A Research About Digital Optical Fiber Transmission Technique For Magnetic Resonance Imaging

With the development of MRI(Magnetic Resonance Imaging)technology,the number of channels for MRI receiver is increasing,and which has higher requirement for the bandwidth and the accuracy of the MRI data transmission.In the conventional MRI systems,MRI signals are usually transmitted using a coaxial cable between the scanning room and the equipment room.There are the loss of MRI signals,the coupling of multi-channel RF cable and the interference of electromagnetic wave in the process of data transmission using a coaxial cable,which would degrade MRI image quality.Based on the shortcomings in the process of the coaxial cable transmission,this paper presents a digital optical fiber transmission scheme.In the scheme,the digital optical fiber transmission has the characteristics of small loss,high SNR,wide bandwidth,large transmission capacity and less affected by electromagnetic waves,so the digital optical fiber transmission scheme can well solve the problems of the coaxial cable transmission.In this paper,through analysis of various serial protocols,we obtain the custom digital optical fiber transmission protocol based on Seriallite protocol.The protocol can achieve the functions of the MRI data multiplexing and demultiplexing,which though Mega Wizard Plug-In Manager tool to generate LPM MUX IP nuclear.We achieves the functions of clock generate and recovery,8B/10B codec,byte string,word alignment,deserialize and differential voltage control though configure the ALTGX IP core.Besides we also design and configure the high speed transceiver reconfiguration module,clock generation module and logical control module.In order to ensure that the excitation signal of the MRI system and the received MRI signal have phase coherence,which requires the excitation unit and the received unit with the same clock source.In this paper,the clock data recovery(CDR)unit is used to recover the clock from the serial MRI data stream,which ensures that the reference clock of the sender and the receiver of MRI data with phase coherence,and finally achieve the digital Optical fiber transmission scheme.In this scheme,the computer is used to read and write the MRI data through the PCIE(Peripheral Component Interconnect Express)bus,and the MRI data is tested by the oscilloscope and SignalTap II logic analyzer,and the clock coherence and the consistency of transmitted/received data is verified.Finally,the human brain MRI image is obtained by image reconstruction,and the feasibility of digital optical fiber transmission scheme is also verified.Based on the Seriallite protocol,the transmission format of the MRI data is defined,and the real-time of transmission is high.The use of the clock recovery unit not only ensures the coherence of the clock,but also does not require a dedicated clock transmission channel,thus simplifying the circuit structure.In addition,the research of digital fiber transmission scheme has laid a foundation for the subsequent digital fiber multi-module cascade transmission,which makes it possible to transfer MRI data of more channels in a single optical fiber.