SEARCH · PubMed Health

Results for “X-Ray Intensifying Screens”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources

PubMedDate not supplied

Heuristic model for understanding x-ray film characteristics.

A simple, heuristic model of a photographic emulsion is described for the purpose of illustrating the fundamental physical processes and emulsion properties which determine the characteristics of an x-ray film (viz., the shape of the H - D curve, film gamma, and film speed). By means of this model, it is shown that the contrast multiplication afforded by an x-ray film (i.e., a film gamma greater than unity) is a direct result of the exponential attenuation of the viewing light by the developed film, and that film gamma is proportional to grain size, grain density, and emulsion thickness. The difference in the H - D curve that is observed when the same film is exposed to light from an intensifying screen or directly to x rays is also predicted by the model.

Models, Theoretical↗

PubMed1986

Patient absorbed doses in digital grey-scale fluorography.

This article describes a preliminary comparison between the levels of patient dose used in digital grey-scale fluorography (DGF) and screen-film radiography. Patient doses were measured in three common radiographic examinations, postero-anterior chest, antero-posterior lumbar spine and lateral lumbo-sacral junction, using thermoluminescent dose-meters and an anthropomorphic phantom. Within the limitations of the image quality currently available in DGF, the findings indicate that digital radiography with the large-field X-ray image intensifier promises significant savings in patient dose compared with conventional radiography.

Film Dosimetry↗

PubMed1985

[Experimental dosimetric comparison between single tomography and multiple simultaneous tomography with Synchroplan in clinical practice].

Reference is made to a dosimetric comparison between single tomography and simultaneous multiple tomography with Synchroplan in 10 patients subjected to nefroangiotomography. Data from several thermoluminescence dosimeters placed on different parts of the body were used in a careful statistical analysis that showed the absence of significant differences in absorbed dose in function of constitutional habitus. It was also found that the dose absorbed for 6 tomograms of the renal cavities in single tomography was about 4 times higher than with the Synchroplan (using a previously experimented set of high-sensitivity intensifying screens), which provides 6 tomograms in the same dynamic phase at different levels for the same exposure.

Body Constitution↗

PubMed1991

Development of a ceiling-suspended angiographic unit for interventional neuroradiology.

A new neuroangiographic unit was developed with a ceiling-suspended gantry, capable of rotation (110 degrees) and craniocaudal angulation (+/- 45 degrees) along the body axis. The gantry could also be rotated 225 degrees at the ceiling suspension axis and sidetracked away from the angiographic table in case of emergency. Two sets of a twin-focus X-ray tube and a 12-inch image intensifier (II) were mounted on the gantry in the isocentric and cross-firing positions. High resolution 1024 x 1024 matrix digital radiography was obtained with a speed of 30 frames/s, while conventional film-screen radiography was obtained at 4 films/s. Rapid film changers were installed and interchangeable with the IIs. The lateral II and X-ray tube could be positioned from either side of the patient. There was no angulated position of the lateral imaging system during angulated anteroposterior or Towne projection of the frontal imaging system. Automatic repositioning of the gantry was possible to the preset position. Stereoscopic, magnification and stereoscopic magnification radiography could be obtained easily in monoplane or biplane mode. Switching from fluoroscopy to radiography and vice versa was possible rapidly and easily. Neuroangiographic as well as interventional procedures were performed expeditiously with lower complication rates. Suspending the gantry from the ceiling made more space available on the floor for the anesthesiologists.

Angiography↗

PubMed1979

[Comparison of screens and screen-film-systems (author's transl)].

Important details are to be payed attention in comparison of different scrreens resp. screen-film-systems: 1. Physical characteristics of different groups of luminescent materials: f.i. calcium tung-state, rare-earths compounds, double halogenides. - 2. Different types of screens: highest details up to highest speed intensifying screens, have to be defined more specifically and differentiated against to each other too. - 3. Besides intensification, resolution has to be included into consideration since one of these dates alone does not allow any statement on the total function of a screen or a screen-film-system. - 4. The technical methodological conditions of apparatuses, object and its positioning have to be defined, f.i. X-ray quality, distances, grid, and in automatically controlled exposition, if necessary, position of ionization chamber as well as absorption of cassetts and screen. - 5. Considering these points gradation curves have to include the whole necessary or interesting diagnostic range. - 6. Due to functional correlation between intensification and resolution, the resolution has to be taken in consideration due to application; its interdependence of density and object (f.i. scattered radiation) is often not taken enough in consideration.

