Brain Imaging and Analysis Center, School of Medicine, Duke University, Durham, North Carolina, USA.
Magn Reson Med. 2012 Jan;67(1):137-47. doi: 10.1002/mrm.23000. Epub 2011 Jun 10.
The derivation of susceptibility from image phase is hampered by the ill-conditioned filter inversion in certain k-space regions. In this article, compressed sensing is used to compensate for the k-space regions where direct filter inversion is unstable. A significantly lower level of streaking artifacts is produced in the resulting susceptibility maps for both simulated and in vivo data sets compared to outcomes obtained using the direct threshold method. It is also demonstrated that the compressed sensing based method outperforms regularization based methods. The key difference between the regularized inversions and compressed sensing compensated inversions is that, in the former case, the entire k-space spectrum estimation is affected by the ill-conditioned filter inversion in certain k-space regions, whereas in the compressed sensing based method only the ill-conditioned k-space regions are estimated. In the susceptibility map calculated from the phase measurement obtained using a 3T scanner, not only are the iron-rich regions well depicted, but good contrast between white and gray matter interfaces that feature a low level of susceptibility variations are also obtained. The correlation between the iron content and the susceptibility levels in iron-rich deep nucleus regions is studied, and strong linear relationships are observed which agree with previous findings.
从图像相位推导出磁化率会受到某些 k 空间区域中滤波器反演条件不良的阻碍。在本文中，压缩感知被用来补偿直接滤波器反演不稳定的 k 空间区域。与使用直接阈值方法获得的结果相比，对于模拟和体内数据集，在产生的磁化率图中，条纹伪影的水平显著降低。此外，还证明了基于压缩感知的方法优于基于正则化的方法。正则化反演和压缩感知补偿反演的关键区别在于，在前一种情况下，整个 k 空间谱估计受到某些 k 空间区域中条件不良的滤波器反演的影响，而在基于压缩感知的方法中，只有条件不良的 k 空间区域被估计。在使用 3T 扫描仪获得的相位测量中计算的磁化率图中，不仅可以很好地描绘富铁区域，而且还可以获得具有低磁化率变化的白质和灰质界面之间的良好对比度。研究了富含铁的深部核区的铁含量与磁化率水平之间的相关性，观察到了强烈的线性关系，与先前的发现一致。
