Dual birdcage coils to control radiation from MRI systems operated without a Faraday cage.

Eliminating the traditional RF-shielded cabin (Faraday cage) used in almost all clinical magnetic resonance imaging (MRI) suites would lower installation costs and facilitate placement in diverse settings. However, this necessitates both a reduction in the electromagnetic (EM) radiation emitted by the RF body transmit system and an attenuation of EM interference (EMI) detected by the RF receive system. While recent advancements have successfully addressed the receive problem through external EMI detection coils and post-processing algorithms to remove interference from the MR images, the transmit problem is less studied and is the primary focus of this work. To tackle this challenge, we introduce a novel approach incorporating a second RF body birdcage coil and an EM absorber system, effectively reducing RF radiation from a 3T MRI system operating without a Faraday cage. We model the radiation from two configurations and compare it to a conventional body coil. The approaches use either a second mirrored-birdcage coil or a second overlapped-birdcage coil to reduce far-field radiation while minimally affecting spin-excitation. Our results demonstrate that both dual-birdcage strategies achieve a 3.1-fold reduction in radiation. Successfully mitigating EM radiation from MRI systems operated without shielded rooms will advance cost-effective MRI installations in diverse clinical/research environments. Our findings encourage further exploration of transmit coil design technology to control and minimize MRI-induced EM radiation. This research contributes to the ongoing efforts in optimizing MRI technology for broader applications and accessibility.