CAMRT Radiography Practice Exam

How is patient dose affected when field size is increased, assuming all other factors remain constant?

1. Decreased dose

2. No change in dose

3. Increased dose

4. Varies by patient

The correct answer is: Increased dose

When the field size is increased, the patient dose increases. This is primarily due to the larger area of tissue exposed to the radiation beam. With a broader field, more of the patient's body is irradiated, which leads to a higher absorption of radiation by the tissues within the expanded field of view. In radiography, as the field size becomes larger while maintaining the same output from the X-ray tube and consistent exposure time, a larger volume of tissue is subjected to the same dose of radiation per unit area. This means that the overall radiation delivered increases, resulting in a higher cumulative dose to the patient. This principle highlights the importance of beam collimation and optimizing field size to minimize unnecessary radiation exposure to the patient while still achieving the necessary diagnostic quality.