A Novel Hybrid Magnet Array Design Approach in High-Performance Portable MRI: Enhancing Magnetic Field Homogeneity and Thermal Stability

The growing demand for timely diagnosis, coupled with the uneven distribution of medical resources, has highlighted the need for portable magnetic resonance imaging (MRI) systems. Although low-field portable MRI systems offer advantages in cost and size, they inherently suffer from lower signal-to-noise ratio (SNR) due to reduced magnetization and weaker precession signal amplitude. However, temperature fluctuations pose significant challenges to the stability of the static magnetic field, ultimately affecting both image quality and overall system performance. To address this issue, a hybrid magnet array combining SmCo and NdFeB elements was proposed and optimized via a metaheuristic algorithm. The resulting array achieves a mean magnetic field strength of approximately 50 mT with a homogeneity of 195 ppm within the 15 cm Diameter of Spherical Volume (DSV), while significantly reducing the temperature-induced field drift. Conventional magnet arrays, especially those composed solely of NdFeB, tend to exhibit significant magnetic field drift under ambient temperature fluctuations, limiting their reliability in uncontrolled environments. Compared to conventional magnets, the proposed design improves the temperature stability of magnetic field homogeneity by a factor of 128, and the temperature stability of the average magnetic field strength by a factor of 1.8, with the average magnetic field strength drift reduced from -1426 ppm/°C to -798 ppm/°C. This novel hybrid magnet array design methodology provides critical theoretical support for addressing the complex demands of portable MRI, including the need for high homogeneity and temperature stability.