CAMRT Radiography Practice Exam

For a large plaster cast, by how much should kVp be increased?

1. 2 - 4 kVp

2. 5 - 7 kVp

3. 8 - 10 kVp

4. 10 - 12 kVp

The correct answer is: 8 - 10 kVp

Increasing the kilovolt peak (kVp) when imaging through a large plaster cast is necessary to ensure adequate penetration of the x-rays through the dense material. Plaster casts are dense and can significantly attenuate x-ray beams, reducing the amount of radiation that reaches the detector or film. The recommended increase of 8 to 10 kVp is appropriate for larger plaster casts because this range is generally sufficient to enhance contrast and image quality while minimizing patient exposure. By adjusting the kVp upwards, the x-ray beam becomes more penetrative, allowing for a clearer image of the underlying structures, such as bones or soft tissues, which might otherwise be obscured by the cast. Lower increases in kVp (2-4 kVp or 5-7 kVp) may not provide enough enhancement for larger casts, leading to potential issues such as increased image unsharpness or missed diagnoses due to insufficient exposure. Likewise, a larger increase beyond 10 kVp could lead to over-penetration, resulting in lost detail and decreased image contrast, which is not desirable in diagnostic radiography. Therefore, the 8 to 10 kVp adjustment strikes an optimal balance for ensuring image quality while effectively compensating for the added material density of large plaster