单电流注入的三维MREIT快速重建及实验

Fast Reconstruction Algorithm and Experiments Based on Single Current Injection for Three Dimensional MREIT

磁共振电阻抗成像(MREIT)是将磁共振成像(MRI)与传统电阻抗成像(EIT)技术相结合的一种电导率成像技术,通过提供成像体精确的几何信息与成像体内部的磁通密度值,改善了电阻抗成像的病态性,使得电导率图像的分辨率显著提高.针对MREIT系统的快速成像问题,在分析磁共振电阻抗成像的数学模型和正逆问题的基础上,提出利用单次电流的磁通密度分量即可进行电导率图像重建的方法,缩短了测量时间,并降低了电极间的电磁干扰;将灵敏度矩阵法扩展到三维MREIT,采用半解析法计算灵敏度矩阵,使得图像重建速度得到提高;并通过仿真与仿体实验验证了该方法的有效性.结果表明获得的电导率分布图像具有较高的分辨率和图像质量,测量与重建时间的缩短为MREIT的临床应用奠定了基础.

Magnetic resonance electrical impedance tomography （MREIT）is an electrical conductivity tomography which combines magnetic resonance imaging （MRI） and conventional electrical impedance tomography （EIT） together. It can provide the exact geometric information and the internal magnetic flux density of the imaging object, improve the ill-posed condition in conventional EIT and obtain the electrical conductivity distribution images with high resolu- tion. In order to achieve fast reconstruction for MREIT, based on forward and inverse problems, a method was pro- posed for electrical conductivity reconstruction with only one current injection. Due to single current injection and one component of magnetic flux density measurement, the scanning time can be reduced and the electromagnetic inter- ference induced by the electrodes can also be decreased; the sensitivity algorithm is expanded to three dimensional space, with the sensitivity matrix obtained by semi-analytical method, thus the reconstruction time can be reduced; at last, simulation and phantom experiments were done to verify the proposed reconstruction algorithm. Both simula- tion results and phantom experiments indicate that, with single current injection, electrical conductivity can be re- constructed with high resolution and high imaging quality. With both scanning and reconstruction time reduced, MREIT is proved to be a promising approach in clinical application.