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TOMOGRAPHY, March 2017, Volume 3, Issue 1: 60-66
DOI: 10.18383/j.tom.2016.00280

Low-Noise Active Decoupling Circuit and its Application to 13C Cryogenic RF Coils at 3T

Juan Diego Sanchez-Heredia1, Esben Søvsø Szocska Hansen2, Christoffer Laustsen2, Vitaliy Zhurbenko1, and Jan Henrik Ardenkjær-Larsen1

1Department of Electrical Engineering, Technical University of Denmark, Kongens Lyngby, Copenhagen, Denmark and 2MR Research Centre, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark

Abstract

We analyze the loss contributions in a small, 50-mm-diameter receive-only coil for carbon-13 (13C) magnetic resonance imaging at 3 T for 3 different circuits, which, including active decoupling, are compared in terms of their Q-factors and signal-to-noise ratio (SNR). The results show that a circuit using unsegmented tuning and split matching capacitors can provide >20% SNR enhancement at room temperature compared with that using more traditional designs. The performance of the proposed circuit was also measured when cryogenically cooled to 105 K, and an additional 1.6-fold SNR enhancement was achieved on a phantom. The enhanced circuit performance is based on the low capacitance needed to match to 50 Ω when coil losses are low, which significantly reduces the proportion of the current flowing through the matching network and therefore minimizes this loss contribution. This effect makes this circuit particularly suitable for receive-only cryogenic coils and/or small coils for low-gamma nuclei.

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