The effect of radiographic magnification on blood vessel imaging with various screen-film systems

It has been shown that the quality of blood vessel images in cerebral angiograms can be improved either by employing radiographic magnification in conjunction with fast screens or by using slower screens and fast film without magnification. It is not known which of these methods results in better images, and under what conditions magnification used with slow screens might result in further improvement. By means of a computer, the dependence of image contrast and sharpness on magnification with various screen-film systems has been studied. One result indicates that, for blood vessel diameters less than 100 mu m and focal spot sizes of 0.3 mm or larger, the use of slow screens without magnification results in better images than those obtained with fast screens and magnification. For blood vessels larger than 300 mu m in diameter and focal spot sizes of 0.3 mm or less, fast screens with magnification can give better images than those obtained using slow screens without magnification.