Electromagnetic Interference Analysis And Suppression Method Of Ultra-low Field MRI System

Compared with the superconducting MRI and CT imaging system,the ultra-low field MRI system for human detection has a broader development prospect.The smaller volume and weight and harmless detection meet the wide use environment,and the lower cost and operation cost are more in line with the market demand.However,the imaging quality and anti electromagnetic interference performance of the system are poor,and the imaging quality is easily affected by the electromagnetic interference of the environment where the system is located.For the better development of ultra-low field magnetic resonance imaging technology,the electromagnetic interference analysis and more perfect anti electromagnetic interference Design for the system is particularly important.In this paper,the electromagnetic interference(EMI)of the existing ultra-low field MRI system in the laboratory is analyzed,and the corresponding EMI suppression measures are designed.Based on the three elements of electromagnetic compatibility of the MRI system,the problem of electromagnetic interference in the system is analyzed from the aspects of conduction and radiation.Passive filtering,shielding,grounding and other suppression measures are adopted for electromagnetic interference.In order to improve the interference suppression effect and achieve the open and lightweight development goals of the imaging system,an active noise reduction technology based on the imaging system is proposed,and the experiment verifies its feasibility Sex.The specific contents include the following aspects:(1)The overall composition and imaging principle of the imaging system are analyzed.From the basic concept of electromagnetic interference,the characteristics of the high-frequency components and transmission lines of the internal circuit of the MRI system are analyzed.The propagation path of the electromagnetic interference of the MRI system is analyzed from both conduction and radiation.(2)Interference analysis of MRI system from harassment source,interference propagation path and anti-interference intensity(EMS).The problem of electromagnetic interference of MRI system is analyzed from two aspects of conduction and radiation,and the interference analysis results are used to design better measures to suppress electromagnetic interference.(3)For the electromagnetic interference problem of MRI system,passive filtering and shielding are adopted to suppress interference.In order to improve the interference suppression effect and the signal-to-noise ratio of the image,this paper designed an active noise reduction method based on MRI system,and made a noise detection sensor.The experiment verifies the feasibility of the active noise reduction method of imaging system,abandons the traditional passive shielding noise reduction method,which is expected to achieve the development goal of open detection and lightweight of imaging system.The results show that the active noise reduction method can better eliminate the influence of electromagnetic interference than the passive filtering and shielding measures.The former mainly deals with the overall noise reduction of MR signal without considering the amount of noise,while the latter is to reduce the noise by blocking the propagation path of electromagnetic noise.Due to the diversity and time-varying of electromagnetic noise,it is difficult to effectively block the propagation of electromagnetic noise.