COL 11(2), 021701(2013) CHINESE OPTICS LETTERS February 10, 2013
Noninvasive blood glucose measurement by
ultrasound-modulated optical technique
Lili Zhu (
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Key Laboratory of Optoelectronic Science and Technology for Medicine of the Ministry of Education,
Fujian Provincial Key Lab of Photonic Technology, College of Photonic and Electronic Engineering,
Fujian Normal University, Fuzhou 350007, China
∗
Corresponding author: hli@fjnu.edu.cn
Received May 19, 2012; accepted September 4; posted online December 25, 2012
We present a method for the noninvasive measurement of blood glucose levels, which are determined by
the ultrasound-modulated optical technique. The metho d is based on the optical scattering coefficient.
A sensitivity analysis of the ultrasound-modulated light signals in a scattering medium is conducted.
Glucose concentrations in intralipid and h emoglobin solutions are measured using the modulation depth
of ultrasound-modulated scattered light. The effects of incident light intensity and sample temperature on
the ultrasound-modulated signals are also estimated. Preliminary ex perimental results suggest that the
proposed method is a promising technique for noninvasive blood glucose measurement.
OCIS codes: 170.1065, 170.1470, 170.7170.
doi: 10.3788/COL201311.021701.
Diabetes mellitus, a common endocrine disease, is one
of the four most dangerous illnesses that pose a threat
to human health. In 2011, the number of diabetics
worldwide amounted to nearly 350 million, twice that 30
years ago
[1]
. China has more than 92 million dia betics,
with another 150 million expected to be diagnosed with
the disease
[2]
. Effectively treating dia betics necessita tes
measuring their glucose levels several times a day to ap-
propriately regulate intensive insulin therapy programs.
The normal procedure for blood glucose measurement is
to draw a small blood sample from a patient’s finger for
assay, relying on a n enzymatic chemical reaction. How-
ever, this procedure is inconvenient and unpleasant, as
well as increas e s the risk of infection. A secure, nonin-
vasive blood glucose mo nito ring approach has therefore
become a pressing requirement for diabetics.
Noninvas ive blood glucos e mo nitoring based on op-
tical metho ds is currently a popular resear ch topic.
Several noninvasive optical methods have been pro-
posed, including near-infrared sp e c troscopy
[3−5]
, scatter
measurement
[6,7]
, Raman spectroscopy
[8]
, and optical co-
herence tomography (OCT)
[9,10]
. These optical meth-
ods are categorized into two types: sp e ctroscopic and
scattering approaches. Absorption signals are consider-
ably reduced by light scattering, and interfering light ab-
sorbers (such as water) persist. Thus, the changes in-
duced by blood glucose in absorption spec tra are min-
imal and unspecific. In co ntrast to sp e c troscopic tech-
niques, sc attering approaches (such as scatter measure-
ment and OCT) do not need specific abs orption bands.
Nevertheless, these methods do not specifically measure
glucose but derive glucose-induced changes in scattering
coefficients. Therefore, other blood analytes and phys-
iological factors (e.g., heartbeat, respiration, and vaso-
constriction) may influence measurement re sults. These
methods mostly present low measurement accuracy, sen-
sitivity, and specificity, prompting further study before
they c an be successfully used in clinical settings.
In this letter, a new optical technique for the non-
invasive measurement of blood glucose levels by the
ultrasound-modulated optical technique is presented; the
measurement is conducted on the basis of the optical
scattering coefficient
[11−13]
. Ultrasound waves sca tter
much less than light waves in biological tissue. With
the proposed technique, ultrasound waves are focused
onto a medium to modulate the diffused light that passes
through the focal zone. Ultrasound-modulated scattered
light, which carries optical and mechanical information of
tissue, can be detected. Because the variations in blood
glucose concentration change the scattering coefficient
of blood
[14,15]
, the glucose concentration in tissue can be
indirectly measured through ultrasound-modulated opti-
cal signals. Compa red with other optical methods based
on the optical scattering coefficient, the proposed ap-
proach minimizes the disturbance from non-target layers
and has easily implementable reconstructive algorithms
because of the localization of ultrasound waves. The
method detects scattered photons rather than ballistic
photons, thereby ena bling detection of signals from deep
tissue. It serves as basis for a new modality for noninva-
sive blood glucos e measurement.
A correla tio n between the modulation depth of
ultrasound-modulated scattered light and glucose con-
centration was observed in phantom experiments. The
effects of incident light intensity and sample temperature
on ultrasound-modulated signals were investigated, and
then used for err or compensation mapping. Preliminary
exp erimental results suggest that the proposed method is
a promising modality for noninvasive blood glucose mea-
surement.
The propagation of ultrasound-modulated light in tis-
sue proceeds in three main stages. Firstly, incident light
travels from the surface to the focused ultrasound region.
The light obeys diffuse theory if distance z from the sur-
face to the fo c used ultra sound zone is sufficiently long
(z >>MFP, mean free path). Light intensity I
z
can be
expressed as
[16]
I
z
= I
0
e
−z
δ
, (1)
1671-7694/2013/021701(5) 021701-1
c
2013 Chinese Optics Letters