Application of copper plates for frequency tuning of surface wired and wireless MRI coils

Abstract

This study shows how a copper plate could be used for frequency tuning of surface wired and wireless MRI coils. For this purpose, it is proposed to place the copper plate directly on their conducting circuit. This leads to increase in the resonance frequency of coils. The effect is most perceptible if the copper plate is comparable in size to the conducting circuit of radiofrequency (RF) coil. The experimental work was performed on a 7.05 T MR scanner using surface MRI coils operating on different resonance frequencies: ¹H (300 MHz), ³¹P (121 MHz), ²³Na (79 MHz), ¹³C (75 MHz). Application of copper plate for frequency tuning of wireless multi-turn multi-gap transmission line resonator (MTMG-TLR) was considered for the first time. The proposed method can be claimed if the nominal variable inductance or capacitance is not enough for tuning the resonance frequency of the MRI coil to a higher frequency range.

Keywords: Copper plate; Frequency tuning; Multi-turn multi-gap transmission line resonator; Multinuclear magnetic resonance; Radiofrequency shielding; Surface coil.