Date of Award

Winter 1-31-1994

Document Type


Degree Name

Master of Science in Biomedical Engineering - (M.S.)


Biomedical Engineering Committee

First Advisor

Frank Y. Shih

Second Advisor

Swamy Laxminarayan

Third Advisor

David S. Kristol


The aim of Computed Tomography is to obtain information regarding the nature of the materials occupying precise positions inside the body. But due to errors in the projection data, which arise due to errors in measurement, beam hardening, missing data and noise, the reconstructed image has artifacts which reduces its diagnostic value. Thus the image obtained has to be processed to remove these artifacts and to improve the quality of the image. This is achieved by iterative reconstruction along with different post-reconstruction processing. Iterative reconstruction is done by repeating the process of projecting the image and creating new projection data which are then back projected to obtain an image of better quality. The algorithms that do these reprojections and back projections remove artifacts caused by errors mentioned above, thus enhancing the diagnostic value of the final image. Also the images obtained may be enhanced by a variety of post-reconstruction processes such as image enhancement techniques. Depending on the method these enhancement techniques may compensate for effects of specific degradation processes or can selectively emphasize or suppress selected features of the image.

This study is a) to test the accuracy of X-ray computed tomography image reconstruction applying a modified reprojection method and b) to enhance the image using a modification of the median filter. The experimental results demonstrated the superior performance of the methods.