Mutual Inductance in Magnetic Resonance Two-Element Phased-Array Square Coils with Strip and Wire Conductors
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Applied Magnetic Resonance
ORIGINAL PAPER
Mutual Inductance in Magnetic Resonance Two‑Element Phased‑Array Square Coils with Strip and Wire Conductors Giulio Giovannetti1 Received: 12 June 2020 / Revised: 13 October 2020 / Accepted: 15 October 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Phased-array coils are extensively employed in Magnetic Resonance (MR) as transmitter and receiver radiofrequency (RF) coils due to their large field-of-view (FOV) and their high signal-to-noise ratio (SNR). Array elements have to be geometrically decoupled for mutual coupling minimization, to achieve coil performance maximization. This paper proposes an analytical method for the mutual inductance calculation between two square loops constituting a 2-element phased-array coil in dependence on the conductor cross-sectional geometry (flat strip and circular wire). Simulation accuracy was evaluated with workbench experimental measurements performed at 21 MHz frequency on two home-built array square coils.
1 Introduction Radiofrequency (RF) coils are used for transmitting and receiving signal in Magnetic Resonance (MR) scanners. When employed as a transmitter, the coil has to generate an homogeneous magnetic field in the desired field-of-view (FOV), while when used as a receiver, the coil has to provide signal with high local sensitivity [1]. Various arrangement of single-element surface and volume coils have been designed and developed, characterized by different geometries and setup, and compared in terms of sensitivity regions and signal-to-noise ratio (SNR) [2]. Phased-array coils, constituted by array of loops with different geometry, can be used in transmission and reception when larger sensitive regions are desirable and for improving the imaging speed and the signal-to-noise ratio (SNR) when dedicated image reconstruction methods are employed [3]. For an optimal array design, the mutual interaction between coil elements has to be minimized, which can be achieved by performing a partial overlap of the adjacent coil elements with the so-called “magic geometry” [4]. * Giulio Giovannetti [email protected] 1
Institute of Clinical Physiology, National Research Council (CNR), I.F.C., C.N.R., Via Moruzzi 1, 56124 S. Cataldo, Pisa, Italy
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G. Giovannetti
This paper proposes an analytical calculation method for investigating how the cross-sectional geometry of the coil conductors (circular wire and flat strip, hereafter named “wire” and “strip”, respectively) affect the mutual inductance between the square elements. Workbench measurements performed on two array square coil prototypes permitted to validate the simulation results.
2 Materials and Methods 2.1 Mutual Inductance Calculation for Wire Conductors The theoretical calculation described in [5] for J current density flowing in singlesquare-loop conductors was employed and adapted for mutual inductance estimation between two square loops constituting a 2-element array coil made by wire conductors. Inductance calcu
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