Development of a High Sensitivity, X-ray Detector Technology Based on Polycrystalline Mercuric Iodide for Volumetric Breast Imaging

项目摘要/摘要 正确识别乳房中可疑肿块的任务常常因为令人困惑的重叠而变得复杂 由乳房X光摄影提供的投影图像中存在的解剖特征。出于这个原因，有 我对通过一种名为数字乳房的技术获得体积信息的兴趣越来越大 断层合成(DBT)。DBT在提高乳腺成像的敏感度和特异度方面显示出希望 与乳房X光检查相比，它提供了有助于区分重叠的乳房组织的深度信息。 这种技术通常使用有源矩阵、平板成像器(AMFP)技术来执行 它包含一个x射线转换器(以一层碘化铯(CSI：Tl)或无定形硒的形式 (a-Se)沉积在像素化阵列上)以检测入射辐射。单个DBT视图通常包括 采集9至25个投影图像，并且临床上希望每次观察的累积剂量为否 比单视角乳房X光检查要多。然而，相对适中的信号量是由 CsI：Tl和a-Se中的每一条X射线都会导致技术限制，这些限制了 获取投影图像-这可能会显著影响图像质量，并阻碍 将剂量降至最低。为了克服这个问题，拟议的研究试图开发一种替代形式的x- 基于多晶碘化汞并使用丝网印刷法制造的射线转换器-参考 作为SP HgI2。SP HgI2已被证明能够提供至少三倍于每条X射线的信号 而不是a-se或csi：tl，因此将有助于解决用于DBT的AMFP的技术限制。 然而，这种新型转换器的进一步开发还需要改进其他重要的转换器和 与成像器相关的属性(包括减少电荷捕获效应和像素间的非均匀性 信号响应)。因此，该项目的具体目标侧重于实现以下方面的高水平业绩 这些属性中的每一个。这些目标将通过对若干 为改善转换器和成像器性能的不同方面而选择的策略。这些战略包括 结合栅极的引入对制造SP HgI2转换器的方法进行了改进 结构安装到这些转换器中。研究的方法论将基于迭代设计、制造 和使用这些策略的原型转换器的评估-使用从给定的 用于改进后续原型的一组原型。转换器将放置在Simple探测器上 衬底(这有助于相对快速地评估有限数量的属性)以及AMFPI 数组(允许完整的性能表征)。新转炉的预期影响 这项研究使技术成为可能，将大大提高数字技术的有效性 乳房断层合成，包括可能的剂量减少--以及促进剂量减少的可能性 在其他应用中，如乳腺CT、透视和锥束CT在放射治疗中的应用。

Project Summary/Abstract The task of correctly identifying suspicious masses in the breast is often complicated by the confusing overlap of anatomical features present in the projection images provided by mammography. For that reason, there has been growing interest in obtaining volumetric information through a technique called digital breast tomosynthesis (DBT). DBT has shown promise for improving sensitivity and specificity in breast imaging compared to mammography by providing depth information that helps to distinguish overlapping breast tissue. This technique is most commonly performed using the technology of active matrix, flat-panel imagers (AMFPIs) which incorporate an x-ray converter (in the form of a layer of cesium iodide (CsI:Tl) or amorphous selenium (a-Se) deposited on a pixelated array) to detect the incident radiation. A single DBT view typically involves acquisition of 9 to 25 projection images and it is clinically desirable that the cumulative dose per view be no more than that of a single-view mammogram. However, the relatively modest amount of signal generated by each X ray in CsI:Tl and a-Se leads to technical limitations that constrain the conditions under which the projection images are acquired – which can significantly affect image quality as well as impede efforts to minimize dose. To overcome this problem, the proposed research seeks to develop an alternative form of x- ray converter based on polycrystalline mercuric iodide and fabricated using a screen-print method – referred to as SP HgI2. SP HgI2 has been shown to be capable of providing at least three times more signal per X ray than a-Se or CsI:Tl and, as a result, would help to address technical limitations in AMFPIs used for DBT. However, further development of this novel converter is required to improve other important converter and imager-related properties (including the reduction of charge trapping effects and non-uniformity in pixel-to-pixel signal response). The specific aims of the project therefore focus on achieving a high level of performance for each of these properties. These aims will be accomplished through systematic investigation of a number of strategies chosen to improve different aspects of converter and imager performance. The strategies consist of modifications to the methods used to fabricate the SP HgI2 converters combined with the introduction of a grid structure into those converters. The methodology of the research will be based on iterative design, fabrication and evaluation of prototype converters employing these strategies – with the information obtained from a given set of prototypes used to improve subsequent prototypes. The converters will be deposited on simple detector substrates (which facilitate relatively rapid evaluation of a limited number of properties) as well as on AMFPI arrays (which allow complete performance characterization). The expected impact of the new converter technology made possible by the research will be a significant improvement in the effectiveness of digital breast tomosynthesis, including possible dose reduction – along with the potential for facilitating dose reduction in other applications such as breast CT, fluoroscopy and cone-beam CT in radiation therapy.