RESUMEN
OBJECTIVES: Relatively low signal/noise (S/N) ratios, which are not substantiated by the results reported here, have been reported for the DenOptix digital intraoral radiography system. Unexplained poor performance has also been reported for imaging of the gingival tissue. I sought to discover the probable sources of the discrepancies and to present data on the effects of pixel size and screen type on noise and resolution. Methods. S/N ratios were measured with an aluminum phantom, and noise was measured with a step-wedge. The radiographs were scanned with both default and special, manufacturer-supplied software to obtain 8-bit rescaled data and 16-bit raw data. The data were compared with previously published data for the DenOptix and Digora systems. RESULTS: The S/N ratios of up to 17 obtained here were much higher than previously reported. Previously reported low ratios and poor performance for the imaging of gingival tissue were likely caused by digital clipping of 8-bit images, which should not affect bony tissue images in normal clinical radiographs. With nonstandard white phosphor screens, S/N ratios of up to 18 were observed, with only a minor loss of resolution. For the smallest pixel size (42 micro m), resolutions of > or =10 line-pairs/mm and > or =8 line-pairs/mm were observed for standard blue and white phosphor screen types. If the smallest pixel size is selected, the noise increases by only 25%, which is much less than the theoretical increase. CONCLUSIONS: In terms of both noise and resolution, the DenOptix system compares favorably with the Digora system. S/N ratios for the DenOptix system are comparable with the best of 6 previously tested systems. With the DenOptix system, the smallest pixel size produces both the best resolution and the best noise characteristics. The selection of 16-bit images prevents digital clipping of 8-bit images.
Asunto(s)
Procesamiento de Imagen Asistido por Computador , Intensificación de Imagen Radiográfica , Radiografía Dental Digital , Aluminio , Encía/diagnóstico por imagen , Humanos , Procesamiento de Imagen Asistido por Computador/instrumentación , Procesamiento de Imagen Asistido por Computador/métodos , Fantasmas de Imagen , Intensificación de Imagen Radiográfica/instrumentación , Intensificación de Imagen Radiográfica/métodos , Radiografía Dental Digital/instrumentación , Radiografía Dental Digital/métodos , Pantallas Intensificadoras de Rayos X/clasificaciónRESUMEN
OBJECTIVE: To determine the sensitometry and 'cross-talk' of a twin screen-film cassette and to assess its clinical potential. MATERIALS AND METHODS: The twin cassette utilises two sets of screens, divided by filter material, to provide an optimised image of the mediastinum and the lungs. The exposure difference for the two images was measured sensitometrically. The contribution to film density of visible light and K-characteristic radiation, from adjacent screens in the absence of a dividing filter, was investigated. RESULT: Clinical experience indicated that an exposure difference of 3.4 between the front and back screens, was optimal. Visible light and K-characteristic radiation from the front screens, contributed up to 20 and 24% respectively, of the back film exposure and screen absorbed energy respectively. This was reduced to 0 and 6% with the use of the filter. CONCLUSIONS: The twin screen-film cassette provides extended latitude to enable optimal visualisation of the lung and mediastinal regions. Adjacent screen 'cross-talk' has been overcome to allow standard and portable chest applications.
Asunto(s)
Pulmón/diagnóstico por imagen , Mediastino/diagnóstico por imagen , Radiografía Torácica/métodos , Pantallas Intensificadoras de Rayos X , Absorción , Artefactos , Análisis Costo-Beneficio , Filtración/instrumentación , Humanos , Luz , Dosis de Radiación , Intensificación de Imagen Radiográfica/economía , Intensificación de Imagen Radiográfica/instrumentación , Intensificación de Imagen Radiográfica/métodos , Radiografía Torácica/economía , Radiografía Torácica/instrumentación , Dispersión de Radiación , Tecnología Radiológica/economía , Tecnología Radiológica/instrumentación , Tecnología Radiológica/métodos , Película para Rayos X , Pantallas Intensificadoras de Rayos X/clasificación , Pantallas Intensificadoras de Rayos X/economía , Rayos XRESUMEN
OBJECTIVE: A new twin screen-film cassette system optimised for conventional chest radiography was evaluated by four thoracic radiologists. MATERIALS AND METHODS: The twin screen-film cassette system produces two film images, the front film optimised for the mediastinal region of the chest, the rear for the lung region. Image degradation on either screen-film system due to internal photon scatter has been virtually eliminated due to the use of a dividing filter. Fifty patients were included in a trial that resulted in a set of chest images for each patient, taken on the same inspiration, by both the twin screen-film cassette and the conventional system. The resultant fifty sets of images were evaluated by four chest radiologists who scored 12 radiographic features of the chest and patient pathologies present, using a paired difference technique. RESULTS: The image quality of the twin screen-film cassette system was judged to be significantly superior to the conventional screen-film system in nine of the 12 radiographic features scored (P < 0.003). In the three other regions and for the patient pathologies, no significant conclusions were drawn. CONCLUSION: The new twin screen-film system showed improved visualisation of radiographic features, particularly in the mediastinal and retrocardiac lung regions. This new system shows promise in both standard and portable clinical applications.
Asunto(s)
Pulmón/diagnóstico por imagen , Mediastino/diagnóstico por imagen , Radiografía Torácica/métodos , Pantallas Intensificadoras de Rayos X , Análisis Costo-Beneficio , Diseño de Equipo , Estudios de Evaluación como Asunto , Filtración/instrumentación , Humanos , Pulmón/irrigación sanguínea , Enfermedades Pulmonares/diagnóstico por imagen , Fotones , Dosis de Radiación , Intensificación de Imagen Radiográfica/economía , Intensificación de Imagen Radiográfica/instrumentación , Intensificación de Imagen Radiográfica/métodos , Radiografía Torácica/economía , Radiografía Torácica/instrumentación , Costillas/diagnóstico por imagen , Dispersión de Radiación , Pantallas Intensificadoras de Rayos X/clasificación , Pantallas Intensificadoras de Rayos X/economíaRESUMEN
The paper provides the technical parameters and data of intensifying X-ray screens made in Russia. They cover both energy properties (sensitivity, spectral characteristics) and the quality of an image (frequency-contrast characteristics, granulation). It is shown in what cases this or that class of screens is preferable to be used.
Asunto(s)
Pantallas Intensificadoras de Rayos X , Diseño de Equipo , Federación de Rusia , Sensibilidad y Especificidad , Pantallas Intensificadoras de Rayos X/clasificación , Pantallas Intensificadoras de Rayos X/estadística & datos numéricosRESUMEN
Main characteristics of radiological intensifying screens were measured. Speed and definition under conditions described before. The different screens-film systems were ranged after their speed factor, at 40, 70 and 120 kV with mention of definition of these systems when measured. Afterglow and abrasion resistance were measured under experimental well definite conditions. Results show that are extant rare earth screens allowing a decrease of X-ray exposure without too great afterglow or mechanical frailty.