Projection X-ray Imaging: Radiography, Mammography, Fluoroscopy

Recent advances in digital detector technology for medical radiography and fluoroscopy have resulted in improved workflow efficiency, operational flexibility, image quality, and diagnostic accuracy. This is attributed to the implementation of portable flat-panel x-ray detector devices able to provide real-time readout, processing, and display of medical images. As a result, digital radiography flat-panel detectors are rapidly replacing computed radiography passive detectors for projection imaging exams and image intensifier detectors for dynamic fluoroscopy exams. Advanced exam capabilities now include digital tomosynthesis and dual-energy radiography; the former is based on rapid acquisition of multiple angle-dependent image projections to synthesize tomographic slabs at selectable depths within the patient, and the latter is based on rapid back-to-back acquisition of the same anatomy at low and high x-ray energies to generate separate soft tissue and bone images. In both situations, superimposition of anatomy is reduced or eliminated, with the possibility of enhanced diagnostic confidence. Increased x-ray absorption efficiency and lower electronic noise of digital radiography detectors compared to computed radiography detectors enable equal image quality at lower patient dose; however, because of a disconnect between image appearance and radiation dose, lower patient dose is not always achieved. Education, training, and implementation of standards such as the International Electrotechnical Commission 62494-1 Digital Radiography Exposure Index are needed to ensure image quality at the lowest appropriate radiation dose. The National Council on Radiation Protection and Measurements can contribute to radiation responsibility in medical imaging by providing guidance on use of digital radiography, including recommendations for acquisition protocols and exposure index standards, for development of radiographic exam diagnostic reference levels, and for oversight of retake and reject analysis.