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Design and comparison of two eight-channel transmit/receive radiofrequency arrays for in vivo rodent imaging on a 7 T human whole-body MRI system.

PURPOSE
Magnetic resonance imaging (MRI) of rodents can be expected to be a growing application, particularly when translatory imaging research "from mouse to man" is envisioned. 7 T high-field human whole-body MR systems provide a powerful platform for high-resolution small animal imaging. For achieving adequate spatial resolution, dedicated radiofrequency coils have to be designed to provide the necessary signal-to-noise ratio (SNR).


METHODS
Two different multichannel transmit/receive radiofrequency (RF) arrays for high-resolution imaging of rodents on a human whole-body 7 T MR system have been developed and evaluated in comparative in vitro phantom experiments and in vivo experiments in rats. The first coil was a one-channel birdcage RF transmit/eight-channel loop RF receive phased-array coil; the second coil was an eight-channel RF transmit/receive stripline phased-array coil with inverted microstrip lines--A coil design that here is described for the first time for dedicated small animal MR imaging.


RESULTS
Both coil setups provided the high SNR necessary for high-resolution MRI in rodents. The eight-channel loop RF array, with its larger inner diameter and transparent layout, provided better overall signal homogeneity and enabled easy visual monitoring; the eight-channel stripline RF array provided overall higher SNR and better parallel imaging acceleration performance.


CONCLUSIONS
The results show that both coil designs are suitable for small animal imaging on 7 T whole-body systems; the preferred coil depends on the demands of the application.