B1+ dependency on frequency in four human organs in three body models for 23Na, 13C and 31P whole-body birdcages at 7T.

This work is presenting a simulation study on X-nuclei imaging at 7T with a birdcage body coil for sodium, carbon and phosphorous. Three models and four imaging targets have been investigated. Although B₁⁺ efficiency generally decreases with frequency, we show that the SAR efficiency, ( B₁⁺/√SAR ) stays more or less constant over the investigated frequencies. Furthermore, it is shown that although every model and every imaging target has one optimal relative phase setting between the birdcage ports, for each frequency there exists one generic phase setting that provides only a minimal drop in performance over all imaging targets and models.