Objective: 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. Methods: 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. Results: 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. Conclusion: 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. Significance: 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.

Flexible and stretchable radiofrequency coils for magnetic resonance imaging represent an emerging and rapidly growing field. The main advantage of such coil designs is their conformal nature, enabling a closer anatomical fit, patient comfort, and freedom of movement. Previously, we demonstrated a proof-of-concept single element stretchable coil design with a self-tuning smart geometry. In this work, we evaluate the feasibility of scaling this coil concept to a multi-element coil array and the associated engineering and manufacturing challenges. To this goal, we study a dual-channel coil array using full-wave simulations, bench testing, in vitro, and in vivo imaging in a 3 T scanner. We use three fabrication techniques to manufacture dual-channel receive coil arrays: (1) single-layer casting, (2) double-layer casting, and (3) direct-ink-writing. All fabricated arrays perform equally well on the bench and produce similar sensitivity maps. The direct-ink-writing method is found to be the most advantageous fabrication technique for fabrication speed, accuracy, repeatability, and total coil array thickness (0.6 mm). Bench tests show excellent frequency stability of 128 ± 0.6 MHz (0% to 30% stretch). Compared to a commercial knee coil array, the stretchable coil array is more conformal to anatomy and provides 50% improved signal-to-noise ratio in the region of interest.

Recent developments in the field of radiofrequency (RF) coils for magnetic resonance imaging (MRI) offer flexible and patient-friendly solutions. Previously, we demonstrated a proof-of-concept single-element stretchable coil design based on liquid metal and a self-tuning smart geometry. In this work, we numerically analyze and experimentally study a multi-channel stretchable coil array and demonstrate its application in dynamic knee imaging. We also compare our flexible coil array to a commonly used commercial rigid coil array. Our numerical analysis shows that the proposed coil array maintains its resonance frequency (<1% variation) and sensitivity (<6%) at various stretching configurations from 0% to 30%. We experimentally demonstrate that the signal-to-noise ratio (SNR) of the acquired MRI images is improved by up to four times with the stretchable coil array due to its conformal and therefore tight-fitting nature. This stretchable array allows for dynamic knee imaging at different flexion angles, infeasible with traditional, rigid coil arrays. These findings are significant as they address the limitations of current rigid coil technology, offering a solution that enhances patient comfort and image quality, particularly in applications requiring dynamic imaging.

Purpose: Supine breast MRI has the potential to improve over standard prone breast magnetic resonance imaging (MRI) in terms of efficiency and image quality, image alignment with diagnostic and treatment procedures, and overall accessibility. This study aims to characterize potential technical challenges of imaging in the supine position: (i) field inhomogeneities, (ii) variations, (iii) respiratory‐induced breast motion, and (iv) supine breast geometry. Methods: Ten healthy subjects were scanned at 3T in both prone and supine positions to quantify and compare (i) and (ii) between both positions, and to assess (iii) in the supine position. Breast image volumes from a wider population (N = 40, healthy volunteers and patients) were analyzed to obtain breast shape metrics to characterize (iv). Results: field inhomogeneity increased from prone positioning (2SD: ) to supine positioning (2SD: ), and flip angle variations (from prescribed ) were greater in the supine position (2SD ranging to ) than in the prone position (2SD ranging to ). Breast tissue displacement (median [IQR] across all analyzed locations and subjects) was similar along A‐P (1.4 [0.5] mm) and R‐L (1.9 [1.5] mm) directions. Breast geometry varied greatly, with the outer breast perimeter ranging from 34 to 68 cm, and maximum breast tissue thickness ranging from 2 to 9 cm. Conclusion: Supine positioning for breast MRI may lead to greater inhomogeneities and greater variations when compared to prone positioning, and breast motion can be substantial. Breast geometry varies greatly among the female population, and shape metrics can inform supine‐dedicated coil development.

A high-density posterior cushion coil (HDPCC) can improve the SNR in pediatric MRI by conforming to the body and minimizing distance to the imaged volume when compared to a conventional rigid built-in table coil array. Posterior coil arrays built into MRI tables are mainstays but provide suboptimal performance in pediatric imaging due to their distance from the imaged volume and lower coil density. Our goal is to improve pediatric MRI by constructing a prototype 30-channel high-density posterior cushion coil (HDPCC) incorporated into a padded cushion. Twenty-five pediatric patients were scanned with the HDPCC, and twenty-five pediatric controls served as the comparison group using standard coils. Two radiologists graded image quality on a 5-point scale. SNR was measured in the right paraspinal musculature and the liver. All images obtained with the HDPCC were diagnostic (mean score 4.13/5). SNR in the superficial tissues of the paraspinal musculature was 34% higher with the HDPCC than with standard coils, while SNR in the deeper tissues of the liver was statistically similar between the two coils. HDPCC yields improved the signal-to-noise ratio in phantoms and pediatric study participants by conforming to the body.