Understanding Chest X-ray Opacity: A Guide to Radiodensity

Radiopacity describes the ability to absorb X-rays, the higher the opacity, the less X-rays can penetrate a substance. The less X-rays that reach the film, the whiter the area will be.

Bones and soft tissue have different radiopacities. Bones are heavily calcified and appear white on chest x-rays, whereas soft tissue allows X-rays to pass through much more easily and so appear dark/black.

Opacity of a Chest X-ray:

* Bone: White/hyperdense

* Muscle: Gray

* Fat: Black/hypodense

* Air: Deep Black

Note: Contrast agents, such as iodine-containing contrast, barium, or air can drastically alter the radiopacity of structures.