Temperature control of permanent magnets in magnetic resonance imaging

NdFeB materials offer an excellent cost-performance ratio for permanent magnets. However, due to their temperature coefficient constraints, magnetic resonance imaging (MRI) systems typically require operation in an airconditioned environment with precise temperature control. This limitation hinders the expansion of MRI applications to more diverse settings. To address this challenge and lay the foundation for broader MRI system applications, this study explores a novel temperature control method for permanent magnets. The goal is to maintain high thermal stability even under significant ambient temperature fluctuations. We propose a dual-PID parallel control method based on a neural network, which incorporates ambient temperature information to generate a unique control signal for precise regulation. In our experiments, conducted in a natural laboratory environment, an metal block was used as the control object, with artificially induced temperature variations to simulate real-world conditions. Over a 10-hour test period, despite ambient temperature fluctuations exceeding 11°C, the magnet's temperature remained stable within 0.06°C. These results demonstrate the effectiveness of our approach in significantly enhancing the thermal stability of MRI permanent magnets in complex environments.