Potential acceleration performance of a 256-channel whole-brain receive array at 7 T

Purpose: Assess the potential gain in acceleration performance of a 256-channel versus 32-channel receive coil array at 7 T in combination with a 2D CAIPIRINHA sequence for 3D data sets.

Methods: A 256-channel receive setup was simulated by placing 2 small 16-channel high-density receive arrays at 2 $\times$ 8 different locations on the head of healthy participants. Multiple consecutive measurements were performed and coil sensitivity maps were combined to form a complete 256-channel data set. This setup was compared with a standard 32-channel head coil, in terms of SNR, noise correlation, and acceleration performance (g-factor).

Results: In the periphery of the brain, the receive SNR was on average a factor 1.5 higher (ranging up to a factor 2.7 higher) than the 32-channel coil; in the center of the brain the SNR was comparable or lower, depending on the size of the region of interest, with a factor 1.0 on average (ranging from 0.7 up to a factor of 1.6). The average noise correlation between coil elements was 3% for the 256-channel coil, and 5% for the 32-channel coil. At acceptable g-factors (< 2), the achievable acceleration factor using SENSE and 2D CAIPIRINHA was 24 and 28, respectively, versus 9 and 12 for the 32-channel coil.

Conclusion: The receive performance of the simulated 256 channel array was better than the 32-channel reference. Combined with 2D CAIPIRINHA, a peak acceleration factor of 28 was assessed, showing great potential for high-density receive arrays.