DIGITAL CHEST RADIOGRAPHY WITH REGIONAL EXPOSURE CONTROL

胸部X线片是发现胸腔积液的主要筛查工具 包括癌症在内的无症状的肺部疾病。然而，由于 胸部组织厚度的变化，X光片是 以较薄的肺之间的光子通量变化较大为特征的 Ara和剩余的厚切片。通过常规方式，这一变化 超出了射线照相胶片的有效曝光范围，并产生 在较厚的身体部位曝光严重不足的图像。而当 数字胸片提供了获取和显示 由于使用了大动态范围，所有身体部位上的投影数据 探测器，它仍然受到图像信号/噪声的影响 在较厚的身体部位产生光子通量。这种不同寻常的 信噪比将限制低对比度的可检测性以及 图像处理和双能量算法在胸部增强中的应用 放射摄影术。 我们最近开发了一种自动扫描“均衡”技术 用于胶片照相，以区域性地调整患者的曝光以响应 对患者进行传播分布，避免大范围漂移 在胶片曝光中。我们将把这种均衡技术应用于数字 胸部X光照相以最小化检测到的光子通量变化和 从而改善了图像信号/噪声分布的均匀性。我们 将扫描技术应用到一个数字胸腔原型上 射线照相系统及区域图像噪声意义的探讨 通过物理测量和低对比度可检测性研究进行控制。我们 将探索一种通过两种方法提高图像质量的新技术 噪声衰减效应的数值补偿方法 分散污染。这些改进的影响将在以下方面进行测试 候选图像处理技术。改进后的图像组合 噪声和增强的散射补偿可以提供一种优化 胸部X光摄影在诊断准确率方面有显著优势 传统的方法。对这项技术的评估将由 低对比度图像质量物理参数的测量 知觉研究和全面的临床评估。

Chest radiography is the main screening tool for the detection of asymptomatic lung disorders including cancer. However, due to the variations in tissue thickness over the chest, the radiograph is characterized by large variation in photon fluence between the thinner lung ara and remaining thick sections. By conventional means this variation falls outside the useful exposure range of radiograhic film and produces images that are severely underexposed over the thicker body parts. While digital chest radiography offers the capability to acquire and display projection data over all body parts due to their use of large dynamic range detectors it is still subject to image signal/noise degradation from the produced photon fluence over the thicker body parts. This nonuniform signal/noise ratio will limit the low contrast detectability as well as the utility of image processing and dual energy algorithms to enhance chest radiography. We have recently developed an automatic scanning "equalization" technique for film radiography to regionally adjust the patient exposure in response to the patients transmission distribution so as to avoid large excursions in film exposure. We will apply this equalization technique to digital chest radiography to minimize the detected photon fluence variations and therby improve the uniformity of the image signal/noise distribution. We will implement the scanning technique to a prototype digital chest radiography system and explore the significance of regional image noise control by physical measurement and low contrast detectability studies. We will explore a new technique in improving image quality through two approaches at numerically compensating the noise degrading effects of scatter contamination. The impact of these improvements will be tested on candidate image processing techniques. The combination of improved image noise and enhanced scatter compensation may provide a means of optimizing chest radiography with significant benefits on diagnostic accuracy over conventional methods. Evaluation of this technique will be made by measurements of physical parameters of image quality, low contrast perception studies and a thorough clinical evaluation.