CAMRT Radiography Practice Exam

Where should the cathode be positioned in relation to the patient for optimal imaging using the anode heel effect in chest decubitus position?

1. On the side that is elevated

2. On the side that is down

3. At the midline of the patient

4. On the opposite side of the imaging plate

The correct answer is: On the side that is down

Positioning the cathode on the side that is down during chest decubitus imaging takes advantage of the anode heel effect, enhancing the image quality. The anode heel effect refers to the phenomenon where X-ray intensity is greater on the cathode side of the X-ray tube compared to the anode side. This is because the X-ray beam is more intense at the cathode due to the geometry of the X-ray tube and the higher energy X-rays produced there. In a decubitus position, where the patient is lying on one side, the side that is down will receive a higher dose of X-ray photons. This helps to improve exposure in the region of interest, typically the chest, which can help in better visualization of anatomical structures such as the mediastinum and lungs. By placing the cathode down, you maximize the density in the area of interest while minimizing it in areas that might not require as much detail, which is especially useful when differentiating between the lungs’ structures. Other positioning options, such as having the cathode at the midline or on the opposite side of the imaging plate, would not utilize the benefits of the anode heel effect effectively. Having the cathode elevated or midline would lead to a