RARE-EARTH SCATTER FRACTIONS IN CHEST RADIOGRAPHY

A beam stop technique was used to measure the densitometric scatter fr actions under three regions of a humanoid chest phantom utilizing LaOB r and Gd2O2S screens. For these receptors, the scatter fractions under the lung and retrocardiac areas were 13%-36% lower than published val ues for CaWO4. In the mediastinal area, there was no significant diffe rence between the CaWO4 and rare-earth phosphors. The use of grids red uces the scatter fraction in all three regions by 40%-75%. With and wi thout a grid, radiographic contrast with Gd2O2S was measured utilizing simulated lesions placed above the lung and retrocardiac areas.