ATLANTAIn a retrospective review of more than 12,000 screening
mammograms, computer technology found 52% of missed cancers, Kunio
Doi, PhD, reported at the Era of Hope meeting, featuring research
sponsored by the US Department of Defense Breast Cancer Research Program.
Computer-aided diagnosis [CAD] cannot pick up lesions that are
invisible at mammography, but it can compensate for some cases of
radiologist oversight, said Dr. Doi, professor of radiology,
University of Chicago. We believe the increasingly positive
results with CAD demonstrate it can serve as a second
opinion for traditional screening mammograms.
In this study, a CAD Prototype Intelligent Workstation, developed by
Dr. Doi and his colleagues, was used to review the mammograms of more
than 22,000 women who had routine screenings in the past 5 years.
Among the first 12,670 women whose charts were analyzed during the
first 3 years, 79 developed breast cancer. Of these 79 cancer
patients, 42 had a negative prior screening mammogram. Retrospective
review of these cases showed that 19 were not visible on mammography,
but of the 23 cases that had a subtle lesion visible in retrospect,
the computer identified 12 of them. The CAD workstation
identified 52% of these missed cancers roughly a year before they
were actually detected, Dr. Doi said.
Under subcontract from the Universitys Department of Defense
grant, radiologists are now using CAD as a concurrent second opinion
for all screening mammograms performed at Grant Square Imaging, La
Grange Memorial Hospital, Hinsdale, Illinois. The center is using the
R2 Technology M1000 ImageChecker, the only CAD device FDA approved to
The radiologists are recording all
cases in which information from the ImageChecker results in
additional patient evaluation (that is, evaluation for findings not
originally perceived by the radiologist). Data analysis from that
study will begin in about 2 years, Dr. Doi said.
The next challenge for CAD is diagnosis, Dr. Doi said.
We have already developed algorithms that guide our system in
distinguishing benign from malignant lesions. I believe that in time,
as we fine-tune those algorithms, CAD will also become an important
tool in helping women avoid unnecessary biopsies in addition to
diagnosing more cancers.
How CAD Works
With the CAD Intelligent Workstation, a laser scanner first
transforms the mammography film into a detailed matrix of digital
data. Microcalcifications appear as tiny white spots, and masses
appear as round or irregular shapes.
Guided by complex programming refined over many years, the
systems computer vision and artificial intelligence algorithms
scan the digital matrix, sift out background findings and normal soft
tissue, then highlight patterns likely to represent lesions.
To detect masses, the computer looks for a deviation from the normal
architectural symmetry of the right and left breasts, using a
To detect clustered microcalcifications, the digitalized mammogram is
processed by a linear filter to improve the signal-to-noise ratio of
microcalcifications on the image. Other techniques are then used to
extract potential signal sites from the noise background and
distinguish true signals from noise or artifacts.
Areas interpreted as suspicious for either masses or
microcalcifications are flagged with arrows (see Figure). After
reviewing the mammograms and the computer output, a radiologist
prepares a report based on experienced judgment.
A service is now available to provide physicians and mammography
centers worldwide with access to CAD technology. A company called
iMammogram.com Inc. (Westlake Village, California) will collect and
return mammographic films by bonded courier, perform the CAD analysis
(which it calls CloserLook), and provide a digital archive for
The companys website, located at www.imammogram.com,
provides case studies showing the potential benefits of CAD review .
In one example, CloserLook review with the ImageChecker found
a cancer in the left breast on a womans annual mammogram.
Retrospective computer review showed that the lesion was present on
the womans prior mammogram performed 16 months earlier.
The company has also signed an agreement with General Electric
Medical Systems to develop a system that will allow mammography
centers to transmit images to iMammograms facility
electronically rather than by courier.
ONI will provide a fuller report on iMammogram.com and its
teleradiology project in an upcoming issue.