CAMRT Radiography Practice Exam

Which of the following is a low-attenuation structure?

1. Iodine filled aorta

2. Rib

3. Calcified arteries

4. Trachea

The correct answer is: Trachea

The trachea is indeed a low-attenuation structure. In radiographic imaging, structures that have a low density or lower atomic number interact less with X-rays, allowing more radiation to pass through them compared to denser structures. This results in a darker appearance on the radiograph. The trachea is primarily composed of cartilage and is filled with air, which contributes to its low attenuation. Air is one of the lowest-attenuation substances seen in imaging, making the trachea appear more radiolucent on X-rays. In contrast, iodine-filled aorta, rib, and calcified arteries are all denser structures. The iodine-filled aorta, for instance, is designed to be highly attenuating due to the contrast material used, which enhances visibility in imaging. Ribs and calcified arteries are composed of bone and dense tissue, making them high-attenuation structures that absorb more X-rays and therefore appear whiter on radiographs.