Influence of the characteristic curve on the clinical image quality of lumbar spine and chest radiographs

Abstract

The "European Guidelines on Quality Criteria for Diagnostic Radiographic Images" do not address the choice of the film characteristic (H&D) curve, which is an important parameter for the description of a radiographic screen-film system. The image contrast of clinical lumbar spine and chest radiographs was altered by digital image processing techniques, simulating images with different H&D curves, both steeper and flatter than the original. The manipulated images were printed on film for evaluation. Seven experienced radiologists evaluated the clinical image quality by analysing the fulfilment of the European Image Criteria (ICS) and by visual grading analysis (VGA) of in total 224 lumbar spine and 360 chest images. A parallel study of the effect of the H&D curve has also been made using a theoretical model. The contrast (DeltaOD) of relevant anatomical details was calculated, using a Monte Carlo simulation-model of the complete imaging system including a 3D voxel phantom of a patient. Correlations between the calculated contrast and the radiologists' assessment by VGA were sought. The results of the radiologists' assessment show that the quality in selected regions of lumbar spine and chest images can be significantly improved by the use of films with a steeper H&D curve compared with the standard latitude film. Significant (p<0.05) correlations were found between the VGA results and the calculations of the contrast of transverse processes and trabecular details in the lumbar spine vertebrae, and with the contrast of blood vessels in the retrocardiac area of the chest.

Comparison of visual grading and free-response ROC analyses for assessment of image-processing algorithms in digital mammography

“…From this, it is doubtful that the fulfilment of the investigated quality criteria for the visualisation of normal structures in a VGA experiment is sufficient for accurate detection of microcalcifications. Similar results, but for a different clinical task, were found in the Tingberg et al study [29]: they investigated the correlation between a VGA experiment and the objective ROC study for the detection of lumbar lesions, and also found no agreement between the two methods.…”

“…Correlation between VGA experiments and more objective ROC studies has previously been investigated, but the results of the few published studies are contradictory [28][29][30]. Pilgram et al [28] found a strong correlation between diagnostic performance and the subjective evaluation of image quality on the diagnosis of craniosynostosis.…”

“…They studied in detail the responses of one observer, who read radiographs having different image quality (obtained with three different methods) for a set of patients with this diagnosis and found that the increase in diagnostic performance resulted primarily from increased specificity, suggesting that, when image quality is being evaluated, specificity and the evaluation of normal structures should be the focus of attention. In the studies of Tingberg et al [29,30], the influence of different characteristic curves on the diagnostic quality of radiographs of the lumbar spine and the chest evaluated with both VGA and free-response forced error (FFE) (an ROC variant) experiments showed mixed results. In the first experiment [29], lumbar spine images were manipulated by adding artificial lesions, and image processing was applied to simulate image appearance from three different screen-film combinations; VGA evaluation and FFE results were in good agreement.…”

“…In the studies of Tingberg et al [29,30], the influence of different characteristic curves on the diagnostic quality of radiographs of the lumbar spine and the chest evaluated with both VGA and free-response forced error (FFE) (an ROC variant) experiments showed mixed results. In the first experiment [29], lumbar spine images were manipulated by adding artificial lesions, and image processing was applied to simulate image appearance from three different screen-film combinations; VGA evaluation and FFE results were in good agreement. In the later paper [30], the authors found that images with greater contrast than the original had significantly improved image quality in the VGA study although this did not affect detectability in the FFE experiment, indicating that VGA has a stronger discriminative power than FFE.…”

Correlation of the clinical and physical image quality in chest radiography for average adults with a computed radiography imaging system

“…The monitors were calibrated to national standards [27]. Image criteria were based on the Council of European Communities (CEC) Quality Criteria [28], slightly revised to reflect modern diagnostic requirements and experiences of other groups [29][30][31][32][33]. Test images (50, 60, 70, 81, 90, 109, 125, 133, 141 and 150 kV) were scored against a reference image at a tube voltage of 102 kV, with negative and positive scores indicating inferior and superior image quality, respectively (tube voltages stated here were those available on the Philips radiographic system).…”