Conductive Thread-Based Stretchable and Flexible Radiofrequency Coils for Magnetic Resonance Imaging

We propose a novel flexible and entirely stretchable radiofrequency coil for magnetic resonance imaging. This coil design aims at increasing patient comfort during imaging while maintaining or improving image quality.

Conductive silver-coated thread was zigzag stitched onto stretchable athletic fabric to create a single-loop receive coil. The stitched coil was mounted in draped and stretched fashions and compared to a coil fabricated on flexible printed circuit board. Match/tune circuits, detuning circuits, and baluns were incorporated into the final setup for bench measurements and imaging on a 3T MR scanner. A fast spin echo sequence was used to obtain images for comparison.

The fabricated coil presents multi-directional stretchability and flexibility while maintaining conductivity and stitch integrity. SNR calculations show that this stretchable coil design is comparable to a flexible, standard PCB coil with a 13-30% decrease in SNR depending on stretch degree and direction. In vivo human wrist images were obtained using the stitched coil.

Despite the reduction in SNR for this combination of materials, there is a reduced percentage of SNR drop as compared to existing stretch coil designs. These imaging results and calculations support further experimentation into more complex coil geometries.

This coil is uniquely stretchable in all directions, allowing for joint imaging at various degrees of flexion, while offering the closest proximity of placement to the skin. The materials provide a similar level of comfort to athletic wear and could be incorporated into coils for a variety of anatomies.