Biomedical subjects

S Kheddache

Publications and source records attributed to S Kheddache.

14 recordsLinked to original sources

PubMed2000

The influence of different technique factors on image quality of lumbar spine radiographs as evaluated by established CEC image criteria.

In this study we have investigated the image quality of lumbar spine radiographs taken after recording technical and physical parameters. Two technical parameters were altered, tube voltage (70 kV and 90 kV for the anteroposterior (AP) projection and 77 kV and 95 kV for the lateral projection) and sensitivity of the film-screen system (sensitivity class 400 and 600). In total, 85 images were included in the study. Entrance surface dose (ESD) was measured using thermoluminescent dosemeters. The mean value of ESD for the different technique groups varied between 1.9 mGy (90 kV, sensitivity class 400) and 4.6 mGy (70 kV, sensitivity class 400) for the AP projection, and between 6.4 mGy (95 kV, sensitivity class 600) and 20.4 mGy (70 kV, sensitivity class 400) for the lateral projection. Image criteria given in the "European Guidelines on Quality Criteria for Radiographic Images" were used to assess image quality. Two evaluation methods have been employed. A straightforward scoring of fulfilled image criteria, and visual grading analysis using the structures defined in the image criteria. The latter method provided a sharper distinction between groups of images taken using different radiographic techniques. The average number of fulfilled image criteria for the AP projections varied between 0.74 (90 kV, sensitivity class 400) and 0.87 (70 kV, sensitivity class 400). For the lateral projection this number varied between 0.79 (95 kV, sensitivity class 600) and 0.84 (77 kV, sensitivity class 600). This study shows that image criteria are useful tools in clinical studies of image quality.

Adolescent↗

PubMed1999

Storage phosphor and film-screen mammography: performance with different mammographic techniques.

The aim of this study was to compare the image quality of storage phosphor plates with that in screen-film radiograms in mammography. Two anode/filter combinations were also compared--Mo/Mo and W/Rh. S Storage phosphor plates, generation IIIN (Fuji, Tokyo, Japan) and a conventional screen-film system (Kodak, Rochester, N. Y.) were evaluated using two mammographic units. One unit had a 0.6-mm focal spot, an anode/filter combination of Mo/Mo and no grid (AMo); the other had a 0.3-mm focal spot, a grid, and two possible combinations of anode/filter Mo/Mo (BMo) and W/Rh (BW). Simulated tumours and microcalcifications were randomly positioned in an anthropomorphic breast phantom (RMI model 165, no. 210-009, Radiation Measurements Inc., Middleton, Wisconsin). The image quality was evaluated using a modified version of receiver operating characteristics analysis. Five observers evaluated 300 films and 300 hard copy images each. Radiation doses were also determined. The image quality of the conventional screen-film images was significantly better than that for the storage phosphor plate mammograms. The BMo system rated best, for the detection of both tumours and microcalcifications, although it was not significantly different from the BW system. Systems BMo and BW rated significantly better than the AMo system for both image receptors studied. The mean absorbed dose was twice as high for the BMo system as for the AMo and BW systems for both conventional and digital technique. The mammograms produced with the screen-film combination gave a significantly better detectability than the storage phosphor plates used in this study. Substantial dose reduction could be achieved using an anode/filter combination of W/Rh instead of Mo/Mo with no significant loss of information in the images.

Breast Diseases↗

PubMed1999

Image quality for five modern chest radiography techniques: a modified FROC study with an anthropomorphic chest phantom.

The purpose of the study was to compare the image quality for one conventional and four digital chest radiography techniques. Three storage phosphor systems, one selenium drum system, and one film-screen system were compared using a modified receiver-operating-characteristics method. Simulated pathology was randomly positioned over the parenchymal regions and the mediastinum of an anthropomorphic phantom. Eight observers (four chest radiologists, one specialist in general radiology, one hospital physicist, and two radiographers) evaluated 60 images for each technique. The selenium drum system (Philips, Eindhoven, The Netherlands) rated best for the detection of parenchymal nodules. Together with the storage phosphor system of generation IIIN (Philips/Fuji), the selenium drum system also rated best for detection of thin linear structures. The storage phosphor system of generation V (Fuji) rated best for the detection of mediastinal nodules. The first generation of the storage phosphor system from Agfa (Mortsel, Belgium) rated worst for the detection of parenchymal nodules and thin linear structures. These differences were significant (p < 0.0001). Averaging the results for all test objects, the selenium drum system and the storage phosphor system of generation V were significantly better than the other systems tested. The film/screen system performed significantly better than the first-generation storage phosphor system from Agfa, equal to the generation IIIN storage phosphor system (Philips/Fuji) and significantly worse than the selenium drum system (Philips) and the generation-V storage phosphor system (Fuji). The conclusion is therefore that the image quality of selenium-based digital technique and of the more recent generations of storage phosphor systems is superior to both conventional technique and storage phosphor systems using image plates of older types.

Anthropometry↗

PubMed1997

Digital mammography using storage phosphor plate technique--optimizing image processing parameters for the visibility of lesions and anatomy.

