Digital Imaging and Computer-Aided Diagnosis
Rapid advances in electronics and computer technology over the past 20 years have created new possibilities for imaging with x rays. Specific receptor systems independent of film allow image formation to be recorded in digital form for improved image transportation, manipulation, and storage. Digital imaging systems that use a photostimulable storage phosphor imaging plate, commonly called computed radiography (CR) systems are now used widely in practice.
The primary advantage of a CR system is that it is designed to optimize image optical density and contrast resolution largely independently of incident x-ray exposure levels. For portable bedside radiographic applications, such as in ICUs, CR systems are reported to produce images of very high quality and of consistent optical density (reducing the need for repeated examinations). When incorporated as part of a picture-archiving and communication system (PACS), CR images can be displayed in the clinical wards or ICU within minutes of exposure. For standard inpatient chest radiography, CR images have been reported to be superior to conventional film radiography for the visualization of the mediastinum, retrocardiac region, and subdiaphragmatic recesses, and to be equivalent or superior to conventional film in the detection and evaluation of pulmonary nodules and opacities. comments
Digital images can be viewed at any of a number of workstations distributed around the hospital in the wards, clinics, operating rooms, and teaching conference areas. Prior and current images can be viewed together. The images can be manipulated in various ways to improve accuracy. Moreover, images from several different modalities (eg, chest radiographs, chest CT scans, and MRI scans) can be viewed simultaneously on the workstations. The images can be linked with their corresponding radiologic reports and demographic data, and diagnostic annotations and measurements can be added if needed.
All of a hospital’s images for many years can be archived on relatively small long-term computer archives. Coordination among the hospital information system, radiology information system, and PACS allows all of a patient’s images to be made available whenever needed. In addition to its key clinical role, the PACS database provides a unique research and teaching archive. A further improvement feature of the digital imaging system is the fact that images can be transferred electronically to other institutions. This will have profound implications in the future for centralization of expertise, for teaching and research collaboration, and for improved clinical communica-tion.