Evaluating the Performance of a Visual Coil in Physiological and Thermal Noise Dominated Regimes at Ultra-High Magnetic Field

Motivation: Advancements in array coil technology may not yield proportional gains in temporal SNR when physiological fluctuations are the primary noise source. Goal(s): We constructed a highly dense array covering the visual cortex and evaluated its noise characteristics and performance as a function of resolution. Approach: We evaluated image SNR and temporal SNR in vivo at 7 Tesla and produced BOLD activation maps using a visual paradigm. Results: The improvement in image SNR with decreased resolution was significantly higher than the improvement in temporal SNR. This suggests physiological noise dominance at the lower resolution. Impact: The image and temporal SNR offered by the visual coil allows for sub-millimeter resolution. Insight into the transition between thermal and physiologically noise dominated regimes will aid in reducing the risk of false positives in fMRI using this dense array.