Design, construction and first experimental results of the high performance LH7 insertable head gradient set at 10.5T

Motivation: Increased gradient performance can address several of technical and physics challenges of UHF MRI. Goal(s): To develop a head gradient coil (known as LH7) for insertion into the body gradient coil of a 10.5T MRI system. Approach: Design innovations include: symmetric folded geometry with variable end-flange angle optimized for shoulder geometry; double Z-primary layer. Results: With 650A, 2000V gradient drivers, the hardware limits of LH7 are Gmax 117mT/m and Smax 900T/m/s. Thermal results demonstrate cooling capacity >45kW. Compared to body gradients, PNS thresholds are 2-3 fold higher. After interfacing LH7 to the CMRR 10.5T, promising experimental characterizations and imaging results have been obtained. Impact: LH7 provides an order-of-magnitude increase in head gradient performance (Gmax*Smax) over body gradients, which, combined with 10.5T B0, should provide major sensitivity and resolution increases for brain mapping by dMRI or fMRI. Experimental results to date are confirming these expectations.