<qa>  What is the sensitivity and specificity of CTC in the unprepared colon?To improve the diagnostic performance of CTC in the prepared colon using improved spatial resolution, advanced image displays, and computer-assisted diagnosis, and to optimize diagnostic performance of CTC in the unprepared colon for colorectal polyp detection using electronic stool subtraction and computer-aided diagnostic techniques. To estimate the sensitivity and specificity of CTC in the unprepared colon for clinically important colorectal neoplasms large adenomas 1 cm and to compare such estimates with colonoscopy. To survey patient acceptance of CTC in the unprepared colon, and to assess implications for health care costs and cost-effectiveness of CTC in the unprepared colon in comparison with other approaches. 