Marek Franaszek PhD, Abstract Co-Author: Nothing to Disclose

Ronald M. Summers MD, PhD, Presenter: Nothing to Disclose

Perry Joseph Pickhardt MD, Abstract Co-Author: Nothing to Disclose

Jong-Ho Richard Choi MD, Abstract Co-Author: Nothing to Disclose

Reliable segmentation of the colon is indispensable for automatic detection of polyps on CT colonography. Positive oral contrast is given to patients to tag out remnants of stool and residual fluids. This adds an extra challenge for colonic segmentation but ultimately is beneficial to the patient because the enhanced fluid helps reveal polyps in otherwise hidden areas. Therefore, we developed a new segmentation procedure which can handle both air- and fluid-filled parts of the colon.

The proposed hybrid algorithm uses modified region growing, fuzzy connectedness and level set segmentation. The procedure organizes individual air- and fluid-filled regions into a graph that enables automatic identification and removal of undesired leakage outside the colon. We tested our algorithm on 160 CT colonography scans containing 183 known polyps (of which 96 were surround by air, 7 were totally submerged in fluid, and 80 were partially in air and partially in fluid). We used manually segmented polyps as landmarks to verify that all parts of the colonic lumen were segmented. To assess the quality of the reconstructed colonic wall, we visually inspected 24 randomly selected cases: half suspected of having leakage, and half predicted to be free of leakage.

All 183 polyps were located in segmented colon, confirming accuracy of the segmentation. In the leakage free category, all 12 cases indeed had no problem with segmentation at any intermediate stage of hybrid procedure. In the category containing cases suspected of leakage, analysis misclassified 3 cases which in fact had no leakage. Remaining 9 cases had indeed severe leakage after the first stage of hybrid segmentation. However, consecutive stages of our procedure identified and removed leakage correctly in all 9 cases. In all visually inspected 24 cases, colonic wall reconstructed with the new method showed striking improvement over the previous simple isosurface derived from original CT images.

Our procedure accurately segments the colon, as proven by polyp landmark experiments and leakage reduction and surface quality evaluations.

J.R.C.: On the medical advisory board of Viatronix, Inc.P.J.P.: On the medical advisory boards of Viatronix, Inc. and Medicsight, Inc.M.F.,R.M.S.,P.J.P.: Patents pending and/or awarded in the subject area of this abstract

Franaszek, M, Summers, R, Pickhardt, P, Choi, J, Hybrid Segmentation of Colon Filled with Air and Opacified Fluid for CT Colonography.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4406245.html