Ananda Kumar1,2, William Alan Edelstein1, Paul Arthur Bottomley1,2
1Radiology, Johns Hopkins University, Baltimore, MD, USA; 2Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, USA
Loop coils are fundamental building blocks of phased arrays. For phased arrays using large numbers of loops, loop size is critical in determining detection efficiency. As loop size decreases, coil noise becomes dominant and adversely affects realizable SNR by increasing system noise figure. There are consequent limits to SNR gains as array element number increases and element size shrinks. 1 dB noise figure contributions are reached for coils with radii 23 mm at 1.5T, 16 mm at 3T and 10 mm at 7T. Constructing arrays out of smaller coils than these at such fields is therefore of questionable value.
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