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目的研发具有自主产权的微型质子电子双共振成像仪,完成成像实验。方法参照自己永磁型MRI主磁体加工的专利技术研制双共振专用的磁极和主磁体,工作空间均匀度达1ppm。研制电子顺磁共振与磁共振结合的新型谐振腔,EPR微波谐振器以H62黄铜为材料制作矩形波导,其内表面抛光加工精度<1μm,表面镀银保证有较高的Q值。微波源由体效应管、变容二极管等组成,发射频率9.37GHz。射频线圈环绕在样品管周围,频率为14.689MHz,插入微波谐振器内形成谐振腔,安装在主磁体空隙内。使用固定的弱梯度磁场实现x,z两个方向的编码,通过拉东变换反投影实现图像重建。成像样本为2,2,6,6-四甲基哌啶-1-氧自由基水溶液。结果成功制作了0.334T微型质子电子双共振成像仪样机,并进行了成像实验,得到了信号强度和信噪比增强的磁共振图像。结论利用永磁体在相对较高主磁场强度的情况下可实现质子-电子双共振成像,但目前图像伪影较大,质量有待提高。
Objective To develop a miniature proton electron dual resonance imager with independent property to complete the imaging experiment. Methods With reference to the patented technology of the permanent magnet MRI main magnet processing, we developed a double resonance dedicated magnetic pole and main magnet, and the working space uniformity reached 1ppm. EPR microwave resonator is made of H62 brass as a rectangular wave guide. The inner surface of the EPR resonator is fabricated with a precision of <1μm. The surface silvering ensures a high Q value. Microwave source by the body effect tube, varactor diodes and other components, the launch frequency of 9.37GHz. RF coil around the sample tube around the frequency of 14.689MHz, inserted into the microwave resonator to form a resonant cavity, installed in the gap of the main magnet. The fixed weak gradient magnetic field is used to realize the coding in both x and z directions and the reconstruction of the image is achieved through the Radon transform backprojection. The imaging sample is 2,2,6,6-tetramethylpiperidine-1-oxyl free radical aqueous solution. Results A prototype of 0.334T miniature proton electron dual resonance imaging instrument was successfully fabricated and the imaging experiment was carried out. The magnetic resonance images with enhanced signal intensity and signal to noise ratio were obtained. Conclusions Proton-electron bi-resonance imaging can be achieved with a relatively high main magnetic field using a permanent magnet. However, image artifacts are larger and the quality needs to be improved.