American Registry of Radiologic Technologists (ARRT) Practice Exam

What is the result of a 15% decrease in KVP on density?

1. Doubles

2. Halves

3. Increases

4. Remains constant

The correct answer is: Halves

A 15% decrease in kilovolt peak (KVP) will lead to a significant reduction in the density of the radiographic image. Density in radiography refers to the degree of darkening on the film or image receptor, which is influenced by the amount of radiation that penetrates the body and reaches the image receptor. When KVP is decreased, the overall energy of the x-ray photons is reduced, which decreases their ability to penetrate the subject being imaged. As a result, fewer photons reach the film or digital detector, ultimately leading to a lighter image. A decrease in KVP by about 15% will typically result in halving the density of the radiograph. This relationship is grounded in the physics of radiation and imaging and is a crucial principle for radiologic technologists to understand in order to produce quality images while minimizing patient dose. Being aware of how changes in KVP affect image characteristics is essential for achieving optimal radiographic quality, particularly in situations that require adjustments based on patient size, body part, or specific examination protocols.