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.

Adult↗

PubMedDate not supplied

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.

Evaluation Studies as Topic↗

PubMedDate not supplied

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)

Humans↗

PubMedDate not supplied

Selective archiving of radiologic images.

The increasing number of radiographic images is a problem in most radiology departments. The problem will be emphasized with the introduction of digital acquisition and storage of radiographs. Changes in image management strategies will therefore become necessary. Such strategies will have great technologic and financial impact and will probably determine the applicability and success of digital radiography. Based on the experience that not all radiographs are equally important and on the assumption that not every image in a radiology archive can be maintained on-line, we investigated the effect of storing only selected, clinically informative radiographs; i.e., clinical data compression. In 165 routine examinations (77 barium enemas, 16 barium meals and 72 urographies) 2433 films were used (14.7 films per examination). We archived only the 461 films (19%) which were considered to be of future informative value. During a one-year follow-up period none of the 1972 removed films was requested. This indicates that a considerable number of films and a considerable amount of image data can be removed from the archive without affecting the clinical work.

Humans↗

PubMedDate not supplied

Digital chest radiography with a large image intensifier. Evaluation of diagnostic performance and patient exposure.

A digital system for chest radiography based on a large image intensifier was compared with a conventional film-screen system. The diagnostic performance was evaluated with special reference to the digital monitor images with a modified version of receiver operating characteristic (ROC) analysis--free response ROC (FROC) analysis--on a chest equivalent phantom. Measurements of spatial resolution and energy imparted were also performed. The detectability of low-contrast objects as well as spatial resolution was better for the full-size film-screen radiographs than for both the digital monitor images and the 100 mm photofluorograms. The image-intensifier system has a potential for considerable dose savings in relation to the conventional technique provided that fluoroscopy is excluded in the positioning of the patients.

Energy Transfer↗

PubMedDate not supplied

Enhanced myocardial protection from preoperative carbohydrate infusion in addition to maintained beta-blockade.

In this study, 28 patients with maintained beta-blockade underwent coronary artery bypass grafting. Twelve of these patients, who received preoperative infusion of carbohydrate-phosphate solution, had a smaller cumulated leakage of CK-B compared to the others, suggesting reduced myocardial damage.

Adrenergic beta-Antagonists↗

PubMedDate not supplied

Cardiac output determination during intravenous cardioangiography using x-ray fluorescence analysis.

Cardiac output was determined with an indicator dilution technique during digital venous angiography of the left ventricle in 11 patients. The contrast medium injected into the right atrium was used as indicator. During and after the injection of contrast medium one blood sample per second was obtained through a catheter placed in the descending aorta. The samples were analyzed for iodine content with x-ray fluorescence analysis and cardiac output determined ad modum Stewart-Hamilton. Thermodilution was used as a reference method. The results indicate that the indicator dilution method with the use of contrast medium might be used for calibration of videodensitometric methods for blood flow measurements.

Adult↗