Correct Option
Barium sulphate is administered as a contrast agent in X-ray examinations of the gastrointestinal tract. It is a radiopaque substance, meaning it effectively absorbs X-rays and prevents them from passing through. When ingested, it coats the internal lining of organs like the stomach, creating a clear outline on the X-ray image. This absorption of X-rays by barium makes the stomach appear as a distinct, bright area against the darker background of surrounding tissues, thereby enhancing the contrast and enabling radiologists to identify abnormalities such as ulcers, tumors, or blockages.
Incorrect Options
Option (a) is incorrect. Barium is not transparent to X-rays; rather, it is radiopaque, meaning it significantly absorbs X-rays and prevents their transmission. This property is crucial for its function as a contrast agent.
Option (b) is incorrect. Standard diagnostic imaging of the stomach primarily utilizes X-rays, not gamma rays. While barium is an effective absorber, its role in this context is specific to X-ray absorption, not gamma ray absorption.
Option (d) is incorrect. While barium sulphate is a white compound, its ability to enhance visibility in an X-ray image is due to its high atomic number and density, which lead to significant X-ray absorption (radiodensity), not its visible light colour. The X-ray image is formed based on differential absorption of X-rays, not visible light reflection.