IEEE Trans Med Imaging. 2018 Jul;37(7):1626-1631. doi: 10.1109/TMI.2017.2786466.
Sodium (Na) MRI provides complementary cellular and metabolic information. However, the intrinsic MR sensitivity of Na is considerably lower compared with that of the proton, making it difficult to measure MR-detectable sodium signals. It is therefore important to maintain the signal-to-noise ratio (SNR) of the sodium signal as high as possible. Double-tuned coils are often employed in combinationwith a H coil, providing structural images and B shimming capability. The double-tuned coil design can be achieved with the use of two geometrically decoupled coils whose B field directions are perpendicular to each other. This can be used to design quadrature-driven, single-nucleus coils to improve SNR, and additionally, this coil can also be utilized as a linear-driven double-resonant mode. Here, we have developed and evaluateda quadrature-enhanced, double-tuned coil. The novel coil uses PIN-diode switches, inserted only in the loop coil, to shift the resonance frequency between H and Na so that Na signals can be acquired in quadrature and the capability of using H function remains. Consequently, the Na SNR values obtained with the double-tuned coil are nearly 33% and 17% higher in comparison with geometrically identical single-tuned coils. SNR plots also show the superiority of double-tuned coil in Na.
钠（Na）MRI 提供了补充的细胞和代谢信息。然而，与质子相比，Na 的固有磁共振灵敏度要低得多，因此很难测量到可检测的 Na 磁共振信号。因此，尽可能保持 Na 信号的信噪比（SNR）尽可能高是很重要的。双调谐线圈通常与 H 线圈结合使用，提供结构图像和 B 匀场能力。双调谐线圈设计可以使用两个几何上解耦的线圈来实现，其 B 场方向相互垂直。这可以用于设计正交驱动的单核线圈来提高 SNR，此外，该线圈还可以用作线性驱动的双共振模式。在这里，我们开发并评估了一种正交增强的双调谐线圈。该新型线圈使用仅插入环形线圈的 PIN 二极管开关来在 H 和 Na 之间切换共振频率，以便可以在正交状态下采集 Na 信号，并且保留 H 功能的使用能力。因此，与几何形状相同的单调谐线圈相比，双调谐线圈获得的 Na SNR 值几乎高 33%和 17%。SNR 图还显示了双调谐线圈在 Na 中的优越性。
