US2012330164A1PendingUtilityA1
Noninvasive measurement of carotenoids in biological tissue
Individually held — no corporate assignee on recordPriority: Jun 6, 2008Filed: Sep 4, 2012Published: Dec 27, 2012
Est. expiryJun 6, 2028(~1.9 yrs left)· nominal 20-yr term from priority
G01N 2201/0221G01N 21/4785G01N 2021/4757G01N 21/65G01N 2021/656A61B 5/443A61B 5/0053G01N 2021/4742G01N 2021/4709A61B 5/0075G01N 2201/0618
45
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Claims
Abstract
A method and apparatus are provided for the determination of carotenoid antioxidants and similar chemical compounds in biological tissue such as living skin. The method and apparatus provide a noninvasive, rapid, accurate, and safe determination of carotenoid levels which in turn can provide diagnostic information of the antioxidant status of tissue. Reflection spectroscopy is used to measure the concentrations of carotenoids and similar substances in tissue. White light is directed upon the area of tissue that is of interest. A small fraction of diffusively scattered light is collected and measured. The tissue is pressured to temporarily squeeze blood out of the measured tissue volume while the reflection spectrum is continuously monitored, displayed, and analyzed in near real time. After an optimal time period of typically 15 seconds, the influence of the dominating hemoglobin and oxyhemoglobin tissue absorptions on the reflection spectra are minimized.
Claims
exact text as granted — not AI-modified1 . A noninvasive method of measuring carotenoid levels in biological tissue, comprising the steps of:
illuminating a localized region of tissue with light that overlaps the absorption bands of carotenoids in the visible and blue spectral regions; applying pressure to the localized region for a predetermined period of time so as to reduce the level of blood chromophores in the localized region; and determining the level of carotenoids in the localized region using reflection spectroscopy.
2 . The method of claim 1 , wherein the pressure is applied to the tissue for about 5 to 20 seconds.
3 . The method of claim 1 , wherein the level of carotenoids is chosen as the difference between the total apparent absorbance of carotenoids and the background absorbance due to all chromophores remaining during the pressurization of the localized region.
4 . The method of claim 1 , wherein the level of carotenoids is chosen as the difference between the total apparent absorbance at or about 478 nm and the background absorbance due to all chromophores remaining during the pressurization of the localized region.
5 . The method of claim 1 , further including the step of restricting blood flow to the localized region.
6 . The method of claim 1 , wherein the light is white light substantially spanning the spectral range from about 350 to 900 nm.
7 . The method of claim 1 , wherein the light is derived from separate sources, one at or about 480 nm and the other at or about 620 nm.
8 . The method of claim 1 , further including the step of:
recording a dark spectrum D(λ) providing a background signal intensity; measuring and storing a reflection standard; and wherein the reflectivity spectrum associated with the carotenoids in the localized region is calculated according to the expression:
R
(
λ
)
=
T
(
λ
)
-
D
(
λ
)
S
(
λ
)
-
D
(
λ
)
·
100
%
where T(λ) and S(λ) are the signals measured at wavelength λ from the tissue and reflectivity standard, respectively, and D(λ) is the signal at any wavelength λ due to the dark spectrum intensity.
9 . The method of claim 1 , further including the step of converting the normalized reflectivity spectrum R(λ) into an “apparent” optical density spectrum A(λ) by taking the decimal logarithm for each spectral data point of the reflectivity spectrum, according to the relation:
A
(
λ
)
=
-
lg
(
R
(
λ
)
100
)
10 . The method of claim 1 , further including the step of comparing the level of carotenoids with normal biological tissue to assess the risk or presence of malignancy or other disease conditions.
11 . The method of claim 1 , wherein the tissue is human skin.
12 . The method of claim 11 , wherein the skin is on a fingertip or other portion of a hand.
13 . A system for measuring carotenoid levels in biological tissue noninvasively, comprising:
a source of light for illuminating a localized region of tissue with light that overlaps the absorption bands of carotenoids in the visible and blue spectral regions; a device for applying pressure to the localized region for a predetermined period of time so as to reduce the level of blood chromophores in the localized region; and a spectrograph for determining the level of carotenoids in the localized region using reflection spectroscopy.
14 . The system of claim 13 , wherein the pressure is applied to the tissue for about 5 to 20 seconds.
15 . The system of claim 13 , wherein the device for applying pressure is an optically transparent element through which the light and reflection spectra pass.
16 . The system of claim 13 , wherein the device for applying pressure is a lens through which the light and reflection spectra pass.
17 . The system of claim 13 , further including a cuff or other device for restricting blood flow to the localized region.
18 . The system of claim 13 , wherein the light source is a white light source substantially spanning the spectral range from about 350 to 900 nm.
19 . The system of claim 13 , wherein the light source comprises separate sources, one at or about 480 nm and the other at or about 620 nm.
20 . The system of claim 13 , wherein:
the device for applying pressure to the localized region for a predetermined period of time is contained in a probe body; light from the source is delivered to the probe through a first optical fiber; and reflectance spectra is carried from the probe body to the Raman spectrograph through a second optical fiber.Join the waitlist — get patent alerts
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