Magnetic resonance coil prototyping and implementation for multi-nuclear small animal imaging

Heteronuclear MR imaging allows investigation into unique disease states. These approaches often require radiofrequency coil designs that are customized for the imaging probe and target. This study addresses the challenges of rapidly prototyping heteronuclear MR coils for small animal imaging applications. We propose the use of 3D-printing molds for inductor shaping connected to a printed circuit board (PCB) via a flexible coaxial cabling to enhance coil reproducibility and utility.

A rapid prototyping pipeline was developed for constructing affordable and sensitive coils. The reproducibility of 3D-printed mold inductors was compared to hand-turned and PCB inductors. A theoretical treatment of the effect of PCB/inductor coupling on tuning/matching conditions was verified under a variety of practical conditions, yielding a simplified approach which allows component selection and assembly with minimal empirical development.

The 3D-printed mold inductors demonstrated higher reproducibility than hand-turned inductors, and PCB RF coils demonstrated the highest reproducibility. The average resonance return loss (S₁₁) across all 3D-printed mold inductors was -40.2 dB ± 4.8 dB, with an average circuit Q factor of 58 ± 12. The presented model predicts resonance characteristics within 1 % of measured values over a range of frequencies and geometries.

The developed prototyping pipeline represents a rapid and effective approach for designing highly reproducible coils with a desired resonance frequency and size that can easily be adapted for a variety of experimental set-ups. All design resources - including an interactive coil-parameter calculator, 3D-models of inductor molds, and PCB files - are available for use at https://medcap.ai/mr-coil-calculator.