CAMRT Radiography Practice Exam

If the pitch in computed tomography increases, what happens to the dose?

1. Pitch and dose are unrelated

2. Increases

3. Stays the same, as dose is controlled by mAs and kV

4. Decreases

The correct answer is: Decreases

An increase in pitch in computed tomography refers to the ratio of the distance the table moves during one full rotation of the X-ray tube to the width of the X-ray beam. When the pitch increases, it means that the table moves further during this rotation, which results in a larger area being scanned in a given time period. As the pitch increases, the X-ray beam is spread over a larger area, leading to a reduction in the radiation dose per unit area of the scanned tissue. This is because the same amount of radiation is effectively shared over a larger volume, thereby decreasing the exposure to any specific area. Consequently, for a given volume of tissue, the overall dose delivered to the patient decreases as the pitch increases. In clinical practice, a higher pitch can improve scan speed and potentially reduce the overall radiation dose, which is particularly important in keeping patient safety a top priority. This makes the correct answer that an increase in pitch results in a decrease in radiation dose.