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

具有非晶硒（a-Se）层作为X射线到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。实际上，a-Se乳房摄影检测器显示出比其他现有商业检测器更上级的乳房图像质量。* 虽然a-Se性质适合乳房X线照相能量范围内的应用，但对于一般的放射照相和荧光透视应用，a-Se必须由更高Z（原子序数）的材料代替。因此，需要一种新材料来实现诊断能量范围内直接转换方法的优点。这一需求在这里得到满足：所提出的研究计划的目的是基于最有前途的光电导体材料，即多晶氧化铅（PbO），将直接转换X射线探测器的进展扩展到荧光和射线照相应用。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更高的空间分辨率。*PbO在射线照相和荧光成像中具有巨大的应用潜力。它比a-Se具有两个明显的优点：*（1）由于其较高的Z，它具有比a-Se更高的X射线检测效率，因此允许用较薄的层有效吸收较高能量的X射线，以及 *（2）它具有较低的电子-空穴对产生能量，因此具有较高的X射线-电荷转换增益。然而，PbO光电导层仍然是实验性的，它们还没有达到与理论极限一样高的转换效率，并且在该技术的现阶段，PbO层还没有显示出用于荧光应用的足够的时间行为。克服这些挑战需要一个全面的计划，PbO物理和材料科学，以了解准备-？这种材料的制造-性能关系，并基于这些知识优化PbO技术。 该拟议计划旨在将改进的PbO技术转移到用于荧光透视的有源矩阵平板成像仪（AMFPI）和用于射线照相的低成本X射线光阀（XLV）探测器中。* 基于PbO的探测器技术的开发是数字X射线成像系统持续发展中的一项重要科学和工程成就。特别地，基于PbO的探测器在较低的X射线曝光下具有更高的灵敏度。其核心受益是减少了获取诊断图像的入射X射线剂量，从而提高了一般X射线照相和介入手术的整体安全性，或者提高了典型X射线照射下的疾病可检测性。因此，拟议的计划最终将有利于加拿大和世界各地的医疗保健。**

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. **