A practical multinuclear transceiver volume coil for in vivo MRI/MRS at 7 T - PubMed (original) (raw)

A practical multinuclear transceiver volume coil for in vivo MRI/MRS at 7 T

Chunsheng Wang et al. Magn Reson Imaging. 2012 Jan.

Abstract

A practical multinuclear transceiver RF volume coil with improved efficiency for in vivo small animal (1)H/(13)C/(23)Na MR applications at the ultrahigh magnetic field of 7 T is reported. In the proposed design, the coil's resonance frequencies for (1)H and (13)C are realized by using a traditional double-tuned approach, while the resonant frequency for (23)Na, which is only some 4 MHz away from the (13)C frequency, is tuned based upon (13)C channel by easy-operating capacitive "frequency switches". In contrast to the traditional triple-tuned volume coil, the volume coil with the proposed design possesses less number of resonances, which helps improve the coil efficiency and alleviate the design and operation difficulties. This coil design strategy is advantageous and well suitable for multinuclear MR imaging and spectroscopy studies, particularly in the case where Larmor frequencies of nuclei in question are not separate enough. The prototype multinuclear coil was demonstrated in the desired unshielded design for easy construction and experiment implementation at 7 T. The design method may provide a practical and robust solution to designing multinuclear RF volume coils for in vivo MR imaging and spectroscopy at ultrahigh fields. Finite difference time domain method simulations for evaluating the design and 7-T MR experiment results acquired using the prototype coil are presented.

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Figures

Figure 1

The multinuclear volume coil with quadrature-drive capability for 7T applications (a) Sketch map. (b) Prototype coil. The coil measured 10.16 cm in diameter and 12.7 cm in length and had no RF shielding utilized. (c) Electrical circuit diagram of the prototype coil.

Figure 2

Measured frequency response of the multinuclear volume coil for 13C (top), 23Na(middle) and 1H (bottom) with the frequency span of 70MHz. Well-defined resonance modes for each nucleus demonstrate proposing behavior of the proposed multinuclear volume coil.

Figure 3

_B_1 field distributions at proton frequency for traditional 24-rung multiple-tuned volume coil (left) and proposed 16-rung multinuclear volume coil with two resonance frequencies at the same time (right). Both cases were normalized to 1W net input power. The _B_1 field at the center of coil increased from 6.57 μT (24-rung coil) to 7.15μT (16-rung coil).

Figure 4

Simulation and actual measurement results comparison. (a) simulation result; (b) zoom-in simulation result with 74 mm diameter (unit in dB); (c) actual measurement result (unit in dB). The _B_1 field distribution was normalized by the _B_1 at the center of the coil, which was indicated as 0 dB.

Figure 5

Proton image (left) and 13C spectra (right) of a cylindrical corn oil phantom acquired using the multinuclear volume coil on a GE whole body 7T MR scanner. Artifacts in the proton image (left) were caused by chemical shift.

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A practical multinuclear transceiver volume coil for in vivo MRI/MRS at 7 T - PubMed (original) (raw)