Radiofrequency (RF) coils fashioned from high-temperature superconductor (HTS) have the potential to increase the sensitivity of the magnetic resonance imaging (MRI) experiment by more than a dozen times compared to conventional copper coils. Progress, however, has been slow due to a series of technological hurdles. In this article, we present the developments that recently led to new perspectives for HTS coil in MRI, and challenges that still need to be solved. First, we recall the motivations for the implementations of HTS coils in MRI by presenting the limits of cooled copper coil technology, such as the anomalous skin effect limiting the decrease of the electric resistance of normal conductors at low temperature. Then, we address the progress made in the development of MRI compatible cryostats. New commercially available low-noise pulsed-tube cryocoolers and new materials removed the need for liquid nitrogen-based systems, allowing the design of cryogen-free and more user-friendly cryostats. Another recent advance was the understanding of how to mitigate the imaging artifacts induced by HTS diamagnetism through field cooling or temperature control of the HTS coil. Furthermore, artifacts can also originate from the RF field coupling between the transmission coil and the HTS reception coil. Here, we present the results of an experiment implementing a decoupling strategy exploiting nonlinearities in the electric response of HTS materials. Finally, we discuss the potential applications of HTS coils in bio-imaging and its prospects for further improvements. These include making the technology more user-friendly, implementing the HTS coils as coil arrays, and proposing solutions for the ongoing issue of decoupling. HTS coil still faces several challenges ahead, but the significant increase in sensitivity it offers lends it the prospect of being ultimately disruptive.

中文翻译：

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MRI射频HTS线圈研制的最新进展与挑战

与传统的铜线圈相比，由高温超导体 (HTS) 制成的射频 (RF) 线圈有可能将磁共振成像 (MRI) 实验的灵敏度提高十多倍。然而，由于一系列技术障碍，进展缓慢。在本文中，我们介绍了最近为 MRI 中的 HTS 线圈带来新视角的发展，以及仍需要解决的挑战。首先，我们通过展示冷却铜线圈技术的局限性，回顾了在 MRI 中实施 HTS 线圈的动机，例如异常趋肤效应限制了低温下正常导体电阻的降低。然后，我们讨论了 MRI 兼容低温恒温器的开发进展。新的商用低噪声脉冲管低温冷却器和新材料不再需要基于液氮的系统，从而可以设计出无冷冻剂且对用户更友好的低温恒温器。最近的另一个进展是了解如何通过场冷却或 HTS 线圈的温度控制来减轻 HTS 抗磁性引起的成像伪影。此外，伪影也可能源自发射线圈和 HTS 接收线圈之间的 RF 场耦合。在这里，我们展示了实施解耦策略的实验结果，该策略利用 HTS 材料的电响应中的非线性。最后，我们讨论了 HTS 线圈在生物成像中的潜在应用及其进一步改进的前景。这些包括使技术更加用户友好，将 HTS 线圈实施为线圈阵列，并为持续存在的去耦问题提出解决方案。HTS 线圈仍然面临着一些挑战，但它提供的灵敏度的显着增加使它具有最终破坏性的前景。