Posted by Ellen on March 02, 2000 at 07:02:01:
Ultrasound Could Replace Blood Testing
Medical Tribune News Service
A new painless way to measure glucose levels
without pricking the skin has been successfully
tested in a small clinical trial and may soon be
available for use by people with diabetes. The
technique may have a variety of other uses as well.
Researchers from Massachusetts Institute of
Technology (www.mit.edu), Cambridge, and
colleagues in Pennsylvania, California, Texas and
Israel presented findings of the first human trials
(involving seven volunteers with type 1 diabetes) of
a noninvasive technique that uses ultrasound to
monitor glucose levels. The study was published in
the March issue of Nature Medicine.
"We're hopeful that this technique could
eventually be used as a universal way of
noninvasively sampling a variety of substances from
humans," said Robert Langer, a study author and
Kenneth J. Germeshausen professor of chemical
and biomedical engineering at MIT.
"Blood tests for any number of things," he
continued, "such as cholesterol and bilirubin, could
someday be replaced with this technique."
The outer layer of skin is composed of dead
cells and fatty layers arranged like bricks and
mortar, respectively, explained Langer. Ordinarily,
that barrier is impenetrable. Ultrasound, however,
disorganizes the fatty layers and creates pathways
through which molecules can travel. This works to
increase the permeability of skin.
In clinical trials and in studies of rats and skin
from human cadavers, researchers applied
ultrasound for two minutes with a frequency of 20
kHz (similar to that used by a dentist to clean teeth).
The ultrasound probe is inserted into a small
glass cylinder, which contains a soap solution and is
applied to the skin. After the ultrasound treatment,
researchers put saline solution into the cylinder and
apply a vacuum to it for five minutes. This procedure
results in the extraction of a very small amount of
fluid from the interstitial spaces surrounding the
cells.
Though the fluid is not blood, it is known to have
the same concentrations that are found in the blood
of glucose and other substances. When compared
with glucose concentrations in blood, the
measurements obtained through this liquid showed
a very close correlation.
The back of the forearm was used for testing,
according to researchers, because it generally has
less hair to interfere with the ultrasound. Glucose
could then be measured continuously for 12 hours.
"This method involves no needles and is
completely painless," said Dr. Robert Gabbay,
assistant professor of medicine at Pennsylvania
State University College of Medicine
(www.psu.edu), Hershey, and a co-author of the
paper. "We know that by self-monitoring the
disease, and keeping glucose levels at a safe level,
individuals can greatly reduce their chance of
additional complications such as blindness and
kidney failure."
Gabbay said that participants were tested using
an ultrasound machine typically found in a research
facility or hospital. But scientists have also
developed a hand-held device so patients could
ultimately test themselves at home. The device is
expected to be available within the next three to five
years. Langer and colleagues have patented the
technology, which is licensed for development to
Sontra Medical, Cambridge, Mass. It "should be
comparable in price to the meters people with
diabetes currently use to test blood glucose levels,"
said study co-author Joseph Kost, a professor at
Ben-Gurion University in Israel (medic.bgu.ac.il) and
an MIT visiting scientist.
The next step, said Gabbay, is to test the
method on a larger group, which he foresees
happening next year.
Nature Medicine (2000; 6:347-350)
(The Medical Tribune Web site is at
http://www.medtrib.com