Humans↗

PubMed1978

[X-ray dose reduction in examination of infant's hip with image-intensifier-fluoroscopy-system (author's transl)].

An image intensifier--70mm camera--fluoroscopy system combined with a conventional X-ray tube is used for routine examination of the infant's hip. The high quality of 85% of these 70mm exposures makes immediate diagnostic interpretation possible. An even higher percentage can be achieved by most exact positioning of the patients. Apart from the radiation protection of the gonades, the X-ray skin dose of the primary beam is reduced by 90-95% compared with full size radiography using film screen combinations. This exposure technique can certainly be used not only for the examination of the infant's hip.

Fluoroscopy↗

PubMed1989

[Insertion of distal screws in interlocking nailing using a new free-hand control device].

While it is technically easy to introduce the proximal screw in interlocking nailing, the torsion of the nail being driven into the medullary canal can make distal locking more difficult. There are two approaches to the insertion of the distal screws: the c-arm-mounted device and the free-hand technique. The Grosse-Kempf c-arm device was introduced in 1978, but it requires modification of the fluoroscopy unit and is time consuming. The free-hand technique has certain disadvantages because of involuntary movement during the change from aiming to drilling. Furthermore, the bulky power drill makes monitoring of the path of the drill bit impossible, and the radiation time can be considerable. A new free-hand distal aiming device for the interlocking nail was therefore designed in our department. The main objectives were to provide a simple, yet precise instrument with few parts that would allow monitoring of the direction during process of penetrating the nail hole. The device consists of two metal rings on both ends of an X-ray translucent cylinder with a central 4-mm hole in it. A pin with a sharp tip (diameter 4 mm, length 160 mm) is inserted through the hole. Using the image intensifier, the device is then placed so that the sharp tip of the pin points to the bone. The device is moved until the two metal rings are superimposed on each other and give the impression of one ring with the nail hole in the middle. On the screen the pin then appears as a dot inside the nail hole.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone Nails↗

PubMedDate not supplied

A digital-radiographic technique for in vitro tissue thickness measurement using iodine displacement.

A novel digital radiographic method has been developed for measuring the thickness of a tissue sample by iodine displacement. This simple, accurate method is useful both in medical research and in the comparison of pathological and clinical findings. Radiographic measurements of tissue samples in air suffer from the limitation that the quantity measured depends on the product of both thickness and radiographic attenuation coefficient. This technique allows one to obtain thickness measurements from a digital radiograph of a tissue sample suspended in a bath of radio-opaque contrast agent. The attenuation of the iodinated contrast agent is much higher than that of tissue or calcium. Thus the resulting image is determined largely by the contour of the surrounding bath, and is only slightly influenced by the composition of the tissue. This technique improves both the accuracy and precision of radiographic thickness determination. In this paper the iodine displacement technique is described and the accuracy and precision of thickness measurements in appropriate phantoms are quantified. This technique has been used with both image intensifier and screen-film based imaging systems to obtain thickness maps of calcified human aorta, with precision better than 4% and spatial resolution of 2.5 mm-1.

Aged↗

PubMedDate not supplied

Investigation of basic imaging properties in digital radiography. 5. Characteristic curves of II-TV digital systems.

