ABSTRACT
As drug carriers, magnetic nanoparticles can specifically bind to tumors and have the potential for targeted therapy. It is of great significance to explore non-invasive imaging methods that can detect the distribution of magnetic nanoparticles. Based on the mechanism that magnetic nanoparticles can generate ultrasonic waves through the pulsed magnetic field excitation, the sound pressure wave equation containing the concentration information of magnetic nanoparticles was derived. Using the finite element method and the analytical solution, the consistent transient pulsed magnetic field was obtained. A three-dimensional simulation model was constructed for the coupling calculation of electromagnetic field and sound field. The simulation results verified that the sound pressure waveform at the detection point reflected the position of magnetic nanoparticles in biological tissue. Using the sound pressure data detected by the ultrasonic transducer, the B-scan imaging of the magnetic nanoparticles was achieved. The maximum error of the target area position was 1.56%, and the magnetic nanoparticles regions with different concentrations were distinguished by comparing the amplitude of the boundary signals in the image. Studies in this paper indicate that B-scan imaging can quickly and accurately obtain the dimensional and positional information of the target region and is expected to be used for the detection of magnetic nanoparticles in targeted therapy.
Subject(s)
Acoustics , Computer Simulation , Magnetics , Magnetite Nanoparticles , TomographyABSTRACT
Objective To solve the problem of the low signal to noise ratio (SNR)and limited imaging quality using single pulse exciting method in magnetoacoustic imaging, as well as the limited imaging speed using wave averaging processing method to magnetoacoustic signal. Methods M-sequence coded exciting method was proposed to enhance SNR imaging efficiency. The SNR improvement and sidelobe level were investigated using M-sequence code by simulation and experiments.Results The SNR of magnetoacoustic signal were 19.4,29.6,and 40.4 dB respectively under 7,31 and 127 bit M-sequence coded excitation. Three bits of M-sequence coded excitation magnetoacoustic signals had the integrated sidelobe level being 14.1,10.0 and 7.6 dB,and the peak sidelobe level being 26.3,24.3 and 21.3 dB.In case the SNR was increased by 40 dB,127 bit of M-sequence coded excitation shortened the sampling and procession time from 53.1 s to 0.520 s when compared with singl-pulse excitation combined with waveform average.Conclusion The coded excitation is significant for magnetoacoustic signal SNR and imaging quality improvement.