评估磁共振成像系统电磁安全的数值计算方法  

Numerical Computation Methods for Evaluating the Electromagnetic Safety of Magnetic Resonance Imaging System

作　　者：牛超群[1,2] 王秋良[1] 李毅[1] 唐文举[1,2] 胡洋[1,2] 朱旭晨[1,2] 

机构地区：[1]中国科学院电工研究所,北京100190 [2]中国科学院大学,北京100190

出　　处：《高电压技术》2017年第8期2442-2453,共12页High Voltage Engineering

基　　金：国家自然科学基金(1154200019)~~

摘　　要：近年来,随着磁共振成像(magnetic resonance imaging,MRI)技术的快速发展,其电磁安全性得到了越来越广泛的重视。为此,综合评述了近几年的研究成果,首先介绍了MRI系统产生的静磁场、梯度场和射频场这3种不同性质的电磁场的生物效应及其安全标准,并在此基础上着重介绍了评估MRI系统电磁安全的数值计算方法,分别就人体数值模型和数值计算方法针对准确度和计算效率详细展开了分析和评价。研究结果表明:当MRI产生的3种电磁场超过一定限值时,会引发生物效应,导致受检者的身体出现不适反应;现有人体模型分辨率高,可较准确地反映真实人体组织,但通用模型限制了高场MRI设备优势的发挥,开发个体体素模型是必然发展趋势;现有的用来评估MRI电磁安全的数值计算方法包括有限元法、矩量法和时域有限差分方法,以及准静态近似方法和混合数值计算方法等衍生计算方法,这些方法能较准确地预测人体组织内的电磁场值,但无法兼顾准确度和高计算效率,仍需进一步改善;现有的安全标准尚不完善,未来应补充开放式MRI系统、PET/MRI多模成像技术以及LINAC/MRI介入治疗系统等新型系统的安全标准。该研究结果可以为MRI设计人员提供参考,帮助补充完善现有的MRI安全标准,在保证安全性的条件下提高系统性能。In recent years, with the development of magnetic resonance imaging （MRI） technology, increasingly attention has been paid to electromagnetic safety of MRI. To summarize the researches in recent years, we introduce the biological effects and safety standards of three different kinds of electromagnetic fields （static magnetic field, gradient field, and ra- dio frequency field） produced by MRI equipment firstly. On the basis of this, the numerical computing methods used for evaluating the electromagnetic safety of Mill are emphatically introduced, in which the human numerical model and nu- merical algorithm are studied in detail and evaluated for both accuracy and efficiency. The results of research show that when the electromagnetic fields generated by MRI exceed a certain limit, they will create significant biological effects, leading to the discomfort reaction of body. The current body voxel model has high resolution and can reflect the real hu- man body to some extent. However, the general model limits the full advantages of high field Mill equipment, and developing a specific voxel model is an inevitable trend. The existing numerical algorithms used to evaluate the MRI electromagnetic safety include finite element method, moment method, and time domain finite difference method, as well as quasi-static approximation methods and mixed numerical calculation methods. These methods can accurately predict the electromagnetic field value in human tissue up to a point, but can not take into account accuracy and efficiency simul- taneously, still need to further improved. The existing safety standards are not yet complete and should add relevant safety standards about open Mill, PET/MRI, LINAC/MRI and other new MRI system. The results can provide references for MRI designers, help to complement the existing MRI safety standards, then to simultaneously improve system perfor- mance and ensure electromagnetic safety.

关 键 词：磁共振成像 电磁场 电磁安全 生物效应 人体数值模型 数值计算方法 

分 类 号：O441[理学—电磁学]