Conventional Film-screen Combination Research Articles

Optimising automatic exposure control in computed radiography and the impact on patient dose

Automatic exposure controls (AECs) used with computed radiography (CR) equipment need to be set for a constant signal level in the resultant images. The response varies with the energy of the X-ray beam in a different way from conventional film screen combinations. Dose to the imaging receptor has been employed in adjustment of the AECs for varying exposure conditions for CR systems installed in hospitals in the west of Scotland. However, other parameters could potentially be applied. In this study, three quantities have been investigated for use in setting the AEC function: the exposure indicator defined by the CR manufacturer, dose to the image receptor and image noise. Experiences gained in setting up the systems are described and results of a patient dose survey are reported.

Development of a quasi-monochromatic source for mammography applications

One of the research topics of the IMI project is the development of a quasi-monochromatic source for mammography applications. Quasi-monochromatic source has been produced via Bragg diffraction on mosaic crystal with a conventional X-ray tube. The system has been characterized in terms of photon flux and exposure rate, capability in low contrast detection, delivered dose and energy resolution properties. Radiographs of test phantoms have been obtained with a conventional screen–film combination.

Solid-state temporomandibular joint imaging: accuracy in detecting osseous changes of degenerative joint disease and determining condylar spatial relations

The purpose of this study was to evaluate the off-label use of an intraoral charge-coupled device (CCD) for extraoral transcranial radiography of the temporomandibular joint. Corrected linear tomograms and transcranial images made with conventional screen–film combinations and a CCD detector were compared with sectioned cadaver specimens. Radiation dosage, qualitative assessment of condylar degenerative features, and condylar position within the glenoid fossa of the 3 modalities were assessed and compared. The CCD method required special adjustments to achieve adequate quality, and it involved greater exposure than the other methods. This use of this intraoral system for extraoral imaging cannot now be recommended, but future refinements might make it more viable.

Paediatric dose reduction with the introduction of digital fluorography.

Fluoroscopy guided examinations in a paediatric X ray department were initially carried out on a unit that used a conventional screen-film combination for spot-films. A new fluoroscopy unit was installed with the facilities of digital fluorography and last image hold. Comparison of equipment performance showed that the dose per image for screen-film and digital fluorography was 3 microGy and 0.4 microGy, respectively. Although the screen-film had superior image quality, the department's radiologist confirmed that digital fluorography provided a diagnostic image. Patient dose measurements showed that introduction of the new unit caused doses to fall by an average of 70%, although fluoroscopy time had not changed significantly. The new unit produced 40% less air kerma during fluoroscopy. The remaining 30% reduction in dose was due to the introduction of digital fluorography and last image hold facilities. It is concluded that the use of digital fluorography can be an effective way of reducing paediatric dose.

Contrast-detail evaluation of a full-field digital mammography system

We have been investigating the potential of large-area flat-panel a-Si:H imaging devices for full-field digital mammography. The performance of a clinical mammographic system specially developed to provide geometric direct magnification equipped with an a-Si:H digital detector in conjunction with a series of Gd/sub 2/O/sub 2/S:Tb phosphor screens was evaluated in terms of image quality and entrance surface dose by using the contrast-detail CDMAM phantom over a range of exposure levels. We also compared the contrast-detail detectability properties of the a-Si:H-based digital imaging system with those of a conventional screen-film combination. The results from this study reveal the superiority of this prototype a-Si:H-based digital imaging system both in terms of contrast-detail resolution and significant entrance surface dose reduction in comparison with the conventional screen-film combination. These advantages are of particular significance in the breast imaging. Therefore, the combination of a-Si:H digital array with the direct magnification mammography system has the potential to fulfil the image quality requirements for full-field digital mammogarphy and to offer significant improvements in the efficient early detection of breast cancer.

Comparison of an asymmetric screen-film combination with a conventional screen-film combination for chest radiography in 51 patients.

Comparison is made between a new asymmetric screen-film combination and a conventional screen-film combination for use in chest radiography. Seven anatomical features were assessed by three consultant radiologists in each of 51 film pairs. A preference was indicated if one system better demonstrated a particular feature. Alternatively, no preference was indicated if the feature was equally demonstrated by both systems or not demonstrated at all. Any pathology incidentally noted which remained unchanged between the two films was localized to lung, mediastinum or bone and marked in the same way. The asymmetric high contrast system scored higher than the conventional system for demonstration of anatomy in both mediastinum and lungs, but no difference emerged between the two systems in the demonstration of pathology. The asymmetric screen-film system showed improved mediastinal and, to a lesser degree, improved lung detail. Further assessment in necessary to define any associated improvement in diagnostic yield.

Storage phosphor radiography

Storage phosphor radiography is a digital technique that uses photo-stimulable, phosphor screens to substitute for conventional screen-film combinations. While the technique is more than 15 years old, it is only recently that technological and economic aspects of these systems have become favourable enough to envisage a more widespread clinical application.

