Magnetic Imaging Of Cardiac Electrical Activity Based On Beamforming

With people’s attention to health problems and the development of modern medical technology,great progress has been made in the development of clinical testing instruments.Superconducting quantum interferometry Deice(SQUID)is one of the most important methods for magnetic imaging of cardiac electrical activity based on Magnetocardiography(MCG)signals measured on the surface of human chest cavity.It is a new technology that can obtain cardiac electrical activity information noninvastively.Compared with existing medical imaging methods,such as magnetic resonance imaging,ultrasound imaging,and computed tomography,it has many advantages: fast imaging speed and high accuracy,no need for auxiliary measurement contrast agent,no direct contact with patients,and so on.Because of these advantages,it will not cause more trauma to patients.Spatial filtering technology is still the method used for non-invasive imaging of cardiac electrical activity using MCG measurement data.How to accurately describe the distribution of reconstructed current sources needs further study,and the accuracy of reconstructed current sources also has room for further improvement.The methods used in this paper are all based on beamforming technology.Beamforming technology is commonly used in cardiac magnetic source reconstruction,but it is subject to many factors,the most important of which is the influence of noise on the reconstruction accuracy.Existing traditional methods have a certain ability of noise reduction,but there are still great accuracy can be further space,aiming at the problem,improve the distribution of the current source intensity of spatial spectrum estimation is presented in this paper the contrast(IIC)beamforming method,on the basis of the improvement of an improved distributed current source spatial spectrum estimation strength contrast(DIIC)beamforming method,DIIC method can reduce the influence of noise very well.By constructing a real symmetric matrix U to constrain the weight matrix of IIC beamforming,it has been proved that it can achieve a good effect.Simulation results show that the source resolution accuracy of DIIC beamforming method is better than IIC method.In measured heart magnetic data analysis,and DIIC IIC method were used respectively to measure the two sets of 36 channels of cardiac magnetic field data of the measurement of healthy people reconstruct the source,the source to reconstruct the time chosen for R wave moment,the results show that the source of DIIC method reconstruction effect is better than the IIC method,so the DIIC method for noise suppression ability is stronger.In addition,this article also in the traditional method of signal subspace of main feature vector(SPEB),on the basis of beamforming is proposed based on an improved signal subspace beamforming method of main feature vector(ISPEB),the improved ISPEB method mainly from two aspects to improve the source reconstruction precision,on the one hand is constrained spatial filter the noise of the output power and gain,On the other hand,the influence of signal principal eigenvectors on the spatial distribution uniformity of noise is compensated.A real symmetric matrix V is used to constrain the weight matrix of SPEB beamformers,which can achieve higher accuracy under the condition of low SNR.The simulation results show that ISPEB has a better source reconstruction effect.In this paper,source reconstruction was carried out on the 36-channel cardiac magnetic field data of two healthy subjects,and the time of source reconstruction was selected as the peak of R-wave.Simulation results show that ISPEB method can better observe the characteristics of cardiac electrical activity of healthy subjects,and the source reconstruction accuracy is improved compared with MVB method and SPEB method.There are 30 figures,2 tables and 71 references.