A simple method was devised to determine the characteristic curve of image intensifier (II)-TV digital imaging systems, which relates the output pixel value to the input relative x-ray intensity. To provide a wide range of x-ray intensities incident on the II, we used an aluminum stepwedge consisting of nine steps with thickness increments of 6.3 mm, together with an 0.81-mm-thick copper plate. The x-ray field was narrowly collimated to the area occupied by the stepwedge in order to reduce the effect of veiling glare. The relative x-ray intensities transmitted through each step of the stepwedge were determined by using screen-film systems. The gradient curve of the system was derived from the slope of the characteristic curve. Results obtained with a Siemens Digitron 2 system showed that its characteristic and gradient curves depended upon the matrix size used, but did not change with the II field size. The validity of the characteristic curve was demonstrated by measurement of iodine attenuation curves obtained with the II-TV digital system at different exposure levels.

Humans↗

PubMed1992

Potential of digital flashing tomosynthesis for angiocardiographic evaluation.

A system for digital flashing tomosynthesis (DFTS) consists of four electrocardiogram-gated and simultaneously flashed x-ray tubes, a 14" image intensifier, a unit for digital subtraction angiography (DSA), a personal computer-hosted transputer network for three-dimensional (3D) reconstruction as well as for quantitative coronary angiography and ventriculography, a display unit and an individual digital archive. DFTS-tomoangiograms may be presented in single slice mode or as multiple slices of arbitrary thickness, using rotating and stereographic presentation of 3D images. DFTS represents a configuration for standardized digital angiocardiography with digital archiving and assures optimal reproducibility and safety. This angiographic configuration is feasible for both ambulatory angiography to allow high volume cardiovascular angiographic screening and for the quantitative assessment of natural progression or potential regression of coronary artery disease resulting from interventional or pharmacological therapy.

Angiocardiography↗

PubMed1987

Technique for verifying treatment fields using portal images with diagnostic quality.

The image quality of portal films for megavoltage photon beams, when using the double-exposure technique, is poor compared to diagnostic quality, X ray images. A technique is described to record on a single film a megavoltage portal image superimposed upon a diagnostic X ray image, which provides the radiotherapist with "diagnostic quality" portal images. The technique uses a commercially available X ray tube mounted on the head of a 60Co unit. The alignment procedure, which uses a leveling device to ensure that the X ray focal spot and 60Co source are at the same location for each exposure, is confirmed by registering on film the image of an alignment marker. An evaluation of film-screen combination showed therapy verification film in a rare earth intensifying screen cassette to be best suited for this technique. The relationship between off-axis dose and the penumbral region of the portal image has been evaluated and should be useful in the interpretation of portal verification film relative to the treatment volume.

Cobalt Radioisotopes↗

PubMed1988

Vertical tomography of the temporomandibular joint with the use of a dental chair and intraoral x-ray unit.

While designs for tomographic imaging are numerous, there are no reports in the literature of a vertical tomographic device based on a principle of patient movement relative to a fixed x-ray source. A vertical tomographic device was constructed with the use of a conventional dental chair to generate tomographic movement and a variable kilovolt (peak) intraoral x-ray unit as the x-ray generator. The device was assembled with commonly available components and construction elements machined from standard metal stock. Images made with 5 x 7 inch cassettes with RP X-Omat film and regular intensifying screens were compared with similar images produced by a commercial linear tomographic device costing about five times as much. Comparison of images of the temporomandibular joint of a tissue-equivalent skull phantom produced by transcranial technique and prototype and control tomograms demonstrated superior imaging produced with tomographic techniques and similar image quality between prototype and control-generated films.

Dental Equipment↗

PubMed1988

A novel X-ray transmission ionization chamber dosemeter for patient dose measurements in diagnostic radiology.

This paper describes an X-ray transmission ionization chamber diagnostic dosemeter for patient dose measurements and control. The chamber uses a commercially available radiofrequency screen as the wall material in a parallel-plate configuration. A digital varactor bridge electrometer serves to measure air kerma times area of fluoroscopic and radiographic beams. Detailed investigations on the characteristics of the chamber such as saturation, sensitivity, energy dependence (50-150 kV), response versus radiation field area, uniformity of response of the chamber, effects of distance and long-term stability have been carried out. The results demonstrate that the chamber meets all the requirements and can measure the incident patient dose with an overall uncertainty of +/- 11%. The chamber can be either mounted on the housing of the light beam diaphragm of the X-ray unit or used as a stand-alone system along with an image-intensifier TV monitor. It is inexpensive to build and is recommended particularly for hospitals in developing countries.

