电工技术学报2024，Vol.39Issue(7)：1923-1931,9.DOI:10.19595/j.cnki.1000-6753.tces.230089
超低场磁共振膝关节正交接收线圈设计
Design of a Quadrature Receive Coil for Ultra-Low-Field Knee Magnetic Resonance Imaging
摘要
Abstract
The radio frequency(RF)receive coil is a key component in a magnetic resonance imaging(MRI)system,and its performance directly affects the quality of the MR images.Currently,the RF coil performance is mostly measured by RF magnetic field inhomogeneity and signal-to-noise ratio(SNR).In SNR calculations,the main contribution to noise is made by the coil resistance,including conductor losses and sample losses caused by RF currents.At low frequencies,the latter can be neglected.The ultra-low-field(ULF)MRI RF receive coil has a low working frequency and,therefore,has different impedance characteristics than the conventional clinical MRI RF receive coil,leading to different optimal RF coil configurations.This paper optimized a knee RF receive coil for an ultra-low field MRI system and investigated the relationship between RF coil construction and performance. Specifically,this paper investigated a knee quadrature receive coil.Theoretically,a quadrature receive coil can improve the SNR by 41% over a single-channel coil.Compared to an array coil,a quadrature receive coil can achieve good imaging results at a lower cost and with less design complexity.The quadrature receive coil in this paper consists of a saddle coil and a Helmholtz coil.Firstly,the support structure and dimensions of the coil were determined,and the optimum size of the saddle and Helmholtz coils was determined by calculating the efficiency of the single-turn receive coil and the RF magnetic field inhomogeneity.Then,the paper further investigated the performance of the optimally sized RF coil in terms of the number of turns.Using the measured coil AC resistance,it is found that the number of turns is a significant feature affecting the AC resistance of the RF coil for ultra-low field MRI,and it is found that an increase in the number of turns leads to a significant increase in the AC resistance,resulting in an increase and then a decrease in SNR as the number of turns increases. Finally,the optimal number of turns for both coils was obtained,and a quadrature receive coil was fabricated.The performance of the quadrature receive coil was evaluated using CuSO4·5H2O phantom and in vivo knee imaging.In phantom imaging,the quadrature receive coil shows a maximum image SNR improvement of approximately 33.5% compared to the single channel coil.In in vivo knee imaging,T1-and T2-weighted images were obtained using GRE3D and FSE sequences,respectively,from which the structural composition of the knee can be clearly observed.The quadrature receive coil shows maximum image SNR improvements of approximately 30.9% and 27.9% ,respectively,over the single-channel coil.The results show that knee imaging in an ultra-low-field MRI system is feasible and that the quadrature receive coil performance is superior to that of a single-channel receive coil.This paper analyses and optimizes the coil from the perspective of the number of turns of the RF receive coil,revealing that the number of turns of the coil is an important factor affecting the SNR of the ULF-MRI RF receive coil,providing new evidence for the design and optimization of RF coils.关键词
磁共振成像/超低场/膝关节成像/正交接收线圈Key words
Magnetic resonance imaging/ultra-low field/knee imaging/quadrature receive coil分类
信息技术与安全科学引用本文复制引用
万裁,何为,沈晟,徐征..超低场磁共振膝关节正交接收线圈设计[J].电工技术学报,2024,39(7):1923-1931,9.基金项目
国家自然科学基金(52077023)、重庆市自然科学基金(cstc2020jcyj-msxmX0340)、重庆市教委自然科学项目(KJQN202100533)和深圳市科技创新委员会(CJGJZD20200617102402006)资助项目. （52077023）
