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利用梯度预饱和和射频预饱和稳态 MRI 信号之间的共享信息。

Utilizing shared information between gradient-spoiled and RF-spoiled steady-state MRI signals.

机构信息

Athinoula A. Martinos Center, Department of Radiology, Massachusetts General Hospital, Boston, MA, United States of America.

Harvard Medical School, Boston, MA, United States of America.

出版信息

Phys Med Biol. 2021 Jan 14;66(1):01NT03. doi: 10.1088/1361-6560/abce8a.

Abstract

This work presents an analytical relationship between gradient-spoiled and RF-spoiled steady-state signals. The two echoes acquired in double-echo in steady-state scans are shown to lie on a line in the signal plane, where the two axes represent the amplitudes of each echo. The location along the line depends on the amount of spoiling and the diffusivity. The line terminates in a point corresponding to an RF-spoiled signal. In addition to the main contribution of demonstrating this signal relationship, we also include the secondary contribution of preliminary results from an example application of the relationship, in the form of a heuristic denoising method when both types of scans are performed. This is investigated in simulations, phantom scans, and in vivo scans. For the signal model, the main topic of this study, simulations confirmed its accuracy and explored its dependency on signal parameters and image noise. For the secondary topic of its preliminary application to reduce noise, simulations demonstrated the denoising method giving a reduction in noise-induced standard deviation of about 30%. The relative effect of the method on the signals is shown to depend on the slope of the described line, which is demonstrated to be zero at the Ernst angle. The phantom scans show a similar effect as the simulations. In vivo scans showed a slightly lower average improvement of about 28%.

摘要

本文提出了梯度翻转和射频翻转稳态信号之间的解析关系。双回波稳态扫描中获得的两个回波在信号平面上位于一条线上,该线的两个轴分别代表每个回波的幅度。这条线的位置取决于翻转的程度和扩散系数。该线终止于对应于射频翻转信号的点。除了证明这种信号关系的主要贡献外,我们还包括了该关系的初步应用的次要贡献,形式是当两种扫描都执行时的启发式去噪方法。这在模拟、体模扫描和体内扫描中进行了研究。对于信号模型,这是本研究的主要课题,模拟结果证实了其准确性,并研究了其对信号参数和图像噪声的依赖性。对于其初步应用于降噪的次要课题,模拟结果表明,该去噪方法可使噪声引起的标准偏差降低约 30%。该方法对信号的相对影响取决于所描述线的斜率,在 Ernst 角处该斜率为零。体模扫描显示出与模拟相似的效果。体内扫描显示出平均改善约 28%。

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