gators scanned the sample with focused
light beams, which hit and excited the
fluorescent pattern, resulting in the
glowing letters emanating from inside
the tissue. They also used the technique
to take images of tumors tagged with
The fluorescence is used only during
the final imaging scan, Yang said, and the
technique works whether the dye is used
“We can form a focused light spot [re-
gardless],” he said. “We chose to do fluo-
rescence imaging here because our tech-
nique is able to generate a sufficiently
strong focused spot to excite fluorophores
to provide image contrast.”
Doctors also could use the technique to
treat cancer with photodynamic therapy,
which currently can be used only at the
surface of tissue because of the way light
is easily scattered. The new method should
make it possible to reach cancer cells
deeper inside tissue.
Left, light enters the tissue sample and is scattered
(blue arrows). From above, ultrasound is focused
into a small area inside the tissue. The ultrasound
shifts the frequency of any light that passes through
that area ever so slightly, changing its color. The
color-shifted light (green) is then recorded. Right, the
recorded light is sent back to retrace its steps to the
small region where the ultrasound was focused –
which means the light itself is focused on that area.
Moth eyes inspire improved x-ray imaging
NEW YORK – A new class of nanoscale materials modeled after
a moth’s eye could improve the light-capturing efficiency of
x-ray machines and similar medical imaging devices.
As with butterflies, moths have large compound eyes composed of many thousand ommatidia – structures comprising a
primitive cornea and lens, connected by photoreceptor cells.
Unlike those of butterflies, however, moth eyes are extraordinarily antireflective, bouncing back only a small portion of the light
that strikes them. This adaptation makes the insects less visible
to predators during their nocturnal flights. Because of this, engineers have looked to the moth eye to help design more efficient
coatings for solar panels and antireflective surfaces for military
City University of New York professor Yasha Yi and colleagues at Tongji University in Shanghai have taken this feature
a step further: They have used the moth eye as a model for developing nanoscale materials that someday could reduce the x-ray
radiation dosages received by patients, while improving the
resolution of the resulting images.
The scientists focused their experiment on “scintillation”
materials – compounds that, when struck by incoming particles,
absorb the energy in the form of light. Such scintillators are used
in radiographic imaging devices to convert the x-rays exiting the
body into visible light signals picked up by a detector to form
A higher x-ray dosage improves output but is not healthy for
patients. As an alternative, Yi’s team found that improving the
scintillator’s efficiency at converting x-rays to light improved
the output. Their new nanomaterial does just that.
The material consists of a 500-nm-thick thin film composed
of a cerium-doped lutetium oxyorthosilicate crystal.
“We need a thin film to fabricate the light-extraction structure,”
Yi told BioPhotonics. The layer was needed so as not to perturb
the scintillation material’s light emission layer.
A scanning electron microscope image of a leaf miner moth’s eye. Moths’ large
compound eyes are extraordinarily antireflective, bouncing back only a small
portion of light that strikes them; now, researchers have used the moth eye as a
model for new nanoscale materials for improved x-ray imaging. Courtesy of