一种磁共振成像谱仪数字化发射系统设计

A digital transmit system design for MRI spectrometer

目的提出了一种磁共振成像谱仪的数字化发射系统设计.方法该设计将发射脉冲信号载波的频率和相位分两次调制,在FPGA内的NCO产生选层偏移频率以及发射脉冲信号的初始相位,在DAC3484内的NCO产生系统中心频率.结果该设计结合了FPGA内NCO频率、相位快速切换和DAC3484内NCO频率调整范围大的优点,可以实现频率、相位的快速切换,同时满足从低场0.07T到高场7T的脉冲信号发射需求,并提高脉冲信号初始相位精度.结论磁共振成像谱仪数字化发射系统采用两次数字化调制,提高了磁共振系统的发射相位精度进而改善了成像质量,是一种可以通用于MRI谱仪的设计.

Objective A digital transmit module of an MRI spectrometer is proposed in this paper.Methods The frequency and phase of the pulse signal is modulated in two steps.The NCO within the FPGA generates the slice selection offset frequency and the initial phase of the pulse signal,the NCO within DAC3484 generates the system center frequency.Results The design combines the advantages of fast phase/frequency switching within FPGA and large range adjustment within DAC,and simultaneously meets the pulse signal modulation frequency requirements that from low field 0.07T to high field 7T,also improves the phase accuracy of pulse signal.Conclusion Two-step digital modulation method is used in transmit module to improve the phase accuracy and thus improves the image quality.This method can be widely applied in MRI spectrometer design.