DIGITAL CHEST RADIOGRAPHY WITH REGIONAL EXPOSURE CONTROL

胸部X线摄影是检测以下疾病的主要筛查工具： 无症状肺部疾病，包括癌症。 但由于 胸部组织厚度的变化，X光片是 其特征在于较薄的肺之间的光子通量变化较大， ara和剩余的厚切片。 通过常规手段， 福尔斯超出了射线照相胶片的有效曝光范围， 在较厚的身体部位上严重曝光不足的图像。 而 数字化胸部X线摄影提供了采集和显示 由于它们使用大动态范围， 检测器，它仍然受到来自图像信号/噪声退化 在较厚的身体部位产生光子通量。 这种不均匀 信噪比将限制低对比度可检测性以及 利用图像处理和双能量算法增强胸部 放射线照相术。 我们最近开发了一种自动扫描"均衡"技术 对于胶片射线照相术， 以避免大的偏移 在胶片曝光中。 我们将把这种均衡技术应用于数字 胸部X线摄影，以最大限度地减少检测到的光子通量变化， 从而改善图像信号/噪声分布的均匀性。 我们 将把扫描技术应用到一个数字胸腔的原型上 X射线摄影系统，并探讨区域图像噪声的意义 通过物理测量和低对比度可检测性研究进行控制。 我们 将探索一种新的技术，通过两个提高图像质量 在数字上补偿噪声退化影响的方法 散射污染 这些改进的影响将在以下方面得到检验： 候选图像处理技术。 结合改善的形象 噪声和增强的散射补偿可以提供优化 胸部X线摄影在诊断准确性方面明显优于 常规方法。 这项技术的评价将由 测量图像质量、低对比度的物理参数 感知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.