Department of Oral Surgery and Oral Radiology, University Medical Center of the Johannes Gutenberg University Mainz, Augustusplatz 2, 55131 Mainz, Germany.
Dentomaxillofac Radiol. 2011 Mar;40(3):170-6. doi: 10.1259/dmfr/84700141.
The aim of this study is to evaluate if theoretically possible edge shifts induced by noise-suppression filters potentially occur on objects found in digital radiographs. Most manufacturers carry out noise-suppression filtering of their images before they are displayed to the user. It is not usually possible for the user to disrupt the function of the filters. The use of these filters can lead to deletion of small image structures.
K-files (ISO size 06, 08, 10 and 15) were placed in the root canals of 6 human teeth located in cadaver jaw segments. File tip positions were measured on original and filtered digital images by three observers. The file position was marked on each filtered image and compared with the unfiltered ones.
The 5 × 5 pixel-sized median and mean filters caused the largest underestimation of measured lengths between -7.87 pixels and -10.8 pixels (-306.93 μm and -421.2 μm). Maximum standard deviation for length differences was found for the calculated position ( = gold standard) and the original unfiltered images with 13.31 pixels. The standard deviation found for the 5 × 5 mean and median filter was 7.62 pixels and 8.68 pixels.
Different studies showed that noise-suppression filters can induce edge shifts in diagnostic radiographs. The high standard deviations found for length differences between the defined gold-standard and the original images indicate that theoretical edge shifts may not be clinically relevant for length measurements of endodontic files.
本研究旨在评估噪声抑制滤波器是否可能导致数字射线照片中物体的理论边缘移位。大多数制造商在将图像显示给用户之前对其进行噪声抑制滤波。用户通常无法干扰滤波器的功能。使用这些滤波器可能会导致小的图像结构丢失。
将 K 型锉（ISO 尺寸 06、08、10 和 15）放置在位于尸体颌骨段中的 6 个人类牙齿的根管中。由三位观察者在原始和过滤后的数字图像上测量锉尖端的位置。在每个过滤图像上标记锉的位置，并将其与未过滤的图像进行比较。
5×5 像素大小的中值和均值滤波器导致测量长度的最小估计值相差-7.87 像素至-10.8 像素（-306.93μm 至-421.2μm）。最大长度差异标准偏差是在计算位置（=金标准）和原始未过滤图像之间找到的，为 13.31 像素。对于 5×5 均值和中值滤波器，发现的标准偏差分别为 7.62 像素和 8.68 像素。
不同的研究表明，噪声抑制滤波器会在诊断射线照片中引起边缘移位。在定义的金标准和原始图像之间的长度差异的高标准偏差表明，理论边缘移位对于根管锉的长度测量可能在临床上并不重要。
