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At least 289 records · Page 16Linked to original sources
PubMed1979

Contact double-contrast cholangiography.

Recently operative cholangiography has become an essential step in biliary surgery. However, an usual technique in which x-ray film is set beneath the patient has its limitation in visualization of fine changes. The author devised a new technique to resolve this problem. A triangular mammography film designed for good positioning is vaccum-packed, coupled with an intensifying screen of the same size, and then is sterilized in advance. Barium solution mixed with Gascon drop (a defoaming agent) is used as contrast material. The duodenum and head of the pancreas are mobilized. Usual cholangiography is performed at first, introducing angiographic media through a catheter placed into the catheter placed into the common duct via the cystic duct. After this study a triangle film pack is set beneath the second part of the duodenum. Two to three milliliters of barium, 1 to 2 ml of Gascon, and 15 ml of air are pushed in; thus a contact double-contrast cholangiogram is obtained. This technique promises clear demonstration of the distal bile duct without risk, and even fine mucosal plicae may be discernible in the film.

Adult↗
PubMed1989

[New diagnostic tools using proton beams obtained from accelerators in KEK (National Laboratory for High Energy Physics), Tsukuba].

The opportunity exists at present for the application of accelerator beam to clinical diagnosis in the Academic City of Tsukuba wherein the National Laboratory for High Energy Physics (KEK) and Tsukuba University Hospital are located. 250 MeV Proton beams have been available both for clinical proton therapy and experimental proton radiography at the Particle Radiation Medical Center (PARMS) (Tsukuba University). Monoenergetic protons are highly sensitive to density variations and are capable of giving radiographs of very high contrast. As an initial step in exploring their diagnostic potential, protons with energies of 250 MeV were used in the projection radiography of animals. Prior to the above experiments, some characteristics of the proton beam were examined. The detector system in this experiment was films with or without intensifying screens. The problem hampering diagnostic potential of proton radiography was multiple scattering.

Angiography↗
PubMedDate not supplied

Noise characteristics of a microchannel plate x-ray image intensifier.

The noise performance of an experimental microchannel plate x-ray image intensifier has been evaluated. The intensifier, constructed for use with photons of energies between 20 and 150 keV, uses an MCP as the photon-to-electron converter. The influence of noise was determined by analysis of the optical-density fluctuations of a photograph of the viewing screen of the intensifier when the conversion layer was exposed to between 1 and 60 mR. Additionally, the contrast-detail performance of the experimental device was determined. The influence of both stochastic noise, due to quantum mottle and pulse-height variations, and structural noise, due to fluctuations in inherent gain from point to point, have been considered by using a model that adds these components.

Models, Theoretical↗
PubMed1992

Analogous filters for beam shaping in diagnostic radiology.

A computer simulation based on photon transport calculation was used to evaluate the properties of a wide variety of materials that could be used for the filtration of x-ray beams. A single filter was added to the inherent filtration. For comparison, the concept of analogous filters was introduced: two filters were considered analogous if both produced the same ratio of entrance exposure at the patient to the energy absorbed in the detector consisting of a pair of intensifying screens positioned immediately behind the water phantom. The efficiency, contrast and integral dose were calculated for filters of odd atomic numbers from 1 to 91 with a large number of different parameters (48,600 different combinations). They include essentially all major diagnostic radiology procedures, except mammography. Only extreme cases are presented here. No magic filter was found which would produce increased contrasts or a decreased integral dose, while maintaining efficiency close to that of aluminium. Filters of some atomic numbers produced increased contrast, but had negligible efficiency. Analogous filters of atomic numbers between 7 and 37 and also between 71 and 91, had almost identical properties but varied efficiencies. Unpredictable behaviour was obtained with filters of atomic numbers 38 to 70, where small changes in atomic number may produce large changes in all the properties due to the presence of K-edge discontinuities.

Computer Simulation↗
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↗
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↗
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↗
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↗
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↗