Lead Oxide (PbO) x-ray-to-charge transducer for direct conversion medical imaging detectors

用于直接转换医学成像探测器的氧化铅 (PbO) X 射线电荷传感器

• 批准号: RGPIN-2020-04311
• 负责人: Reznik, Alla
• 金额: $ 2.99万
• 依托单位: Lakehead University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762567
• 关键词: Lead; Oxide; PbO; ray; charge

X-ray imaging detectors rely on indirect or direct conversion of x-ray quanta to an electron signal. In the direct method, the x-ray quanta are absorbed in a photoconductor which is deposited directly on imaging electronics and acts as an x-ray-to-charge transducer. X-ray absorption creates electron hole pairs, which are subsequently separated by a bias field to generate a signal. The charges are moved by an electric field making it possible to create an image with a thick detector layer without significant loss of resolution. The conversion process can be up to ten times more efficient than for the indirect method, thus making it possible to improve both spatial resolution and dose efficiency down to the lowest required radiation exposure. This is only possible if the right photoconductor with an appropriate x-ray quantum efficiency, temporal performance, x-ray-to-charge conversion gain and good transport properties can be developed. Recently, my research group at Lakehead University synthesized a new photoconductor material for direct conversion x-ray imaging systems called, amorphous Lead Oxide (a-PbO). a-PbO has enormous potential for applications in radiographic and fluoroscopic imaging. It is a suitable high-Z (atomic number) material with distinct advantages over amorphous selenium (a-Se) - currently the only commercially viable x-ray photoconductor in direct conversion x-ray detectors - such as: it has higher x-ray detection efficiency than a-Se due to its higher atomic number, and thus permits effective absorption of higher energy x-rays with a thinner layer, (2) it has lower electron-hole pair creation energy, and hence a higher x-ray-to-charge conversion gain. This has a potential to reduce the radiation dose needed for medical X-rays to the fundamental quantum and spatial resolution limits. Although very promising, a-PbO layers are still experimental. More work on a-PbO photoconductor is now needed to assure technical feasibility to produce large area detectors with a photoconductive layer deposited directly on the imaging array, to optimize PbO technology and to enhance a-PbO properties as an x-ray-to-charge convertor. The objectives of this NSERC Discovery program are two-fold: to undertake comprehensive material science research into a new photoconductor material for x-ray imaging systems, namely amorphous Lead Oxide, and to develop functional prototypes of x-ray detectors based on this material for fluoroscopic and radiographic applications. The new a-PbO technology will achieve the theoretical limit of high detective quantum efficiency at low dose rates allowing the detector to be x-ray quantum noise limited at the low exposures. This in turn will allow the reduction of the incident x-ray dose to acquire an image and, thereby, to improve the overall safety of diagnostic and image-guided interventional procedures.

X 射线成像探测器依赖于 X 射线量子到电子信号的间接或直接转换。在直接方法中，X 射线量子被光电导体吸收，该光电导体直接沉积在成像电子器件上并充当 X 射线电荷转换器。 X 射线吸收产生电子空穴对，随后电子空穴对被偏置场分离以产生信号。电荷通过电场移动，从而可以创建具有厚探测器层的图像，而不会显着损失分辨率。转换过程的效率比间接方法高十倍，从而可以将空间分辨率和剂量效率提高到所需的最低辐射暴露。只有能够开发出具有适当 X 射线量子效率、时间性能、X 射线到电荷转换增益和良好传输特性的正确光电导体，这才有可能。最近，我在湖首大学的研究小组合成了一种用于直接转换 X 射线成像系统的新型光电导体材料，称为非晶氧化铅 (a-PbO)。 a-PbO 在射线照相和荧光成像方面具有巨大的应用潜力。它是一种合适的高Z（原子序数）材料，与非晶硒（a-Se）相比具有明显的优势 - 目前是直接转换X射线探测器中唯一商业上可行的X射线光电导体 - 例如：它具有更高的X射线由于其较高的原子序数，其探测效率高于 a-Se，因此可以用更薄的层有效吸收更高能量的 X 射线，(2) 它具有较低的电子空穴对产生能量，因此具有更高的 X 射线充电转换增益。这有可能将医用 X 射线所需的辐射剂量降低到基本的量子和空间分辨率极限。尽管 a-PbO 层非常有前景，但仍处于实验阶段。现在需要对 a-PbO 光电导体进行更多工作，以确保生产大面积探测器的技术可行性，光电导层直接沉积在成像阵列上，优化 PbO 技术并增强 a-PbO 作为 X 射线充电的特性转换器。 NSERC 发现计划的目标有两个：对用于 X 射线成像系统的新型光电导体材料（即非晶态氧化铅）进行全面的材料科学研究，并开发基于该材料的 X 射线探测器的功能原型。荧光镜和放射线照相应用。新的a-PbO技术将在低剂量率下达到高探测量子效率的理论极限，从而使探测器在低曝光下受到X射线量子噪声的限制。这反过来将减少获取图像时入射的 X 射线剂量，从而提高诊断和图像引导介入手术的整体安全性。