Which factors influence patient radiation dose?

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

Answer: (D)

Patient dose is determined by three interacting areas: technique factors, patient characteristics, and how the study is performed with the equipment. Technique factors—the exposure settings you select (mA, exposure time, and kVp), plus the use of filtration, collimation, grids, and automatic exposure control—directly set how much radiation is produced and how much reaches the patient. Higher exposure settings or longer times raise dose, while appropriate kVp and proper filtration and tight collimation help minimize unnecessary exposure without sacrificing image quality. Patient characteristics such as size and tissue composition dictate how much exposure is needed to obtain a diagnostic image; larger patients typically require more exposure, and shielding of radiosensitive tissues reduces dose to those areas. The way the exam is conducted with the equipment—technique optimization, positioning, distance, detector efficiency, and the goal to avoid repeats—also influences dose. Because each of these areas can change the amount of radiation imparted, all of them contribute to the patient dose.