Study of PEDRI (Proton Electron Double Resonance Imaging)

为了研制0.2 Testar质子电子双共振成像（PEDRI），对微波应用器进行了研究。核磁共振频率为8 MHz， EPR频率为5.6 GHz。核磁共振射频应用器是一个螺线管或鸟笼线圈。EPR微波应用器必须能够承受5w的连续波，并产生约10mm X 20mm的均匀磁场。本研究采用TE_<10>的矩形波导作为基本施加器，以获得上述微波磁场。我们测量了(1)不带法兰的波导，(2)带法兰的波导，(3)端接网格的TE101腔谐振器和(4)导电板的磁场分布。用于测量磁场的拾取线圈的内径为1mm。电线的直径是0.3毫米。以下三点是显而易见的。(1)切割波导孔径处的磁场强度约为最大值的1/10，磁场主要集中在波导壁较长边的中心，且分布不均匀。磁场分布均匀性定义为磁场强度的最小值/最大值，孔径处为0.09，孔径外侧为0.45。(2)带法兰的波导在孔径处磁场分布均匀性为0.14，优于孔径处磁场分布均匀性，即孔径外侧磁场分布均匀性为0.70。(3)以栅格端接的TE101腔腔谐振腔的场分布均匀性最佳值为0.37。(4)以开路端接并与切割波导相连的导板，其场强分布均匀性最好。

In order to develop a 0.2 Testar PEDRI (Proton Electron Double Resonance Imaging), microwave applicators have been studied.The frequencies are 8 MHz for NMR and 5.6 GHz for EPR.A NMR RF applicator is a solenoid or a birdcage coil. An EPR microwave applicator must be able to withstand 5 W CW and to generate homogeneous magnetic fields of about 10 mm X 20 mm. In this study, a basic applicator consists of a TE_<10> rectangular waveguide to obtain microwave magnetic fields mentioned above. We measured distribution of magnetic fields of (1) a waveguide without a flange, (2) a waveguide with a flange, (3) a TE101 cavity resonator terminated by grids and (4) a conducting plate. The inner diameter of the pick up coil used for the measurement of the magnetic field is 1 mm. The diameter of the wire is 0.3 mm.Following three matters have become obvious. (1) The magnetic field strength at the aperture of a cut waveguide is about 1/10 of the maximum value, the magnetic field mainly concentrates at the center of the longer side of the waveguide-wall and the distribution of the field is not homogeneous. The magnetic field distribution homogeneity which is defined as the minimum value /the maximum value of the field strength is 0.09 at the aperture and is 0.45 at the outer side of the aperture. (2) The magnetic field distribution homogeneity of the waveguide with the flange is 0.14 at the aperture and is better homogeneous than the magnetic field distribution at the aperture, that is, 0.70 at the outer side of the aperture. (3) The best value of the field distribution homogeneity for the TE101 cavity resonator terminated by grids is 0.37. (4) The homogeneity of the field strength distribution for a conducting plate which is terminated by the open-circuit and connected to the cut waveguide has the best homogeneity.