Optimizing an array-compressed parallel transmission system for dynamically RF-shimmed multislice brain imaging at 7T

Motivation: Ultra-high field imaging has several advantages like high SNR but require expensive RF shimming hardware to mitigate image shading artifacts caused by transmit RF field inhomogeneity. Goal(s): We developed a low-cost, highly customizable hardware solution to extend conventional RF shimming capabilities. Approach: We used array compressed parallel transmission system with an optimal network and fixed optimal weights designed to sit inside the bore with the coil arrayResults: The optimal network achieved about two-fold improvement in RF homogeneity compared to conventional circularly polarized network. Impact: This is the first time a design framework is described to optimize a full acpTx system for a desired imaging application. This hardware-centric approach has no additional pre-scan preparation or time considerations, lending itself to future clinical use.