Proceedings Article | 17 March 2008
KEYWORDS: Image segmentation, Virtual colonoscopy, Colon, Tissues, Computer aided design, Computer aided diagnosis and therapy, Signal attenuation, Forward error correction, Colorectal cancer, Image processing
Electronic cleansing (EC) is a method that segments fecal material tagged by an X-ray-opaque oral contrast agent in CT
colonography (CTC) images, and effectively removes the material for digitally cleansing the colon. In this study, we
developed a novel EC method, called mosaic decomposition, for reduction of the artifacts due to incomplete cleansing of
heterogeneously tagged fecal material in reduced- or non-cathartic fecal-tagging CTC examinations. In our approach, a
segmented colonic lumen, including the tagged regions, was first partitioned into a set of local homogeneous regions by
application of a watershed transform to the gradient of the CTC images. Then, each of the local homogeneous regions
was classified into five different material classes, including air, soft tissue, tagged feces, air bubbles, and foodstuff, based
on texture features of the tile. A single index, called a soft-tissue index, is formulated for differentiation of these
materials from the submerged solid soft-tissue structures such as polyps and folds. Here, a larger value of the index
indicates a higher likelihood of soft tissue. Then, EC is performed by first initializing the level-set front with the
classified tagged regions, and the front is evolved by use of a speed function that was designed, based on the soft-tissue
index, to reserve the submerged soft-tissue structures while suppressing the air bubbles and foodstuff. Visual assessment
and application of our computer-aided detection (CAD) of polyps showed that the use of our new EC method
substantially improved the detection performance of CAD, indicating the effectiveness of our EC method in reducing
incomplete cleansing artifacts.
