Japanese National Computed Tomographic (CT) Colonography Trial

The investigators will evaluate the sensitivity of CTC in detecting colorectal polyps and
cancers (at least 6 mm in diameter) in 1,500 subjects at increased risk of colorectal cancer
(CRC), using optical colonoscopy as the reference standard. The primary endpoint will be
sensitivity in the detection of colorectal polyps and cancers that are at least 6 mm in
diameter. The secondary endpoints will include specificity and predictive values in the
detection of colorectal polyps and cancers.

This clinical study will also evaluate the differences of the detection accuracies between
human readings with and without computer-aided detection (CAD) that automatically detects
colonic lesions in CTC images and presents the detected lesions to the readers. This
clinical study will also compare performance between radiologists and gastroenterologists in
detecting colorectal lesions in CTC images.

All the CTC images and their interpretations, optical colonoscopy reports and images, and
pathology reports of resected colorectal lesion will be prospectively collected from 12
Japanese hospitals participating in the trial. All patients' information will be completely
anonymized at each site before any analysis of the data takes place.

Inclusion Criteria:

- Outpatients who are eligible for optical colonoscopy.

- Aged 20 years or older.

- Major functions of organs of the subjects are in a good condition.

- Signed informed consent forms are obtained from the patients.

Exclusion Criteria:

- Known colorectal polyps or cancers at any site at the time of enrollment.

- Patients with inflammatory bowel disease.

- Fulfillment of clinical criteria for diagnosis of FAP or HNPCC (Amsterdam criteria).

- Serious medical conditions that may increase the risk of optical colonoscopy or are
so severe that screening would have no benefit.

- Previous colorectal surgery.

- Gastric or intestinal stenosis, abdominal adhesions, bowel obstruction or
perforation, toxic megacolon.

- Evidence of an increased risk in carrying out bowel preparation or CTC exams.

- Possibility of pregnancy.

- Optical colonoscopy or barium enema carried out within the last 3 years.

- Patients with psychological conditions that contraindicate colonoscopy or that make
them irrelevant to participate in the trial.

- Iodine hypersensitivity.

- Severe thyroid disease.

- Claustrophobia.

- Severe deafness.

- Subjects whose eligibility for this clinical trial is not appropriate by other
reasons.