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Cheng Z, Sun Z, Wang J, Jia K. Magneto-acousto-electrical tomography using nonlinearly frequency-modulated ultrasound. Phys Med Biol 2024; 69:085014. [PMID: 38422542 DOI: 10.1088/1361-6560/ad2ee5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Accepted: 02/29/2024] [Indexed: 03/02/2024]
Abstract
Objective. In this study, nonlinearly frequency-modulated (NLFM) ultrasound was applied to magneto-acousto-electrical tomography (MAET) to increase the dynamic range of detection.Approach. Generation of NLFM signals using window function method-based on the principle of stationary phase-and piecewise linear frequency modulation method-based on the genetic algorithm-was discussed. The MAET experiment systems using spike, linearly frequency-modulated (LFM), or NLFM pulse stimulation were constructed, and three groups of MAET experiments on saline agar phantom samples were carried out to verify the performance-respectively the sensitivity, the dynamic range, and the longitudinal resolution of detection-of MAET using NLFM ultrasound in comparison to that using LFM ultrasound. Based on the above experiments, a pork sample was imaged by ultrasound imaging method, spike MAET method, LFM MAET method, and NLFM MAET method, to compare the imaging accuracy.Main results. The experiment results showed that, through sacrificing very little main-lobe width of pulse compression or equivalently the longitudinal resolution, the MAET using NLFM ultrasound achieved higher signal-to-interference ratio (and therefore higher detection sensitivity), lower side-lobe levels of pulse compression (and therefore larger dynamic range of detection), and large anti-interference capability, compared to the MAET using LFM ultrasound.Significance. The applicability of the MAET using NLFM ultrasound was proved in circumferences where sensitivity and dynamic range of detection were mostly important and slightly lower longitudinal resolution of detection was acceptable. The study furthered the scheme of using coded ultrasound excitation toward the clinical application of MAET.
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Affiliation(s)
- Zhizhuo Cheng
- College of Information and Communication Engineering, Faculty of Information Technology, Beijing University of Technology, Beijing 100124, People's Republic of China
| | - Zhishen Sun
- College of Information and Communication Engineering, Faculty of Information Technology, Beijing University of Technology, Beijing 100124, People's Republic of China
| | - Jianfei Wang
- Beijing Key Laboratory of Nonlinear Vibrations and Strength of Mechanical Structures, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing 100124, People's Republic of China
| | - Kebin Jia
- College of Information and Communication Engineering, Faculty of Information Technology, Beijing University of Technology, Beijing 100124, People's Republic of China
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Li P, Chen W, Guo G, Tu J, Zhang D, Ma Q. General principle and optimization of magneto-acousto-electrical tomography based on image distortion evaluation. Med Phys 2023; 50:3076-3091. [PMID: 36815305 DOI: 10.1002/mp.16317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 02/08/2023] [Accepted: 02/13/2023] [Indexed: 02/24/2023] Open
Abstract
BACKGROUND As a novel non-invasive multi-physics imaging methodology, the magneto-acousto-electrical (MAE) technology is capable of detecting electric conductivity changes for biological tissues, exhibiting prosperous perspectives in medical applications. However, the acoustic beam was often simplified to a straight line or a focused one, being perpendicular to layered boundaries of tissues in previous studies. Linear-scanning measurements were carried out to reconstruct B-mode MAE images for layered models without considering the radiation pattern of transducers. Obvious image distortions in both shape and brightness were observed in experiments without any reasonable explanation. PURPOSE This study aims to establish a general physical model for MAE measurements and solve the problem of B-mode image distortion, and hence provide theoretical and technical supports for the improvement of MAE imaging in practical applications. METHODS By considering the radiation pattern of actual transducers and the inclined angle of electric conductivity boundaries, a general principal of MAE measurements applicable for objects of arbitrary shapes is proposed based on the theories of acoustic radiation, Hall Effect and electrical detection. The influences of inclined conductivity boundaries and transducer directivities are numerically analyzed with Matlab programming and also demonstrated by experimental measurements. To evaluate the degree of B-mode image distortion, the deformation length (3 dB amplitude decrease) of approximate straight lines for a circular model is defined as L = dtan(βm /2), with d and βm being the measurement distance and the half radiation angle of the main-lobe, respectively. The rotary-scanning-based MAE tomography (MAET) is employed to reduce the image distortion, and the rotation angle step is further optimized based on the criterion of the boundary radius fluctuation coefficient <0.01 mm. RESULTS The experimental results of MAE signals and B-mode images as well as MAETs show good agreements with simulations. It is demonstrated that, as the increase of the inclined angle, the MAE decreases rapidly with an extended time interval and reaches the 20 dB amplitude decrease when the angle exceeds 12°. Meanwhile, the deformation length of B-mode MAE imaging increases with the increase of the radiation angle for the transducer with a weaker radiation pattern, and hence results in a more serious image distortion. A smaller rotation angle step should be adopted to the MAET system with a longer deformation length, and the optimized maximum angle step of 12° is also achieved for the omnidirectional radiation of point sources with a long deformation length. CONCLUSION The image distortion is originated from the amplitude decrease, the time shift and the time interval expansion of MAE signals introduced by the deformation length and the incident angle. The favorable results demonstrate that the fast high-resolution imaging can be accomplished by the minimum rotations of the rotary-scanning-based MAET using an actual transducer, and also provide an optimized scheme for the rotary-based MAET without scanning using a linear array of point sources.
