Silent 3D MRSI at Ultrasonic gradient speeds using a dual-axis head insert gradient at 7T

Motivation: MRSI offers metabolic insights but suffers from long scan times, even at low resolutions. Techniques like EPSI are noisy and require multiple interleaves at 7T, limiting clinical feasibility. Goal(s): Bring MRSI resolution and scan times closer to traditional imaging, without compromising spectral quality or patient comfort. Approach: Silent encoding at 20 kHz using a dual-axis gradient accelerated 3D-FID-CSI (3.5×3.5×5 mm³) from 3h50min to 10min, validated with 7T scans, field camera, B0, and sound measurements. Results: A series of novel technical improvements that demonstrate fast and high-resolution MRSI, without any of the typical trade-offs. Impact: Ultrasonic encoding offers a paradigm shift in MRSI, bringing resolutions and scan times closer to imaging techniques. All without the typical trade-offs: preserving spectral bandwidth, while maintaining patient comfort by lacking gradient noise - paving the way for practical, high-resolution MRSI.