Recent Advances and Challenges in the Development of Radiofrequency HTS Coil for MRI

Abstract

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.

Extensive topographic remapping and functional sharpening in the adult rat visual pathway upon first visual experience

“…Hence, BOLD-fMRI signals faithfully represent these specific features while offering a very high resolution, longitudinal investigation, and a comprehensive whole-pathway vantage point. To the best of our knowledge, our work is the first fMRI-based retinotopic mapping and SF tuning curves in the rat visual pathway, and we note that the high-resolution (125x125 μm 2 ) population RFs that could be mapped using this approach can probably be extended in the future using denoising techniques (Ades-Aron et al 2021; Veraart et al 2016) and/or adaptation of the system to cryogenic coils (Labbé et al 2021; Ratering et al 2008; Baltes et al 2009).…”

Conductor Losses in Radiofrequency Coils for Magnetic Resonance below 3T: Estimation Methods and Minimization Strategies

“…Labbe et al [ 65 ] presented an overview of the recent advances in the design of RF HTS coils and the potential applications of HTS coils and explained the technological hurdles that slow down their development and prospects for further improvements. Parts of these hurdles can be overcome with the development of MRI-compatible cryostats that avoid the use of liquid nitrogen and provide more easy-to-use and more user-friendly cryogen systems.…”

Efficient PCA denoising of spatially correlated MRI data

“…Hardware improvements, such as more efficient coil designs, provide higher signal-to-noise ratio (SNR) from the coil (Kaza et al, 2011; Rodríguez and Medina, 2005; Roemer et al, 1990; Schmitt and Rieger, 2021). More recently, the introduction of cryogenic coils has shown how suppression of thermal noise by a factor of ∼2-10 can produce improvements in image quality (Hall et al, 1991; Kwok and You, 2006; Niendorf et al, 2015; Poirier-Quinot et al, 2008); however, these coils are expensive and difficult to handle (Labbé et al, 2021, 2020). On the other hand, suppression of noise via image processing is a very active field of research, which can potentially provide significant gains in SNR, synergistically with improved coil designs.…”