Effect of radiographic magnification on image contrast of blood vessels

Blood vessel phantoms 0.5--4 mm in diameter were radiographed with a 0.1 mm x-ray tube with and without scattering medium. The contrast of the blood vessel images was determined by densitometry. Without scattering medium, magnification did not increase the image contrast for 1 mm or larger vessels. With scattering medium, contrast improved significantly due to the reduction of scattered radiation by the air gap between object and film.