Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany.
Magn Reson Med. 2011 Jan;65(1):190-4. doi: 10.1002/mrm.22602.
For the validation of complex diffusion imaging techniques like q-ball imaging that aim to resolve multiple fiber directions, appropriate phantoms are highly desirable. However, previous q-ball imaging phantoms had diffusion anisotropies well below those of in vivo white matter. In this work, fiber phantoms of well-defined geometry are presented. The fibers are wound on a spherical spindle yielding high packing densities and consequently high diffusion anisotropies (fractional anisotropy 0.93 ± 0.02 at b = 500 s/mm(2)). Phantoms with 90° and 45° crossing angle were constructed both with two crossing types. In the "stacked" crossing, two fiber strings were wound consecutively to simulate two touching fibers, in the "interleaved" crossing, fibers were wound alternately. The stacked crossing allows the alteration of partial volumes, whereas the interleaved crossing provides constant partial volumes, allowing e.g. the easy alteration of the SNR by varying the slice thickness. Exemplary q-ball imaging validation measurements using different b-values and slice thicknesses are presented.
为了验证旨在解析多个纤维方向的复杂扩散成像技术（如 q-ball 成像），合适的仿真是非常需要的。然而，以前的 q-ball 成像仿体的扩散各向异性远低于活体白质。在这项工作中，提出了具有明确定义几何形状的纤维仿体。纤维缠绕在一个球形轴上，产生高的堆积密度，从而产生高的扩散各向异性（在 b = 500 s/mm²时分数各向异性为 0.93 ± 0.02）。构建了具有 90°和 45°交叉角的两种交叉类型的仿体。在“堆叠”交叉中，两个纤维串连续缠绕以模拟两个接触纤维，在“交错”交叉中，纤维交替缠绕。堆叠交叉允许改变部分体积，而交错交叉提供恒定的部分体积，例如通过改变切片厚度来轻松改变 SNR。给出了使用不同 b 值和切片厚度的示例 q-ball 成像验证测量。
