The Time-frequency Analysis Of The Magnetoacoustic Signals Of Different Materials In Magnetoacoustic Tomography

Magnetoacoustic tomography(MAT)is an emerging noninvasive electrical conductivity imaging that combines the high dielectric contrast of tissues and excellent resolutions of ultrasonography.Magnetoacoustic is based on the Lorentz force induced magnetoacoustic(MA)signals to reconstruct the distribution of electrical conductivity of tissues.The analysis of magnetoacoustic signals play an important role in MAT.Firstly,we analyze the characteristics of MA signals of different material under different experiment condition based on the optimized MAT system.The MA signals have been analyzed and compared in the time domain and the frequency domain with varying pulsed stimulation,varying intensity of static magnetic,different frequency-responses of transducers and different characteristic of samples,respectively.This paper firstly optimized and tested the MAT experiment system,which can help to improve the signal-to-noise ratio of the system and ensure the accuracy,reliability and stability of the experimental process.Secondly,we analyzed the characteristic of magnetoacoustic signals produced by different samples and found that the biological tissue and the tissue-like samples still produce acoustic signals without the static magnetic field.It means that there be non-MA signals in tissue and the tissue-like samples.In order to further discuss the non-MA signals in MAT,a series of experiment study has been implemented.The non-MA signals is induced by a non-Lorenz-force source.We found that the non-Lorenz-force source is a scalar source,which is a quadratic function of stimulation intensity,a liner function of conductivities and rigidities of materials based on the experiment results.It proposed that the non-MA signals is the thermoacoustic(TA)signals.To further evaluate the experimental signals,the theoretical simulation has been carried outbased on the MA formula and the TA formula.In this paper,we analyze the MA signals of different material under different experiment condition and investigate the Non-Lorenz-force source in tissue-like materials.All the studies could contribute to optimize MAT method and improve MAT imaging quality.