CAREER: Towards Fast, Multi-Parametric, Low-Radiation X-Ray Microscopy

这项提议采用多学科方法，旨在开发新的理论技术，并将其应用于开发仪器和信号处理算法，以使层析X射线显微镜能够在生物样品上实际使用。在本提案所涉及的许多生物研究中，对非破坏性和定量显微镜有很大的需求；也就是说，样品制备不会改变样品或使样品变形，细节可以清楚地看到，图像捕捉到高分辨率，成像过程本身不会破坏样品。光学显微镜的透光性差，图像分辨率低，因此样品制备通常需要切片、固定、染色和标记方法，这些方法会损坏样品。另一方面，X射线在生物材料中穿透得更深，可以像在医学应用中看到的那样，对活的、完整的标本进行无损成像。X射线还有一个优势，那就是生物样本中的扩散和散射最小，这可以导致非常高的图像分辨率。然而，当前形式的吸收X射线显微镜对比度差，分辨率低，对样品的辐射剂量较高。拟议的新一代断层X射线显微镜将在低辐射剂量下提供准确、多参数和高分辨率的定量成像数据；多模式显微镜的第一代原型将在项目期间进行测试。让K-12和本科生参与这种跨学科研究，首先需要让他们掌握基本技能和知识，以解决物理、数学、工程和生物之间的交叉问题。学生将从休斯顿地区贫困的学区招生，为了保持他们对STEM科目的兴趣，将启动同伴指导计划，并为准备不足的本科生提供特别支持。为了进一步激励学生坚持STEM科目，组织的夏令营将突出跨学科的职业机会，并为本科生和高中生创造研究机会。X射线的频率比可见光高得多，因此提供了非常高分辨率和无损显微镜的可能性。该项目将开发各种方法，以充分发挥X射线显微镜在生物科学应用中的潜力。该项目涉及开发使用新技术的X射线相衬成像，例如快速脉冲X射线管、光子计数光谱探测方案和算法，以利用从每个探测到的X射线光子获得的最大信息。这一提议的科学目标包括理论方法、基于蒙特卡罗模拟的剂量效率X射线相衬显微镜系统的设计、系统的构建以及额外的多模显微镜原型的开发。将对一系列生物学问题进行调查，以测试成像系统的好处。开发的方法将得到广泛传播，最初的原型将提供给从事一系列生物学应用的研究人员。

Using a multi-disciplinary approach, this proposal aims to develop novel theoretical techniques and the apply them to develop instrumentation and signal processing algorithms to enable the practical use of tomographic x-ray microscopes on biological samples. There is a significant need for nondestructive and quantitative microscopy in many biological investigations that this proposal addresses; that is, that sample preparation does not alter or deform the sample, that the details can be seen clearly and images captured with high resolution, and that the imaging process itself does not destroy the sample. Optical microscopes suffer from poor light penetration and low image resolution so sample preparation often requires slicing, fixing, staining and tagging methods that damage the samples. On the other hand, X-rays penetrate deeper in biomaterials and can image live, whole specimens nondestructively as is seen in medical applications. X-rays also have the advantage that there is minimal diffusion and scattering in biosamples, which can result in very high image resolution. However, current forms of absorption x-ray microscopy have poor contrast, low resolution and deliver high radiation doses to specimens. The proposed new generation of tomographic x-ray microscopes will provide quantitatively accurate, multi-parametric and high-resolution imaging data at low radiation dose; a first-generation prototype for a multimodality microscope will be tested during the project period. Engaging K-12 and undergraduate students in this type of interdisciplinary research will first require giving them the basic skills and knowledge for tackling problems that cross between physics, mathematics, engineering and biology. Students will be recruited from disadvantaged Houston-area school districts, and to retain their interest in STEM subjects a peer-mentoring program will be started, with special support provided for under-prepared segments of undergraduate students. To further motivate students to stick with STEM subjects organized summer camps will highlight interdisciplinary career opportunities and create research opportunities for undergraduates and high-school students. X-rays are of significantly higher frequency than visible light and thus offer the possibility of very high resolution and nondestructive microscopy. This project will develop methods to fully realize the potential of x-ray microscopes for bioscience applications. The project involves developing x-ray phase-contrast imaging using novel technology such as fast-pulsing x-ray tubes, photon-counting spectral detection schemes and algorithms to utilize the maximum information from each detected x-ray photons. The scientific goals of this proposal include theoretical methods, the design of a dose-efficient x-ray phase-contrast microscopy system on the basis of Monte Carlo simulations, construction of the system, and the development of an additional multimodality microscope prototype. A range of biological problems will be investigated to test the benefits of the imaging system. The developed methods will be broadly disseminated and the initial prototypes will be made available to researchers working on an array of biological applications.