Comparison of film-screen combination and digital fluorography in gastrointestinal barium examinations in a clinical setting

Objective: Digital fluoroscopy systems have been developed for gastrointestinal barium studies. We compare the performance of a commercially available digital fluoroscopy system with conventional film-screen combinations in gastrointestinal barium studies. Methods: Two consecutive groups of outpatients underwent diagnostic barium examinations of esophagus, stomach, or colon using either a film-screen technique ( n = 32) or a digital fluoroscopy system with an 8-bit gray scale ( n = 31). A standardized biphasic protocol was employed in all patients by the same set of investigators and scored subjectively for contrast performance in single-contrast and double-contrast mode and for spatial resolution. Results: For the whole group there were no significant differences between the two techniques. In the subgroup of esophagus studies, digital fluoroscopy performed better during the fullcolumn part of the examination. In the subgroup of colon studies, the film-screen technique performed better during the doublecontrast part of the examination. To reach sufficient spatial resolution with the digital system (884 2 matrix), the smallest input screen had to be used (23 cm), resulting in a higher number of exposures than with the film-screen combination ( P = 0.006). The average amount of film used was not significantly different. Conclusion: In a clinical setting the contrast performance and spatial resolution of digital fluoroscopy systems can be comparable with conventional film-screen combinations.

Digital skeletal radiography.

Digital radiography may be defined as an imaging system in which conventional X-rays are used, but in which conventional film-screen combinations are replaced by radiation detectors connected to computer systems to produce the image. Today, digital radiography for examination of the musculoskeletal system is routine in many departments. The systems used most for such digital radiography are based on imaging plates, using phosphor storage screens, but there are also several other systems developed or under development in which the imaging plate is no longer needed.

Evaluation of a low-dose digital X-ray system with improved spatial resolution

We present results from an evaluation of a significantly improved version of the Siberian Digital Radiographic Device (SDRD). The SDRD is already in clinical use in Novosibirsk and Moscow where it produces images of high diagnostic value at considerably lower doses than conventional film-screen combinations. It uses a fast multiwire proportional chamber with highly parallel readout as a detector. Improvements in the readout system have given a reduction by a factor of two in the pixel size. We have used well established methods to compare imaging performance of the new SDRD with the old version as well as with a film-screen combination used in routine clinical practice in the UK. At the same level of exposure the threshold contrast for objects of the order of the pixel size is two times better for the new SDRD than for the old one, and the minimum size of objects visible in the image is two times smaller (0.25 mm) for the new system than for the old SDRD (0.5 mm).

The detection of foreign bodies in soft tissue—Comparison of conventional and digital radiography

The vast majority of glass and metallic foreign bodies can be detected with conventional radiography. The visibility of common woods and plastics is, however, unknown. To assess their radiographic visibility, various woods and plastics of equal size were inserted into fresh porcine tissue. The pork was then radiographed, under identical conditions, using conventional film-screen combination and a FUJI computed radiographic system utilizing its edge-enhancement facility. The visibility of the compounds was scored by four radiologists for both systems at various times post-insertion. Plastics were found to vary widely in visibility. Dried timbers were visible initially but became isodense with time due to absorption of fluid from surrounding tissues. Fresh woods were invisible from the outset. The computed radiographs improved the visibility of objects visible with conventional radiography but did not bring about visualization of those invisible to normal film-screen combinations. In conclusion the visibility of woods and plastics is variable. Some improvement in visibility can be brought about by the use of digitally edge-enhanced computed radiographs.

Hand radiographs: a comparative study of digital luminescent radiography (DLR) and conventional screen-film system combinations

A total of 102 matched hand radiographs were taken by digital luminescent radiography (DLR) and conventional) screen film system combinations. In DLR two differently postprocessed images were obtained from each data set: A display with low-spatial frequency enhancement filtered to took like a conventional radiograph was placed opposite a display with high-edge enhancement. Conventional and digital images were evaluated rank only and separately by four radiologists, using a questionnaire. Using DLR proved diagnostically equivalent to the conventional technique except for a diminished visibility of subtle erosions and fissures. High-frequency enhancement did not provide additional diagnostic information and led to artifacts at the edges of metal prostheses. Densitometry confirmed an optimized density of digital radiographs. The main argument for the employment of digital techniques is the availability of data for picture archiving and communications systems.

Evaluation of a new low-dose digital X-ray system

The Siberian digital radiographic device (SDRD) is in clinical use in Novosibirsk and Moscow where it produces images of high diagnostic value at considerably lower dose levels than conventional film-screen combinations. The authors have made contrast-detail measurements to compare its imaging performance with film-screen systems used in clinical practice in the UK. They have also compared clinical doses for Russian SDRD examinations with doses for the equivalent examinations in the UK. The SDRD performs better than the UK film-screen systems for large low-contrast objects at all exposure levels, and requires lower doses, by up to two orders of magnitude, when compared for a range of common examinations.

