An Advanced Technology Flat-Panel Imager for Fluoroscopy

描述（由申请人提供）：自20世纪80年代以来，广泛的研究工作已经导致主动矩阵平板成像仪（amfpi）在这十年中实际应用于许多医学x射线应用。其中包括锥束计算机断层扫描（CBCT）的成像程序。虽然与传统的胶片屏幕和x射线图像增强系统（XRIIs）相比，amfpi具有许多优势，但该技术仍然存在一些明显的局限性。在低曝光下，AMFPI图像质量会下降，因此，例如，它无法在整个透视曝光范围内与XRIIs的图像质量相匹配。其次，amfpi受到图像伪影的影响，源于阵列中非晶材料中的电荷捕获。这种伪影在大量放射线曝光后不久获得透视图像时尤其突出，这种现象称为重影。最后，amfpi的最大可实现帧率是有限制的。在此提案之前的研究已经确定了一种创新的，非常有前途的策略来克服这些限制，包括用多晶硅tft取代大多数传统amfpi中使用的非晶硅薄膜晶体管（a-Si:H tft）。这允许创建具有像素内放大器的相当复杂的阵列-称为有源像素（AP）架构。再加上与这些更复杂的像素电路兼容的新型a-Si:H光电二极管结构的结合，多si AP阵列将克服上述各种限制，同时保留传统amfpi的许多有利特性。研究的目标是开发一系列性能越来越高、面积越来越小、具有这些理想特性的原型阵列。目标是：(1)开发具有更好性能的原型（更高的探测量子效率，更低的电荷捕获效应，更高的帧速率）-涉及迭代设计，制造和评估越来越复杂的AP原型。(2)定量建模（包括级联系统分析和详细电路仿真），为阵列设计提供指导，并协助原型评估。(3)详细描述单个多晶硅tft和其他测试电路的特性，以支持电路模拟活动，并通过改进制造技术为改进阵列性能提供指导。(4)创造实现上述目标所需的各种工具（数学、软件、固件和硬件）。这项研究的成功结论将导致创造一种技术，该技术提供的图像质量仅受X射线和X射线转换器的基本特性的限制，减少伪影并提高帧速率。最终，这将提高图像质量和/或减少透视程序的剂量，并促进先进的临床应用，包括乳房和胸部断层合成，以及乳腺和血管造影程序的CBCT。公共卫生相关性：在拟议的研究中开发的新型x射线成像技术的实际应用将显著增强成像能力，最终以多种方式改善患者护理。例如，与现有的x射线技术相比，新技术将有助于在非常低的剂量下实现更高质量的图像（有助于在透视过程中最大限度地减少患者的剂量），并能够可视化较小和/或低对比度的特征（有助于在乳房x线摄影检查中识别可疑物体）。此外，强烈预期新技术将使先进的应用（包括用于胸部和乳房成像的断层合成或锥束计算机断层扫描技术）成为可能，这些应用需要以相对较低的剂量快速获取多个高质量图像，以便产生三维解剖视图。

DESCRIPTION (provided by applicant): Extensive research efforts since the 1980s have resulted in the practical introduction of active-matrix flat-panel imagers (AMFPIs) to numerous medical x-ray applications in this decade. These include \ imaging procedures involving cone beam computed tomography (CBCT). While AMFPIs offer many advantages compared to traditional film-screen and x-ray image intensifier systems (XRIIs), the technology nevertheless suffers from several significant limitations. AMFPI image quality degrades at low exposures so that, for example, it cannot match the image quality of XRIIs across the entire fluoroscopic exposure range. Secondly, AMFPIs are subject to image artifacts, originating from the trapping of charge in amorphous materials in the arrays. Such artifacts are particularly prominent when fluoroscopic images are acquired shortly after a large radiographic exposure - a phenomenon called ghosting. Finally, the maximum achievable frame rates of AMFPIs are restrictive. Research leading up to this proposal has identified an innovative, highly promising strategy for overcoming these limitations, involving substitution of the amorphous silicon thin-film transistors (a-Si:H TFTs), used in most conventional AMFPIs, with polycrystalline silicon (poly-Si) TFTs. This allows creation of considerably more sophisticated arrays with in-pixel amplifiers - referred to as an active pixel (AP) architecture. Coupled with the incorporation of novel a-Si:H photodiode structures that are compatible with these more complex pixel circuits, poly-Si AP arrays would overcome the various limitations listed above, while preserving the many favorable properties of conventional AMFPIs. The objectives of the research focus on the development of a series of increasingly higher performance, small area, prototype arrays that exhibit these desirable properties. The objectives are: (1) Development of prototypes with progressively better performance (higher detective quantum efficiency, lower charge trapping effects, higher frame rates) - involving iterative design, fabrication and evaluation of increasingly sophisticated AP prototypes. (2) Quantitative modeling (involving cascaded systems analysis and detailed circuit simulations) to provide guidance in array design and assist in prototype evaluation. (3) Detailed characterization of the properties of individual poly-Si TFTs and other test circuits to support the circuit simulation activities and to provide guidance in improving array performance through improvements to fabrication techniques. (4) Creation of the various tools (mathematical, software, firmware and hardware) required to accomplish the above objectives. The successful conclusion of this research will result in the creation of a technology that offers image quality limited only by the fundamental properties of X rays and x-ray converters, reduces artifacts and increases frame rates. Ultimately, this will improve image quality and/or reduce dose for fluoroscopic procedures, as well as facilitate advanced clinical applications including breast and chest tomosynthesis, and CBCT for breast and angiographic procedures. PUBLIC HEALTH RELEVANCE: The practical application of the novel x-ray imaging technology to be developed in the proposed research will offer significant enhancement of imaging capabilities, ultimately improving patient care in a wide variety of ways. For example, compared to existing x-ray technologies, the new technology will facilitate the realization of higher quality images at very low doses (helping to minimize dose to the patient in fluoroscopic procedures) and enable the visualization of smaller and/or lower contrast features (assisting in the identification of suspicious objects in mammographic examinations). Moreover, it is strongly anticipated that the new technology will enable advanced applications (involving tomosynthesis or cone beam computed tomography techniques for chest and breast imaging) that require rapid acquisition of multiple, high quality images at relatively low doses per image in order to produce three dimensional anatomical views.