Effciency Enhanced Mega Electronvolt Cone Beam Computed Tomography (EMECT) a succession project to the project X-ray 3D Computed Tomography with Mega Electronvolt Source (CTOMES)

在本研究计划中，我们提出一种改善兆电子伏特（MeV）锥束x射线成像对比度和图像质量的方法。总体思路是通过引入高度优化的探测器侧滤波来提高探测到的主辐射与散射辐射的比例。所提出的工作的关键部分将是结合计算跟踪和修正所提出方法的辅助空间分辨率损失，以及提供一种方法来实验跟踪光谱系统响应的改进，并将其用于精确的硅模拟。运行能量超过1兆电子伏特的高能（HE）工业x射线计算机断层扫描（CT）系统已经运行了十多年。然而，由于在这些能量下产生大量的样品散射辐射，这些系统通常设计在扇形光束设置中，使用通常高度准直的线性探测器。结合平板探测器的锥束计算机断层扫描（CBCT）装置可以极大地提高速度和分辨率，因为它通常用于能量低至600千电子伏特（keV）的x射线系统中。然而，由于样品、环境和探测器本身散射的辐射造成的伪影，在MeV工业CT背景下的锥束设置通常没有足够的图像质量。在锥形光束设置中，这种二次辐射不能通过准直来避免，但它是背景信号的主要部分，同时降低对比度和空间分辨率。在锥形光束采集几何结构中，HE系统的x光片受到物体散射辐射的显著增加。此外，商用平板探测器针对低能量x射线光束进行了优化，其闪烁层保持薄，以避免成像系统的点扩展函数（PSF）的退化。对于MeV工业CT系统，由于x射线光子到信号的低非线性转换，薄磷屏导致检测效率低。本课题的研究目的是通过实验研究这些特性，并引入一种利用附加检测器滤波来提高图像对比度的方法。

In this research project proposal we propose a contrast and image quality improvement for Mega Electronvolt (MeV) cone beam X-Ray imaging. The overall idea is to improve the ratio of detected primary to scattered radiation by introducing highly optimized detector-sided filtering. Key part of the proposed work will be the combination with computational tracking and correcting the subsidiary spatial resolution loss of the proposed method, as well as providing a method to track experimentally the introduced improvements in spectral system response and use this for accurate in-silico simulations.High Energy (HE) industrial X-ray Computed Tomography (CT) systems operating with energies exceeding one Mega Electronvolt have been in operation for over a decade. However, due to the large amount of specimen-scattered radiation created at these energies, these systems are typically designed in a fan-beam setting using a linear detector which is usually highly collimated. HE setups could benefit greatly from the increase in speed and resolution provided by a Cone Beam Computed Tomography (CBCT) setup incorporating a flat-panel detector as it is typically used in X-ray systems with lower energies up to 600 Kilo Electronvolt (keV). However, a cone-beam setup in the context of MeV industrial CT often does not have sufficient image quality, due to artifacts caused by radiation, which is scattered from the specimen, the environment and the detector itself. In a cone beam setup such secondary radiation cannot be avoided by collimation, but is the main part of the background signal and decreases both contrast and spatial resolution. The radiographs of a HE system in cone-beam acquisition geometry, suffer from a significant increase in object-scattered radiation. Moreover, commercially available flat-panel detectors are optimized for lower energy X-ray beams, with a scintillation layer that is kept thin in order to avoid a degradation of the Point-Spread Function (PSF) of the imaging system. For MeV industrial CT systems the thin phosphorous screens cause a low detection efficiency due to the low and non-linear conversion of X-ray photons into signal. Investigating those properties experimentally and introducing an improvement term of image contrast by the use of additional detector filtering is purpose of this research project.