Equipment Design↗

PubMed1977

Eye dose measurements using conventional and rare-earth screens during tomography of the para-nasal sinuses.

Eye dose measurements have been performed when using medium speed conventional and rare-earth screen-film combinations during tomography of the para-nasal sinuses. The measurements show that using conventional intensifying screens with the A.P. view a total eye dose of about 20 rad may be given during an examination. This eye dose can be reduced by 98% using the P.A. position. If rare-earth screen/film combinations are employed the eye dose measured in the A.P. view was reduced by 75% of that obtained with conventional screens without detectable loss of image quality. A total eye dose reduction of about 99.5% was measured in the P.A. view with the rare-earth systems.

Ear, Middle↗

PubMed1978

[Trends in dental radiology--a review of the literature].

Dental radiology is experiencing a marked improvement in equipment and its comfort of use. The production of intensifying screens with calcium tungstate stratification causes considerable diminution of radiation damage although at the price of changes in the structure of the picture. Xeroradiography is stagnating after promising beginnings. The protection of the patient against radiation has improved and recent work shows that in the dental field, more care must be given to preserve the lens of the eye from radiation hazard. Pantomography as a diagnostic means is progressing although it has not been able to substitute for the conventional radiography. TMJ radiography does not make exception in the same sense, so the knowledge of the correct use of special cranial radiographs remains.

Humans↗

PubMed1992

[The influence of the spectrum and the type of exposure on the contrast of double-sided coated x-ray film].

The present article describes the circumstances concerning the use of testing aids such as sensitometers with one-sided exposure. It is shown which phenomena must be considered if radiographic films coated on both sides are exposed with a) standard pocket sensitometers (one-sided exposure), b) lab sensitometers (double-sided exposure to ANSI Ph 2.9 [1964]), c) x-radiation in the cassette, intensifying screen and film system (to DIN 6867 T 1). The effect of the emission spectrum on the resulting contrast factor is described. The importance of different emulsion technologies (e.g. orthochromatic anticross-over films) for the contrast factor with one-sided exposure is described. The cross-over factor (c.o.), the apparent variation in sensitivity of the front and back emulsion with one-sided exposure, is the cause of the reduction in the contrast factor (G average) as against double-sided exposure: delta G(%) = c.o.2 x 10(3)/8.4

Lighting↗

PubMed1982

[An analysis of the diagnostic information derived from screening as against films during radiological examination of the stomach (author's transl)].

The value of screening procedures (with image intensifiers and television monitor) was compared with films during the radiological examination of the stomach, using a double contrast method. In one experiment, the diagnostic accuracy of experienced radiologists using screening only was compared with standardised films. There was a definite improvement using films. The reason for this was not the difference in the technical excellence of the images, but depended on the cognitive processes which lead the doctor to a diagnosis. For this purpose, static pictures provide a better basis than dynamic, rapidly changing and brief views seen during screening. The results lead to certain considerations concerning the methods for the radiological examination of the stomach.

Diverticulum↗

PubMedDate not supplied

Large-image intensifier photofluorography and conventional radiography in pulmonary emphysema. Correlation with computed tomography.

Large-screen image intensifier (II) photofluorography was compared with full-size screen-film chest radiography in the diagnosis of pulmonary emphysema in 84 patients. Photospot films and conventional radiographs were interpreted independently by three radiologists. Computed tomography (CT) was used as an independent reference technique, and diagnostic performance of chest radiography in various CT patterns of emphysema was evaluated. The difference in diagnostic sensitivity for emphysema in favor of conventional chest radiography over photofluorography (0.65 versus 0.56) was statistically significant (p less than 0.05). Specificity of the imaging modalities was equal: 0.78 in full-size films and 0.77 in photospot films. All CT patterns of emphysema had great false negative response rates in chest radiography, which is an inaccurate technique for the diagnosis of emphysema. CT is required for reliable radiologic evaluation of emphysema.

Emphysema↗