Colon CAD: Breaking Down Barriers

The stage is set for computer-assisted detection’s next target; colon CAD is poised to make its mark in the next two years. One of the primary barriers in the U.S. to colon CAD—the lack of reimbursement for screening CT colonography—is starting to crumble. And several vendors, including iCAD Inc., Medicsight and Siemens Medical Solutions, are developing easy-to-use colon CAD solutions with low false-positive rates.

In the United States, the Centers for Medicare & Medicaid Services’ (CMS) recently called for a national coverage analysis for screening CT colonography. And, the recent American College of Radiology Imaging Network National CT Colonography Trial results showed screening colonography’s performance is comparable to gold-standard invasive colonoscopy. “Screening CT colonography is gaining traction,” says Judy Yee, MD, chief of radiology at San Francisco Veterans Administration Medical Center in California. “As screening CT colonography is implemented, we want to make sure the review is as accurate and sensitive as possible.”

The bar for CT colonography and colon CAD is fairly high. CAD software should have sensitivity equal to or better than a human reader for lesions of six millimeters or more coupled with acceptable specificity and interpretation time, says Yee. “The good news,” says Abraham Dachman, MD, professor of radiology at the University of Chicago, “is that colon CAD has progressed extremely rapidly.” The false-positive rate has dropped tremendously and CAD software helps readers avoid errors of omission, the primary error in virtual colonoscopy review.

On the IT front, CAD should integrate into the CT colonography platform, allowing the reader to shift back and forth between the CT and CAD data. St. Mark’s Hospital and Academic Institute in London uses Medicsight’s ColonCAD with Vital Images Vitrea advanced visualization software. “The quality of the integration enables rapid second-reader review and cross reference of findings,” explains David Burling, MD, consultant gastrointestinal radiologist.

Solid integration should be combined with flexibility, says Burling. “CAD isn’t the same tool to all readers.” Some rely on primary 2D review, and others begin with 3D review. Some readers use CAD synchronously as they read a case, while others use it post-review like a spellchecker.

Burling also recommends reviewing sensitivity and specificity to determine which CAD system matches the practice’s needs. A large symptomatic patient population may be geared to a CAD system with rich measurement and interpretation tools. Screening targets tend to be small polyps and subtle abnormalities, so a highly sensitive CAD tool may be best.

CAD software also may incorporate automatic measurement tools to facilitate follow-up CT studies and clinical treatment. These tools may be the tip of a value-added iceberg. “Vendors are doing work to automatically download images and measurements into templated reports,” Yee says. Such features promise to make colon CAD an indispensable solution for screening CT colonography.


On the mark

Colon CAD is on the brink of widespread use in clinical practice. Reimbursement for screening CT colonography seems to be on the horizon; CAD should play an important role too as it can provide added clinical confidence for novice readers, while providing features to streamline clinical care and workflow. The future seems clear. “Colon CAD will be the standard of care,” predicts Yee.