基于边界元逆问题法的超低场磁共振大鼠脑部成像双通道射频线圈优化设计  

Optimal Design of Rat Brain Dual-Channel RF Coils for Ultra-Low-Field Magnetic Resonance Imaging Based on Boundary Element Inverse Problem Method

作　　者：孟凡钦 郭轶[2] 何为[1] 徐征[1] Meng Fanqin;Guo Yi;He Wei;Xu Zheng(College of Electrical Engineering,Chongqing University,Chongqing 400044,China;Central Hospital,Chongqing University,Chongqing 400014,China)

机构地区：[1]重庆大学电气工程学院,重庆400044 [2]重庆大学附属中心医院,重庆400014

出　　处：《电工技术学报》2025年第1期25-35,63,共12页Transactions of China Electrotechnical Society

基　　金：国家自然科学基金(52077023);重庆市科卫联合项目(2023MSXM016)资助。

摘　　要：目前超低场磁共振成像(MRI)质量较差,为提升图像信噪比,射频线圈需尽可能贴近成像区域从而提升信噪比。该文采用间接边界元法并从逆问题角度求出线圈流函数分布,再利用线性规划寻找最优线圈结构。为验证超低场MRI诊断颅脑疾病的有效性,采用上述方法,在54 mT下针对大鼠头-脑几何形状设计了双通道射频接收线圈,并对大鼠脑卒中及脑外伤模型进行成像试验研究。试验结果表明,54mTMRI能够检出水肿和血肿病变,且与病理切片或临床3T MRI图像结果相符。同时,通过脑外伤模型7天的追踪观察,54 mT图像中病变的信号演变规律与高场影像一致。针对特定成像对象和非规则布线曲面,该文利用间接边界元逆问题法设计高信噪比射频接收线圈,大鼠模型试验证明超低场磁共振成像技术具有脑卒中与脑外份早期诊断与床旁影像监护潜力与价值。Magnetic resonance imaging(MRI)plays an irreplaceable role in modern clinical practice especially for brain diseases due to its excellent soft tissue imaging resolution,radiation-free nature,and rich imaging parameters.The ultra-low-field(ULF)MRI technology(<0.1 T)is characterized by its small size,light weightmaking it more suitable for mobile imaging scenarios and enables rapid imaging examinations for emergency patients.But the weaker background field results in a lower signal-to-noise ratio(SNR)in ULF MRI images.To enhance the signal-to-noise ratio(SNR),it is crucial for the radio frequency(RF)coil to be positioned close to the imaging area while maintaining excellent performance.To ensure that the RF coil conforms closely to the shape of the sample,an optimization algorithm is required,which should consider the conditions and requirements of wiring and the imaging target area,thus enabling the design of a distributed winding method.In this study,the indirect boundary element method was employed to determine the coil current distribution from an inverse problem perspective.The term of indirect means that a density function needs to be introduced as an intermediate variable to bridge the gap between magnetic induction intensity of the target area and the current stream function on the wiring surface.Then,linear programming is used to obtain the optimal layout of RF coil conductors that closely resemble the simulated current distribution.To validate the effectiveness of ULF MRI in diagnosing cranial diseases,above-mentioned method was applied to design a dual-channel RF receive coil for the head-brain geometric shape of the rat at 54 mT.The performance of proposed RF receive coil was then evaluated by CuSO4 solution phantom sample imaging tests and the signal-noise-ratio of the dual-channel coil images increased by 15.0%and 21.4%compared to the single-channel images,while the homogeneity remained unchanged.Imaging experiments were conducted on rat models with ischemic stroke,hemorrhagic stroke,and traumatic bra

关 键 词：磁共振成像 超低场 射频线圈 边界元逆问题 颅脑疾病 

分 类 号：TM15[电气工程—电工理论与新技术]