The portable light-weight magnetic resonance imaging system can be deployed in special occasions such as Intensive Care Unit (ICU) and ambulances, making it possible to implement bedside monitoring imaging systems, mobile stroke units and magnetic resonance platforms in remote areas. Compared with medium and high field imaging systems, ultra-low-field magnetic resonance imaging equipment utilizes light-weight permanent magnets, which are compact and easy to move. However, the image quality is highly susceptible to external electromagnetic interference without a shielded room and there are still many key technical problems in hardware design to be solved. In this paper, the system hardware design and environmental electromagnetic interference elimination algorithm were studied. Consequently, some research results were obtained and a prototype of portable shielding-free 50 mT magnetic resonance imaging system was built. The light-weight magnet and its uniformity, coil system and noise elimination algorithm and human brain imaging were verified. Finally, high-quality images of the healthy human brain were obtained. The results of this study would provide reference for the development and application of ultra-low-field magnetic resonance imaging technology.
移动式轻量化的磁共振成像系统可部署于重症监护室、救护车等特殊场合，使床旁脑卒中监护成像、救护车上移动脑卒中成像成为可能。相比于中高场系统，超低场磁共振成像设备采用轻量化的永磁体设计，结构紧凑，方便移动，但在没有电磁屏蔽房的情况下其图像质量极易受外部电磁干扰噪声的影响且硬件设计上还存在诸多关键技术问题有待解决。本文从系统硬件设计及环境电磁干扰消除两个方面展开研究，研发了50 mT移动式无屏蔽磁共振成像系统样机，从磁体的永磁结构、梯度和射频线圈系统以及电磁噪声消除算法等方面进行了系统研究，最终获得了高质量的人脑图像，为超低场磁共振成像技术的临床应用打下了基础。.
Keywords: Magnetic resonance imaging; Noise reduction; Shielding-free; Ultra-low field.