Ultra-High-Field MRI: Engineering Challenges and Opportunities

초록

Ultra-high-field magnetic resonance imaging (UHF MRI) refers to MRI systems operating at a static magnetic field of 7 Tesla or higher. Compared to conventional clinical MRI, these systems significantly enhance measurement performance-including improved signal-to-noise ratio (SNR), increased susceptibility-based contrast, and superior spectroscopic resolution-thereby expanding the scope and density of information obtainable through magnetic resonance experiments. Recently, UHF MRI has transitioned from fundamental development to practical system implementation for human imaging, with the full-scale installation of large-scale UHF MRI facilities signaling rapid technological progress. However, as magnetic field strength increases, system components such as superconducting magnets, gradient systems, and radio-frequency (RF) transmit/receive structures are subjected to various engineering constraints. Decisions regarding the selection and operation of these elements determine the ultimate success of the system. In high-field environments, these constraints include reduced RF signal wavelengths resulting in poor transmit homogeneity, increased local power absorption (SAR), and the need for a balance between high switching performance, heat dissipation, and mechanical stability in gradient systems. Furthermore, in superconducting magnet design, factors such as the properties of superconducting materials, cryogenic cooling methods, shielding structures, and operating modes are critical determinants for performance and operational feasibility. Within this context, various research groups have implemented UHF MRI systems through diverse design strategies and technical choices. This paper examines the design approaches observed in UHF MRI systems currently in operation or under construction. By analyzing these approaches, the study investigates the engineering challenges and development potential of UHF MRI systems, providing insights into the future direction of next-generation hardware technology.

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