|Computer-Aided Polyp Detection Software in Combination with
Virtual Colonoscopy is as Effective as Traditional Optical Colonoscopy
A study led by the National Institutes of Health Clinical Center finds that
computer-aided detection (CAD) software in conjunction with a procedure commonly
called virtual colonoscopy can deliver results comparable to conventional optical
colonoscopy for detecting the most worrisome types of polyps.
The study is published in the December 2005 issue of the American Gastroenterological
Association journal, Gastroenterology. The work also was presented November
29, 2005 at the annual meeting of the Radiological Society of North America.
Virtual colonoscopy (CT colonography) is a minimally invasive radiological procedure.
The colon is viewed using a CT scan so there is no need for sedation or insertion
of a colonoscope, but a full bowel prep still is required. Virtual colonoscopy
is under investigation as a screening method for colorectal cancer, which is
the second leading cause of cancer death in America.
“Proper screening can prevent colorectal cancer. It is important for the scientific
and medical community to explore and perfect methods that may encourage more
people to get checked,” says Ronald M. Summers, M.D., Ph.D., the lead author
of the study. Dr. Summers is a senior investigator and staff radiologist at the
NIH Clinical Center. He is the chief of the clinical image processing service
and chief of the virtual endoscopy and computer-aided diagnosis laboratory in
the Department of Radiology.
Virtual colonoscopy uses a CT scan to create two- and three-dimensional images
of the colon. The process produces 600 to 1,000 images that are interpreted by
a radiologist. Computer-aided detection software then serves as a second set
of eyes and identifies sites that warrant closer inspection. The radiologist
again reviews these sites to make the final diagnosis.
This study set out to assess the performance and sensitivity of CAD for virtual
colonoscopy in a large screening group of patients with no symptoms of colorectal
After training the CAD system on the virtual colonoscopies of a separate group
of 394 patients, Dr. Summers and his colleagues used the CAD system on 792 patients
at three medical centers. In one day, the patients underwent both virtual colonoscopy
and conventional optical colonoscopy which is considered the gold standard for
screening. The procedures were done to detect adenomas, benign growths that may
become cancerous if not removed.
When CAD was applied to each CT colonography scan, it detected 89.3 percent
of patients having adenomas 10mm or larger, compared to 85.7 percent for conventional
colonoscopy. CAD detected 85.4 percent of patients having adenomas 8mm or larger,
compared to 89.6 percent for conventional colonoscopy. CAD’s false positive rates
were 2.1 false positive detections per patient for polyps 10 mm or greater and
6.7 false positive detections per patient for polyps 8 mm or greater. A review
of the false positives led the researchers to conclude that most would be easily
identifiable as such.
CAD detected cancer in two patients while optical colonoscopy initially detected
only one. The colonoscopist found the second cancer after getting word that virtual
colonoscopy had detected an abnormality.
“The fact that this worked so well on a large number of patients indicates that
this is a robust technique,” says Dr. Summers. “We believe it will work well
in clinical practice, but more testing in the clinical environment still is needed.”
“Research into better ways to screen for and prevent disease is an important
aspect of NIH’s clinical research mission,” says John I. Gallin, M.D., director
of the NIH Clinical Center. “Studies like this demonstrate how collaboration
enriches research. We appreciate the contribution of patients, who are our partners
in research, and the teamwork of our colleagues.”
Screening patients came from National Naval Medical Center in Bethesda, Maryland,
Walter Reed Army Medical Center in Washington, D.C. and San Diego Naval Medical
This study was done in conjunction with researchers from the National Naval
Medical Center, Walter Reed Army Medical Center and Uniformed Services University
of the Health Sciences in Bethesda, Maryland. Jianhua Yao, Ph.D., Perry J. Pinkhardt,
M.D., Marek Franaszek, Ph.D. Ingmar Bitter, Ph.D., Daniel Brickman, B.S., Vamsi
Krishna, B.A., J. Richard Choi, ScD, M.D participated in the study.
The NIH Clinical Center is the clinical research hospital of the National
Institutes of Health. Through clinical research, physicians and scientists
translate laboratory discoveries into better treatments, therapies and interventions
to improve the nation's health.
The National Institutes of Health (NIH) — The Nation's Medical Research
Agency — includes 27 Institutes and Centers and is a component of
the U. S. Department of Health and Human Services. It is the primary Federal
agency for conducting and supporting basic, clinical, and translational medical
research, and it investigates the causes, treatments, and cures for both common
and rare diseases. For more information about NIH and its programs, visit http://www.nih.gov.