Biomedical subjects
Publications and source records attributed to U Welander.
The basic mathematics for elliptical narrow beam rotation radiography are deduced and exemplified. An analysis of the functioning principle of elliptical systems shows that the essential factor in the image formation is the form of the evolute of the ellipse, which determines the projection of the object. The image layer does not necessarily coincide with the ellipse.
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The definition of the blurring of narrow beam rotation radiography is revived. The relative value of the blurring is considered to be the most reliable measurement. Calculations of the layer thickness should be based on the definition of the relative blurring. Experimental tests were performed, which confirm the mathematically presented hypothesis and also confirm the validity of the mathematical model of narrow beam rotation radiography presented by WELANDER (1974).
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Technical aspects of photographic subtraction of original films in black and white and blue and white (Medichrome) under standard development conditions available in any roentgen unit are described. The adjustment necessary to control the gamma-value of the masking film takes advantage of the capacity of some graphic films to respond with different gamma-values on variation of the color of the exposure light.
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The layer formation in rotation narrow beam radiography is analysed mathematically. It is shown that the blurring, and consequently the layer formation, is due primarily to the width of the beam; no blurring and no layer formation occur if the beam is of negligible width. The blurring is significantly affected by the magnification factor in the specific central projection typical of narrow beam rotation methods, where the rotation centre serves as an imaginary focus.
The purpose of subtraction of angiographic images is to demonstrate the vessels free of superimposed, disturbing image noise. With the aid of physical film parameters the theoretic basis for an optimum subtraction technique is presented.
The distortion of morphologic object elements, for distortion, at the exposure of a panoramic image has been determined mathematically and experimentally. As models the square, the circle, the rhomb, and the equilateral triangle were used. The general characteristics of the form distortion in narrow beam rotation radiography are analysed and described.
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Explore the source record for details and available documents.