Stitching Stretchable Radiofrequency Coils for MRI: A Conductive Thread and Athletic Fabric Approach

Objective: We propose a novel flexible and entirely stretchable radiofrequency coil for magnetic resonance imaging. This coil design aims at increasing patient comfort during joint imaging while maintaining or improving image quality. Methods: Conductive silver-coated thread was stitched in a zigzag pattern onto stretchable athletic fabric to create a single-loop receive coil. The stitched coil was mounted in a draped and stretched fashion 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. Results: The fabricated coil presents multi-directional stretchability and flexibility while maintaining conductivity and stitch integrity. Quality factor measurements and SNR calculations show that this stretchable coil design is comparable to a flexible, standard PCB coil. Detailed human wrist images were successfully obtained in vivo using the stretched, stitched coil. Conclusion: The resulting MR images and SNR calculations support further experimentation into more complex coil geometries. Significance: This coil is uniquely stretchable in all direction and allows for joint imaging at various degrees of flexion. Additionally, this coil offers the closest proximity of placement to the skin with materials that provide a similar level of comfort to that of athletic wear and compression sleeves. This stitched design could be incorporated into coils for a variety of anatomies.