Optimal Experiment Design for Magnetic Resonance Fingerprinting: Cramér-Rao Bound Meets Spin Dynamics.
Optimal Experiment Design for Magnetic Resonance Fingerprinting: Cramér-Rao Bound Meets Spin Dynamics.
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DOI：
10.1109/tmi.2018.2873704
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发表时间：
2019-03
影响因子：
10.6
通讯作者：
Wald LL
中科院分区：
文献类型：
--
作者：
Bo Zhao;Haldar JP;Congyu Liao;Dan Ma;Yun Jiang;Griswold MA;Setsompop K;Wald LL
磁共振指纹识别是一种新的定量成像范式，它可以在一次实验中同时获得多个磁共振组织参数图。在本文中，我们提出了一个估计理论框架来进行MR指纹识别的实验设计。具体来说，我们描述了一个离散时间动态系统来模拟自旋动力学，并推导了一个估计理论界，即cram<s:1> - rao界（CRB），以表征MR指纹实验的信噪比（SNR）效率。然后，我们制定了一个优化的实验设计问题，该问题确定了一系列采集参数，以最大的信噪比效率编码MR组织参数，同时尊重图像解码/重建过程中的物理约束和其他约束。我们通过数值模拟、模拟实验和体内实验来评估所提出方法的性能。我们证明了优化的实验大大减少了数据采集时间和/或改进了参数估计。例如，优化后的实验使T2地图的精度提高了约2倍，而与T1地图的精度保持相似或略好。最后，作为一个值得注意的观察，我们发现优化的采集参数序列似乎是高度结构化的，而不是像传统的MR指纹识别实验中规定的随机/伪随机变化。
Magnetic resonance (MR) fingerprinting is a new quantitative imaging paradigm, which simultaneously acquires multiple MR tissue parameter maps in a single experiment. In this paper, we present an estimation-theoretic framework to perform experiment design for MR fingerprinting. Specifically, we describe a discrete-time dynamic system to model spin dynamics, and derive an estimation-theoretic bound, i.e., the Cramér-Rao bound (CRB), to characterize the signal-to-noise ratio (SNR) efficiency of an MR fingerprinting experiment. We then formulate an optimal experiment design problem, which determines a sequence of acquisition parameters to encode MR tissue parameters with the maximal SNR efficiency, while respecting the physical constraints and other constraints from the image decoding/reconstruction process. We evaluate the performance of the proposed approach with numerical simulations, phantom experiments, and in vivo experiments. We demonstrate that the optimized experiments substantially reduce data acquisition time and/or improve parameter estimation. For example, the optimized experiments achieve about a factor of two improvement in the accuracy of T2 maps, while keeping similar or slightly better accuracy of T1 maps. Finally, as a remarkable observation, we find that the sequence of optimized acquisition parameters appears to be highly structured rather than randomly/pseudo-randomly varying as is prescribed in the conventional MR fingerprinting experiments.