Radiation safety considerations for diagnostic radiology personnel.

In radiation protection, the guiding philosophy is ALARA (as low as reasonably achievable), and states have regulatory authority. Dose limits are in part based on effective dose equivalent and differences in tissue sensitivities. In diagnostic radiology, the main source of occupational dose is scattered radiation from the patient--particularly from fluoroscopically guided procedures. Personnel stand near patients for long times, and angulated geometries with C-arm equipment may result in high personnel doses from backscatter. For all procedures, judicious applications of time, distance, and shielding affect dose. Appropriate use includes collimating properly, optimizing beam-on time, minimizing distances between image intensifier and patient, ensuring sufficient distance between patient and x-ray tube, and optimizing exposure rates for image quality and dose. Although dose limits typically regulate maximum whole-body dose, protective clothing worn by fluoroscopists reduces personnel risks; weighting factors can be applied to estimate effective dose equivalent. Pregnant personnel have lower limits, which apply only with voluntary declaration of pregnancy. With appropriate precautions, fetal doses can typically remain within recommended limits without changes in occupational tasks. Radiation workers in each state must ensure that regulations are appropriate. Then, for protection of both employee and employers, the rules can and must be followed.