CAMRT Radiography Practice Exam

What part of the x-ray tube is responsible for controlling penumbra?

1. Collimator

2. Focal Spot

3. Filtration

4. Tube housing

The correct answer is: Focal Spot

The part of the x-ray tube that is primarily responsible for controlling penumbra is the focal spot. The focal spot refers to the area on the anode where the x-ray beam is generated. Its size directly influences the sharpness of the image produced during radiographic procedures. A smaller focal spot results in better image resolution and less penumbra, leading to clearer and more defined edges in the radiographic image. A larger focal spot can lead to more pronounced penumbra, resulting in less distinct edges. The other components play supportive roles in the overall function of the x-ray tube but do not specifically control penumbra in the same way. The collimator limits the size of the x-ray beam and can help in reducing scatter, thus indirectly affecting image quality. Filtration helps to remove low-energy x-rays that do not contribute to diagnostic quality but does not influence penumbra. The tube housing protects and contains the x-ray tube, ensuring safety during operation, but it does not affect the quality of the image regarding penumbra.