Liu Jing, Redmond Michael J, Brodsky Ethan K, Alexander Andrew L, Lu Aiming, Thornton Francis J, Schulte Michael J, Grist Thomas M, Pipe James G, Block Walter F
Department of Electrical and Computer Engineering, University of Wisconsin-Madison, E3/311 Clinical Sciences Center, WI 53792-3252, USA.
IEEE Trans Med Imaging. 2006 Feb;25(2):148-57. doi: 10.1109/TMI.2005.861706.
Time-resolved contrast-enhanced magnetic resonance (MR) angiography (CE-MRA) has gained in popularity relative to X-ray Digital Subtraction Angiography because it provides three-dimensional (3-D) spatial resolution and it is less invasive. We have previously presented methods that improve temporal resolution in CE-MRA while providing high spatial resolution by employing an undersampled 3-D projection (3D PR) trajectory. The increased coverage and isotropic resolution of the 3D PR acquisition simplify visualization of the vasculature from any perspective. We present a new algorithm to develop a set of time-resolved 3-D image volumes by preferentially weighting the 3D PR data according to its acquisition time. An iterative algorithm computes a series of density compensation functions for a regridding reconstruction, one for each time frame, that exploit the variable sampling density in 3D PR. The iterative weighting procedure simplifies the calculation of appropriate density compensation for arbitrary sampling patterns, which improve sampling efficiency and, thus, signal-to-noise ratio and contrast-to-noise ratio, since it is does not require a closed-form calculation based on geometry. Current medical workstations can display these large four-dimensional studies, however, interactive cine animation of the data is only possible at significantly degraded resolution. Therefore, we also present a method for interactive visualization using powerful graphics cards and distributed processing. Results from volunteer and patient studies demonstrate the advantages of dynamic imaging with high spatial resolution.
时间分辨对比增强磁共振（MR）血管造影（CE-MRA）相对于X射线数字减影血管造影越来越受欢迎，因为它提供三维（3-D）空间分辨率且侵入性较小。我们之前提出了一些方法，通过采用欠采样三维投影（3D PR）轨迹来提高CE-MRA的时间分辨率，同时提供高空间分辨率。3D PR采集增加的覆盖范围和各向同性分辨率简化了从任何角度对脉管系统的可视化。我们提出了一种新算法，通过根据3D PR数据的采集时间对其进行优先加权，来生成一组时间分辨的三维图像体积。一种迭代算法为重新网格化重建计算一系列密度补偿函数，每个时间帧一个，利用3D PR中的可变采样密度。迭代加权过程简化了对任意采样模式进行适当密度补偿的计算，提高了采样效率，从而提高了信噪比和对比噪声比，因为它不需要基于几何形状的闭式计算。当前的医学工作站可以显示这些大型的四维研究，然而，只有在分辨率显著降低的情况下才能对数据进行交互式电影动画显示。因此，我们还提出了一种使用强大图形卡和分布式处理进行交互式可视化的方法。志愿者和患者研究的结果证明了高空间分辨率动态成像的优势。
