Introduction Array coils for MRI use highly reflective, low-noise preamplifiers to boost signal levels while minimizing, respectively, inductive coupling [1] and added noise. The noise factor [2], i.e., the loss of SNR due to noise added by the preamp (or noise figure, NF, when expressed in dB) depends on the admittance seen by the preamplifier's input, Ys = Gs + iBs, according to the expressio...
