Which term is used to denote structures that appear lighter on a radiograph?

• A. Radiolucency
• B. Radiopacity
• C. Density
• D. Contrast

Answer: (B)

The key idea is that how light or dark a structure looks on a radiograph reflects how much X-ray radiation it blocks. Structures with high density absorb more X-rays and therefore appear lighter on the image. This property is called radiopacity, and the structures described as radiopaque show up as light or white. In contrast, radiolucent areas are darker because they transmit more X-rays. Density is a broader term about how light or dark an image is in general, and contrast refers to the difference in density between adjacent structures, not to a single structure’s appearance. So the term for structures that appear lighter is radiopacity.