The AAPM/RSNA physics tutorial for residents. Typical patient radiation doses in diagnostic radiology.

ABSTRACT

Factors affecting patient dose in all x-ray imaging modalities include beam energy, filtration, collimation, patient size, and image processing. In conventional radiography, the most important determinant of acceptable patient dose is use of the highest peak kilovoltage that results in diagnostic images. Digital radiography allows a much wider range of exposures than conventional radiography for producing diagnostic images. However, operators must be aware of the subtle differences in techniques used with digital systems to avoid unnecessary increases in patient dose. Low-dose mammography requires lower ranges of peak kilovoltage; different target materials, filters, and screen-film combinations; special attention to breast thickness, composition, and compression during the study; and different standards for grids, magnification, and optical density. Although peak kilovoltage and tube current are important for controlling patient dose in fluoroscopy, collimation, source-to-skin and patient-to-image intensifier distances, and control of beam-on time have perhaps greater importance. Computed tomography (CT) involves greater patient dose than conventional radiography, and, although the primary radiation dose is delivered to smaller volumes, dose calculations must account for dose received by adjacent tissue sections. Many variables are involved in fetal exposure and fetal dose effects, but a solid understanding of them can help in developing responsible patient management practices.