NEW ORLEANSScintimam-mography utilizing a radionuclide already
approved by the FDA for cardiac imaging has been shown to compare
favorably with standard mammography in a new study presented at the
99th annual meeting of the American Roentgen Ray Society.
Conducted by Michael A. Blake, MD, (currently a fellow in body
imaging at Brigham and Womens Hospital, Boston) and his
colleagues (Drs. C. Williams, E. McDermott, and G. Duffy at St.
Vincents and St. Annes Hospitals, Dublin, Ireland), the
study prospectively compared technetium tetrofosmin
scintimammog-raphy with conventional mammography. The results showed
the new technique to be especially useful in women with dense breasts.
Another radionuclide, technetium sestamibi, is already in use for
breast scin-timammography. Technetium tetrofosmin is similar in
uptake and localization to sestamibi, but tetrofosmin is much easier
to prepare, Dr. Blake said.
The study population was composed of 106 women with clinically or
mam-mographically detected abnormalities that warranted biopsy. Each
woman underwent both technetium tetrofosmin scintimammography and
conventional mammography prior to biopsy, and the imaging results
were correlated with pathologic outcome.
Conventional mammography is problematic in women with dense
breasts or where there is architectural distortion due to prior
surgery and scarring, Dr. Blake explained. And
scintimammog-raphy does not require breast compression, he added.
In this technique, images are taken for 10 minutes each in prone
lateral and anterior supine positions, beginning 10 minutes after
intravenous injection of the radionuclide. The injection is well
tolerated by patients.
Sensitivity and Specificity
The sensitivity of scintimammography was a bit lower than that of
conventional mammography, 79.1% vs 85.7%, respectively; but
scintimammography scored much better than conventional mammography on
specificity, accuracy in distinguishing benign from malignant
lesions, and positive predictive value. The negative predictive value
(84.1%) of scintimammography was about the same as that of
conventional mammography (81.6%).
Most of the false-positive scintimam-mograms were due to highly
cellular benign conditions, such as fibroadenoma, whereas the
false-negative scans were mostly due to small tumors, Dr. Blake
Scintimammography was especially valuable in detecting malignancies
in dense breast tissue. The four cancers detected by
scintimammography but missed by conventional mammography were all in
Detecting Positive Nodes
Nodal involvement was studied in 23 cases, 13 of which were found to
have metastatic nodal involvement at biopsy. Scintimammography
detected 9 of the cases with malignant lymph nodes, with only one
false-positive result, he said.
Dr. Blake indicated that technetium tetrofosmin scintimammography had
91.9% accuracy in distinguishing benign from malignant lesions, but
he emphasized that it is a complementary technique to conventional
mammography, and is not a replacement for other complementary
The technique can help doctors target the most appropriate area for
biopsy, or it can help reduce biopsies by differentiating scar
There are occasions when something looks bad on mammogram, but
with the help of this test, it proves to be just a scar from previous
surgery, for example, Dr. Blake said.
He also noted that their findings in the small sample of patients
with nodal involvement suggest another promising area for research.