NEWS: Computer Simulations Help Fine-tune Laser Attack On Cancer
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Computer Simulations Help Fine-tune Laser Attack On Cancer
ScienceDaily (Mar. 25, 2009) — Two
lasers may be better than one when attacking cancer cells, according to a paper
by Rice University scientists.
Yildiz Bayazitoglu, Rice's H.S. Cameron Chair Professor of Mechanical
Engineering and an authority on heat transfer and fluid flow, and doctoral
student Jerry Vera are using computer simulations to quantify the effect of
heating nanoparticles with near-infrared lasers to kill cancer tumors without
damaging healthy tissue.
They hope to raise the efficiency of destroying tumors by fine-tuning
methods of heating them based on the size and composition of not only the tumor
but also the surrounding tissue.
The paper summarizing their results is published in the January issue of the
International Journal of Heat and Mass Transfer.
The researchers found that attacking a tumor with two lasers can heat it
more thoroughly than a single laser. For tumors as large as one centimeter,
simulations showed opposing lasers surgically inserted via fiber optics in a
minimally invasive procedure produced the most uniform temperature profile in
every case.
Lasers and nanoparticles are already being used to treat cancer. A Houston
company founded by Rice scientists Jennifer West and Naomi Halas, Nanospectra
Biosciences, Inc., is conducting human tests of a system that uses nanoshells
heated by near-infrared lasers to kill tumors. Bayazitoglu, West and Halas are
all part of Rice's Laboratory for Nanophotonics.
The Bayazitoglu group's approach would refine such treatment by taking into
account the light-scattering properties of nanoparticles. Their concern is that
nanoparticles near the surface of a tumor will block a laser from reaching
those at the center.
"Think about it this way: If you’re driving on a very foggy
night, you can only see just so far no matter how good your headlights
are," wrote Vera in an article about the research. "That's because
the millions of small water droplets in the air absorb and scatter the light,
deflecting the beams from your headlights before they can reflect off of
whatever’s ahead of you on the road.
"Nanoparticles dispersed within a tumor do exactly the same thing.
They're very good at absorbing laser light and generating heat, but within
particularly thick tumors, that same quality prevents a lot of the light from
reaching deeper into the tissue."
Bayazitoglu said this phenomenon, called "extinction," is
"highly undesirable." A uniform temperature profile of at least 60
degrees Celsius has to be created to kill the whole tumor. "Raising the
temperature on one end but not the other will simply allow the tumor to
re-grow, and that doesn't solve the problem – or cure the patient."
The density and placement of nanoparticles in the tumor are important, said
Bayazitoglu. "Ideally, you should put nanoparticles at the center of the
tumor, then kill it from the center out," she said.
Laser treatment may be effective even if nanoparticles are not used, she
said. "If the tumor has good absorption properties, slow heating can do a
good job of killing the cancer, because the heat has time to get inside. If
you're doing that, sometimes it's better not to use nanoparticles."
With so many tissue types and the great variety of cancers people face, the
importance of accurate simulations cannot be overemphasized, the researchers
said. They hope the ability to calculate scenarios will allow doctors to find
the best laser therapy to produce the perfect heating environment.
The research was funded by the Alliances for Graduate Education and the
Professoriate program through the National Science Foundation.
Journal reference:
1.
Jerry Vera and Yildiz Bayazitoglu. Gold nanoshell density variation
with laser power for induced hyperthermia. International Journal of Heat and
Mass Transfer, 2009; 52 (3-4): 564 DOI: 10.1016/j.ijheatmasstransfer.2008.06.036
Adapted
from materials provided by Rice
University.
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