Scattered radiation in chest radiography

It is well known that scattered radiation degrades image constrast. Scattered radiation has not been considered a serious problem in chest radiography because the lungs have an effective tissue thickness of only about 10 cm. The chest, however, contains tissue of varying thicknesses and cross-scatter from one region to another can result in very high scatter-to-primary (S/P) ratios in some areas of the chest. Scatter-to-primary ratios were found to be very high in the central mediastinum, lung periphery and cardiac shadow. Three scatter reduction methods used in chest radiography were compared. A moving-slit device in combination with a grid was found to be the most effective scatter removal technique.