A Compact MRI Spectrometer Using Optical Fiber Transmission for Multichannel Signal Acquisition

Abstract

In magnetic resonance imaging (MRI), the method of acquiring signals close to the receiving coil and transferring the acquisition data via optical fibers can avoid electromagnetic (EM) interference and crosstalk in signal transmission to the greatest extent possible. The challenge lies in determining how to realize data transmission cost-effectively and maintain phase coherence between the radio frequency (RF) generator and the signal receiver. This article presents a design for an optical fiber spectrometer that is based on an optical fiber transmission scheme with lightweight resource consumption. The proposed spectrometer is composed of a main unit and an acquisition unit with four receiving channels. The acquisition data are uploaded to the main unit using the SerialLite II protocol, which has a very high transmission rate and is simple to implement in a field-programmable gate array (FPGA) device. The parameters and instructions are sent to the acquisition unit based on the use of a self-defined packing and conventional 8b/10b encoding, and a 60 MHz clock is also transmitted for decoding and signal sampling. To maintain phase coherence, specific timing information is appended to the downloaded initialization instruction for the digital local oscillator (LO) of the digital down converter (DDC) to ensure time alignment of the initialization events. Test results show that the transmission rate for the acquisition data reaches approximately 1440 Mb/s, and phase coherence is maintained reliably. Imaging experiments in a 0.35 T MRI system achieved satisfactory image quality.