The AAPM/RSNA Physics Tutorial for Residents: Clinical Applications of Basic X-ray Physics Principles

The application of basic x-ray physics principles to clinical radiography requires consideration of many factors that have complex interrelationships. For any given radiographic examination, proper understanding and application of each of these factors is essential. The exposure factors - tube voltage, tube current, and exposure time - determine the basic characteristics of radiation exposure to the patient and image receptor. In addition, equipment factors (focal spot size, grid use, x-ray generator design) and geometry (source-object distance and source-image receptor distance) also influence patient dose and the quality of the radiograph. The basis for evaluation of exposure parameter selection is the optimization of image quality, including contrast, density, motion unsharpness, and geometric unsharpness, while minimizing patient exposure. Selection of radiographic technique often involves consideration of trade-offs between various measures of image quality and exposure.