An Additional Gradient Axis Integrated into a Whole-Body Bore Coil for Prospective Silent MRI with Ultrasonic-encoding

Motivation: To enable silent whole-body MRI using ultrasonic encoding, an additional low inductance gradient coil can be integrated between the RF-rods and RF-shield of a bore coil. However, the resulting effect on RF efficiency is unclear. Goal(s): To demonstrate the feasibility of placing a gradient coil under the RF-shield without affecting RF efficiency. Approach: A Maxwell gradient coil was integrated into a bore coil. We measured the gradient field and compared RF efficiency with and without the extra gradient. Results: A gradient field was successfully induced without greatly affecting RF efficiency. For efficiency validations, volunteer images were obtained with and without the integrated coil. Impact: Placing a low inductance gradient coil within the empty space in a bore coil allows an independent gradient axis to be driven at 20kHz. This may address high-voltage and PNS concerns when extending to whole-body silent MRI.