Choi Mina, Ghammraoui Bahaa, Badano Aldo
Fischell Department of Bioengineering, University of Maryland, College Park, MD, 20742, United States of America.
Division of Imaging, Diagnostics, and Software Reliability, Office of Science and Engineering Laboratories, CDRH/USFDA, Silver Spring, Maryland 20993, United States of America.
PLoS One. 2017 Oct 31;12(10):e0186451. doi: 10.1371/journal.pone.0186451. eCollection 2017.
Small-angle x-ray scattering (SAXS) imaging can differentiate tissue types based on their nanoscale molecular structure. However, characterization of the coherent scattering cross-section profile of relevant tissues is needed to optimally design SAXS imaging techniques for a variety of biomedical applications. Reported measured nervous tissue x-ray scattering cross sections under a synchrotron source have had limited agreement. We report a set of x-ray cross-section measurements obtained from planar SAXS imaging of 1 mm thick mouse brain (APP/PS1 wild-type) coronal slices using an 8 keV laboratory x-ray source. Two characteristic peaks were found at 0.96 and 1.60 nm-1 attributed to myelin. The peak intensities varied by location in the slice. We found that regions of gray matter, white matter, and corpus callosum could be segmented by their increasing intensities of myelin peaks respectively. Measured small-angle x-ray scattering cross sections were then used to define brain tissue scattering properties in a GPU-accelerated Monte Carlo simulation of SAXS computed tomography (CT) using a higher monochromatic x-ray energy (20 keV) to study design trade-offs for noninvasive in vivo SAXS imaging on a small-animal head including radiation dose, signal-to-noise ratio (SNR), and the effect of skull presence on the previous two metrics. Simulation results show the estimated total dose to the mouse head for a single SAXS-CT slice was 149.4 mGy. The pixel SNR was approximately 30.8 for white matter material whether or not a skull was present. In this early-stage proof-of-principle work, we have demonstrated our brain cross-section data and simulation tools can be used to assess optimal instrument parameters for dedicated small-animal SAXS-CT prototypes.
小角X射线散射（SAXS）成像可以根据组织的纳米级分子结构区分组织类型。然而，为了针对各种生物医学应用优化设计SAXS成像技术，需要对相关组织的相干散射截面轮廓进行表征。据报道，在同步加速器源下测量的神经组织X射线散射截面的一致性有限。我们报告了一组X射线截面测量结果，这些结果是使用8 keV实验室X射线源对1毫米厚的小鼠大脑（APP/PS1野生型）冠状切片进行平面SAXS成像获得的。在0.96和1.60 nm-1处发现了两个归因于髓磷脂的特征峰。峰强度随切片位置而变化。我们发现，灰质、白质和胼胝体区域可以分别根据其髓磷脂峰强度的增加进行分割。然后，在使用更高单色X射线能量（20 keV）的SAXS计算机断层扫描（CT）的GPU加速蒙特卡罗模拟中，使用测量的小角X射线散射截面来定义脑组织的散射特性，以研究在小动物头部进行无创体内SAXS成像的设计权衡，包括辐射剂量、信噪比（SNR）以及颅骨存在对前两个指标的影响。模拟结果表明，单个SAXS-CT切片对小鼠头部的估计总剂量为149.4 mGy。无论是否存在颅骨，白质材料的像素SNR约为30.8。在这项早期原理验证工作中，我们已经证明我们的脑截面数据和模拟工具可用于评估专用小动物SAXS-CT原型的最佳仪器参数。
