Which of the following factors influence patient radiation dose?

• A. 1, 2 and 3
• B. 1 and 2
• C. 2 and 3
• D. 1 and 3

Answer: (A)

Dose to a patient is determined by a combination of three broad influences: the exposure technique factors used to generate the beam, the geometry of the exposure, and the patient’s own characteristics. The technique factors set how much energy is delivered to the tissues—higher tube current or longer exposure time increases the number of photons interacting with the body, raising dose, while beam quality and filtration shape how that energy is deposited. The geometry, including how large the irradiated field is and how close the tube is to the patient, governs how much tissue actually receives that energy; a larger field or shorter distance generally increases the dose to the patient. The patient’s size and tissue composition affect how easily X-rays penetrate and how much exposure is required to obtain a diagnostic image; larger or denser patients typically need more exposure, which raises dose, whereas smaller patients need less. Because all three areas influence dose, acknowledging all of them provides the correct, comprehensive understanding of what drives patient radiation dose.