Double‐layered dual‐tuned RF coil using frequency‐selectable PIN‐diode control at 7‐T MRI

Abstract

This article presents a dual-tuned (DT) radiofrequency (RF) coil for signal acquisition of 2 nuclei, namely, hydrogen ( 1 H) and sodium ( 23 Na), in the ultra-high magnetic field of a 7-T magnetic resonance imaging (MRI) system. The doublelayered dual-tuned (DLDT) coil comprises a 2-loop coil configuration per singlepair geometry, with the 1 H and 23 Na coils being located on the outside and inside, respectively. The 1 H and 23 Na single-pair elements are tuned to resonance frequencies of 297.20 and 78.61 MHz, respectively. The single-pair geometry of the DLDT coil is extended to an 8-pair configuration to cover the human head, and the operation mode is transmission/reception (Tx/Rx). The 8-pair DLDT Tx/Rx coil array is designed with a non-overlapped single pair between the 1 H coil elements for geometric decoupling, and capacitive decoupling is implemented to minimize the mutual inductance coupling. The 2 resonance frequencies are fed through a single RF port to a common matching board, and each frequency is selected using the voltages at both ends of a PIN diode. Through use of the PIN diode in the DLDT coil configuration, with a voltage drop at both ends, different resonance frequencies can be selected for each coil element in accordance with the diode ON/OFF state. The experiments conducted showed that the proposed DLDT coil is effective in acquiring signals of 1 H and 23 Na in the MRI system. K E Y W O R D Sdouble-layered dual-tuned (DLDT) coil, magnetic resonance imaging (MRI), multinuclear, PIN diode

Design of a Coplanar Interlayer Gapped Microstrips Arrangement for Multi-Nuclei (1H, 19F, 31P, and 23Na) Applications in 7T MRI

“…To perform multinuclear MRI, RF coils that can operate at the required frequencies must be designed [32]. In general, the RF coils in MR must be capable of transmitting uniform RF fields and exhibit strong field intensity.…”

A Review on the RF Coil Designs and Trends for Ultra High Field Magnetic Resonance Imaging

“…Several designs have been proposed for different x-nuclei. For example, a double-tuned RF coil with frequency selection via PIN diode control was implemented for a 7T MRI system for 1 H and 23 Na (110). The coil comprised a pair of double-tuned loop coils, as shown in Figure 20a.…”

Acquisition strategies for spatially resolved magnetic resonance detection of hyperpolarized nuclei

“…For example, at 3 T, 128 MHz for 1 H is sample noise dominated, whereas 32 MHz for 13 C has relatively more noise contribution from the coil [52], meaning improved coil design can be more impactful. Dual resonance coils are also available for 1 H and 13 C, 23 Na, or 31 P, [48, [53][54][55][56][57][58], which are useful for heteronuclear 1 H- 13 C decoupling [48,59] and polarization transfer applications, which involve simultaneous transmission on multiple frequency channels. Triple resonance coils [60,61] can also be helpful for B 1 calibration of hyperpolarized compounds containing 13 C by using signal from natural abundance 23 Na, because their Larmor frequencies are similar.…”