Reduction of radiation exposure in radiography of the chest.

Reduction of patient exposure in chest radiography by means of copper filtration was investigated for a range of filter thicknesses at kilovoltages commonly employed for the postero-anterior and lateral projections. The influence of copper filtration on tube output, beam quality, entrance and midplane exposures, tube load, and image contrast was determined from physical measurements and evaluation of phantom images. The results indicate that entrance exposure may be reduced by 30-40% and midplane exposure by approximately 24% through the use of a 0.32-mm copper filter, with an acceptable increase in tube load and only minor changes in the appearance of the images.