Determine the feasibility to differentiate polyps from stool with or without the use of contrast agents and to assess the feasibility and accuracy of dual energy techniques in a pilot patient study.

1.1 Formulate algorithms that use dual-energy information to quantitatively measure specific material density of colon polyps in physics based simulation.

1.2 Determine optimal scanning parameters on prototype CT equipment.

2.1 Measure the material composition density and Hounsfield number of polyps with and without simulated contrast enhancement.

2.2 Measure the accuracy of dual-energy techniques to differentiate between polyps and stool and if needed using a combination of simulated intravenous enhanced polyps and contrast material tagged stool.

3.0 Asses the clinical performance of dual-energy CTC for the detection of larger polyps 1 cm or larger without cathartic preparation.

Mayo Clinic, Rochester, Minnesota and Mayo Clinic, Scottsdale, Arizona Colonoscopy schedules.

Inclusion Criteria:

• Participants with a known colorectal polyp or colon carcinoma with pathology, at or greater than 1 cm in size on a colonoscopy that is completed either eight weeks before or after CT Colonography study visit.
• If receiving iodine oral or IV contrast, must have a creatinine less than 1.4 on record within last 30 days of study visit date. If no creatinine is available, one will be drawn for enrollment criteria purposes.

Exclusion Criteria:

• Pregnant females.
• Presence of colostomy or right hemicolectomy.
• Inflammatory bowel disease (Crohn's, chronic ulcerative colitis).
• Familial polyposis syndrome.
• Pregnant female.
• Creatinine at or greater than 1.4
• Severe or uncontrolled COPD or COLD.
• Iodine contrast allergy.