Computer aided diagnosis (CAD) system assist the doctors in several diagnostic tasks , one of them could be lung lesion detection. A major difficulty in the analysis of chest radiographs is due to invisibility of abnormalities caused due to superimposition of rib cage shadow on main lung tissue which is to be examined. Suppressing the rib cage shadow over lung tissue with no much medical information loss would therefore be helpful for the doctors to manually identify the abnormality such as lung nodules and hence save reasonable amount of time. The presence of rib cage shadow over lung tissue, often proves to be obstacle for visibility of nodules and further analysis of lung. Use of reasonable model of simple cells in mammalian vision system such as Gabor Filter helps to extract most of the ribcage features followed by enhancement of image contrast and manual segmentation of lung area. Enhancement of image contrast is carried out by using CLAHE method. This project demonstrates the process of computer aided ribcage shadow suppression with the help of Gabor filter.