How close are we to the theoretical maximum SNR in portable low field MRI?

Motivation: Many groups build their own low field scanners, with different component designs. Relative performances have not been well documented due to a lack of detailed specifications and tests. Goal(s): To provide a set of measurements to benchmark the performance of low field scanners. Approach: The theoretical signal is calculated from first principles, including coil Q-value and transmit efficiency. Experimental data is acquired using different coils/samples and compared with the theoretical value. The effect of external noise sources and sub-optimal coil construction is also considered. Results: Experimental data agree well with theoretical predictions both for "optimal" and deliberately sub-optimal conditions. Impact: A framework has been established to estimate the signal-to-noise ratio obtainable on any given design of point-of-care low field imaging system.