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Transillumination
or Diaphanography
In
transillumination, light is shone through the breast to illuminate
its interior structure (3). By using beams of light in the red and
near-infrared spectrum, transillumination produces an image of breast
tissue on film, usually through video systems that permit simultaneous
recording and viewing on a monitor.
This
technique is based on the principle that different types of tissues
(i.e., cancerous and normal tissues) will manifest different patterns
of light scatter and absorption; therefore, the transmission of
light through the breast will vary in identifiable ways.
Within
the breast, adipose (fatty) breast tissue typically absorbs less
light and thus allows greater light transmission. Both glandular
breast tissue and cancerous tissue absorb more light and allow comparably
less light transmission; however, the increased vascularity of carcinoma
yields comparably lower light transmission than normal glandular
breast tissue.
Transillumination
has at least four important limitations as a method for breast cancer
screening.
- First,
transillumination is not sufficiently sensitive or specific to
be an acceptable screening technique for breast cancer.
- Second,
transillumination is especially ineffective in detecting small
(less than 1 cm) tumors.
- Third,
the sensitivity of transillumination is substantially diminished
for tumors near the chest wall and for women with dense breast
tissue, because dense breast tissue produces greater light scatter.
-
Fourth, transillumination cannot distinguish clearly between the
increased vascularity associated with cancer and the increased
vascularity associated with different areas of normal breast structure,
some benign breast conditions, and internal hemorrhage associated
with recent biopsy.
Source:CDC
Morbidity and Mortality Weekly Report
Return
to-> Diagnosing
Breast Cancer - Tools & Techniques
Elsewhere
on the Web:
MedlinePlus
Encyclopedia - Transillumination
Transillumination
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