Department of Radiological Technology, Nagoya University School of Health Sciences, 1-20 Daikominami 1-chome, Higashi-ku, Nagoya, 461-8673, Japan.
Phys Med. 2010;26(3):157-65. doi: 10.1016/j.ejmp.2009.11.003. Epub 2009 Dec 29.
By using the CT images obtained by subtracting two CT images acquired under the same conditions and slice locations, we have devised a method for detecting streak artifacts in non-uniform regions and only radiological noise components in CT images. A chest phantom was scanned using 16- and 64-multidetector row helical CT scanners with various mAs values at 120kVp. The upper lung slice image was employed as a target image for evaluating the streak artifacts and radiological noise. One hundred parallel line segments with a length of 80 pixels were placed on the subtracted CT image, and the largest CT value in each CT value profile was employed as a feature variable of the streak artifacts; these feature variables were analyzed with the extreme value theory (Gumbel distribution). To detect only the radiological noise, all CT values contained in the 100 line profile were plotted on normal probability paper and the standard deviation was estimated from the inclination of its fitted line for the CT value plots. The two detection methods devised in this study were able to evaluate the streak artifacts and radiological noise in the CT images with high accuracy.
通过使用在相同条件和切片位置下获取的两幅 CT 图像相减，我们设计了一种方法来检测 CT 图像中非均匀区域中的条纹伪影和仅存在的放射噪声分量。使用 16 排和 64 排多层螺旋 CT 扫描仪，在 120kVp 下以不同的 mAs 值对胸部体模进行扫描。将上肺切片图像用作评估条纹伪影和放射噪声的目标图像。在减去的 CT 图像上放置了 100 个长度为 80 像素的平行线段，并将每个 CT 值轮廓中的最大 CT 值用作条纹伪影的特征变量；这些特征变量使用极值理论（Gumbel 分布）进行分析。为了仅检测放射噪声，将 100 条线轮廓中的所有 CT 值绘制在正态概率纸上，并从拟合线的倾斜度估计 CT 值图的标准偏差。本研究中设计的两种检测方法能够非常准确地评估 CT 图像中的条纹伪影和放射噪声。
