Digital Chest Radiography with a Large Image Intensifier

Comparative assessment of digital and analog radiography: diagnostic accuracy, cost analysis and quality of care

OBJECTIVE

The aim of this study was to compare digital and conventional radiography for diagnostic accuracy, direct costs, and quality of care.

MATERIALS AND METHODS

Diagnostic accuracy was assessed by a critical review of the literature on sensitivity, specificity and ROC analysis of these imaging techniques and by a survey with a panel of radiologists. Direct costs and quality of care were evaluated with a before/after study of the implementation of digital radiography in a Department of Radiology in 'Hospices Civils de Lyon' (France). We included 292 patients and measured duration of examinations and direct costs of equipment, films, maintenance and depreciation. To evaluate any changes in working conditions and patient management, a questionnaire was filled out by the staff of the department.

RESULTS

Diagnostic accuracy with digital radiography was equivalent to that of conventional radiography but there were wide variations depending on the type of examination. In 1993, although digital radiography resulted in savings of FF 18,000 including tax (US$ 3600) on film consumption for 1 year of examinations, there was a global additional cost of FF 253,000 (US$ 50,600) for maintenance and depreciation. Results showed a nonsignificant tendency to reduced procedure times for all examinations. Working conditions improved, including greater availability for the patient, improved safety, and increased job interest.

CONCLUSION

Digital radiography can be introduced into a large hospital to improve patient and staff conditions, at a higher cost than analog radiography, and depending on the type of examinations performed by the radiology department.

Digital chest radiography--comparing two types of CRT monitors in a ROC experiment with a chest phantom

Two principally different 1000-line CRT (cathode ray tube) monitors connected to a digital image intensifier system for chest radiography were compared in terms of image quality and viewing comfort. Image quality was assessed by means of ROC analysis. Five observers tried to find simulated pathology positioned over the lungs and the mediastinum of an anthropomorphic phantom. The observers also graded the viewing comfort of the two CRTs in terms of flicker, light levels, and general comfort. No significant difference in the detection of simulated pathology was demonstrated between the two monitors. A slight preference for the newer CRT (Imlogix) was seen as compared to the older standard CRT (Siemens) regarding flicker and general comfort.

Digital fluoroscopic radiology: evaluation of the clinical impact

The use of digital image intensifier radiography (DIIR) for examinations in projection radiography is becoming more common. Fluoroscopic controlled contrast studies (barium- or iodine-based), particularly of the gastrointestinal tract, can be performed quickly and easily with a considerable decrease in radiation exposure. A wide dynamic range permits a constant high image quality with fewer incorrect exposures. The limited spatial resolution of large image intensifier input screens is the major drawback of DIIR. Digital image acquisition enables post-processing, digital storage and transfer of images, thus allowing an integration into PACS-systems. Imaging capabilities and clinical applications are described here.

Digital chest radiography: should images be presented in negative or positive mode?

The observer performance for video monitor images presented in positive mode ('bones black') was compared to that of images presented in negative mode ('bones white') in a digital system for chest radiography based on a large image intensifier. In the first part of the study (I), the original, non-linear grey-scale reversal performed in the computer of the digital image intensifier system (DS1000) was studied together with fixed and variable settings of light and contrast. In the second part of the study (II), true grey-scale reversal performed in a minicomputer (Micro VAX II) where the images were also processed with edge and contrast enhancement, was studied. The time spent viewing the images was also recorded. Before the second part of the study, the image intensifier system was optimized with regard to spatial and contrast resolution and dose settings. Simulated pathology was randomly positioned over the lungs and the mediastinum of an anthropomorphic phantom. Observer performance was evaluated with Receiver Operating Characteristic (ROC) analysis on the digital images. In the first part of the study, a significant advantage for the positive images was seen, but no significant difference between fixed and variable settings of light and contrast. In the second part of the study, no significant difference in the detectability of the test structures was seen between positive and negative images. A significant improvement in the detectability was seen between the first and the second part of the study for the nodules over the mediastinum in both negative and positive images. No significant difference in the time spent observing positive and negative images, was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of optimization and image processing in digital chest radiography: an ROC study with an anthropomorphic phantom

A digital system for chest radiography based on a large image intensifier was compared to a conventional film-screen system. The digital system was optimized with regard to spatial and contrast resolution and dose. The images were digitally processed for contrast and edge enhancement. A simulated pneumothorax and two simulated nodules were positioned over the lungs and the mediastinum of an anthropomorphic phantom. Observer performance was evaluated with ROC analysis. Five observers assessed the processed digital images and the conventional full-size radiographs. The time spent viewing the full-size radiographs and the digital images was recorded. For the simulated pneumothorax, the results showed perfect performance for the full-size radiographs and detectability was high also for the processed digital images. No significant difference in the detectability of the simulated nodules was seen between the two imaging systems. The results for the digital images showed a significantly improved detectability for the nodules in the mediastinum as compared to a previous ROC study where no optimization and image processing was available. No significant difference in detectability was seen between the former and the present ROC study for small nodules in the lung. No difference was seen in the time spent assessing the conventional full-size radiographs and the digital images. The study indicates that processed digital images produced by a large image intensifier are equal in image quality to conventional full-size radiographs for low-contrast objects such as nodules.

Radiographic reporting directly from the TV monitor of a digital chest radiography system

The practical usefulness of a digital large image intensifier system was tested on 400 consecutive, routine chest examinations. Reading and reporting was carried out directly from the digital images on the TV monitors. For each patient images were also read independently from 100 mm photofluorograms. When the reports for each examination were compared, there was total agreement in reporting in 40% of the cases and clinically insignificant differences in interpretation in 56%. In the remaining 16 patients (4%), the opinion of the observers differed as to whether significant disease was present or not. However, these disagreements could not be related to imaging technique. We believe that a majority of chest examinations can be performed with digital technique and can be read directly from the monitor screen.