Cardiorenal sodium MRI at 7.0 Tesla using a 4/4 channel H/ Na radiofrequency antenna array.

PURPOSE

Cardiorenal syndrome describes disorders of the heart and the kidneys in which a dysfunction of 1 organ induces a dysfunction in the other. This work describes the design, evaluation, and application of a 4/4-channel hydrogen-1/sodium ( H/ Na) RF array tailored for cardiorenal MRI at 7.0 Tesla (T) for a better physiometabolic understanding of cardiorenal syndrome.

METHODS

The dual-frequency RF array is composed of a planar posterior section and a modestly curved anterior section, each section consisting of 2 loop elements tailored for Na MR and 2 loopole-type elements customized for H MR. Numerical electromagnetic field and specific absorption rate simulations were carried out. Transmission field ( ) uniformity was optimized and benchmarked against electromagnetic field simulations. An in vivo feasibility study was performed.

RESULTS

The proposed array exhibits sufficient RF characteristics, homogeneity, and penetration depth to perform Na MRI of the heart and kidney at 7.0 T. The mean field for sodium in the heart is 7.7 ± 0.8 µT/√kW and in the kidney is 6.9 ± 2.3 µT/√kW. The suitability of the RF array for Na MRI was demonstrated in healthy subjects (acquisition time for Na MRI: 18 min; nominal isotropic spatial resolution: 5 mm [kidney] and 6 mm [heart]).

CONCLUSION

This work provides encouragement for further explorations into densely packed multichannel transceiver arrays tailored for Na MRI of the heart and kidney. Equipped with this technology, the ability to probe sodium concentration in the heart and kidney in vivo using Na MRI stands to make a critical contribution to deciphering the complex interactions between both organs.

© 2019 International Society for Magnetic Resonance in Medicine.