Research on Image Perception of Abnormal Findings

我们研究了射线噪声和解剖噪声对微小异常发现的检测能力的影响，并采用四选一强制选择方法研究了噪声水平对高斯白噪声背景下模拟肺结节检测性能的影响。结果与基于信号检测理论的结果基本一致。结节的可探测性与局部周围解剖结构灰度值的基本统计度量关系不大，而与信噪比有关。接下来，我们从局部角度，以结节周围肋骨结构的存在为焦点，探讨了解剖噪声对胸片上描绘的细小肺结节可探测性的影响。Samei等人提出的方法。被应用到我们的研究中。从常规胸片图像中，考虑肋骨结构提取正方形区域，正方形图像的中心分别位于肋骨的上缘、肋骨的内侧、肋骨的下缘和相邻两根肋骨之间的中心，并将模拟结节数字化叠加在提取的正方形图像的中心上。通过使用一组经过处理的图像，我们进行了图像阅读研究。结果表明，结节周围肋骨结构的存在对检测性能有显著影响，位于相邻肋骨中心的结节的检测能力最好。此外，除相邻肋骨之间的中心外，结节的可探测性按肋骨上缘、肋骨内缘和肋骨下缘的顺序呈递减趋势，但这些差异很小。一定大小的射线噪声也会影响结节的检测。

We have studied how radiographic noise and anatomic noise will affect the detectability of subtle abnormal findings.The influence of noise level on the detection performance of simulated lung nodules in the Gaussian white noise background has been investigated by using a four-alternative forced choice method. Results were mostly in agreement with the ones derived from the signal detection theory. The nodule detectability had little relation to the fundamental statistical measures of gray scale values of the local surrounding anatomic strucures, and was related to the signal-to-noise ratio.Next, we have accessed the influence of anatomic noise on the detectablity of subtle lung nodules depicted on chest radiographs, from a local aspect in which the existence of rib structure surrounding nodules is the focus. The method proposed by Samei et al. was applied to our study. From the normal chest radiography images, square regions were extracted by considering rib structure ; the centers of these square images were on the upper margin of a rib, the inside of a rib, the lower margin of a rib, and the center between two adjoining ribs ; and the simulated nodules were digitally superimposed on the centers of these extracted square images. By using a set of these processed images, we have performed the image reading study. Results indicated a significant effect of the existence of rib structure surrounding the nodule on the detection performance, and the detectability of the nodules on the center between two adjoining ribs was significantly the best. Further, the detectability of the nodules other than on the center between two adjoining ribs showed a tendency to decrease in the order of the upper margin, the inside, and the lower margin of a rib ; however, these differences were few. Radiographic noise of a certain size can also influence the nodule detection.