一种基于毛细管X光透镜的微型锥束CT扫描仪

Micro cone-beam CT scanner based on X-ray polycapillary optics

活体小动物成像系统是疾病研究、新药开发的重要组成部分.其中,X射线微型锥束计算机断层成像(X-ray micro cone-beam computed tomography,Micro-CBCT)能实现数十至数百微米空间分辨率的解剖结构成像研究.Micro-CBCT成像仪的一个关键挑战是其空间和对比度分辨率主要取决于X射线源焦斑大小、探测器分辨率和系统几何结构等因素.为提高Micro-CBCT的空间分辨率、对比度分辨率和成像均一性,本文基于毛细管X光透镜研制了一款能够调控照射X射线束斑孔径的Micro-CBCT扫描仪,用于小动物成像研究.此系统由微焦斑X射线源、非晶硅平板探测器、旋转工作台和控制电脑组成,并采用Feldkamp-Daivs-Kress算法重建投影图像.对该系统的性能进行了测试,结果表明,系统在10%调制传递函数下的空间分辨率为9.1 lp/mm,提高了1.35倍.同时,由于毛细管X光透镜对低能X射线的吸收和散射抑制作用,实现了2倍以上的对比度增强,减轻了多色X射线束硬化效应引起的图像均一性恶化问题.应用该Micro-CBCT系统对麻醉小鼠进行了活体成像,验证了该系统在小动物成像研究中的实用性.

In-vivo small animal imaging system is an important part of disease research and new drug development.It is essential for living small animal imaging system to be able to provide the anatomical structure,molecular and functional information.The X-ray micro cone-beam computed tomography(micro-CBCT)can perform longitudinal study with a resolution of tens-to-hundreds of microns in a short imaging time at a relatively low cost.Furthermore,it is easy to combine with other modalities to provide abundant information about small animals.A key challenge to the micro-CBCT scanner is that its spatial and contrast resolution determined primarily by the X-ray focal spot size,the detector element size,and the system geometry.Aiming to improve the spatial resolution,contrast resolution,and imaging uniformity of the micro-CBCT system,we use the X-ray poly cap illary optics for adjusting the X-ray source.A micro-CBCT based on X-ray poly capillary optics with a large field of view is constructed for the small animal imaging study.The micro-CBCT system is composed of microfocus X-ray tube with an attached polycapillary focusing X-ray lens,amorphous silicon-based flat panel detector,rotation stage,and controlling PC.The Feldkamp-Daivs-Kress(FDK)algorithm is adopted to reconstruct the image.The system performances are evaluated.The magnification of this micro-CBCT system is 1.97.The results show that the spatial resolution of the system at 10%modulation transfer function(MTF)is9.1 lp/mm,which is 1.35 times higher than that in the case of no optics.The image uniformity deterioration caused by hardening effect is effectively alleviated by filtrating the low energy X-rays with the X-ray polycapillary optics and the contrast enhancement is more than twice.The anesthetic rats are imaged with this micro-CBCT system in vivo and the practicability of the system in small animal imaging research is verified.