Monday, 4/7/97
Imaging techniques provide breakthrough for surgery
UCLA’s Optical Intrinsic Imaging provides operating doctors with
clear pictures of brain activity
By Kathryn Combs
Daily Bruin Contributor
The phrase "a picture is worth a thousand words" has been
meaningful over the years to people across the world. However, a
picture may now be worth a life thanks to a recent technological
discovery by researchers at UCLA.
Optical Intrinsic Imaging (OIS) is a technique that uses a
super-sensitive CCD (charge coupling device) camera to take high
resolution pictures of both electrochemical and vascular activity
in the brain.
During an operation, this can allow neurosurgeons to more
carefully define which regions of the brain they can and cannot
remove when making surgical corrections.
"It’s a way in which you can look at the location of where the
brain is active," said Dr. Arthur Toga, co-director of the UCLA
division of brain mapping.
"We don’t always understand the brain circuitry that is
responsible for many behaviors … OIS helps us to understand how
the brain works," he said.
Developed in conjunction with ongoing brain mapping research at
UCLA, this technology was initially used in 1993 to examine
activity in the brains of animals.
Anne Blood, a graduate student in the neuroscience doctorate
program at UCLA, has been working on the development of this
technology since she first came to UCLA in 1992.
"What this optical technique measures is changes in reflectance
from the surface of the brain," said Blood, adding that these
reflections occur because physiological processes in the brain have
optical properties.
"Things like blood flow and blood volume are correlated with
neuronal activity, and you can see them using this technique," she
continued.
Essentially, when the brain is active, it requires a certain
amount of energy. This energy is supplied, in the form of sugars
and oxygen, to the brain via increased blood flow.
However, according to researchers on this project, such as
Blood, these changes are so minute that they cannot be detected by
the naked human eye, making this technique vital as a guide for
neurosurgeons.
"We’re within tens of microns," said Toga. "The thickness of a
human hair is a few hundred microns."
"A lot of techniques like PET (Positron Emission Tomography) and
FMRI (Functional Magnetic Resonance Imaging) use vascular measures
to infer neuronal activity," said Blood.
The advantage of OIS over other techniques, such as PET and
FMRI, is that it appears to measure better electro-physiological
activity of the brain. However, vascular measurements still
frequently interfere with the collection of data, a problem that
researchers are currently trying to overcome.
Andy Cannestra, a fourth-year MD/Ph.D. student and also a
researcher working on this project, is partly responsible for
bringing this technology to the operating room.
"When I came here to UCLA, the optical system was running in
animals," said Cannestra. "However, it was only being utilized in
animals."
With the help of some of his colleagues, Cannestra spent the
first nine months of his research implementing the OIS system in
the operating room and was able to use this technique for the first
time in late 1994.
"It worked great," said Cannestra. "However, it was beginner’s
luck. Subsequently there remained problems to be dealt with and it
has taken three years of refinement to get to the point we are at
now," he said.
"Now the system is quite robust. There’s always improvements
that can be made, but currently there is no difficulty in imaging
any given patient," he added.
Cannestra explained that this technique helps neurosurgeons to
more accurately predict where the active regions of the brain are
and which of these regions are responsible for specific functions,
such as speech or vision.
"It turns out that we don’t have any high resolution techniques
(aside from OIS) for measuring brain activity and in the operating
room, when you’re operating near the eloquent cortex, it is really
important to map these areas so that we stay away from them," he
said.
The eloquent cortex is the region of the brain that is
responsible for vital functions such as motor, hearing, speech,
vision and sensation.
"During an operation, we have to identify regions of the brain
that are still working properly to avoid damage to those when, for
example, a tumor is being resected," Toga said.
"One of the things that a surgeon has to do is to try to avoid
damaging areas of the brain that would have a profound negative
impact on the quality of life for that person," he continued.
OIS, while still in the research and development stage, has been
used on approximately 25-30 different patients at the UCLA Medical
Center, according to Toga. This technique is being researched by
other universities and hospitals as well.
Researchers say they are hopeful that this technique will become
a part of routine clinical practice within the next few years but
stated that there is still rigorous testing to be done.UCLA
Department of Neurology
Highlighted areas are the result of wrist stimulation.