Optical instrument helps diagnose and monitor peripheral arterial
18 September 2012
An optical diagnostic tool created by Columbia University
researchers may soon make it easier to diagnose and monitor one of the
most serious complications of diabetes, peripheral arterial disease
PAD, which is marked by a narrowing of the arteries caused by plaque
accumulation, frequently results in insufficient blood flow to the
body’s extremities and increases a person’s risk for heart attack
and stroke. The new technique is reported in the Optical Society’s
(OSA) open-access journal Biomedical Optics Express.
This new noninvasive imaging technique — known as dynamic diffuse
optical tomography imaging (DDOT) — uses near-infrared light to map
the concentration of haemoglobin in the body’s tissue. This mapping
can reveal how effectively blood is flowing to patients’ hands and
“Currently, there are no good methods to assess and monitor PAD
in diabetic patients,” explains Andreas Hielscher, Ph.D., professor
of Biomedical and Electrical Engineering and Radiology, and director
of the Biophotonics and Optical Radiology Laboratory at Columbia
“Patients with PAD experience foot pain, called ‘claudication,’
while walking,” adds Gautam Shrikhande MD, assistant professor of
surgery, and director of the Vascular Laboratory at Columbia’s
Medical Center. “This pain continues, even at rest, as the disease
progresses. In more advanced stages, PAD patients develop sores or
ulcers that won’t heal. Then, cell death, a.k.a. ‘gangrene’, occurs
and amputation is often the only solution. It’s extremely important
to diagnose PAD early, because medication and lifestyle changes can
alleviate the disease.”
This is where DDOT can help. “We’ve successfully used DDOT to
detect PAD in the lower extremities,” says Michael Khalil, a Ph.D.
candidate working with Hielscher at Columbia. “One key reason why
DDOT shows so much promise as a diagnostic and monitoring tool is
that, unlike other methods, it can provide maps of oxy, deoxy and
total haemoglobin concentration throughout the foot and identify
problematic regions that require intervention.”
“Using instrumentation for fast image acquisition lets us observe
blood volume over time in response to stimulus such as a pressure
cuff occlusion or blockage,” said Hielscher.
To map and monitor the presence of haemoglobin, the protein that
carries oxygen in the blood, red and near-infrared light is shone at
different angles around areas that are susceptible to arterial
disease. These specific wavelengths of light are then absorbed or
scattered, depending on the concentration of haemoglobin.
“In the case of tissue, light is absorbed by haemoglobin. Since
haemoglobin is the main protein in blood, we can image blood
concentrations within the foot without using a contrast agent,”
Hielscher points out. Contrast agents pose the risk of renal failure
in some cases, so the ability to monitor PAD without using a
contrast agent is a great advantage.
Since more than 25 million people (8% of the population) in the
United States are diabetic, this diagnostic tool has the potential
to make it significantly simpler to diagnose and monitor diabetics
with PAD in the future.
Khalil, Hielscher, and colleagues hope to bring their diagnostic
tool to market and into clinics within the next 3 years.
Dynamic diffuse optical tomography imaging of peripheral arterial
disease. Biomedical Optics Express, Vol. 3, Issue 9, pp. 2288-2298