Röntgenuntersuchungen der peripheren Gelenke: Vergleich der digitalen Lumineszenzradiographie (DLR) mit Filmfoliensystem

175 matched skeletal x-ray examinations were carried out by digital luminescent radiography (DLR) and conventional screen-film system combinations. In digital luminescent radiography (DLR) two differently postprocessed images were obtained from one x-ray exposure: A display with low spatial frequency enhancement was opposed to a second display with high edge enhancement. Conventional and digital images were evaluated randomly and separately by four radiologists using a questionnaire. DLR proved to be diagnostically equivalent to the conventional technique except for a diminished visibility of subtle erosions and fissures. As major advantages of DLR maybe pointed out that faulty exposures were avoided by the automatic adjustment of image brightness and that the soft tissue margins could be more easily delineated in displays with high edge enhancement than in conventional radiography. However, digital displays with high edge enhancement did not provide additional diagnostic information and led to artifacts at the edges of metal prostheses.

Direct comparison of conventional and computed radiography with a dual-image recording technique.

To compare the image quality of computed radiographic (CR) with conventional screen-film images, the authors used a dual-image recording technique. Images were simultaneously acquired with a conventional screen-film combination and a storage-phosphor imaging plate loaded into a single cassette. Wiener spectra and modulation transfer function were compared for both image types. A preliminary observer performance test was conducted with chest images obtained with the dual-image recording technique on portable and fixed equipment. Analysis of physical parameters and observer test results suggests that the conventional screen-film system can provide slightly superior image quality, although the CR system has some advantage in bedside applications.

Assessment of Digital Chest Radiography Using Stimulable Phosphor

In this pilot study, conventional and digital radiography of the chest was compared in 170 patients. Two digitized radiographs, one frequency modified and one simulating the conventional film-screen combination, and the conventional films were reviewed independently by 5 radiologists with different experience. In spite of the smaller size and lower spatial resolution of the digitized compared with the conventional radiograph, only slight differences were revealed in the observation of different pulmonary and mediastinal changes. Digitized radiography is therefore considered suitable for chest examinations.

Digital radiography of the spine, large bones and joints using stimulable phosphor

The value of digital radiography in musculoskeletal disorders was investigated by assessing its ability to depict anatomic structures and common radiologic features as compared with the conventional film-screen combination. the digital image that was frequency modified was superior to conventional films in delineating soft tissue structures and for areas with large attenuation differences. the conventional film-screen system was superior in depicting small anatomic structures and in identifying the zone close to prostheses. This was explained by the high spatial resolution of the conventional film system and the disturbing halo effect around the prosthesis seen with digital images. the halo effect is an overshoot caused by the unsharp masking operator, which was in this series not changed for individual examinations. the exposure (radiation dose) could be reduced to 50 per cent using the digital system, without any loss of information

Digital urography using stimulable phosphor

In a urographic experimental study in six rabbits conventional film-screen images were compared with digitized images. Two digitized images were examined, one simulating the conventional film-screen combination, and one frequency modified. the nephrographic and excretory phases of four different doses of contrast medium (iohexol, 350 mg l/ml) were investigated in each rabbit (4, 2, 1, and 0.5 ml/kg body weight). No differences were found between the different doses of contrast medium for the two imaging systems. with digitized images the exopsure (radiation dose) could be decreased to 12.5 per cent of the conventional film-screen combination without any loss of information

Digital Radiography of the Spine, Large Bones and Joints Using Stimulable Phosphor

The value of digital radiography in musculoskeletal disorders was investigated by assessing its ability to depict anatomic structures and common radiologic features as compared with the conventional film-screen combination. The digital image that was frequency modified was superior to conventional films in delineating soft tissue structures and for areas with large attenuation differences. The conventional film-screen system was superior in depicting small anatomic structures and in identifying the zone close to prostheses. This was explained by the high spatial resolution of the conventional film system and the disturbing halo effect around the prosthesis seen with digital images. The halo effect is an overshoot caused by the unsharp masking operator, which was in this series not changed for individual examinations. The exposure (radiation dose) could be reduced to 50 per cent using the digital system, without any loss of information.

Digital Radiography Using Laser Stimulated Luminescence for Evaluation of Urinary Calcifications

One hundred consecutive patients were investigated with both a conventional film-screen combination and digital radiography using a laser stimulated luminescence technique in order to evaluate differences in detecting urinary tract stones. All patients were referred either for follow-up of previously known stones or for symptoms. The images were reviewed by two radiologists who had the single clinical information that the patients might have urinary stones. Following review, the two techniques were compared and a consensus was obtained. One hundred and eighteen stones were found in 41 patients without any statistical differences in sensitivity between the two imaging systems.