Automated teniae coli detection and identification on computed tomographic colonography

Abstract

Purpose: Computed tomographic colonography (CTC) is a minimally invasive technique for colonic polyps and cancer screening. Teniae coli are three bands of longitudinal smooth muscle on the colon surface. Teniae coli are important anatomically meaningful landmarks on human colon. In this paper, the authors propose an automatic teniae coli detection method for CT colonography.

Methods: The original CTC slices are first segmented and reconstructed to a 3D colon surface. Then, the 3D colon surface is unfolded using a reversible projection technique. After that the unfolded colon is projected to a 2D height map. The teniae coli are detected using the height map and then reversely projected back to the 3D colon. Since teniae are located at the junctions where the haustral folds meet, the authors apply 2D Gabor filter banks to extract features of haustral folds. The maximum response of the filter banks is then selected as the feature image. The fold centers are then identified based on local maxima and thresholding on the feature image. Connecting the fold centers yields a path of the folds. Teniae coli are extracted as lines running between the fold paths. The authors used the spatial relationship between ileocecal valve (ICV) and teniae mesocolica (TM) to identify the TM, then the teniae omentalis (TO) and the teniae libera (TL) can be identified subsequently.

Results: The authors tested the proposed method on 47 cases of 37 patients, 10 of the patients with both supine and prone CT scans. The proposed method yielded performance with an average normalized root mean square error (RMSE) ( ± standard deviation [95% confidence interval]) of 4.87% ( ± 2.93%, [4.05% 5.69%]).

Conclusions: The proposed fully-automated teniae coli detection and identification method is accurate and promising for future clinical applications.

Figure 1

Colon and teniae coli configuration. Adapted from [A. Huang, D. Roy, M. Franaszek and R. M. Summers, “Teniae coli guided navigation and registration for virtual colonoscopy,” Proceedings of the IEEE Visualization Conference (2005), pp. 279–285] Copyright [2005], American Institute of Physics.

Figure 2

The preprocessing steps of obtaining height map for teniae detection. (a) 2D slice from prone CTC. The arrows indicate locations of three teniae in the wall of one part of the colon. It is very difficult to see teniae on 2D CTC slices. (b) Colon segmentation of image (a). (c) Reconstructed 3D colon surface. (d) 3D flattened colon surface. (e) Unfolded colon mapped to a rectangular region. (f) 2D height map image.

Figure 3

(a) Spatial response profile of the even Gabor function. (b)–(e) Intensity plots of even Gabor filters with orientation: $0,\pi /4,\pi /2\mathrm{,}\mathrm{and}\mathrm{\hspace{1em}}3\pi /4$. (f) Spatial response profile of the odd Gabor function. (g)–(j) Intensity plots of odd Gabor filters with orientation: $0,\pi /4,\pi /2\mathrm{,}\mathrm{\hspace{1em}}\mathrm{and}\mathrm{\hspace{1em}}3\pi /4$.

Figure 4

Illustration of detection process of one tenia. (a) 2D Gabor filter response to height map image. (b) Sobel operator with thresholding applied to image (a). (c) Detected fold centers. (d) Connected fold centers. (e) A detected tenia.

Figure 5

Illustration of how to locate fold centers. (a) Image before fold center location. (b) Integration of image (a) along its horizontal direction. (c) The located vertical coordinates of fold centers. (d) Example of rectangular ROI, highlighted in rectangle, used to locate the horizontal coordinate. (e) Magnified image of the ROI, and integration of the ROI in vertical direction. Vertical lines indicate the detected local maxima. (f) Detected haustral fold centers superimposed on image (a).

Figure 6

A pair of supine (a, c) and prone (b, d) CTC: (a, b) Teniae highlighted on 3D colon surfaces. (c, d) Teniae marked on CTC slice.

Figure 7

Teniae coli identification. (a) The relationship between the locations of the ICV and the three teniae on a transaxial CTC slice; (b) Teniae projected on coronal view; (c) Teniae projected on sagittal view; (d) Teniae highlighted on 3D colon surface (back to front view).

Figure 8

Teniae coli detection results in portion of the colon of three different cases (a, b), (c, d), (e, f). (a), (c), and (e): height maps. (b), (d), and (f): detection results (white line) and manual reference standard (black line).

Figure 9

(a) An example of flattened colon with different colon regions (ascending, transverse, and descending) labeled. Detected teniae also shown on the colon. The obscurity of descending colon is presented and only two teniae were detected on descending colon. (b) and (c) Two examples of different patients illustrate one of the teniae ended at the descending colon, pointed by arrows. Case shown in (c) is the same case in Fig. 6a.

Figure 10

Example showing how number of teniae coli varies from region to region. In the ascending colon, three teniae coli are detected; in the lower part of the descending colon, only two teniae are detected (TO and TM).