基于近场耦合阵列的腔内磁共振无线射频线圈

doi:10.19595/j.cnki.1000-6753.tces.251475

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Abstract Purpose: In magnetic resonance imaging (MRI), conventional sur face radio frequency (RF) coils often exhibit insufficient signal-to-noise ratio (SNR) when imaging deep-seated organs. The study aims to enhance the imaging sensitivity of deep tissues by proposing a coil architecture that integrates a wireless endocavitary RF coil with an external multi-channel surface array, while avoiding significant increases in medical cost or system complexity.
Methods: Based on near-field coupling theory, a dual-channel wireless endocavitary coil was designed and implemented, operating inductively with a 24-channel flexible surface array for signal reception. Adjacent wireless elements were decoupled through geometric overlapping, enabling each unit to resonate independently during the signal reception phase. Each element was integrated with a passive detuning circuit, consisting of lumped capacitors, inductors, and bidirectional diodes. During the RF transmission phase, the diodes became forward-biased, forming a parallel resonant circuit with the lumped components. This configuration effectively opened the coil loop, thereby preventing interference with the transmit magnetic field and reducing the risk of specific absorption rate (SAR) increase. An equivalent physical model was established, and an analytical relationship between SNR and coil loading was derived. Theoretical analysis indicated that, while maintaining a large mutual inductance between the wireless and surface coils, minimizing the loading effect of the wireless coil is critical for maximizing SNR. Guided by this principle, the coil was optimized by encapsulating it in three layers of heat-shrink tubing to reduce loading while preserving efficient electromagnetic coupling.
Subsequently, B1-field and SAR simulations were conducted to assess field distribution and safety. Imaging experiments were performed on a 5 T whole-body MRI system using recently euthanized adult beagle dogs, to evaluate the proposed design under realistic anatomical conditions. Two configurations were compared under identical geometric positioning and imaging parameters: (1) the dual-channel wireless endocavitary coil combined with the 24-channel surface array, and (2) the surface array alone. Quantitative SNR analysis was performed within regions of interest (ROIs) encompassing the prostate and surrounding tissues.
Results: Simulation results demonstrated that the introduction of the wireless coil substantially enhanced the B1- field intensity in the prostate region. SAR simulations confirmed that, owing to its approximately -40 dB detuning performance, the wireless coil did not produce any significant local SAR elevation during transmission, ensuring operational safety. Experimental results further validated the performance of the proposed system: compared with the surface array alone, the inclusion of the wireless endocavitary coil yielded an average SNR improvement of approximately 97% within the prostate ROI, confirming its efficacy in enhancing deep-tissue signal reception.
Conclusion: The proposed hybrid design combining a wireless endocavitary coil with a multi-channel surface array provides a feasible and efficient solution for improving MRI sensitivity in deep anatomical regions. The system achieves high SNR without increasing SAR risk, while maintaining a simple structure and low manufacturing cost—making it suitable for disposable clinical use to alleviate hygiene concerns and enhance patient acceptance. Beyond prostate MRI, the proposed approach shows potential for extension to other deep-organ imaging applications, offering a promising direction for next-generation wireless RF coil systems that balance practicality, economy, and image quality.

Key words： Magnetic resonance imaging radio frequency coil wireless endocavitary coil prostate imaging signal to-noise ratio

Received: 21 August 2025

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	Mo Zhiguang
	Wu Bing
	Zhang Xiaoliang
	Li Ye

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Mo Zhiguang,Wu Bing,Zhang Xiaoliang等. Wireless Endocavitary Magnetic Resonance Radio Frequency Coil Based on a Near-Field Coupling Array[J]. Transactions of China Electrotechnical Society, 2026, 41(17): 5768-5778.

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