A modified Fourier-based phase unwrapping algorithm with an application to MRI venography
A modified Fourier-based phase unwrapping algorithm with an application to MRI venography
复制标题
DOI：
10.1002/jmri.21230
复制
发表时间：
2008-03-01
影响因子：
4.4
通讯作者：
Ewing, James R.
中科院分区：
文献类型：
--
作者：
Bagher-Ebadian, Hassan;Jiang, Quan;Ewing, James R.
目的：提出用于展开 MRI 相位图的单步确定性程序。材料和方法：使用先前为光学应用开发的算法，将拉普拉斯算子应用于 MRI 相位图的傅里叶空间。修改了原始的基于傅里叶的相位展开算法，以便解调完成傅里叶空间中所需的信号对称化。为了评估该方法在存在热噪声的情况下的性能，在 k 空间中的不同噪声水平下模拟了一组包裹相位图，并评估了该算法在不同信噪比 (SNR) 水平下的响应稳定性。为了证明其在 MRI 中的实用性，该算法应用于磁敏度加权成像 (SWI) 研究的包裹相位图，然后用于生成静脉图。结果：在模拟相位包裹中，该算法正确地再现了各种相位梯度和噪声的原始相位。该过程速度很快，并在 SWI 图像中生成了有用的静脉结构图。结论：一种快速稳定的单步确定性方法可用于展开 MRI 相位图，可用于 SWI 和静态磁场不均匀性绘图等应用。
Purpose: To present a single-step deterministic procedure for unwrapping MRI phase maps.Materials and Methods: Using an algorithm previously developed for optical applications, Laplacian operators were applied in the Fourier space of the MRI phase map. The original Fourier-based phase unwrapping algorithm was modified so that demodulation accomplished the required signal symmetrization in Fourier space. To evaluate the method's performance in the presence of thermal noise, a set of wrapped phase maps were simulated at different levels of noise in k-space, and the response of the algorithm at different levels of signal-to-noise ratio (SNR) was evaluated for stability. To demonstrate its utility in MRI, the algorithm was applied to the wrapped phase maps of susceptibility-weighted imaging (SWI) studies, which were then used to generate venograms.Results: In simulated phase wrapping, the algorithm correctly reproduced the original phase for a wide range of phase gradients and noise. The procedure was fast and produced useful maps of venous structures in SWI images.Conclusion: A fast and stable single-step deterministic method for unwrapping MRI phase maps is available for such applications as SWI and mapping of static magnetic field inhomogeneity.