ORLANDOThe technology for mammography to go digital is here,
but it may take 5 or 10 years for the transition because of the
higher costs that the newer method entails, Maria Kallergi, PhD, said
at the Joint Cancer Conference of the Florida Universities.
Dr. Kallergi is assistant professor of radiology, University of South
Florida, and director of the H. Lee Moffitt Cancer Centers
Digital Medical Imaging & Analysis Program. There, she said,
we have the first clinical digital mammography unit from
GE. [The GE DMR 2000D, formerly known as the GE Senographe
2000D. See ONI March 2000, page 13.]
Digital mammography has certain major advantages over standard
mammography, Dr. Kallergi said. You can process the images in
various ways. For example, you can apply algorithms to manipulate the
gray scale values. The enhancement and manipulation of images
produces a variety of visual effects that, together, convey more
diagnostic information than is possible with standard x-ray
The computer can detect areas of suspicious tissue and can heighten
their display in starkly contrasting black-and-white images. Some
images end up looking like contour mapswith bumps to indicate
the presence of masses or calcifications, she said.
At the Digital Medical Imaging & Analysis Program, she said,
researchers are focusing on computer-assisted diagnosis (CAD), which
allows the automatic detection and benign/malignant classification of
masses and calcifications in mammograms. CAD detection methods, she
said, can currently reach a sensitivity of 90% to 95%, with fewer
than one false calcification cluster per image and fewer than two
false masses per image.
Soft copies of the digital images can be stored in and displayed on
the computer, or images can be printed as hard copies on a laser
printer (at a cost of about $5 per print). No more lost
films promises to be one considerable advantage of digital
mammography, she said.
Digital mammograms do require copious storage space in a
computers memory. A single digital mammogram has a size
of about 90 million bytes. A huge amount of space is required for
each patient, Dr. Kallergi said.
She discussed pending projects that involve networking. In one
scenario, various hospitals could convey their digital images to an
expert cancer center, such as Moffitt, for diagnosis.
Transmission times for the images vary enormously depending on
whether the means for conveying the data is wired or wireless.
With a 56k modem, it takes 4 hours to send one mammogram,
she said, while the transmission time via satellite is less
than 5 seconds. The key to speeding up the transmission time
via standard wired or wireless means, she said, will be image
compression via mathematical processes.
In summary, Dr. Kallergi said, while the standard mammography film
still does better in terms of spatial resolution and cost,
the newer method performs better in terms of contrast,
detection efficiency, versatility, and safety.