Southard T E, Southard K A
Department of Orthodontics, University of Iowa, Iowa City.
Oral Surg Oral Med Oral Pathol. 1993 Jun;75(6):767-73. doi: 10.1016/0030-4220(93)90437-9.
The purpose of this investigation was to compare image noise in D- and E-speed radiographic film and to establish a basis for choosing a particular speed of film for study of trabecular changes in alveolar bone. Eleven D-speed and 11 E-speed radiographs were made at varying exposures and developed along with unexposed film of each type to produce uniform optical densities that range from approximately 0.05 to 2.5. Profiles (scan lines) were made of each film at a spatial resolution of 0.02 mm. Noise was quantified for each profile using three measures: the standard deviation of the profile pixel intensity, I(x), about the mean, I(x); the coefficient of variation of I(x) about I(x); and Wiener spectral analysis. Results indicate that the average magnitude of noise for D- and E-speed film over this range of optical densities exceeds 4% and 6%, respectively; the average noise content of E-speed film was 25% to 35% greater than D-speed; and noise energy of both films is concentrated at low spatial frequencies and low optical densities.
本研究的目的是比较D速和E速X线胶片中的图像噪声，并为选择用于研究牙槽骨小梁变化的特定胶片速度建立基础。以不同的曝光量制作了11张D速和11张E速X线片，并与每种类型的未曝光胶片一起显影，以产生范围约为0.05至2.5的均匀光学密度。以0.02毫米的空间分辨率对每张胶片制作轮廓（扫描线）。使用三种测量方法对每个轮廓的噪声进行量化：轮廓像素强度I(x)关于均值I(x)的标准差；I(x)关于I(x)的变异系数；以及维纳频谱分析。结果表明，在这个光学密度范围内，D速和E速胶片的平均噪声幅度分别超过4%和6%；E速胶片的平均噪声含量比D速胶片大25%至35%；并且两种胶片的噪声能量都集中在低空间频率和低光学密度处。
