CHICAGOComputer-aided detection (CAD) has been shown to improve the
identification of breast malignancies on film-based mammography in studies
involving large databases of films, said Kathryn O’Shaughnessy, PhD, director
of clinical and regulatory affairs, R2 Technology, Inc., Los Altos, California.
Now, the method has been shown to be equally accurate in the analysis of
full-field digital mammography images, she said at the 87th Scientific Assembly
and Annual Meeting of the Radiological Society of North America (abstract 995).
Dr. O’Shaughnessy and her associates studied 90 biopsy-proven breast
cancers, including 67 invasive carcinomas and 23 cases of ductal carcinoma in
situ (DCIS), that had been diagnosed on a full-field digital system (GE Medical
Systems’ Senographe 2000 D) during screening or diagnostic mammography at
Most of the studies (82) were diagnostic. More than 60% of the lesions in
the study were less than 2 cm in size; only a few were over 3 cm, she pointed
Images that had been acquired on a digital detector were sent to a soft copy
review workstation. The investigators used R2 Technology’s ImageChecker to
analyze each image and flag regions of interest. They then compared the flagged
regions to exact lesion locations provided by the radiologists at the clinical
CAD was considered to be correct if the system placed a marker at the site
of a mass or a microcalcification that had been previously marked and annotated
by a radiologist in at least one view. CAD results also had to distinguish
between calcifications and mass lesions in order to be labeled as correct.
Results from CAD screening of digital mammograms were compared with those
achieved by the same CAD system when examining 1,083 biopsy-proven breast
cancers and 346 normal breasts that had been imaged with conventional film
screen mammography. The total number of false-positive marks for either masses
or microcalcifications was tallied for every normal case.
On the digital images, the CAD system correctly marked 33 of 34
micro-calcifications (97%) and 47 of 56 mass lesions (84%) for an overall
sensitivity of 89%. The average number of false marks on normal cases was 0.55
per image. These results were equivalent to those obtained with film screening
mammography. CAD correctly identified 399 of 406 microcalcifications (98%) and
580 of 677 masses (86%), for an overall sensitivity of 90%. The average number
of false marks on normal cases was 0.5 per image. There was no statistical
difference between CAD performed on full-field digital mammograms or film mammo-grams,
Dr. O’Shaughnessy said.