A 750-MHz Electronically Tunable Resonator Using Microstrip Line Couplers for Electron Paramagnetic Resonance Imaging of a Mouse Tumor-Bearing Leg
A 750-MHz Electronically Tunable Resonator Using Microstrip Line Couplers for Electron Paramagnetic Resonance Imaging of a Mouse Tumor-Bearing Leg
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DOI：
10.1109/tbme.2017.2743232
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发表时间：
2018-05-01
影响因子：
4.6
通讯作者：
Hirata, Hiroshi
中科院分区：
文献类型：
--
作者：
Amida, Tatsuya;Nakaoka, Ririko;Hirata, Hiroshi
目的：这项工作的目的是开发一种工作频率为 750 MHz 的电子可调谐振器，用于对小鼠荷瘤腿进行连续波电子顺磁共振 (CW-EPR) 成像。方法：谐振器采用多线圈平行间隙结构，样品空间直径16 mm，长度20 mm。微带线耦合器与变容二极管结合使用，以实现谐振频率调整并减少变容二极管的非线性效应。通过有限元方法对谐振器进行建模，并进行微波电路仿真以阐明其射频特性。结果：对可调谐谐振器的谐振频率、可调谐频带和射频磁场转换效率进行了评估。所开发的谐振器提供了中心频率为747 MHz的4 MHz可调频带和34 mu T/W-1/2的转换效率。为了演示这种可调谐谐振器在 EPR 成像中的应用，获得了样品溶液和小鼠荷瘤腿的三维 EPR 图像。结论：所开发的可调谐谐振器满足了我们对体内 EPR 成像的初步要求，如果在未来的实际应用中出现任何问题，可以使用现有的有限元和电路模型进一步改进。意义：这项工作可能有助于促进荷瘤小鼠的EPR成像在癌症相关研究中的应用。
Objective: The purpose of this work was to develop an electronically tunable resonator operating at 750 MHz for continuous-wave electron paramagnetic resonance (CW-EPR) imaging of a mouse tumor-bearing leg. Methods: The resonator had a multi-coil parallel-gap structure with a sample space of 16 mm in diameter and 20 mm in length. Microstrip line couplers were used in conjunction with varactor diodes to enable resonance frequency adjustment and to reduce the nonlinear effects of the varactor diodes. The resonator was modeled by the finite-element method and a microwave circuit simulation was performed to clarify its radiofrequency characteristics. Results: A tunable resonator was evaluated in terms of its resonance frequency, tunable frequency band, and conversion efficiency of the RF magnetic field. The developed resonator provided a tunable frequency band of 4 MHz at a central frequency of 747 MHz and a conversion efficiency of 34 mu T/W-1/2. To demonstrate the application of this tunable resonator to EPR imaging, three-dimensional EPR images of a sample solution and a mouse tumor-bearing leg were obtained. Conclusion: The developed tunable resonator satisfied our initial requirements for in vivo EPR imaging and may be able to be further improved using the present finite-element and circuit models if any problems arise during future practical applications. Significance: This work may help to promote EPR imaging of tumor-bearing mice in cancer-related studies.