Chen S K, Hollender L
Department of Oral Medicine, School of Dentistry, University of Washington, Seattle 98195, USA.
J Dent. 1995 Aug;23(4):205-8. doi: 10.1016/0300-5712(95)91183-n.
Flatbed scanners with the transparency scanning option can be used to digitize radiographs. The physical performance of this type of scanner was studied with regard to the digitizing of radiographs, including the dynamic range, the reproducibility and the homogeneity.
An Artix ArtiScan (Artix Technologies Inc., Milpitas, CA, USA) flatbed scanner with imaging editing software Aldus PhotoStyler (Aldus Corporation, Seattle, WA, USA) was used to digitize a stepped exposure image on Kodak T-MAT G films (Kodak, Rochester, NY, USA). The stepped exposure image was scanned at various locations and with different scanning settings. The pixel values of the resulting digital images were analysed. The stepped exposure image was also scanned by a laser densitometer to measure the optical densities of the steps on the film for comparison.
Using the default scanning settings, the digitized images had pixel values distributed in a narrower range than that of the optical density values of the films. The range of the pixel values was widened by increasing the scanning time. Even then, the resulting pixel value profile was not identical to the optical density profile measured on film. The characteristic curve of this digitizing system was steeper than that of the film. Different pixel value distributions were obtained when the stepped exposure image was scanned at different positions on the scanning field, and when scans were obtained at different times. Reproducible results could be acquired when the images were scanned in the same area of the scanning field without changing the scanning settings and after the power had been on for a few minutes.
In order to obtain digitized radiographs of any reliability from flatbed scanners, these should be carefully calibrated at the operating conditions.
具备透明片扫描功能的平板扫描仪可用于将X光片数字化。针对X光片数字化，研究了这类扫描仪的物理性能，包括动态范围、再现性和均匀性。
使用一台Artix ArtiScan（美国加利福尼亚州米尔皮塔斯市Artix Technologies公司）平板扫描仪及成像编辑软件Aldus PhotoStyler（美国华盛顿州西雅图市Aldus公司），对柯达T-MAT G胶片（美国纽约州罗切斯特市柯达公司）上的阶梯曝光图像进行数字化处理。在不同位置和不同扫描设置下扫描该阶梯曝光图像。分析所得数字图像的像素值。还用激光密度计扫描该阶梯曝光图像，以测量胶片上各阶梯的光密度用于比较。
使用默认扫描设置时，数字化图像的像素值分布范围比胶片的光密度值范围更窄。通过增加扫描时间可拓宽像素值范围。即便如此，所得像素值曲线仍与胶片上测得的光密度曲线不同。该数字化系统的特性曲线比胶片的更陡。在扫描区域的不同位置扫描阶梯曝光图像以及在不同时间进行扫描时，会得到不同的像素值分布。当在扫描区域的同一区域进行扫描且不改变扫描设置，并且在开机几分钟后进行扫描时，可获得可重复的结果。
为了从平板扫描仪获得具有任何可靠性的数字化X光片，应在操作条件下对其进行仔细校准。
