Fecal tagging

Papanikolaou N, Grammatikakis J, Maris T, Lauenstein T, Prassopoulos P,Gourtsoyiannis N (2003) MR colonog-raphy with fecal tagging comparison between 2D turbo FLASH and 3D FLASH sequences. Eur Radiol 13 448-452... 

Bielen D, Thomeer M, Vanbeckevoort D et al (2003) Dry preparation for virtual CT colonography with fecal tagging using water-soluble contrast medium initial results. Eur Radiol 13 453 -458... 

Goehde SC, Descher E, Boekstegers A et al (2005) Dark lumen MR colonography based on fecal tagging for detection of colorectal masses accuracy and patient acceptance. Abdom Imaging 30 576-583... 

Lauenstein TC, Goehde SC, Ruehm SG et al (2002) MR Colonography with barium-based fecal tagging initial clinical experience. Radiology 223 248-254... 

Lefere PA, Gryspeerdt SS, Dewyspelaere J et al (2002) Dietary fecal tagging as a cleansing method before CT colonography initial results polyp detection and patient acceptance. Radiology 224 393-403... 

Lefere P, Gryspeerdt S, Marrannes J et al (2005) CT colonography after fecal tagging with a reduced cathartic cleansing and a reduced volume of barium. AJR Am J Roentgenol 184 1836-1842... 

Several studies have shown that patients acceptance of CTC is greater than conventional colonoscopy or double contrast barium enema (Taylor et al. 2003). Development of minimal bowel prep or prep-less CTC through fecal tagging and electronic cleansing appears to be within reach, thus making a truly prep-less colorectal screening test an attractive possibility (Lefere et al. 2002). 

Annular structuring lesions may be misinterpreted as either spasm (Figs. 8.14 and 8.15) or residual fecal material. The use of fecal tagging with an oral contrast agent (Thomeer et al. 2003 Zalis et al. 2003 Pickhardt et al. 2005) seems to help in avoiding interpretive errors caused by residual fecal material. 

Therefore, there is the need for fecal tagging fecal tagging reduces false positive diagnosis (Lefere et al. 2002 Gryspeerdt et al. 2002) (Figs. 8.21-8.23). 

Effect of Fecal Tagging and Digital Bowel Cleansing 146... 

The second problem was partly addressed by Lefere et al. (Lefere et al. 2002, 2004a, b), who showed that dietary fecal-tagging CTC could be a viable alternative to full colon cleansing. However, the third obstacle remains problematic. In particular, the detection performance among readers can... 

The CAD system at the University Hospital Gast-huisberg achieved an 80% hy-polyp sensitivity, with 8.2 false positives per patient (4.1 false positives per data set), based on 18 patients, with 15 polyps 5 mm in 9 patients (Kiss et al. 2002). In this study, fecal tagging was used for most of the cases. A group at Stanford reported a 100% sensitivity with 7.0 false positives per data set (only the supine data set of each patient was used) based on 8 patients that included a total of 7 polyps >10 mm in 4 patients (Pair et al. 

Fig. 11.10. Example of false positives in CAD for fecal-tagging CTC. (Courtesy of R Lefere, M.D., Stedelijk Ziekenhuis, Roeselare, Belgium)...

Although encouraging, the results of these studies are limited and are not conclusive therefore, CAD for fecal-tagging CTC remains a subject for future research. 

Since bowel preparation is recognized as the most uncomfortable step in the workflow of a conventional colonoscopy as well as for CTC (Gluecker et al. 2003), in order to improve patient compliance, new reduced bowel preparation, or laxative-free study protocols, are under evaluation. Because of the presence of fecal/fluid residues, not completely removed by the absence of complete taxation, fecal tagging is mandatory. In terms of examination accuracy, several experiences have shown results similar to protocols including full bowel preparation (Iannaccone et al. 2004 McFarland and Zalis et ak 2004 Lefere et al. 2005 Dachman et al. 2007 Johnson et al. 2007). 

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