Evaluation of 7 Tesla
pTx
Body Coils Regarding Transmit and Receive Performance
Johannes A. Grimm, Oliver Kraff, Markus W. May, Max Lutz, Stephan Orzada, Thomas M. Fiedler, Steen Moeller, Simon Schmidt, Harald H. Quick, Armin M. Nagel, Mark E. Ladd, Sebastian Schmitter ABSTRACT
Purpose
Most sites develop and use custom coils for 7 T body MRI since no standard pTx body coil exists, leading to diverse coil designs differing in transmit element type, layout, and number of receive channels. This study investigates and compares eight existing coils, including one remote body coil array and seven local arrays, regarding their transmit and receive performance.
Methods
Phantom measurements were conducted with all coils on the same 7 T scanner, using the same phantom and imaging protocol. Transmit performance was compared in terms of B 1 + efficiency and coverage. Receive performance was compared in terms of SNR, coverage, noise correlation, and g‐factors.
Results
Mean B 1 + efficiency ranged from 2.02 to 4.33 μT/√kW across configurations, lowest for the remote array and highest for an 8Tx8Rx local array. Central SNR ranged from 278 to 1072, increasing with receive element count and peaking for an 8Tx32Rx configuration. HF‐excitation‐coverage ranged from 34 to 384 mm, and HF‐receive‐coverage from 135 to 384 mm, with the remote array combined with a local 32Rx array achieving highest coverage. Acceleration performance improved with increasing receive element count in the corresponding direction. An 8Tx16Rx and an 8Tx32Rx arrays performed best in LR‐/AP‐direction and the 32Rx array in HF‐direction.
Conclusion
No existing local pTx coil provides universally optimal performance, as each design offers different advantages in either B 1 + efficiency, coverage, SNR, or acceleration. Among the local arrays, the 8Tx32Rx array (C5) might represent a reasonable compromise with respect to the parameters evaluated in this study, as it exhibits the highest central SNR, high coverage, and acceleration.