Wenli Cai PhD, Presenter: Nothing to Disclose

Bob Liu PhD, Abstract Co-Author: Nothing to Disclose

Hiroyuki Yoshida PhD, Abstract Co-Author: Patent holder, Hologic, Inc Patent holder, Median Technologies

Partial volume effects and inhomogeneity are two major artifacts in electronic cleansing (EC) for non-cathartic CT colonography (CTC). Our purpose was to develop a novel method of EC for non-cathartic dual-energy CTC using a subvoxel multi-spectral material classifier and a regional material decomposition method for differentiation of residual fecal materials from colonic soft-tissue structures.

An anthropomorphic colon phantom, which was filled with a mixture of aqueous fiber (psyllium), ground foodstuff (cereal), and non-ionic iodinated agent (Omnipaque iohexol, GE Healthcare, Milwaukee, WI), was scanned by a dual-energy CT scanner (SOMATON, Siemens) with two photon energies: 80 kVp and 140 kVp. The dual-energy CTC images were subjected to a dual-energy EC scheme, in which a multi-spectral material classifier was used to compute the fraction of each material within one voxel by an expectation-maximization (EM) algorithm. This was followed by a regional texture segmentation method for material decomposition to identify homogeneous sub-regions (tiles) as fecal materials from other tissue types by use of texture features from dual-energy CTC images. The results were compared with the registered CTC images of native phantom without fillings.

The classification accuracy of the multi-spectral material classifier was 94.7% for air-tagging boundary (AT-boundary) caused by the partial volume effect and 96.7% for residual materials (foodstuffs and air bubbles) caused by inhomogeneous tagging. The classification overall accuracy after the regional material decomposition was improved up to 99% for both AT-boundary and residual materials.

Dual-energy EC scheme can substantially reduce the partial-volume effect and inhomogeneity artifacts in EC for non-cathartic CTC.

Our new Dual-energy EC method with reduced subtraction artifacts can provide diagnostically useful visualization of the colonic lumen in CTC examinations.

Cai, W, Liu, B, Yoshida, H, Dual-energy Electronic Cleansing Scheme for Noncathartic CT Colonography: A Phantom Study.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8016625.html