using the Novikov–Agaltsov functional algorithm and the additive correlation method

Results from numerical modeling of the Novikov–Agaltsov functional algorithm which allows us to reconstruct scalar-vector acoustic inhomogeneities are presented. On the other hand, a vector map of flow velocities is recovered using experimental data obtained via ultrasonic tomograph and processed by means of spatial correlation method.

Principles of obtaining and processing of acoustic signals in linear and nonlinear tomographs

Physical, mathematical, and engineering problems related to creating two fundamentally different types of tomographs (so-called linear and nonlinear tomographs) are considered. The tomographs under development are designed for diagnosing pathological tumors of soft biological tissues at early stages of their growth.

Functional-analytical solution to an acoustic tomography problem, based on data from point transducers

A two-dimensional version of the functional-analytical algorithm for solving the inverse scattering problem is considered and modeled. Acoustic fields, transmitted and received by quasi-point transducers, are used as experimental data. The algorithm is mathematically rigorous and does not require either linearization of the models or iterations, making it attractive for a variety of applications in acoustic tomography.

Operating principles of linear acoustic tomograph

An enhanced linear acoustic tomograph is designed for the early medical diagnosis of pathological neoplasms of soft biological tissues. Problems associated with additional prospects for tomographic imaging are discussed.