Since the introduction of digital radiography 3 decades ago, digital systems have largely replaced screen-film radiography at many imaging facilities in the United States. Digital radiography systems use a variety of specialized X-ray detectors, conversion methods, and processing algorithms to convert X-ray energy to numeric data for electronic display, transmission, and storage. In general, digital systems may be categorized as either computed radiography or digital radiography. Computed radiography uses a cassette-based system that is similar to conventional screen-film cassettes, with a separate laser scanning process to extract X-ray intensity data. In contrast, digital radiography uses several approaches to directly convert X-ray energy to digital data without the need for a separate scanning step. Digital detectors are able to produce clinically useful images across a much broader range of input radiation doses than film-based imaging. As a result, it can be difficult for the technologist to determine when a patient is receiving more radiation than needed to obtain a useable image. Exposure indicators and deviation index values have been developed to provide the technologist with feedback about the intensity of radiation received at the detector, and about how this intensity compares with a preset target value. As with screen-film radiography, successful digital imaging requires consideration of many technical factors, including collimation, exposure control, and the use of antiscatter grids. Digital radiography may provide several advantages in comparison with screen-film radiography, including greater ability to manipulate image processing and acquisition parameters, compatibility with electronic recording-keeping and archiving systems, reduced need for film and film processing materials, smaller storage space, and shorter imaging times. This article provides an overview of potential advantages and limitations of digital methods of X-ray detection and processing, how to identify appropriate radiation exposure levels, and other technical considerations.
After reading this article, the participant should be able to:
- Assess 3 different digital radiography methods and describe the basic operating principles of each.
- Describe the use of the Exposure Index and Deviation Index in digital radiography.
- Discuss advantages and disadvantages of digital radiography.
- Identify factors that contribute to excess radiation exposure.
Categories: Digital Radiography, X-Ray/Radiography