Howard Hughes Medical Institute - Janelia Research Campus, Ashburn, Virginia.
Laboratory of Functional and Molecular Imaging, NIH/NINDS, Bethesda, Maryland.
Magn Reson Med. 2019 Apr;81(4):2238-2246. doi: 10.1002/mrm.27615. Epub 2018 Nov 25.
To develop switchable and tunable labels with high contrast ratio for MRI using magnetocaloric materials that have sharp first-order magnetic phase transitions at physiological temperatures and typical MRI magnetic field strengths.
A prototypical magnetocaloric material iron-rhodium (FeRh) was prepared by melt mixing, high-temperature annealing, and ice-water quenching. Temperature- and magnetic field-dependent magnetization measurements of wire-cut FeRh samples were performed on a vibrating sample magnetometer. Temperature-dependent MRI of FeRh samples was performed on a 4.7T MRI.
Temperature-dependent MRI clearly demonstrated image contrast changes due to the sharp magnetic state transition of the FeRh samples in the MRI magnetic field (4.7T) and at a physiologically relevant temperature (~37°C).
A magnetocaloric material, FeRh, was demonstrated to act as a high contrast ratio switchable MRI contrast agent due to its sharp first-order magnetic phase transition in the DC magnetic field of MRI and at physiologically relevant temperatures. A wide range of magnetocaloric materials are available that can be tuned by materials science techniques to optimize their response under MRI-appropriate conditions and be controllably switched in situ with temperature, magnetic field, or a combination of both.
利用具有在生理温度和典型 MRI 磁场强度下具有尖锐一阶磁相变的磁热材料，开发具有高对比度比的可切换和可调谐 MRI 标签。
通过熔融混合、高温退火和冰水淬火制备了典型的磁热材料铁-铑（FeRh）。在振动样品磁强计上对切割成线的 FeRh 样品进行了温度和磁场依赖的磁化测量。在 4.7T MRI 上进行了 FeRh 样品的温度依赖性 MRI。
温度依赖性 MRI 清楚地表明，由于 FeRh 样品在 MRI 磁场（4.7T）和生理相关温度（~37°C）下的尖锐磁态跃迁，图像对比度发生了变化。
由于 FeRh 在 MRI 磁场和生理相关温度下的一阶磁相变很尖锐，因此它可用作高对比度比的可切换 MRI 造影剂。有多种磁热材料可供选择，可以通过材料科学技术进行调整，以优化其在 MRI 适当条件下的响应，并通过温度、磁场或两者的组合进行可控的原位切换。
