Shining new light on epithelial cancers
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Conceptual drawing
of the angled illumination probe
(28K
JPG)
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n inexpensive fiber-optic probe can now noninvasively
look for pre-cancerous or early-cancerous lesions in epithelial tissue
such as the skin and cervix with much better precision. The diagnostic
test works because when you shine light of a certain wavelength, or
color, on biological molecules, they absorb it and emit fluorescent
light of a different color, says Assistant Professor Nimmi
Ramanujam. “The color and the intensity of the light can tell
you something about the molecules you’re looking at,” she
says.
However, because the current technology averages
what it “sees” over a range of tissue depths, the test isn’t
as accurate as it could be, says Ramanujam.
In work funded by a National Cancer Institute collaborative
grant, she and Research Assistants Quan Liu and Changfang Zhu are developing
improvements to the existing fiber-optic probe that could tell physicians
exactly what they’re seeing at different tissue depths.
The additional information is important, she says,
because epithelial tissue consists of two “layers.” The
top portion is comprised of cells, while underneath, a structural element
called the stroma contains collagen and blood vessels and provides nutrients
to the cells on top. And when, for example, cervical epithelial tissue
starts to transform to a diseased state, those two layers respond differently
and physicians using the current averaging technique could miss the
change.
The secret to gathering the additional information
is in the angle of approach. While today’s optical probes deliver
the light perpendicular to the tissue via one fiber and collect the
fluorescence via another, Ramanujam’s group discovered that by
changing the angle
of illumination delivery, they can control the depth at which the light
penetrates the tissue. “And then by having different illumination
angles, you get a much wider range of selectivities to different layers,”
she says. “You’re in a sense dissecting out the layers without
physically cutting them apart.”
The advance will enhance physicians’ ability
to identify pre-cancerous or early-cancerous changes in tissue. In addition,
it requires only a simple refinement to existing optical imaging systems
without increasing their complexity or cost.
The group is patenting the discovery via the Wisconsin
Alumni Research Foundation.