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Affiliation(s)
- Peixia Li
- School of Computer and Electronic Information, Nanjing Normal University, Nanjing, China
| | - Wei Chen
- School of Computer and Electronic Information, Nanjing Normal University, Nanjing, China
| | - Gepu Guo
- School of Computer and Electronic Information, Nanjing Normal University, Nanjing, China
| | - Juan Tu
- Institute of Acoustics, Nanjing University, Nanjing, China
| | - Dong Zhang
- Institute of Acoustics, Nanjing University, Nanjing, China
| | - Qingyu Ma
- School of Computer and Electronic Information, Nanjing Normal University, Nanjing, China
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Sun T, Hao P, Chin CT, Deng D, Chen T, Chen Y, Chen M, Lin H, Lu M, Gao Y, Chen S, Chang C, Chen X. Rapid rotational magneto-acousto-electrical tomography with filtered back-projection algorithm based on plane waves. Phys Med Biol 2021; 66. [PMID: 33725674 DOI: 10.1088/1361-6560/abef43] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Accepted: 03/16/2021] [Indexed: 11/12/2022]
Abstract
Magneto-acousto-electrical tomography (MAET) is designed to produce conductivity images with high spatial resolution for a conducting object. In a previous study, for an irregular conductor, transverse scanning and rotational methods with a focus transducer were combined to collect complete electrical information. This kind of method, however, is time-consuming because of the transverse scanning procedure. In this study, we proposed a novel imaging method based on plane ultrasound waves and a new aspect of projection in rotational MAET. In the proposed method, we achieved the projection in each rotation angle by using plane waves rather than mechanical scanning of the focus waves along the transverse direction. Thus, the imaging time was significantly saved. To verify the proposed method, we derived a measurement formula containing a lateral integration, which built the relationship between the measurement formula and the projection under each rotation angle. Next, we constructed two different numerical models to compute magneto-acousto-electrical signals by using a finite element method and reconstructed the corresponding conductivity parameter images based on a filtered back-projection algorithm. Then, simulated signals under different signal-to-ratios (6, 20, 40, and 60 dB) were generated to test the performance of the proposed algorithm. To improve the image quality, we further analysed the influence of the filters and the frequency scaling factors embedded in the filtered back-projection algorithm. Moreover, we computed the L2norm of the error in case of different frequency scaling factors and measurement noises. Finally, we conducted a phantom experiment with a 64-element linear phased array transducer (center frequency of 2.7 MHz) and reconstructed the conductivity parameter images of the circular phantom with an elliptical hole. The experimental results demonstrated the feasibility and time-efficiency of the proposed rapid rotational MAET.
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Affiliation(s)
- Tong Sun
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Penghui Hao
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Chien Ting Chin
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Dingqian Deng
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Tiemei Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Yi Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China
| | - Mian Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Haoming Lin
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Minhua Lu
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Yi Gao
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Siping Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Chunqi Chang
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
| | - Xin Chen
- School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen 518060, People's Republic of China.,Guangdong Provincial Key Laboratory of Biomedical Measurements and Ultrasound Imaging, Shenzhen 518060, People's Republic of China.,National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, Shenzhen 518060, People's Republic of China
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Sun Z, Liu G, Guo L, Xia H, Wang X. Effect of the secondary process on mass point vibration velocity propagation in magneto-acoustic tomography and magneto-acousto-electrical tomography. Technol Health Care 2016; 24 Suppl 2:S683-9. [PMID: 27177099 DOI: 10.3233/thc-161196] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND As two of the new biological electrical impedance tomography (EIT), magneto-acoustic tomography (MAT) and magneto-acousto-electrical tomography (MAET) achieve both the high contrast property of EIT and the high spatial resolution property of sonography through combining EIT and sonography. As both MAT and MAET contain a uniform magnetic field, vibration and electrical current density, there is a secondary process both in MAT and in MAET, which is MAET and MAT respectively. OBJECTIVE To analyze the effect of the secondary process on mass point vibration velocity (MPVV) propagation in MAT and MAET. METHODS By analyzing the total force to the sample, the wave equations of MPVV in MAT and MAET - when the secondary processes were considered - were derived. The expression of the attenuation constant in the wave number was derived in the case that the mass point vibration velocity propagates in the form of cylindrical wave and plane wave. Attenuations of propagation of the MPVV in several samples were quantified. RESULTS Attenuations of the MPVV after propagating for 1 mm in copper or aluminum foil, and for 5 cm in gel phantom or biological soft tissue were less than 1%. CONCLUSION Attenuations of the MPVV in MAT and MAET due to the secondary processes are relatively minor, and effects of the secondary processes on MPVV propagation in MAT and MAET can be ignored.
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Affiliation(s)
- Zhishen Sun
- Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Guoqiang Liu
- Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China
| | - Liang Guo
- Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China.,College of Control Theory and Engineering, China University of Petroleum, Qingdao, Shandong, China
| | - Hui Xia
- Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China
| | - Xinli Wang
- Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China
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