Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
Magn Reson Med. 2017 Nov;78(5):2035-2041. doi: 10.1002/mrm.26556. Epub 2016 Dec 7.
To accelerate simulation of off-resonance artifacts in steady-state gradient echo MRI by using fast Fourier transforms and demonstrate its applicability to metal object localization.
By exploiting the repetitive nature of steady-state pulse sequences it is possible to use fast Fourier transforms to calculate the MR signal. Based on this principle, a method for fast simulation of off-resonance artifacts was designed. The method was validated against Bloch simulations and MRI scans. Its clinical relevance was demonstrated by employing it for template matching-based metal object localization, as applied to a titanium cylinder, an oxidized zirconium knee implant, and gold fiducials.
The fast simulations were accurate compared with actual MRI scans of the objects. The differences between the fast simulations and Bloch simulations were minor, while the acceleration scaled linearly with the number of phase-encoding lines. The object localization method accurately localized the various metal objects.
The proposed simulation methodology provided accurate 3D simulations of off-resonance artifacts with a lower computational complexity than Bloch simulations. The speed of the simulations opens up possibilities in image reconstructions involving off-resonance phenomena that were previously infeasible due to computational limitations, as demonstrated for metal object localization. Magn Reson Med 78:2035-2041, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
通过使用快速傅里叶变换加速稳态梯度回波 MRI 中的离频伪影模拟，并证明其在金属物体定位中的适用性。
通过利用稳态脉冲序列的重复性，可以使用快速傅里叶变换来计算 MR 信号。基于这一原理，设计了一种快速模拟离频伪影的方法。该方法通过与 Bloch 模拟和 MRI 扫描进行对比来验证。通过将其应用于基于模板匹配的金属物体定位，证明了其临床相关性，该方法应用于钛圆柱体、氧化锆膝关节植入物和金基准点。
快速模拟与物体的实际 MRI 扫描结果非常吻合。快速模拟与 Bloch 模拟之间的差异很小，而加速程度与相位编码线的数量呈线性关系。物体定位方法能够准确地定位各种金属物体。
所提出的模拟方法提供了比 Bloch 模拟更低计算复杂度的离频伪影的准确 3D 模拟。模拟速度为以前由于计算限制而不可行的涉及离频现象的图像重建开辟了可能性，这在金属物体定位方面得到了证明。磁共振医学 78:2035-2041,2017。© 2016 作者 磁共振医学由 Wiley 期刊出版公司代表国际磁共振医学学会出版。这是根据知识共享署名非商业许可协议的条款授予的许可，在任何媒体中使用、分发和复制原始作品，只要原始作品正确引用且不用于商业目的。
