IEEE Trans Med Imaging. 2019 Oct;38(10):2389-2399. doi: 10.1109/TMI.2019.2898202. Epub 2019 Feb 11.
Magnetic particle imaging (MPI) is a promising new tracer-based imaging modality. The steady-state, nonlinear magnetization physics most fundamental to MPI typically predicts improving resolution with increasing tracer magnetic core size. For larger tracers, and given typical excitation slew rates, this steady-state prediction is compromised by dynamic processes that induce a significant secondary blur and prevent us from achieving high resolution using larger tracers. Here, we propose a new method of excitation and signal encoding in MPI we call pulsed MPI to overcome this phenomenon. Pulsed MPI allows us to directly encode the steady-state magnetic physics into the time-domain signal. This in turn gives rise to a simple reconstruction algorithm to obtain images free of secondary relaxation-induced blur. Here, we provide a detailed description of our approach in 1D, discuss how it compares with alternative approaches, and show experimental data demonstrating better than 500- [Formula: see text] resolution (at 7 T/m) with large tracers. Finally, we show experimental images from a 2D implementation.
磁粒子成像(MPI)是一种很有前途的新型示踪剂成像方式。对于 MPI 来说,最基本的稳态非线性磁化物理通常预测随着示踪磁核尺寸的增加,分辨率会提高。对于较大的示踪剂,并且考虑到典型的激励上升速率,这种稳态预测会受到动态过程的影响,这些过程会导致明显的二次模糊,并阻止我们使用较大的示踪剂来实现高分辨率。在这里,我们提出了一种我们称之为脉冲 MPI 的新的 MPI 激励和信号编码方法来克服这种现象。脉冲 MPI 允许我们将稳态磁物理直接编码到时域信号中。这反过来又产生了一种简单的重建算法,以获得没有二次弛豫引起的模糊的图像。在这里,我们在一维情况下详细描述了我们的方法,讨论了它与替代方法的比较,并展示了实验数据,证明了在 7 T/m 时使用大示踪剂可以获得优于 500- [公式:见正文] 的分辨率。最后,我们展示了二维实现的实验图像。
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