高场磁共振并行发射与接收射频系统的关键问题研究

The image artifacts and safety issue caused by transmit profile inhomogeneity and specific absorption rate (SAR) raising in subjects are two of the main problems of high field magnetic resonance imaging (MRI). Parallel transmit and receive radio frequency (RF) system is capable to provide the feasibility of utilizing RF shimming and high efficiency multi-channel coil, which are the key solutions for these problems. In this study,we focus on multi-channel coil design and real time transmit power monitoring of parallel transmit and receive system in high field MRI. Based on our preliminary studies, multi-channel coil performance evaluation, structure optimization, coil decoupling techniques, RF shimming strategy with transmit power estimation and RF power monitoring system will be investigated. Additionally, we will present multi-channel coil performance evaluation method, consisting of both coil efficiency and parallel imaging capability, and SAR control method during RF shimming. The signal coupling and power coupling mechanism of multi-channel unitary structure coil will be demonstrated as well. Structure optimization method based on ultimate coil efficiency and transmit power estimation model based on power coupling matrix will be verified. An 8 channel transmit and 32-64 channel receive RF system will be fabricated. The success of this proposed project will advance high field MRI technologies and provide both theoretical and technical foundation for the leap-forward development of high field MRI technologies and equipment with independent intellectual property rights.

高场磁共振系统目前面临的核心问题是激发磁场不均匀产生图像伪影以及人体特异吸收率升高带来的安全问题。并行发射与接收射频系统具有射频匀场能力和高效率的多通道线圈，是解决上述问题的关键。本课题针对高场磁共振并行发射与接收射频系统的多通道线圈设计和发射能量预测与监控的问题，在前期研究基础上，开展多通道线圈性能评估、结构优化和基于能量预测的射频匀场，以及多通道一体化线圈的解耦技术和发射能量实时监测系统的研究，提出综合考虑线圈效率和并行成像能力的多通道线圈性能评估与射频匀场时的能量控制问题的解决方法，阐明多通道一体化线圈的信号耦合与能量耦合机制，验证基于线圈效率上限的结构优化方法和基于能量耦合的射频发射能量预测模型，实现8通道发射，32-64通道接收的射频系统。本项目的成功实施，将促进高场磁共振技术的发展，为自主高端磁共振成像技术与装备的创新和跨越式发展提供理论依据与技术基础。

高场磁共振系统目前面临的核心问题是激发磁场不均匀产生图像伪影以及人体特异吸收率升高带来的安全问题。并行发射与接收射频系统具有射频匀场能力和高效率的多通道线圈，是解决上述问题的关键。针对高场磁共振并行发射与接收射频系统的多通道线圈设计和发射能量预测与监控的问题，建立了数值仿真分析射频线圈性能和优化高场MRI系统射频线圈结构参数的方法；明确了多端口一体化射频线圈各端口的耦合机理，并提出一种对负载效应不敏感的的解耦方法；建立了基于多通道射频线圈能量耦合的SAR分析模型，提出一种结合数值仿真结果的SAR预测和实时监测的方法。搭建一套8通道射频发射系统的SAR分析监测平台，为工程实践积累经验。在项目执行期内，按计划执行。结合本课题研究，发表了国际期刊SCI论文4篇，参加ISMRM等国际学术会议3次发表会议论文6篇，国际会议分会特邀报告1次，申请发明专利6项，组织国际学术研讨会1次，培养硕士研究生2名。所开发的高场MRI多通道射频系统具有自主知识产权，完成了项目的预期工程成果和学术成果。在上述理论研究的基础上，针对临床诊断需求，开发了用于血管壁斑块成像的8通道颈动脉线圈和32通道高灵敏磁共振血管斑块成像射频线圈。获得了高分辨率颅内外血管壁图像，图像质量超过现有商用产品。为脑卒中这一我国致死率和致残率最高的疾病提供了早期预警和精确诊疗的影像工具。相关工作在首台CFDA认证的国产自主知识产权3T磁共振系统上实现产业化。开发的多通道射频发射系统的相关技术，也在首台国产3T磁共振系统上实现了技术转移，系统指标达到跨国企业主流产品水平。这一系统打破了跨国企业对我国3T高场磁共振系统的长期垄断。本项目的成功实施，促进了高场磁共振技术的发展，为自主高端磁共振成像技术与装备的创新和跨越式发展提供理论依据与技术基础。