An Algorithm for Automatic Optimisation of Transmit Array Coil Tune and Match Applied in a Cardiac TEM Coil at 7T

Christopher T. Rodgers¹, Graeme A. Keith¹, Aaron T. Hess², Carl Snyder³, University of Minnesota University of Minnesota Vaughan³, Matthew D. Robson¹

7T body MRI requires transmit array coils. The popular TEM resonator design requires time consuming ~30min manual adjustments for each subject. This can be mechanised using piezo-actuators to drive the adjustment capacitors. We implement a system for monitoring coil RF characteristics in situ using RF pulses from the scanner. We characterise 4 potential optimisation metrics before introducing a simple, robust, efficient algorithm that automates coil tuning in less than 5 minutes. We close by explaining how auto-tuning may give not just faster, but actually superior coil tuning by optimising at isocentre and by monitoring power reflected through all RF channels.