| Magnetic Resonance Imaging(MRI)technology emerged in the 1970s and has become an important tool in clinical diagnostics,medical and life science research because of its advantages of no damage,no ionizing radiation,and multiple imaging parameters.Conventional MRI is 1H imaging,mainly imaging water in living organisms,so 1H imaging contains little metabolic information.Compared with 1H,31P is Widely involved in the energy metabolism process in living organisms,so r31P imaging has been a hot topic in the field of aprotic imaging research.However,due to the weakness of the c1P signal,it is necessary to combine 31P imaging with 1H imaging for localization and B0 shimming.The traditional MRI system only supports single-nuclear imaging.To obtain 1H image and 31P image,two scans are required,which not only doubles the imaging time,but also causes mismatching between 1H image and 31P image.1H/31P dual-nuclear parallel imaging can simultaneously acquire 1H image and 31P image in one scan,shorten the dual-nuclear imaging time and ensure the registration between 1H image and 31P image.Therefore,1H/31P dual-nuclear parallel imaging is an important research direction of 31P imaging.Multi-nuclear parallel imaging coil is one of the key components of multi-nuclear parallel MRI system which is different from traditional MRI system.Whether the MRI system can perform multi-nuclear parallel imaging experiment directly affected by the multi-nuclear parallel imaging capability of RF coil.Based on the research requirements of 1H/31P dual-nuclear parallel imaging,dual-nuclear parallel imaging coil is studied in this paper.The main contents of this thesis can be summarized as follows:(1)The generation principle of uniform magnetic field and the resonance mode of the birdcage coil were analyzed,then the relationship between the feeding position of birdcage coil and the direction of the B1 field was analyzed and verified by simulation.The design scheme of double birdcage coil which can realize dual-frequency resonance was simulated,and the results show that the scheme can achieve the dual-frequency resonance while ensuring the isolation between the double channels.At last,the principle of active detuning of birdcage coil was introduced and analyzed,then the active detuning circuit was designed base on it.(2)The relationship between the angle of saddle coil and the uniformity of the B1 field was simulated.Then,according to the simulation results,I designed the structure of the 1H saddle receiving coil and the 31P double saddle array receiving coil.The theory of the inductive decoupling was analyzed,and a LC parallel trap was used to improve the adaptability of the inductive decoupling method.Finally,the principle of passive detuning was briefly introduced.(3)Based on the design scheme,a 1H/31P dual-nuclear parallel imaging coil which consisted of a low-pass birdcage coil(1H transmitting coil),a high-pass birdcage coil(3 P transmitting coil),a saddle coil(1H receiving coil),a double array coil(31P receiving coil)was fabricated.The isolation of the two birdcage coil is greater than 25 dB and the isolation between coil elements of array coil is greater than 20 dB.At last,the parallel MRI experiments were carried out on the 4.7T magnet system with the home-made multi-nuclear parallel MRI console,and parallel MRI images of 1H and 31P were obtained successfully,which verified the feasibility of the design scheme. |
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