基于高精度磁共振梯度卡的数字涡流预补偿方法  

The digital method for eddy-current precompensation based on high resolution gradient waveform generator

作　　者：杨帆[1] 徐俊成[1] 姚守权 李建奇[1] 蒋瑜[1] YANG Fan;XU Juncheng;YAO Shouquan;LI Jianqi;JIANG Yu(Shanghai Key Laboratory of Magnetic Resonance,School of Physics and Electronic Science,East China Normal University,Shanghai 200062,China)

机构地区：[1]华东师范大学物理与电子科学学院,上海市磁共振重点实验室,上海200062

出　　处：《磁共振成像》2020年第5期354-359,共6页Chinese Journal of Magnetic Resonance Imaging

基　　金：国家自然科学基金资助项目(编号:21874045);上海市科技创新行动计划资助项目(编号:19142202900)。

摘　　要：目的介绍一种基于高精度梯度卡的数字涡流预补偿方法。材料与方法使用现场可编程门阵列(field programmable gate array,FPGA)对序列设计的标准梯度波形进行实时计算得到补偿波形,将标准梯度波形和补偿波形分别送入两片独立的数模转换器(digital-to-analog converter,DAC),对模拟信号进行叠加产生补偿后波形;采用高速时钟和同步触发设计方法,对包含五组时间常数的预补偿波形进行了实时计算。结果在20 bit的DAC基础上实现了优于23 bit的高精度数字涡流预补偿方法;大大缩短了预补偿波形相对触发信号的延时,并保证每次的延时恒定不变。结论经过实验验证,相较于模拟与传统数字涡流预补偿方法,高精度数字方法在涡流预补偿上效果更好。Objective: A digital method for eddy-current precompensation based on high resolution gradient waveform generator is proposed. Materials and Methods: Digital precompensation waveform is calculated from standard gradient waveform by field programmable gate array(FPGA). Then the original waveform and precompensation waveform are transmitted into two separated digital-to-analog converters(DAC) and transformed to analog signals respectively. Finally, compensated waveform is generated by adding the two analog waveforms. Besides, the precompensation waveform described by five various exponential decay terms is calculated timely using high-speed clock and synchronization trigger method. Results: Digital eddy-current precompensation based on two 20 bit DACs achieved higher resolution, and more precise than 23 bit resolution. Meanwhile, this method considerably reduced delay time between compensated waveform and trigger signal as well as keep it constant. Conclusions: High resolution method achieves better experimental result than analog or traditional digital eddy-current precompensation method.

关 键 词：磁共振成像 梯度 涡流预补偿 预加重 现场可编程门阵列 数模转换器 

分 类 号：R445.2[医药卫生—影像医学与核医学]