Digital mammograms from a storage phosphor plate system for general radiography were compared to conventional mammograms by means of visual grading analysis (VGA). For the digital images, image processing parameters were optimized and evaluated through observer preference analysis (OPA). The results of the VGA showed significantly better gradings for the conventional mammograms for parenchyma, linear structures, and cysts, and significantly better gradings for the digital mammograms for the skin surface. For calcifications, no significant difference was seen. For the OPA, contrast enhanced mammograms graded significantly best. Using standard image processing, the digital mammograms were considered as adequate for diagnosis in 49% of the cases, as uncertain in 20%, and as inadequate in 31%. However, the observers differed considerably in their gradings both in the VGA and in the OPA.

Calcinosis↗

PubMed1996

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.

Computers↗

PubMed1996

Digital chest radiography--optimizing image processing parameters for the visibility of chest lesions and anatomy.

The effect of varying the degree of contrast and edge enhancement upon the visibility of chest lesions and anatomy was evaluated in a digital image intensifier system for chest radiography. Visual grading analysis was used as method for the evaluation. Conventional radiographs served as reference images. Ten observers graded the visibility of four regions of interest: (1) fine linear structures, (2) mediastinal anatomy, (3) rounded opacities, (4) vessels, and also graded the overall quality of 17 chest images. The images had been subjected to three grades of image processing: one basic, one intermediate, and one extreme. In all, 2730 observations were made. The basic image processing was the best for the visibility of regions 2, 3, and 4 and for the overall quality. The intermediate image processing was best for the fine linear structures. The extreme image processing rated lowest for all regions and especially for the overall quality.

Humans↗

PubMed1993

In search of optimum chest radiography techniques.

A nation-wide study of chest radiography in Sweden had previously revealed a large variation in the physical and technical factors involved, in particular the radiation dose. In this study the image quality could not be assessed unambiguously. The aim of the present study was to try to establish a correlation between visual grading of radiographs and physical and technical factors in order to find the optimum chest X-ray system. The physical and technical performance of 24 chest units was evaluated. Radiographs were taken of an anthropomorphic chest phantom supplied with test structures simulating various pathologies. Image quality was assessed by visual grading analysis of the radiographs. The physical and technical parameters of the units rated best were used to exemplify good radiographic practice. The results were in agreement with the recommendations issued by the Commission of the European Communities (CEC). It was also shown that low radiation dose is compatible with high-quality radiographic imaging of the chest.

Humans↗

PubMed1993

Image intensifier based digital chest radiography. Visibility of lesions and anatomy.

Contrast- and edge-enhanced digital monitor images from an image intensifier system for chest radiography were compared to conventional radiograms using visual grading analysis. Eleven observers graded the visibility of rounded opacities, the carinal region, fine line structures, and also compared the overall quality of images from 20 patients. The results showed significantly better visibility on the digital monitor for the rounded opacities and the mediastinum compared to the conventional radiograms. The overall quality of the digital images was also considered better. However, the digital images showed significantly inferior visibility for the line structures in comparison with the conventional radiograms. Our study indicates that the present contrast- and edge-enhanced digital images, with a spatial resolution of 1,024 x 1,024 pixels and a contrast resolution of 8 bits, are superior to conventional radiograms for the visualization of mediastinal anatomy and rounded opacities. The clinical importance of the inferior visibility of fine line structures is not clear.

Adult↗

PubMed1992

Chest x ray films from construction workers: International Labour Office (ILO 1980) classification compared with routine readings.

The extent of agreement between International Labour Office (ILO) and clinical readings of chest x ray films from construction workers was studied. From a survey of 5898 workers 258 subjects with a profusion of small opacities of > or = 1/1 and a stratified sample of subjects with profusion < 1/1 were selected. Only 41% of the films classified as ILO profusion category > or = 1/1 were clinically recorded as non-normal for the parenchyma. The proportion of films recorded as pneumoconiotic (or possibly so) was especially low for irregular opacities (22%), but increased with the profusion category (both rounded and irregular) as well as with the size of rounded opacities (p 3/11, q 12/25, r 3/4). Only with the profusion category > or = 2/1 were most of the films recorded as pneumoconiotic. The specificity and sensitivity were highest in the geographical areas where a few clinical readers had assessed many films each. The proportion of false negative clinical reports was low for circumscribed pleural thickening of the chest wall (9%) and diaphragmatic pleural thickening (6%). For calcified pleural changes and for the combination of diffuse pleural thickening and obliteration of the costophrenic angle, false negative reports were absent. The present study shows an unsatisfactory sensitivity for clinical compared with ILO readings as a means for screening the parenchyma of workers with a risk of pneumoconiosis.

Humans↗

PubMed1989

Digital chest radiography with a large image intensifier. An ROC study with an anthropomorphic phantom.

The diagnostic performance of two systems for chest radiography was studied. One system was based on a large image intensifier, the other was a conventional film-screen system. The images from the image intensifier were studied either on a digital TV screen or on 100 mm photofluorograms. Receiver operating characteristic curve analysis was performed on images of an anthropomorphic chest phantom. Low-contrast MMAP (methyl methacrylate polymer) nodules and simulated vessels were positioned over the parenchymal and the mediastinal region of the phantom. Five observers assessed the digital monitor images, photofluorograms, and conventional full-size radiograms. The results showed a significantly superior detectability for the full-size radiograms over the digital monitor images both in the parenchyma and in the mediastinum. No significant difference was found between photofluorograms and digital images.

Humans↗

PubMedDate not supplied

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.

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

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↗