World's first liquid-nitrogen-cooled high-temperature superconducting MRI system developed for human joint imaging
We have successfully developed the world’s first liquid nitrogen-immersed HTS MRI system, with a central magnetic field of approximately 1.021 T, a room temperature bore diameter of approximately 300 mm, and a spatial magnetic field homogeneity of approximately 7.98 ppm over a 160-mm-diameter spherical surface, and achieved clinical diagnostic-level imaging of the human ankle joint. In the future, we will combine solid nitrogen cooling technology to develop a human whole-body HTS MRI system with a higher magnetic field and persistent mode, which will be applied in clinical diagnosis, reduce costs, and achieve universal healthcare.
Significance
Magnetic resonance imaging (MRI) is an indispensable tool for in vivo imaging in life sciences research and clinical diagnosis, and it is also a high-end medical device that countries around the world are striving to develop. With advances in second-generation high-temperature superconducting (HTS) tapes (REBCO tapes) and HTS magnet technology, MRI magnet technology is gradually transitioning from low-temperature superconducting (LTS) magnet technology to better-performing HTS magnet technology. The REBCO HTS magnet, with a higher operating temperature range and higher current-carrying density, has brought engineering paradigm innovation to MRI systems. The HTS MRI system can operate stably in the liquid nitrogen temperature range, completely eliminating dependence on liquid helium, and has a more compact size than the LTS MRI system. Currently, although some HTS MRI magnets have been designed or constructed internationally, they have not been operated in the liquid nitrogen temperature range or integrated with MRI systems for imaging.1,2,3,4,5 In January 2026, the Institute of Electrical Engineering of the Chinese Academy of Sciences (IEECAS) achieved a pioneering milestone by successfully developing the world’s first liquid-nitrogen-cooled HTS MRI system, which operated stably for over 3 months and acquired clinical diagnostic-grade images of the human ankle joint. It may completely change the current situation for MRI systems that rely on liquid helium by reducing cooling costs and simplifying maintenance and may give rise to new types of mobile MRI equipment, thereby expanding medical accessibility.
The REBCO MRI system
Figure 1 shows the REBCO MRI system, core indicators, and imaging effects. The REBCO MRI system operates in a liquid nitrogen immersion environment and is cooled by a refrigerator to maintain the liquid nitrogen cooling environment, ensuring zero volatilization of liquid nitrogen. Figure 1A shows the REBCO MRI system with a central magnetic field of 1.021 T and a room temperature bore diameter of 300 mm. As shown in Figures 1B and 1C, the spatial magnetic field homogeneity over a 160-mm-diameter spherical surface is optimized from an initial 823.65 ppm to 7.98 ppm, and the average magnetic field stability within 48 h is about 0.27 ppm/h, which meets the high imaging requirements of MRI. First, we placed a cylindrical phantom with a diameter of 83.2 mm and a thickness of 50.1 mm at the center of the imaging area to conduct a benchmark test. The imaging results are shown in Figure 1D, and the uniformity of the central plane of the image reached 0.96. Then, we conducted a human ankle joint imaging test, and the results are shown in Figure 1E. The T1-weighted images and fat-suppressed T2 images are clear and free of artifacts.
