Novel reconstruction algorithm of magnetoacoustic tomography based on ring transducer array for acoustic speed inhomogeneous tissues

Abstract

Purpose Magnetoacoustic tomography with magnetic induction (MAT‐MI) is a technique that utilizes the acoustic signals induced by magnetic stimulation to reconstruct the electrical impedance distribution in biological tissues. Most algorithms ignored the fact that acoustic properties in human tissues are heterogeneous, which lead to distortion and blurring of small reconstructed objects. In this study, a novel algorithm is proposed for exact reconstruction of the sound source distribution in acoustic heterogeneous tissues. Methods Based on the ring transducer array, we develop an algorithm which combines algebraic reconstruction technique (ART) and time reversal method. Different to existing reconstruction methods, the ultrasonic transmission tomography (UTT) and the MAT‐MI can be completed in same system, which decreases the system complexity. The sound velocity distribution is reconstructed with the ART so that the propagation time of the magnetoacoustic signals in the heterogeneous tissue is corrected. And then, the sound source image is reconstructed based on the time reversal method from new sound pressure data. Both numerical simulations and phantom experiments are established to validate the proposed method. Results Compared with the results without consideration of the variation on acoustic speed, sound sources reconstructed by our method are more consistent with the model in terms of size and shape. Conclusions The novel algorithm can be used to reconstruct the high‐accuracy image of MAT‐MI sound source in the sound velocity inhomogeneous media. In addition, this method is applicable to scenarios that the prior knowledge of the imaging targets is unknown. The signal acquisition time of MAT‐MI in acoustically heterogeneity media is greatly reduced due to the introduction of ring transducer array into the imaging system. Therefore, our method will promote the application of MAT‐MI in noninvasive early diagnosis of tumor for preclinical study.

A Review on the Coupled Method of Using the Magnetic and Acoustic Fields for Biological Tissue Imaging

“…Subsequently, researchers of the Hebei University of Technology, Zhang et al [5] , proposed a split Bregman method to solve the inhomogeneity of the sound velocity medium. The problem was also investigated in a recent study by Wang et al [6] , where an algebraic iteration algorithm and a time-reversal method were used to reconstruct the distribution of an inhomogeneous sound velocity medium. Considering the irregular conductivity distribution problem, a mathematical framework and an optimal control method for reconstructing the anisotropic conductivity tensor were proposed by the Ecole Normale Supérieure de Paris [7] , which proved the convergence of the algorithm.…”

Detailed Analytical Approach to Solve the Magnetoacoustic Tomography with Magnetic Induction (MAT-MI) Problem for Three-Layer Objects

“…The electric field and the eddy current density vectors inside the object can be described as follows [2][3][4][6][7][8][11][12][13][14][15][16][17]:…”

“…In case of a sufficiently short pulse, after splitting the temporary magnetic field for the functions of space and time, the Lorentz force density can be expressed as [2][3][4][6][7][8][11][12][13][14][15][16][17]:…”

“…In the MAT-MI, the divergence of the force arising from (2) leads to ultrasonic vibrations and produces a mechanical wave resulting from the following wave equation [2][3][4]:…”

“…Recently, several noninvasive electromagnetic imaging methods were developed to determine the electrical conductivity distribution of various low-conductive objects. Among them, magnetoacoustic tomography with magnetic induction (MAT-MI) was recently established [2], which overcomes the unwanted shielding effect occurring in electrical impedance tomography (EIT), magnetoacoustic tomography with current injection (MAT-CI) [3], and magneto-acoustic tomography (MAT) [4][5][6] as well as defeats the problem of low spatial resolution of magnetic induction tomography (MIT) [7]. The MAT-MI technique-as a multiphysics imaging approach-is based on the coupling of electromagnetism and ultrasound into one hybrid method.…”