Condition for optimal preamplifier decoupling in one-turn single- and multi-gap shielded loop MRI detectors

Shielded loops have recently attracted keen interest in the design of Magnetic Resonance Imaging (MRI) detector arrays. To prevent unwanted detuning of array elements, preamplifier decoupling is used. So far, the decoupling circuit design was based on intuitive approach of minimizing impedance presented to the terminals of the loop. The approach leads to decent but not optimal results. In this paper a systematic analytical method is used to derive the exact condition for maximum decoupling of shielded loops in array. The condition describes precisely what impedance should be presented to the terminals of the loop for best decoupling. It is shown that the method is valid for single- and multi-gap shielded loops with and without integrated reactive components across the gap. The presented results are useful in the design of MRI receive arrays of shielded loop coils with optimal decoupling.