A rigid, stand-off hybrid dipole, and birdcage coil array for 7 T body imaging

To design a robust and patient friendly radiofrequency coil array (8-channel transmit and 16-channel receive) for cross-sectional body imaging at 7 T, and to improve our understanding of the combination of dipole and loop like elements for ultra high field strengths.

The hybrid coil array was optimized in eletromagnetic simulations. Considered array candidates were the dipole, loop and birdcage array. The winning design was constructed and the signal-to-noise (SNR) was compared to a close fitting array at 3 T. Transmit and receive properties for different body sizes were assessed, and multi-parametric maps were acquired with the Plug-and-Play MRF method.

The winning design consists of a dipole array for transceive combined with a birdcage array for receive only. The central SNR improved by a factor of 3 as compared to a 3 T system with a local receive array. A transmit efficiency between 2.4 and 3.9 μT/kW, a specific absorption rate efficiency of 0.25 to 0.53 μT/W/kg, and a high SNR was achieved in the center for the targeted patient population.

The constructed coil array is easy to handle, safe, and patient friendly, allowing further development of abdominal imaging at 7 T. Quantitative MRI in the abdomen is possible with Plug-and-Play MRF using the designed coil array. Magn Reson Med 80:822-832, 2018. © 2017 International Society for Magnetic Resonance in Medicine.