Ultrafast laser x-ray in-vivo phase-contrast micro-CT

描述（由申请人提供）：新兴的光子技术，如超快激光，为克服传统生物医学成像模式的局限性提供了新的范例。在这个项目中，我们建议开发在线x射线相衬微型ct系统，该系统将利用超快激光x射线（ULX）源。这种新光源通过激光束照射固体目标产生x射线。任何固体（金属或非金属）都可以作为目标。ULX在x射线中比传统的微聚焦管提供更多的能量，从而允许更快的扫描。此外，ULX产生的窄x射线光谱主要由特征线组成。这些可以很容易地定制（通过改变激光束目标）成像任务。相衬微型ct将允许高分辨率测量活体动物x射线折射率的真实（x射线相移）和虚构（x射线吸收）分量的空间分布。这与使用微焦x射线管的传统微型ct形成对比，后者只能绘制x射线吸收系数的三维分布。因此，我们期望打开x射线相移3D成像提供的新信息通道，在常规吸收图测量的基础上，在不增加剂量的情况下显著提高micro-CT的软组织低对比度分辨率，从而改善小动物模型的癌症成像。在适当的时候，这种方法可以扩展到临床CT扫描仪，提供高平均功率的超快激光器。

DESCRIPTION (provided by applicant): Emerging photonic technologies, such as ultrafast lasers, provide a new paradigm for overcoming the limitations of traditional biomedical imaging modalities. In this project, we propose to develop in-line x-ray phase-contrast micro-CT system that will utilize an ultrafast laser-based x-ray (ULX) source. This new source produces x-rays through irradiation of a solid target by the laser beam. Any solid (metal or non-metal) can be used as a target. ULX delivers more power in x-rays than a conventional microfocal tube is able to provide, thus allowing for much faster scans. Further, ULX generates narrow x-ray spectra that consist mainly of characteristic lines. These can be easily tailored (by changing laser beam target) to the imaging task. The phase-contrast micro-CT will allow high-resolution measurements of the spatial distribution of the real (x-ray phase-shift) and the imaginary (x-ray absorption) components of the x-ray refractive index in a living animal. This is in contrast to conventional micro-CT, using a microfocal x-ray tube, which can only map 3D distribution of the x-ray absorption coefficient. Therefore, we expect that'opening the new channel of information provided by the x-ray phase-shift 3D mapping, in addition to conventional absorption map measurement, will significantly increase soft tissue low-contrast resolution of micro-CT without any dose increase, thus allowing improved imaging of cancer in small animal models. In due course, this method could be expanded to clinical CT scanners, providing that the high average power ultrafast lasers become available. Compact, robust, ultrafast lasers are commercially available, and their characteristics are rapidly improving. We plan to construct and explore imaging performance of an in vivo in-line x-ray phase-contrast ULX micro-CT system. This goal will be accomplished by completing the following tasks: i) design and optimization via computer simulations of the optimal system geometry and the focal spot size and shape; ii) design and optimization via computer simulations of ULX spectra; iii) experimental implementation and optimization of the selected system design; iv) development of image processing tools for correction, extraction, enhancement, and fusion of the extracted phase-contrast and absorption tomographic data and improved fusion of absorption and phase-contrast images; v) assemble a cone-beam ULX phase-contrast micro-CT system (with optimized geometry, energy, focal spot, and detector) and begin exploration of the imaging performance of the whole system and comparison with conventional micro-CT, using phantoms and in vivo imaging of oral cancer mouse model.