FILTER WHEEL EQUALIZATION IN CHEST RADIOGRAPHY - DEMONSTRATION WITH APROTOTYPE SYSTEM

PURPOSE: To determine the feasibility of using the filter wheel equali zation (FWE) technique for radiographic equalization in chest radiogra phy. MATERIALS AND METHODS: An FWE system with two rotating wheels (on e far each lung) with 25 lung-shaped, 1.0-mm-thick copper templates wa s constructed. Preexposure images were acquired; the computer used the se images to select and position templates for each lung. An equalized radiograph was then produced. Radiographs were acquired in two male v olunteers (both 33 years of age) and in a phantom. RESULTS: Optical de nsities in the lungs and nonlung areas on a conventional phantom radio graph were 2.07 and 0.55, respectively; after equalization, the corres ponding optical densities were 2.06 and 1.42. Outside the lungs, radio graphic contrast (difference in optical density) increased threefold; in the lungs, there was a very small decrease in radiographic contrast due to beam hardening. Well-equalized and relatively artifact-free ra diographs were obtained with a 20-msec exposure time. CONCLUSION: The FWE system was shown in the laboratory to be feasible.