Image magnification in digital fluoroscopy.

Image magnification is inherent in radiography. In digital fluoroscopy, the three components of magnification are geometric, electronic and photographic. In this study, the total magnification factor of a digital imaging system was determined by two methods, 1) comparison of measurements of a known object to its image and 2) calculation of geometric, electronic and photographic magnification from the imaging system specifications. Both methods were employed for various focal-film distances, image intensifier tube modes and laser printer formats. Results of these two methods were different due to the detrimental effect of penumbra on image quality with increasing magnification. If a radiographic image is to be used to approximate object size, then a technique should be used that will minimize magnification. In digital fluoroscopy this is achieved with the shortest object-film distance (assuming a fixed focal-object distance), largest image intensifier mode and greatest number of images per sheet of film.

X-ray enlargement modified for use in experimental animal science.

The primary enlarged x-ray image is produced by a reduction of the focal-film-distance to 80 cm at a given focal size of 0-15 mm. The advantages of this technique as compared to conventional x-ray methods are exemplified with x-ray images from the shoulder joint of a European hamster, a pseudoarthrosis in the foreleg of a beagle, and a renovasography of a rat. The principles of the technique and its significance for investigations using small laboratory animals are discussed.