CIF:Small:Coded Aperture Spectral X-Ray Tomography

光谱断层扫描已成为医学成像和国土安全的关键成像方式。它提供了材料辨别，为识别原子组成、化学目标和爆炸物提供了有用的线索。它依靠的原理是，不同化学材料的x射线吸收具有依赖于所使用的x射线能量的特性。因此，能够区分x射线能量的探测器使得区分具有相似x射线衰减特性的不同材料成为可能。不幸的是，能量分辨x射线探测器在许多应用中过于昂贵。其他检测器技术通常以成本换取获取速度，并且在许多情况下，实际限制需要有限的角度或次采样投影几何形状，从而导致图像重建中的严重伪影。这项研究探索了编码x射线照明投影，它可以用标准的集成探测器捕获，同时为能量分辨图像重建提供信息。编码测量具有较低的辐射剂量。它们也可以复用，以保证在有限角度情况下的鲁棒性。本研究探索彩色x射线编码投影，以规避当前探测器的限制。不是通过衰减的x射线来测量物体，而是首先对x射线的振幅和光谱进行编码，以已知的模式调制x射线场，有效地产生低剂量的结构化x射线束，询问物体的特定体素。仔细设计编码孔径及其位置，以及开发利用结构化照明的快速计算逆算法，可以为光谱层析成像的应用提供优势。各种计算机断层扫描（CT）几何正在考虑包括断层合成，扇束，和锥束。用于验证潜在理论概念的测试平台是项目的中心部分。

Spectral tomography has emerged as a key imaging modality for medical imaging and homeland security. It offers material discrimination providing useful cues for identifying atomic composition, chemical targets, and explosives. It relies on the principle that the X-ray absorption of different chemical materials has characteristics that depend on the energy of the X-rays used. Thus, detectors that can differentiate between X-ray energies make it possible to discriminate different materials having similar X-ray attenuation properties. Unfortunately, energy resolving X-ray detectors are prohibitively costly for many applications. Other detector technologies often trade cost for acquisition speed and, in many cases, practical limitations require limited angle or subsampled projection geometries that lead to severe artifacts in image reconstruction. This research explores coded X-ray illumination projections which can be captured with standard integrating detectors yet provide information for energy-resolved image reconstructions. The coded measurements have lower radiation dose. They can also be multiplexed for robustness in limited angle scenarios.This research explores colored X-ray coded projections to circumvent current detector limitations. Rather than measuring objects by the attenuated X-rays, the X-rays are first coded in amplitude and spectra that modulate the X-ray field in a known pattern, effectively creating lower-dose structured X-ray bundles that interrogate specific voxels of the object. Careful design of the coded apertures, their placement, and the development of fast computational inverse algorithms that exploit the structured illumination can provide advantages in the application of spectral tomography. Various computerized tomography (CT) geometries are being considered including tomosynthesis, fan-beam, and cone-beam. A test-bed for validating the underlying theoretical concepts is a central part of the project.