Development of an adjustable surface coil for low-field magnetic resonance imaging-guided breast interventions

As breast cancer becomes the most common malignant tumor in women, magnetic resonance imaging (MRI)-guided breast interventions have gradually demonstrated their practical value in clinical practice.

Low-field MRI systems have emerged as a new option for breast intervention platforms due to their high openness, low cost, mobility, and the ability to facilitate real-time surgical procedures. Here, we designed an adjustable splint-integrated surface coil combining butterfly and ring units for 0.35 T MRI-guided breast interventions.

Electromagnetic simulations were first conducted to analyze the radiofrequency field distribution in the imaging region, with near-field simulations evaluating the adjustable coil under various configurations. Subsequently, bench tests were performed to analyze the S-parameter of the coil circuit while measuring both the Q-factor and Q-ratio, ensuring compliance with standard electrical performance requirements. Then, phantom imaging quantified MR image signal-to-noise ratio (SNR) to compare quality across different configurations and determine the two-channel adjustable coil design for low-field MRI-guided breast interventions. MRI compared the adjustable surface and volume coils using a silicone breast phantom and two volunteers with splint spacing adjusted to 80 or 40 mm based on breast size, while SNR maps visually compared image quality across different configurations. The final ex vivo porcine liver puncture experiment validated the clinical applicability of the two-channel adjustable surface coil.

The adjustable coil demonstrated high SNR (> 130) in clinically relevant breast compression scenarios (< 40 mm spacing), with adequate performance in the planar dual-channel configuration (SNR = 108.98) compared to curved designs (SNR = 99.87). And the four-channel coil overlap decoupling compromised grid accessibility, justifying the final selection of a simplified two-channel planar design that balances imaging quality and interventional practicality for MRI-guided breast procedures. The two-channel adjustable surface coil observably outperformed conventional volume coils, providing SNR improvements ranging from 14% to 43% for both phantoms and breast tissue in MRI-guided interventions. Additionally, the ex vivo porcine liver puncture experiment validated the clinical feasibility of the complete MRI-guided interventional workflow utilizing the adjustable coil system, demonstrating 1 mm targeting precision.

This adjustable surface coil is designed to work with the open low-field MRI system, providing high imaging SNR for real-time guidance during breast interventional surgeries and holding remarkable potential for extension to diverse MR imaging applications.