Design, construction and performance testing of a 1.5 T cryogen-free low-temperature superconductor whole-body MRI magnet

Abstract

This work describes the design, construction, and testing of a 1.5 T cryogen-free LTS NbTi whole-body magnet with a bore diameter of 850 mm that is suitable for clinical MRI applications. The magnet was actively shielded and passively shimmed to achieve the confinement within a 0.5 mT stray magnetic field at 2.5/4 m radial/axial positions and 12.1 ppm field inhomogeneity over the 45 mm DSV. The magnet was conductively refrigerated using a two-stage GM cryocooler and can be maintained at a steady temperature of below 5.7 K during MRI scanning. The MRI scanner assembled with the designed cryogen-free magnet demonstrated stable performance and provided MRI images with good quality and high contrast.

A novel joint-less coil: promising unprecedented magnetic field stability to solve the persistent current mode issue in 2G-HTS magnet application

“…In MRI magnets, the typical guaranteed long-time field decay needs to be less than 0.1 ppm h −1 , while the maximum time stability required for successful imaging would be 0.5 ppm h −1 [3,5,22]. The magnetic field stability of the magnet is 0.065 ppm h −1 as shown in figure 4, which is sufficient for MRI and shows that the joint-less HTS coil maintains a reasonable persistent current.…”