UC Berkeley-UCSF Graduate Group in Bioengineering, University of California Berkeley and University of California San Francisco, https://bioegrad.berkeley.edu/.
Department of Bioengineering, University of California Berkeley, Berkeley, California 94720, United States.
Nano Lett. 2023 Mar 8;23(5):1717-1725. doi: 10.1021/acs.nanolett.2c04404. Epub 2023 Feb 23.
Magnetic particle imaging (MPI) is a sensitive, high-contrast tracer modality that images superparamagnetic iron oxide nanoparticles, enabling radiation-free theranostic imaging. MPI resolution is currently limited by scanner and particle constraints. Recent tracers have experimentally shown 10× resolution and signal improvements with dramatically sharper M-H curves. Experiments show a dependence on interparticle interactions, conforming to literature definitions of superferromagnetism. We thus call our tracers superferromagnetic iron oxide nanoparticles (SFMIOs). While SFMIOs provide excellent signal and resolution, they exhibit hysteresis with non-negligible remanence and coercivity. We provide the first quantitative measurements of SFMIO remanence decay and reformation using a novel multiecho pulse sequence. We characterize MPI scanning with remanence decay and coercivity and describe an SNR-optimized pulse sequence for SFMIOs under human electromagnetic safety limitations. The resolution from SFMIOs could enable clinical MPI with 10× reduced scanner selection fields, reducing hardware costs by up to 100×.
磁共振粒子成像（MPI）是一种敏感、高对比度的示踪剂模态，可以对超顺磁氧化铁纳米粒子进行成像，实现无辐射的治疗诊断成像。MPI 的分辨率目前受到扫描仪和粒子的限制。最近的示踪剂已经通过实验显示出 10 倍的分辨率和信号改善，具有更陡峭的 M-H 曲线。实验表明，这取决于粒子间的相互作用，符合超顺磁性的文献定义。因此，我们称我们的示踪剂为超顺磁氧化铁纳米粒子（SFMIOs）。虽然 SFMIOs 提供了优异的信号和分辨率，但它们表现出滞后现象，具有不可忽略的剩磁和矫顽力。我们使用一种新的多回波脉冲序列，首次对 SFMIO 的剩磁衰减和再形成进行了定量测量。我们用剩磁衰减和矫顽力来描述 MPI 扫描，并描述了一种在人体电磁安全限制下针对 SFMIO 的 SNR 优化脉冲序列。SFMIO 的分辨率可以实现临床 MPI，其扫描仪选择场减少了 10 倍，硬件成本降低了 100 倍。
