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Biomedical subjects

F Goos

Publications and source records attributed to F Goos.

7 recordsLinked to original sources
PubMed1986

[Sharpness of detail and density in film-screen systems].

A study of detail perceptibility and of screens based on rare earths, using different types of films, shows that the intensifying action of these screens has a voltage gradient; however even the lowest intensifications are still above those of CaWO4 special screens. Sharpness of definition is very great at low kV values. There is a rapid drop as the density increases, this drop being due to a "saturation" effect. This effect becomes less and less noticeable at medium and high kV levels. Medichrome film shows a satisfactory visualisation of details even at very high densities. Screens with maximum intensifying effect with films of great sharpness of detail but less sensitivity do not offer any advantage over medium-intensifying screens with medium-sensitive films; this also applies to the required dose.

Densitometry↗
PubMed1985

[Simultaneous tomography using higher-sensitivity screens].

Experiments were carried out for performing multiplane tomography using rare earth screens. These screens provided adequately regular exposures at various levels and with good details. Dose reduction of at least 50% can be achieved.

Absorption↗
PubMed1979

[Experimental study on image quality when using screens in mammography (author's transl)].

1. Different type of screens and x-ray films have been investigated using a Kodak mamma-phantom I.T.O. 745 and compared with conventional non screen industrial film radiography. 2. Dosisreduction by using screens depends on the used film/screen system. It is possible to reach a relation of 1 : 10. 3. The information depends on type of screen and of type of film. Therefore, it is possible to reach the information of non screen industrial film radiographs. 4. A suitable film/screen system allows without loss of any diagnostic information to replace non screen industrial films needing a high exposure dosis by a film/screen system needing decreases dosis.

Female↗
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↗
PubMed1977

[Application of intensigying screens on the basis of rare earths (author's transl)].

Investigations on intensifying screens with rare earths are presented with special regard to clinical application. Speed, gradation (gamma), resolution as well as contrast transfer factor (ctf) are examined and compared with corresponding results of CaWO4 Special Screens. The examined screens on Lanthan and Gadolinium base show a marked kV dependence especially at lower voltage (for instance 40 kV) which is unfavourable. The speed of these screens is lower than that of CaWO4 Special screens. Lanthan screens (MR 400/SE 4 LG 17) intensify twice to three times (MR 600/SE 6) compared with CaWO4 Special Screens. Intensification of the Gadolinium screens is lower except the screen/film combination alpha 8/XM which is only due to the higher speed of the XM film. Resolution and contrast transfer factor are in the range of CaWO4 Special Screens with the exception of the highest intensifying systems MR 600/SE 6 respectively alpha 8/XM with lower resolution and contrast transfer factor. Gradation is nearly the same with CaWO4 Secial Screens. The mottle caused by rare earth screens is due to a.) its own structure and b.) to quantum noise disturbing the image quality. Clinical application is demonstrated with a phantom and further discussed.

Mathematics↗