Polycrystalline Lead Oxide (PbO) photoconductor: physics and application in direct conversion x-ray medical imaging detectors

以非晶硒（a-Se）层作为x射线电荷换能器的直接转换x射线探测器彻底改变了辐射医学成像。事实上，a-Se乳房x线摄影探测器显示乳房图像质量优于其他现有的商用探测器。***虽然a-Se的性质适合在乳房x线摄影能量范围内的应用，但对于一般x线摄影和透视应用，a-Se必须用更高Z（原子序数）的材料代替。因此，需要一种新的材料来实现直接转换方法在诊断能量范围内的优势。这一需求在这里得到了解决：提出的研究计划的目标是将直接转换x射线探测器的进步扩展到最有前途的光导体材料，即多晶氧化铅（PbO）的荧光和射线成像应用。与现有的商业间接转换方法相比，新的氧化铅光电导体技术将实现更高的灵敏度和改进的空间分辨率。PbO在放射成像和透视成像方面具有巨大的应用潜力。与a- se相比，它有两个明显的优点：***(1)由于其较高的Z，它比a- se具有更高的x射线探测效率，从而允许更薄的层有效吸收高能量的x射线；***(2)它具有更低的电子-空穴对产生能量，因此具有更高的x射线-电荷转换增益。***然而，PbO光导层仍处于实验阶段-它们尚未达到理论极限的转换效率，并且在目前的技术阶段，PbO层尚未显示出足够的荧光应用的时间行为。克服这些挑战需要一个全面的PbO物理和材料科学计划，以了解制备-？该材料的制造-性能关系，并基于此知识优化PbO技术。该计划旨在将改进的PbO技术转移到用于荧光检查的有源矩阵平板成像仪（AMFPI）和用于放射照相的低成本x射线光阀（XLV）探测器中。基于pbo的探测器技术的发展是数字x射线成像系统不断发展的重要科学和工程成就。特别是，pbo基探测器在较低的x射线照射下具有更高的灵敏度。这样做的核心好处是，要么减少入射x射线剂量以获得诊断图像，从而提高一般放射照相和介入程序的总体安全性，要么提高典型x射线照射时的疾病可检出性。因此，拟议的计划最终将使加拿大和全世界的医疗保健受益。**

Direct conversion x-ray detectors with amorphous selenium (a-Se) layer as x-ray-to-charge transducers revolutionized radiation medical imaging. Indeed, a-Se mammographic detectors show breast image quality superior to other existing commercial detectors. ***Although a-Se properties fit applications in the mammographic energy range, for general radiographic and fluoroscopic applications a-Se has to be replaced by higher Z (atomic number) material. Therefore there is a need for a new material to realize the advantages of direct conversion methods in the diagnostic energy range. This need is addressed here: the objective of the proposed research program is to extend the advances of direct conversion x-ray detectors to fluoroscopic and radiographic applications on the basis of the most promising photoconductor material, namely Polycrystalline Lead Oxide (PbO). The new Lead Oxide Photoconductor technology will achieve higher sensitivity and improved spatial resolution over existing commercial indirect conversion methods. ***PbO has enormous potential for applications in radiographic and fluoroscopic imaging. It has two distinct advantages over a-Se: ***(1) it has higher x-ray detection efficiency than a-Se due to its higher Z and thus permits effective absorption of higher energy x-rays with thinner layer, and ***(2) it has lower electron-hole pair creation energy, and hence a higher x-ray-to-charge conversion gain.***However, PbO photoconductive layers are still experimental-they have not yet achieved conversion efficiency as high as the theoretical limit, and at the present stage of the technology, PbO layers have not yet shown adequate temporal behavior for fluoroscopic applications. Overcoming these challenges requires a comprehensive program on PbO physics and material science to understand the preparation-?fabrication-property relationships in this material and to optimize PbO technology based on this knowledge. The proposed program aims to transfer an improved PbO technology into Active Matrix Flat Panel Imagers (AMFPI) for fluoroscopy and low-cost X-ray light valve (XLV) detectors for radiography. ***The development of PbO-based detector technology is an important scientific and engineering accomplishment in the continuing development of digital x-ray imaging systems. In particular, PbO-based detectors have greater sensitivity at lower x-ray exposures. This has the core benefit of either reducing the incident x-ray dose to acquire a diagnostic image, and thereby improve the overall safety of general radiography and interventional procedures, or to improve disease detectability at typical x-ray exposures. As such, the proposed program will ultimately benefit healthcare in Canada and worldwide. **