What is the appearance of positive contrast on a radiograph?

Positive contrast agents, such as barium or iodine, are used in radiography to enhance the visibility of specific structures within the body. These contrast agents have high atomic numbers, which means they absorb more X-rays compared to surrounding tissues. When X-rays pass through an area containing a positive contrast agent, fewer X-rays reach the film or digital detector. This results in the area appearing lighter or white on the radiograph.

The appearance of white is critical in diagnosing conditions as it allows radiologists to identify abnormalities or changes in the anatomy that would otherwise be difficult to visualize. In contrast, negative contrast agents (like air) would appear darker on a radiograph, outlining structures in a different way.