WASHINGTONA new technique employing high-resolution contrast-enhanced
magnetic resonance imaging (MRI) can distinguish between benign and malignant
breast lesions by showing lesion perfusion patterns (images and
Figure 1). Hadassa Degani, PhD, head of the Department of
Biological Regulation, the Weizmann Institute of Science, Rehovot, Israel,
discussed the method, developed in her lab, at the Susan G. Komen Breast
Cancer Foundation 5th Annual Conference on Innovations in Quality Care.
The new technique appears promising not only as a diagnostic tool but also
as a means of monitoring the effects of antiangiogenic agents and
chemotherapy regimens in breast cancer patients, Dr. Degani commented (see
Figure 2 ).
Earlier work by Dr. Degani and her colleagues in which they monitored
perfusion of tumors in animal models of breast cancer provided valuable
information about the physiology of the microvasculature of benign and
malignant lesions, she said. Two parametersmicrovascular permeability and
extracellular volume fractionproved to be most useful in making the
distinction between normal and cancerous tissue.
Unlike normal tissues, perfusion in tumors is "irregular and
heterogeneous," Dr. Degani said. The immature blood vessels of malignant
tumors differ from normal vessels by being "much leakier" (ie, having higher
permeability). Differences in cell density are also important. Cancer cells
are "more crowded" than normal ones, she said. Contrast agents, therefore,
will slowly fill up the larger empty spaces in normal tissues relative to the
fast fill up of the lower extracellular volume fraction for cancerous tissue.
The new method uses gadolinium-DPTA as a contrast material. Images are
obtained via the three-time-point (3TP) method developed in Dr. Degani’s lab.
Using 3TP, contrast-enhanced im-ages are recorded at three time pointsone
before the contrast agent is administered into the bloodstream (t0) and two
afterwards (t1 and t2). The wash-out pattern between t1 and t2
is displayed
as a color hue (with red typical of cancerous tissue, green indeterminant for
cancer, and blue typical of benign tissue). The wash-in rate between t0 and
t1 is displayed as color intensity.
Special 3TP software, using mathematical algorithms, relates the color
hue/intensity pattern to the two perfusion parameters, with red (typical of
cancer) indicating high microvascular permeability and low-to-medium
extracellular volume fraction. The software program then provides a
combination image that overlays the color-coded dynamic parameters onto the
conventional MR images showing morphology.