Résumé
Delivering the radiation dose to the target volume and minimizing the dose to normal tissues are the main objectives in radiotherapy. The aim of our study is to enhance the contrast of the portal image to increase the accuracy of delineation of the organs in the irradiation field. The software was written based on local enhancement of the pixel values in image matrix. The portal images were digitized by charged coupled device [CCD] in compatible format to be read with this program. This program was applied as an m-file in MATLAB imaging tool box to the matrices of the portal images. The imaging parameters before and after application of the program were compared. The quantitative information of images was obtained. Analysis of the mean and standard deviations of the results has shown that the difference of the criteria between two groups of the images is significant [p< 0.01]. In qualitative analysis, final images scores were based on "special weight ". The result of this test confirms the superior quality of the post-processed images from the professional view point. Superiority of final images within the three studied parameters by the experts [superiority of lung image, superiority of thorax and its soft tissue images] can be used to increase the accuracy of the treatment set up and decrease the probability of normal tissue complications