NEW ORLEANSA modification of SPECT (single proton emission
computed tomography) scintimammog-raphy with the radionuclide
technetium sestamibi is a promising adjunct to equivocal mammograms
that are difficult to interpret, said David H. Feiglin, MD, professor
of radiology, SUNY Health Science Center, Syracuse. He presented the
findings of his collaborative study at the American Roentgen Ray
Society annual meeting.
Currently, the procedure for SPECT reconstruction of sestamibi
distribution in breast tissue utilizes standard filtered back-projection
(FBP) algorithms. Streak artifacts with no resolved uptake in breast
tissue occur due to confounding high activity in heart and liver.
Dr. Feiglin and his colleagues have developed a new statistical
algorithm to provide clinically useful images of sestamibi in the
First, a breast phantom was created, utilizing a variety of hollow
spheres of known diameter placed between saline bags strapped to a
standard chest phantom. Their location was spacially confirmed using
multiplanar MR imaging.
The levels of radioactivity during SPECT imaging could be varied over
a wide range. The breast phantom allowed collection of large data
sets for analysis.
The algorithmic function derived from the phantom studies was then
applied before SPECT reconstruction, to compress the dynamic range of
the data. Standard FBP was subsequently utilized, with the
appropriate inverse algorithm applied afterward to decompress the
data. Finally, scatter correction was applied.
The newly modified procedure was tested in 18 women with small,
palpable breast masses. After x-ray mammography, and before needle
biopsy, planar imaging and SPECT (both standard and modified)
scintimammography were performed. Planar imaging was done both before
and after SPECT imaging. MR imaging was also performed.
Conventional SPECT failed in all 18 cases. With standard SPECT,
we saw nothing in the breast, Dr. Feiglin said, but the
modified SPECT procedure detected three tumors not found on planar
imaging. Overall, the new procedure was superior to planar
imaging and similar to MR imaging.
Modified SPECT certainly improves on standard SPECT
imaging, Dr. Feiglin said. Even at low levels of activity
you can discern activity you cant see with the standard