Straightening the colon with curved cross sections: An approach to CT colonography

Rationale and Objectives. The purpose of this study was to straighten digitally and consistently the colon with curved cross sections and to compare the results with planar cross-section-based processing for computed tomographic (CT) colonography. Materials and Methods. In electric field-based straightening, curved cross sections are formed along electric force lines because of electric charges digitally distributed along the colon central path. Four straightening experiments were conducted on CT scans of a colonoscopy phantom. Representative images were studied for polyp detectability and feature distortion. Two further trials involved patient data to demonstrate the clinical feasibility of this method. Results. In colon straightening with planar sections, a polyp was counted multiple times in both phantom and patient studies where the polyps were in central path turns with substantial curvature. Furthermore, opposite the central path turns, the colon walls were undersampled with planar sections. Straightening with curved sections produced consistent mappings. Image distortion was present in straightening with curved sections, but the conspicuity of polyps was maintained. In the soft-straightening process, trilinear interpolation greatly suppressed the surface-or volume-rendering noise associated with nearest neighbor interpolation. Conclusion. Straightening with curved sections outperforms straightening with planar sections in terms of polyp detectability. This approach eliminates the navigation difficulties of current CT colonography and may have clinical use.