[Comments on the standards for acceptance and consistency testing of systems for digital radiography]. / Kommentierungen zu den Normen zu Abnahme- und Konstanzprüfungen bei digitalen Radiographiesystemen (Projektionsradiographie).

Due to German regulations, acceptance and consistency tests have to be obtained by 12.31.2005 for all equipment used for computed radiography according to special standards published in DIN 6868. This article familiarizes all users with the most important aspects of these standards. In addition, explanatory and background information for establishing these regulations are provided.

[Comparison of conventional full spine radiographs and fluoroscopic scanning method in young patients with idiopathic scoliosis]. / Vergleich von konventioneller Wirbelsäulenganzaufnahme und fluoroskopischer Scan-Methode bei jungen Patienten mit idiopathischer Skoliose.

PURPOSE: Evaluation of low-dose full spine radiographs using fluoroscopic images for the assessment of the Cobb angle measurement in patients with scoliosis. MATERIAL AND METHODS: Twenty-one consecutive patients (aged 10 - 27 years, mean age 14 years) with a conventional full spine examination (film speed class 800) underwent a follow-up exam using digital pulsed fluoroscopy (Multi Diagnost 4, Philips Medical Systems, Eindhoven, The Netherlands). The mean follow-up was 9 months. During a synchronized scan with a C-arm speed of 4 cm/sec fluoroscopic images were stored with a pulsed frequency of 3 images per second. The single images were merged and reconstructed to one image with the software Easy Spine (Philips medical Systems, Eindhoven, The Netherlands). The corresponding dose-area product values (DAP) of both methods were compared. Three independent observers assessed Cobb angles and image quality for each technique. RESULTS: The mean DAP values for conventional imaging was 94.9 cGy x cm (2) and for fluoroscopy 7.8 cGy x cm (2), respectively. A significant dose reduction of 91.8 % (CI 91 % to 95 %) was calculated. The average absolute angle difference between the observers was found to be 2.7 degrees for conventional imaging and 2.4 degrees for the fluoroscopic method. Interobserver standard deviation of 2.9 degrees was lower than the 5.3 degrees for conventional images. Image quality was better in the conventional images. CONCLUSION: Using the scanning method, we could achieve a mean reduction of the radiation dose of 92 %, while the accuracy of the Cobb angle measurements was comparable for both techniques despite of reduced image quality of digital fluoroscopy.

Reducing the radiation dose during excretory urography: flat-panel silicon x-ray detector versus computed radiography.

OBJECTIVE: The purpose of the study was to examine the possibilities for reducing radiation exposure in uroradiology using digital flat-panel silicon X-ray detector radiography. We compared the subjectively determined image quality of abdominal radiographs and urograms obtained on a digital flat-panel detector radiography system with those obtained on a computed radiography system. SUBJECTS AND METHODS. Fifty patients who had a clinical indication for urography underwent unenhanced abdominal imaging that was alternately performed using flat-panel silicon X-ray detector radiography or computed radiography. For patients who required a second radiograph with contrast medium, the examination modality was changed to avoid exposing the patients to excess radiation. The images obtained on flat-panel X-ray detector radiography were obtained at half the radiation dose of the images obtained on computed radiography (800 speed vs 400 speed). The resulting 50 pairs of images were interpreted by four independent observers who rated the detectability of structures of bone and the efferent urinary tract relevant to diagnosis and compared the image quality. RESULTS: At half the radiation dose, digital flat-panel X-ray detector radiography provided equivalent image quality of the liver and spleen, lumbar vertebrae 2 and 5, pelvis, and psoas margin on abdominal radiographs. The image quality obtained with digital flat-panel X-ray detector radiography of the kidneys, the hollow cavities of the upper efferent urinary tract, and the urinary bladder was judged to be statistically better than those obtained with computed radiography. CONCLUSION: With half the exposure dose of computed radiography, the flat-panel X-ray detector produced urograms with an image quality equivalent to or better than computed radiography.

[Comparison of flat-panel radiography and computed radiography in urography]. / Vergleich der digitalen Flachdetektorradiographie mit der digitalen Lumineszenzradiographie bei Urogrammen.

PURPOSE: To evaluate the diagnostic value of digital flat-panel radiography in uroradiology the i. v. urograms of patients who had been examined with computed radiography and digital flat-panel radiography were compared regarding image quality. METHODS: 50 patients who underwent clinically indicated i. v. urography were examined with digital flat-panel radiography and computed radiography. In order to avoid unnecessary double exposure to X-rays, patients were examined either by flat-panel or computed radiography before injection of contrast media. Each further clinically indicated exposure after administration of contrast media was done by alternating the other examination technique. The digital images were compared by 4 radiologists regarding image quality for the detection of defined anatomic structures. RESULTS: Digital flat-panel radiography showed an image quality of the liver, spleen and both kidneys that was similar to computed radiography. The urinary tract, lumbar spine, pelvis and psoas muscle were significantly better visible on flat-panel radiography images. CONCLUSIONS: Compared to computed radiography there is no loss of image information by using digital flat-panel radiography in uroradiology. On the contrary, some anatomic structures on abdominal survey images show better image quality. In conclusion, digital flat-panel radiography has the potential to replace computed radiography in uroradiologic examinations.

Detection of porcine bone lesions and fissures: comparing digital selenium, digital luminescence, and analog film-screen radiography.

