一种基于线性零磁场的动脉血管扫描成像方法仿真

Simulation of an Arterial Scanning Imaging Method Based on Linear Zero Magnetic Field

基于磁电耦合效应的血流检测及血管成像是实现心血管疾病早期诊疗的有效方法之一。该文基于磁场与血流耦合电效应,设计一种用于动脉血管扫描成像的组合线圈结构,产生带有零磁场线(FFL)区域的线性梯度磁场;在此结构的基础上,通过控制激励电流驱动FFL实现成像区域双向扫描;结合卷积神经网络(CNN)实现磁电耦合信号与血管信息的非线性映射,进而提出一种基于线性零磁场的动脉血管扫描成像新方法。采用多物理场仿真软件COMSOL对基于线性零磁场的血管扫描成像方法进行建模,求解磁电耦合信号,验证了所提出方法的合理性和有效性。结果表明,线性梯度磁场模式下的磁电耦合信号含有血管位置、半径等信息;CNN重建血管位置误差平均值为1.5694 mm,重建血管半径的方均误差(MSE)和相关系数(CC)平均值分别为0.0548和0.9870。研究结果可用于血管成像装置设计及后续相关临床应用提供研究支撑。

Cardiovascular diseases,such as coronary artery stenosis and coronary heart disease,have become prominent in human health.Nowadays,existing diagnostic techniques in clinical practice are unsuitable for early cardiovascular disease prediction and monitoring due to trauma,high cost,radiation problems,and operation complexity.In this paper,the coupling electric effect of magnetic field and blood flow is studied,and slow imaging speed caused by an extensive range of uniform magnetic fields is considered.Then,a linear gradient magnetic field for arterial scanning imaging method is proposed.Firstly,the topology of a combined coil for arterial vascular scanning imaging is proposed for generating a linear gradient magnetic field with a field-free line(FFL)configuration.Secondly,FFL is moved by adjusting the excitation current to realize a two-directional electronic scan of the imaging region.In addition,the curved FFL scanning trajectory is corrected.Then,the numerical simulation model of arterial scanning imaging is established by COMSOL,and the voltage signals of magnetoelectric coupling are solved by the finite element method(FEM).Finally,convolutional neural networks(CNN)are used to realize the nonlinear mapping between the magnetoelectric coupled signals and the vascular information.The coordinates of the center position and the radius of the blood vessel are obtained to reconstruct the arterial vascular image.When the current amplitude of the gradient coil changes from 8 A to 30 A,the peak value of the magnetic field intensity in the Y-axis z direction varies from 0.024 T to 0.089 T,and the magnetic field gradient increases accordingly.The FFL is generated by superimposing the alternating driving field and the linear gradient magnetic field line.Injecting cosine alternating currents into the driving coil,FFL is electronically scanned in the yz-plane.The translated range of FFL is-30 mm to 40 mm in the y-direction and-20 mm to 25 mm in the z-direction.The CNN is trained by simulation datasets,and nonlinear mapping between the induced voltage signal and the vascular information is established.The average error of the vessel position reconstructed is 1.5694 mm.The mean squared error(MSE)and correlation coefficient(CC)of the reconstructed vascular radius are 0.0548 and 0.9870,respectively.The proposed topology of the combined coil for generating FFL has shown the potential advantage in real-time imaging of arteries.By adopting the correction coefficient in the gradient coil current,the FFL offset height can be dynamically compensated,and the linear correction of the FFL trajectory has been realized.Using CNN,a nonlinear mapping between the magneto-electric coupling signal of blood flow in linear gradient zero field excitation and the vascular information can be established,thereby obtaining the arterial vessel profile image.However,in the practical design of the imaging system,several factors must be considered,such as coil turns,coil group geometry,FFL translating the field of view(FOV),imaging speed,and image resolution.Further studies will focus on adjusting the position of each coil or optimizing the structure of combined coils for the clinical requirements of blood vessel images.