Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, USA.
Neuroimage. 2013 Jan 1;64:650-70. doi: 10.1016/j.neuroimage.2012.08.072. Epub 2012 Aug 31.
The ensemble average propagator (EAP) describes the 3D average diffusion process of water molecules, capturing both its radial and angular contents. The EAP can thus provide richer information about complex tissue microstructure properties than the orientation distribution function (ODF), an angular feature of the EAP. Recently, several analytical EAP reconstruction schemes for multiple q-shell acquisitions have been proposed, such as diffusion propagator imaging (DPI) and spherical polar Fourier imaging (SPFI). In this study, a new analytical EAP reconstruction method is proposed, called Bessel Fourier Orientation Reconstruction (BFOR), whose solution is based on heat equation estimation of the diffusion signal for each shell acquisition, and is validated on both synthetic and real datasets. A significant portion of the paper is dedicated to comparing BFOR, SPFI, and DPI using hybrid, non-Cartesian sampling for multiple b-value acquisitions. Ways to mitigate the effects of Gibbs ringing on EAP reconstruction are also explored. In addition to analytical EAP reconstruction, the aforementioned modeling bases can be used to obtain rotationally invariant q-space indices of potential clinical value, an avenue which has not yet been thoroughly explored. Three such measures are computed: zero-displacement probability (Po), mean squared displacement (MSD), and generalized fractional anisotropy (GFA).
整体平均传播子 (EAP) 描述了水分子的 3D 平均扩散过程，同时捕捉了其径向和角度内容。因此，EAP 可以比方向分布函数 (ODF) 提供更丰富的关于复杂组织微结构特性的信息，ODF 是 EAP 的角度特征。最近，已经提出了几种用于多 q 壳采集的分析 EAP 重建方案，例如扩散传播子成像 (DPI) 和球形极坐标傅里叶成像 (SPFI)。在这项研究中，提出了一种新的分析 EAP 重建方法，称为贝塞尔傅里叶方向重建 (BFOR)，其解基于对每个壳采集的扩散信号的热方程估计，并在合成和真实数据集上进行了验证。本文的很大一部分专门用于使用混合非笛卡尔采样对多个 b 值采集进行 BFOR、SPFI 和 DPI 的比较。还探索了减轻 EAP 重建中吉布斯环效应的方法。除了分析 EAP 重建之外，上述建模基础还可以用于获得具有潜在临床价值的旋转不变 q 空间指数，这一途径尚未得到彻底探索。计算了三个这样的度量：零位移概率 (Po)、均方根位移 (MSD) 和广义各向异性分数 (GFA)。
