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PubMed1977

Sensitivity of radiographic screens to scattered radiation and its relationship to image contrast.

For incident X-ray beams of greater than 60 kVp, intensifying screens of rare earth phosphors produced higher radiographic image contrast in the presence of scattered radiation than did screens of calcium tungstate. This was attributed to fundamental energy absorption interaction differences. X-ray absorption is a function of the position of the k-absorption edge of the screen phosphor relative to the X-ray energy spectra of the primary and scattered X-rays. Spectral measurements of X-ray absorption showed that the ratio of primary absorption to scattered absorption is higher for the rare earth screens, causing lower relative sensitivity to the non-information-containing scattered radiation from the radiographic object.

Gadolinium↗
PubMedDate not supplied

Test cassette for measuring peak tube potential of diagnostic x-ray machines.

A test cassette employing a modification of the Ardran-Crooks attenuation technique for measuring peak tube potential (and half-value layer) is described. The technique employs a radiographic intensifying screen which is exposed to a hardened x-ray beam. Copper penetrameters are used to determine the attenuator thickness which reduces the light output from the screen to that transmitted by an optical attenuator over an adjacent area of the screen. The test cassette was calibrated by using x-ray machines whose high voltages were measured electrically. The test cassette has a measurement precision of +/- 1 kVp and an accuracy of +/- 3 kVp or better in the range 50-130 kVp for x-ray generators with the same voltage waveform.

Quality Control↗
PubMed1978

[Filmsizes; physical-technical aspects of x-ray image recording (author's transl)].

Formats of full-size radiographs are determined by the dimensions of the anatomy to be recorded, the enlargement factor is always larger than unity. Given a certain film screen combination exposure and film-density cannot be chosen independently--whereas with X-ray I.I. fluorography this is possible. In the former case they depend on X-ray absorption, energy efficiency and the luminescent spectral emission of the screens in combination with the corresponding characteristics of the photographic film. The respective characteristics of standard film-screen combinations and those based on rear earth screens are discussed and compared. X-ray image intensifier fluorography is presented as a logical enlargement of I.I. fluoroscopy, in itself and indispensable tool in X-ray diagnostics. Its real or imaginary pro's and con's are elucidated.

Fluoroscopy↗
PubMed1978

[Experimental study of intensifying screens used in diagnostic radiography (author's transl)].

A physical experimental study of intensifying screens for diagnostic radiography was set up. Experimental conditions were identical with those of medical practice. Spectra speeds of several films and spectral emission of intensifying screens were built up. Speeds of screen-film combinations, as well as definitions, were measured. Results are available to range the different screens-film systems after their speed factor, at 40, 70 and 120 kV, with mention of definition of these systems. It so objectively appears that rare-earth intensifying screens make possible a decrease of X-ray exposure for patient under a factor 2 to 2,5 and a less early wearing of apparatus, namely of X-ray tubes.

Evaluation Studies as Topic↗
PubMed1979

The Nicholas Research Award for Radiographers 1977: anatomical and radiological registration in whole body computed tomography.

Accurate registration of a section 13 mm in depth in different patients or reregistration in the same patient during whole body computed tomography is a significant problem. The method described here attempts to overcome some of these difficulties. The feasibility of using the EMI Scanner X-ray tube and a pair of Kodak Lanex intensifying screens in a vacuum pack cassette has been examined. A registration system which as an accuracy to within 1 pixel has been described. This technique has its major application in the registration and recognition of the axial skeleton, on fixed bony structures. The registration of soft tissue structures, subject to greater physiological variation poses problems which are the subject of further investigation.

Bone and Bones↗
PubMed1979

[Examinations of rare-earth film-screen-systems for image detectors in mammography (author's transl)].

Intensifying screens based on Gd2 O2 S : Tb were analysed for x-ray exposure reduction and resolution using in mammorgraphy. The contrast of these screens coupled with a single emulsion film was tested and the density dominante was determined. A resolution grid on this density exposured shows the detail resolution and judge the quality profile of these new film-screen-combinations. To all factors was compared a non-screen industrial film for long time processing. The application of Gadolinium intensifying screens in mammography allowed an exposure reduction of 75% at the same image quality like a nonscreen industrial film.

Female↗
PubMed1979

[Modern urography].

An IVP optimum quality should be tailored to the particular needs of a given case and consequently most be supervised by the radiologist when it is being performed. The most meticulous technique is needed, the adequate amount of contrast medium should be used, compression of the ureters should be performed and under optimum conditions tomography during the nephrographic phase should be performed whenever the circumstances should require it. With only very few exceptions no significant differences between different contrast media exist. The use of medium speed high contrast x-ray films as well as the use of rare earth intensifiers screens avoid the need for extremely powerful generators that are very costly. Film processing is a critical step in obtaining a good study and should be automatic.

Contrast Media↗
PubMed1978

[New aspects concerning exposure factors during direct geometrical X-ray magnification (author's transl)].

The paper is concerned with the use of rare-earth intensifying screens in order to overcome some of the exposure problems during magnification techniques using very small focal spots. Theoretical experiments and tests with biological objects indicate that the use of high intensifying screens under these circumstances is acceptable and useful. A comparison has been carried out between the results of conventional techniques without magnification and magnification techniques using very small focal spots and rare-earth intensifying screens.

Film Dosimetry↗
PubMed1979

Application of magnification radiography to the biliary system.

Magnification radiography was applied for the diagnosis of the biliary tract diseases including cancer. Our X-ray unit was consisting of HITACHI DR-155-23 U-6M-55P and 0.1 mm focal-spot tube, FFD 80 cm giving a magnification of x2 with the conditions of 60 kVp, 20 mA, 0.8 sec. Intensifying screens such as Kyokko LH II (for a standard sized subject) or DuPont Q II (for an obese subject) were used in combination with Fuji RX films. We confirmed a high diagnostic value in revealing early lesions of this sytem. The skin dose test indicated that this technique was routinely applicable with safety for clinical use.

Biliary Tract↗
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↗
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↗
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↗
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↗
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↗