In computed radiography, which term describes the three-dimensional element mapped by a digital image pixel?

• A. Pathology
• B. Density
• C. Voxel
• D. Artifact

Answer: (C)

In digital radiography, a pixel is a two-dimensional element, but the image data correspond to a volume in the object. The three-dimensional element described by a digital image pixel is a voxel, which stands for a volumetric pixel and represents a small volume of tissue whose attenuation contributes to the pixel’s brightness. This voxel concept is why the image appears as a 2D grid even though it conveys information about a 3D structure.

Pathology and artifact are not geometric elements of the image, and density refers to the brightness or attenuation value shown, not the 3D element itself.