Optimizing magnetite nanoparticles for mass sensitivity in magnetic particle imaging
Optimizing magnetite nanoparticles for mass sensitivity in magnetic particle imaging
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DOI：
10.1118/1.3554646
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发表时间：
2011-03-01
期刊：
影响因子：
3.8
通讯作者：
Krishnan, Kannan M.
中科院分区：
文献类型：
--
作者：
Ferguson, R. Matthew;Minard, Kevin R.;Krishnan, Kannan M.
目的：磁粒子成像(MPI)以磁性纳米粒子(MNPs)为示踪材料，显示出作为快速层析成像平台的巨大潜力。到目前为止，用于成像的MNPs的磁性还没有得到优化。由于纳米粒子的磁性具有很强的尺寸依赖性，为了确定在任意驱动场频率f(0)下MPI的最佳MNP特性，作者探索了不同尺寸的MNP对成像性能的影响。方法：合成不同尺寸的单分散MNP，并对其磁性进行表征。他们的MPI响应是使用定制的MPI收发器进行实验测量的，该收发器旨在检测MNP磁化的三次谐波。选择了适合于小动物成像的驱动场幅H-0=6mTµ(-1)(0)和频率f(0)=250 kHz。实验结果用基于朗之万超顺磁理论的动态MNP磁化模型进行了解释。结果：实验结果表明，MPI信号强度随MNP直径的变化明显，与模拟结果一致。MPI信号与MNP大小的关系图中的最大值表明，对于所选择的f(0)，存在一个特定的大小是最佳的。结论：在250 kHz的MPI实验中，作者观察到直径为15 nm的MNP产生的最大信号幅度。作者预计，这一结果的物理基础，即磁弛豫随MNP尺寸的变化，将在其他实验条件下影响MPI。(C)2011年美国医学物理学家协会。[DOI：10.1118/1.3554646]
Purpose: Magnetic particle imaging (MPI), using magnetite nanoparticles (MNPs) as tracer material, shows great promise as a platform for fast tomographic imaging. To date, the magnetic properties of MNPs used in imaging have not been optimized. As nanoparticle magnetism shows strong size dependence, the authors explore how varying MNP size impacts imaging performance in order to determine optimal MNP characteristics for MPI at any driving field frequency f(0).Methods: Monodisperse MNPs of varying size were synthesized and their magnetic properties characterized. Their MPI response was measured experimentally using a custom-built MPI transceiver designed to detect the third harmonic of MNP magnetization. The driving field amplitude H-0=6 mT mu(-1)(0) and frequency f(0)=250 kHz were chosen to be suitable for imaging small animals. Experimental results were interpreted using a model of dynamic MNP magnetization that is based on the Langevin theory of superparamagnetism and accounts for sample size distribution and size-dependent magnetic relaxation.Results: The experimental results show a clear variation in the MPI signal intensity as a function of MNP diameter that is in agreement with simulated results. A maximum in the plot of MPI signal vs MNP size indicates there is a particular size that is optimal for the chosen f(0).Conclusions: The authors observed that MNPs 15 nm in diameter generate maximum signal amplitude in MPI experiments at 250 kHz. The authors expect the physical basis for this result, the change in magnetic relaxation with MNP size, will impact MPI under other experimental conditions. (C) 2011 American Association of Physicists in Medicine. [DOI: 10.1118/1.3554646]