A Dual Detector for X-Ray Attenuation and Phase Imaging

描述（由申请人提供）： 目的：总体目标是开发一种新的诊断X射线成像技术，同时采集衰减和相位图像。挑战：利用具有高空间相干性的第三代同步辐射X射线源进行的先驱研究已经证明，相衬可以显着提高诊断成像的灵敏度。然而，同步加速器X射线源的成本、尺寸和可用性不适合临床应用。因此，提出了一种新型的场发射X射线源，具有高空间相干性和双探测器系统。方法：利用纳米尖端技术，研制出一种用于X射线源电子枪的超级针尖。尖端由纳米材料制成，其零维电子结构和非欧姆跳跃传导将允许高达2 x 107 A/cm 2的电流密度而不会烧坏。通过使用电子束诱导沉积，超级尖端将与微型Orbitron真空泵和离子镜集成，以避免污染和电子发射体的离子轰击。预期的最终产品是具有小焦斑（小于0.025ram）的X射线源，并且同时具有高管电流（大于25 mA），从而提供具有高空间相干性的亮源。有了这样一个新的源，一个双检测器系统将被开发来获取衰减和相位衬度图像的基础上的同轴全息原理，并将开发一种算法来重建这两个图像的相位图像。将进行全面测量，以表征申报系统在临床条件下的性能。这包括分辨率、对比度和量子效率的客观测量，以及基于分辨率的主观测量。临床获益：所提出的技术具有以下临床友好的功能：（1）系统的源到检测器的距离不超过1米，这是通过使用所提出的具有高空间相干性的场发射源来实现的;（2）两个图像，相位对比和衰减图像在一次曝光中以常规剂量水平采集，以实现相位恢复。(3)与常规X射线图像相比，重建的相位图像提供了显著改善的组织-病变对比度，因为组织和病变之间的相位差比常规衰减对比度大数百倍。总结：通过结合基于纳米技术的场发射源、双探测器系统和相位重建算法，所提出的研究将在诊断X射线成像中创造一种新的灵敏方式。

DESCRIPTION (provided by applicant): Objective: The overall objective is to develop a new diagnostic x-ray imaging technique that acquires both attenuation- and phase-images simultaneously. Challenges: Pioneer research performed with the 3rd generation synchrotron x-ray sources with high spatial coherence has proved that phase-contrast can significantly improve the sensitivity of diagnostic imaging. However, the costs, size and availability of a synchrotron x-ray source do not fit to clinical applications. A novel field-emission x-ray source with high spatial coherence and a dual-detector system is therefore proposed. Methods: Cutting-edge nanotechnology will be applied to fabricate a super tip for the electron gun of the x-ray source. The tip is made of the nanocrystal material, whose zero-dimensional electronic structure and non-Ohmic hopping conduction will allow a current density as high as 2 x 107 A/cm2 without burning out. By using the electron beam induced deposition the super tip will be integrated with a miniature Orbitron vacuum pump and an ion mirror to avoid contamination and the ion bombardment of the electron emitter. The anticipated end product is an x-ray source with a small focal spot (less than 0.025 ram), and at the same time, a high tube current (greater than 25mA), thus providing a bright source with high spatial coherence. With such a new source, a dual detector system will be developed to acquire both attenuation- and phase-contrast images based on the in-line holography principle, and an algorithm will be developed to reconstruct a phase-image from these two images. Comprehensive measurements will be conducted to characterize the performance of the proposed system under clinical conditions. That includes objective measurements of resolution, contrast and quantum efficiency, and observer-based subjective measurements. Clinical benefits: The proposed technique has the following clinically friendly features: (1) The source-to-detector distance of the system is no more than 1 m; this is achieved by using the proposed field emission source with high spatial coherence; (2) Two images, a phase-contrast and an attenuation image are acquired at one exposure at the conventional dose level to enable phase-retrieval. (3) The reconstructed phase-image provides a significantly improved tissue-lesion contrast as compared with conventional x-ray images, because the phase differences between tissue and lesion are hundreds times larger than conventional attenuation contrast. Summary: By combining the nano-technology-based field emission source, a dual-detector system, and a phase-reconstruction algorithm, the proposed research would create a new sensitive way in diagnostic x-ray imaging.