aSi/CsI FP digital chest imaging with scatter rejection

尽管最近商业化的平板探测器改进了DQEs，但区域探测器投影x射线成像固有的两个问题仍然存在并降低了低对比度性能：(1)探测器在严重衰减区域的光子影响低；(2)缺乏有效的方法来抑制散射辐射。期望通过改进的dqe可以解决这些问题或使其变得不那么重要，这在某种程度上是不切实际的。数字探测器的一个主要优点是数字图像处理和分析的前景。然而，这种好处是很难实现的，由于低信噪比在严重衰减的区域，图像处理往往发现最使用。为了解决上述问题，我们建议构建和研究一个基于aSi:H和CsI:Tl的平板探测器的扫描均衡数字射线照相（SEDR）系统。采用区域可调光束宽度的狭缝扫描成像，可实现有效的散射抑制和曝光均衡。预曝光图像将用于计算扫描所需的光束宽度调制，从而消除了使用辐射探测器阵列的需要。一种新的图像读出方案将用于提供电子后准直，以实现散射抑制，而不需要衰减初级x射线，也不需要使用笨重的后准直器。将实现一种重新缩放技术，将均衡的数字胸部图像转换为具有传统胸部图像外观的图像，但具有增强的对比度和均衡的信噪比。为了评估所提出的技术，我们将测量和表征所提出的SEDR系统的性能。我们将研究和演示使用幻影图像来改善图像质量。我们还将对350名患者进行全面的ROC研究，比较扫描均衡DR胸部图像与经过和未经数字图像增强处理的常规DR图像。该系统有望通过以下方式改善数字胸部图像的低对比度性能：(1)在不衰减初级x射线的情况下更有效地抑制散射辐射；(2)增加重衰减区域的x射线影响，以提高信噪比，减少散射辐射的影响；(3)为进一步的数字图像处理和分析提供高质量的图像数据，提高比噪比，均衡信噪比，而不会在重衰减区域受到过多的噪声限制。

Despite improved DQEs of recently commercialized flat- panel detectors, two problems intrinsic to projection x-ray imaging with area detectors remain and degrade the low contrast performance: (1) low photon fluences at the detector in heavily attenuated regions, and (2) lack of efficient methods to reject scattered radiation. The expectation that these problems would be resolved or become less important through improved DQEs is somewhat illusive. One major benefit with digital detectors is the prospect of digital image processing and analysis. However, this benefit is hard to realize due to the low signal-to-noise ratios in heavily attenuated regions where image processing often finds most use. To resolve the above mentioned problems, we propose to construct and investigate a scanning equalization digital radiography (SEDR) system using an aSi:H and CsI:Tl based flat-panel detector. Slit scanning imaging with regionally adjustable beam width will be used to achieve effective scatter rejection and exposure equalization. A pre-exposure image will be used to compute the necessary beam width modulations for the scan, eliminating the need for using a radiation detector array. A novel image readout scheme will be used to provide electronic aft-collimation to achieve scatter rejection without attenuating primary x-rays and without using a heavy, bulky aft-collimator. A re-scaling technique will be implemented to convert equalized digital chest images into images with the appearance of conventional chest images but with enhanced contrast and equalized SNRs. To evaluate the proposed technique, we will measure and characterize the performance of the proposed SEDR system. We will study and demonstrate image quality improvements with phantom images. We will also conduct a comprehensive 350 patient ROC study to compare the scanning equalization DR chest images with regular DR images with and without digital image enhancement processing. The proposed system is expected to improve the low contrast performance of digital chest images by: (1) more effectively rejecting scattered radiation without attenuating primary x-rays, (2) increasing x-ray fluences in heavily attenuated regions to improve SNRs and reduce impact of scattered radiation there, (3) providing high quality image data with improved contrast-to-noise ratios and equalized SNRs for further digital image processing and analysis without suffering excessive noise limitations in heavily attenuated regions.