OBJECTIVE: The purpose of our study was to compare the diagnostic performance of a digital selenium detector (Thoravision) with that of analog film-screen systems and digital luminescence radiography in skeletal radiography for the detection of fissures and lesions in porcine bones. MATERIALS AND METHODS: One hundred bones taken from domestic pigs (50 ribs and 50 femurs) were divided into two equal groups. Fissures and bone lesions were created in 50 bones and 50 served as controls. The bones were examined using film-screen systems, digital luminescence radiography, and digital selenium radiography at various doses. Digital selenium radiography exposure values were adapted to the image geometry differing from the reference methods with a detector focus distance of 2.15 m. Four radiologists independently evaluated image quality and detectability of fissures and lesions on a five-point scale of confidence. Statistical evaluation was based on receiver operating characteristic curve analysis. RESULTS: Fissures and bone lesions were detected most reliably using the mammography film-screen system, but the difference in the results of the analog and digital reference images did not achieve statistical significance. CONCLUSION: Compared with analog film-screen systems, the lower spatial resolution of the digital selenium and digital luminescence radiography systems does not affect detectability of fissures and bone lesions in porcine bone. Selenium is effective in skeletal radiography for detecting fissures and bone lesions. With digital selenium and digital luminescence radiography, the surface dose can be cut to half that required for 200-speed film-screen systems without losing any diagnostically relevant information.

[Clinical aspects of image quality and doses in gated pulsed imaging]. / Klinische Aspekte zu Bildqualität und Dosis bei gittergesteuerter gepulster Durchleuchtung.

PURPOSE: The relations between image quality in last image hold images and dose in grid controlled fluoroscopy in comparison to the continuous mode need to be characterised and recommendations for the clinical application of this technique should be given. MATERIAL AND METHODS: Spatial resolution, signal-noise ratio and, contrast-detail visibility were evaluated by phantom measurements in grid controlled pulsed and continuous fluoroscopy. Dose was measured at the image intensifier entrance. Image quality of last image hold (LIH) images of clinical examinations was graded in relation to single shot exposures. RESULTS: Signal-noise ratio and contrast-detail visibility depend on the dose per puls. Spatial resolution and contrast-detail visibility in grid controlled fluoroscopy are superior than to in the continuous mode. Image quality of the LIH images from the grid controlled fluoroscopy was improved. Radiation exposure could be reduced to 10-46%. CONCLUSIONS: Combinations of puls-dose and -frequency are recommended for achieving extensive dose reduction and improved image quality of LIH images.

[Digital selenium radiography: a comparison of the picture quality of thoracic images in normal and reduced image formats based on the structural anatomical details]. / Digitale Selenradiographie: Vergleich der Bildqualität von Thoraxaufnahmen in normalem und verkleinertem Bildformat anhand anatomischer Detailstrukturen.

PURPOSE: Is there a loss of information when using selenium radiographic images displayed with reduced image format compared to full format? METHOD: Digital selenium radiographic chest images in two planes were obtained in 35 patients for medical reasons. The digital data sets of each patient were separately displayed in full format on two different films and were printed in reduced format on one film. The format was reduced to 61% of the full format using an acquisition matrix of 2166 x 2488 pixels, an image display matrix of 4000 x 5000 pixels and a film format of 43 x 49 cm. All images were anonymously evaluated by four independent readers using a questionnaire concerning anatomic structures. RESULTS: Format reduction did not result in a loss of information in diagnostically relevant anatomic details. CONCLUSIONS: Displaying digital selenium radiographic data sets of thoracic view in two planes on one film presumably does not lead to a loss of diagnostic information. This procedure may help to reduce film costs.

[Studies of image quality and dose in digital subtraction angiography]. / Untersuchungen zu Bildqualität und Dosis bei der DSA.

METHODS: The dose needed for high image quality in l.a. DSA, was determined by investigation of the necessary relationship between dose and image quality. This method is based on measurements of the signal-to-noise ratio and of the contrast-detail detectability. It has been tested on two different systems (Philips integris V3000, Philips Diagnost 97). RESULTS: Our measurements prove that an image intensifier entrance dose of 1.1 microGy (image intensifier diameter 38 cm) is sufficient for high image quality in DSA. An increased dose value does not lead to an improvement in image information. For details larger than the pixel size the 512 matrix produces a higher signal-to-noise ratio with a higher contrast-detail detectability, whereas higher spatial resolution results by the use of a 1024 matrix. In rotational angiography, high image quality can be achieved at an image intensifier entrance dose of 1.1 microGy. In contrast to sequences without rotation, image quality is decreased through movement unsharpness. As the maximum exposure time 25 ms should be selected. The use of a 1024 matrix does not lead to a better spatial resolution in rotational angiography.

The future of digital imaging.

For most applications, conventional film based methods may be replaced by digital imaging. This trend is influenced technically by the advent of more efficient detectors, improved image processing methods, faster computers, brighter and sharper displays and larger systems for image storage and archiving. The evolution of digital imaging reflects the fast development of information technology. Work in radiology departments will change. Information systems will organize the registration and administration of patient data, the scheduling of examinations, management of work flow and the generation of reports. Images will be taken without film cassettes and will be directly displayed on monitors for reporting. Digital imaging provides greater flexibility in processing, transmitting and displaying images. A larger dynamic range and improved contrast resolution lead to a consistently high image quality. This must lead to new rules of diagnosing images and quality assurance. Interfaces are interrelating imaging modalities, displays, the administration and the archive system to each other. The resulting net has to be safe, stable and fault-tolerant. Digital imaging systems will depend much more on the proper function of the interrelated systems in the network.