| Magnetic Resonance Imaging（MRI）technology has become a significant tool in the clinical diagnosis of modern medicine.As the critical components of magnetic resonance imaging equipment,the RF coil determine the imaging performance.It is the key to the frontier research of living magnetic resonance spectroscopy for dual-tuned RF coils,and its development is of great significance for the study of the diagnosis and metabolic changes of various diseases such as tumors.But,the structure of the dual-tuned coil is complicated,and the difficulty in designing,manufacturing,and debugging is greatly increased.In this paper,the high-performance dual-tuned RF coil with complex structure is taken as the research object.The design and test method of the complex structure dual-tuned RF coil are analyzed systematically.The main contents include circuit design,electromagnetic simulation,production debugging and imaging experiments of dual-tuned RF coils.A 1H/31P dual-tuned transceiver integrated multi-channel RF array coil system for ultra-high magnetic field 7T MRI was designed in this paper.Firstly,the field-circuit joint simulation method is used to model and data analyze the proposed coil,and the electromagnetic field distribution generated by the RF coil,as well as the reflection coefficient and transmission coefficient,are obtained,and the SAR value and B1+field distribution generated in the tissue are analyzed numerically.The strength,uniformity,transmission efficiency of launch field B1+and specific absorption rate of the proposed dual-tuned coil were evaluated initially to verify the feasibility of the proposed dual-tuned RF coil operation from a simulated view.The connection between the RF coil and the MRI system needs to be realized through the corresponding peripheral interface circuit of the RF front end.The paper explains the circuit principle of RF transceiver components,power dividers and phase shifters and the index requirements of components.The relevant parameters are optimized through simulation,and the corresponding circuit fabrication and debugging are completed.The actual test results show that the RF sub-components basically agrees the corresponding performance index requirements.A 1H/31P dual-tuned multi-channel RF coil for the 7T MRI system was produced in this paper,and completed the debugging of the coil circuit such as tuning and matching.The actual 1H/31P dual-tuned coil is used for imaging experiments based on the 7T MRI system to further evaluate the performance of the coil,and verify the electromagnetic simulation results and the feasibility of proposed 1H/31P dual-tuned RF coil in ultra-high magnetic field magnetic resonance imaging applications.Finally,the proposed coil system transmits and receives time-sharing work,realizes RF coil multiplexing,and realizes high-resolution spectroscopy imaging.The imaging results show that the 1H/31P dual-tuned RF coil exhibits good imaging performance,solves the coupling problem between the two nuclide coils and the coupling problem between the excitation and reception channels and the problem of RF magnetic field non-uniformity at high frequencies,its orthogonal transmit/receive characteristics can increase the sensitivity of MR signal reception,and effectively reduce RF transmit power,improve magnetic field uniformity,improve image signal-to-noise ratio.The phantom image indicates that the signal-to-noise ratio distribution of the coil is basically consistent with the electromagnetic field distribution obtained by electromagnetic simulation.That is,the universal equivalent circuit model can effectively simulate the spatial magnetic field distribution of the RF coil.The testing results of the proposed dual-tuned coil demonstrates the feasibility of this design in ultra-high field 7T dual-tuned MR imaging and spectroscopy studies,and has laid a certain theoretical and experimental basis for promoting the development of new applications for ultra-high field MRI in the human body. |
