A digitization process is normally divided into two stages: the sampling stage, in which its
spatial resolution is defined, and the quantization stage, in which the resolution of the gray
tones of the image is defined. These two stages are very important, because they determine
the level of information that the image will contain after being digitized [6, 7, 8]. There are
some methods for digitizing of radiographs that will be described briefly below.
2.1 Photography with CCD (Charge-Coupled Device) Cameras
Charge-coupled devices are the most widely used equipment for image digitization. Initially,
X-ray films were digitized by placing them on a lightbox and photographing them with a
CCD camera [9, 10, 11, 12]. In this process, the energy of the light photons captured by the computer to be processed digitally with the purpose of removing noise, improving contrast,
and segmentation.
camera is converted into voltage for each image pixel; the number of pixels is determined
from spatial resolution. Then, each voltage of the pixels corresponds to a gray level
(resolution of gray levels). Then the digitized radiographic images are transferred to the