Method of measuring biological component concentration and apparatus therefor

• US 20040142402A1
• Filed: 11/20/2003
• Published: 07/22/2004
• Est. Priority Date: 11/15/2001
• Status: Active Grant

• Current Assignee: PHC Holdings Corporation
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Tsurugi, Mitsuhiro, Maruo, Katsuhiko
• Granted Patent: US 7,333,841 B2
• Time in Patent Office: Days
• US Class Current: 435/14
• CPC Class Codes: A61B 2562/0242 for varying or adjusting the optical path length in the tissue
• CPC Class Codes: A61B 5/1075 for measuring dimensions by non-invasive methods, e.g. for determining thickness of tissue layer A61B8/0858 takes precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

A method for calculating a biological component density of this invention comprises steps of irradiating a light of NIR spectrum to a skin of a subject, receiving the light of NIR reflected from the skin to obtain NIR spectrum data thereof, and substituting the NIR spectrum data into a predetermined calibrating equation to obtain a biological component density of the subject such as glucose density. This invention is characterized by preparing a plurality of the calibrating equations which are different from each other and are specific to each of plural groups which are classified in terms of a skin thickness parameter indicative of a skin thickness with respect to individuals of a species to which the subject belongs, determining the skin thickness parameter of the subject with a non-invasive technique and identifying the group of the subject in accordance with the determined skin thickness parameter, and deriving one of the calibrating equations in match with the identified group in order to calculate the biological component density of the subject.

Claims

1. A method of calculating a biological component density of a subject, said method comprising the steps of:

irradiating a light of NIR (near infrared) spectrum to a skin of the subject;

receiving said light of NIR reflected from said skin to obtain NIR spectrum data thereof;

substituting said NIR spectrum data into a predetermined calibrating equation to obtain a biological component density such as glucose density of said subject;

characterized in that (wherein) preparing a plurality of the calibrating equations which are different from each other and are each specific to each of a plural groups which are classified in terms of a skin thickness parameter indicative of a skin thickness with respect to individuals of a species to which said subject belongs;

determining said skin thickness parameter of the subject with a non-invasive technique and identifying the group of the subject in accordance with the determined skin thickness parameter,

deriving one of said calibrating equations in match with the identified group in order to calculate the biological component density of the subject.

2. The method as set forth in claim 1, wherein

said skin thickness parameter is determined by statistically analyzing said NIR (near infrared) spectrum reflected from the skin of the subject.

3. The method as set forth in claim 2, wherein

said NIR (near infrared) spectrum is analyzed based upon a principal component analysis.

4. The method as set forth in claim 1, wherein

said NIR (near infrared) spectrum reflected from the skin of the subject is analyzed with respect to an absorption coefficient of said spectrum at a frequency at which the spectrum is expected to show specific absorption due to existence of subcutaneous fat of the individual, thereby determining said skin thickness parameter based upon said absorption coefficient.

5. The method as set forth in claim 4, wherein

said frequency is within a range of 1700 nm to 1800 nm.

6. The method as set forth in claim 2, wherein

said NIR spectrum is irradiated to said skin selectively through one of a plurality of different incident paths which are spaced by different distances along a skin surface from a common reflective path through which said NIR spectrum is reflected out from the skin, said different incident paths being assigned as being specifically suitable to said groups, respectively, said NIR spectrum irradiated through one of said incident paths and reflected from said skin being analyzed to determine said skin thickness parameter in order to select one of said different incident paths assigned to one of said groups identified by the determined skin thickness, said selected incident path being made active to irradiate said NIR spectrum to said skin so as to obtain said NIR spectrum data reflected from said skin, said NIR spectrum data being processed by use of the calibrating equation specific to one of said groups determined by said skin thickness parameter.

7. The method as set forth in claim 1, wherein

said skin thickness parameter is determined by use of an ultrasound thickness gauge.

8. The method as set forth in claim 1, wherein

said skin thickness parameter is determined by use of an optical coherence tomography.

9. A device for calculating a biological component density of a subject, which comprises:

a light source generating a light having a NIR (near infrared) spectrum;

an incident guide directing said light to a skin of said subject;

a reflective guide directing the NIR spectrum reflected back from within said skin;

a sensor receiving said NIR spectrum through said reflective guide to provide NIR data thereof;

a processing unit which substitutes said NIR data into a predetermined calibrating equation to calculate the biological component density such as glucose density of said subject, characterized in that (wherein) said device further includes;

a skin thickness memory storing a plurality of the calibrating equations which are different from each other and which are each specific to each of a plural groups classified in terms of a skin thickness parameter indicative of a skin thickness with respect to individuals of a species to which said subject belongs; and

a means for determining the skin thickness parameter with an non-invasive technique to identify the group of the subject in accordance with the determined skin thickness parameter;

said processing unit operating to derive one of said calibrating equations from said skin thickness memory in match with the identified group in order to calculate the biological component density of the subject.

10. The device as set forth in claim 9, wherein

said incident guide has a light projecting end adapted to be held in close proximity to said skin, and said reflective guide has a light receiving end adapted to be held in close proximity to said skin, said light receiving end being spaced from said light projecting end by a distance of 2 mm or less across said skin.

11. The device as set forth in claim 10, wherein

said incident guide and said reflective guide are made respectively by optical fibers which are integrated into a single probe head having an object end to which said light projecting end and said light receiving end are exposed, said probe including a plurality of different incident guides and a single reflective guide, said different incident guides having individual light projecting ends which are spaced by different distances, respectively from said light receiving end on said object end, a selector being provided to selectively couple one of said different incident guides to light source so as to direct said NIR spectrum through selected incident guide, said processing unit further including:

a table storing a relation between each one of said groups and each one of said different light incident guides; and

a module which analyzes said NIR data statistically based upon the NIR spectrum irradiated through one of said incident paths and received from said skin to determine said skin thickness parameter and to identify the corresponding one of said group, said module operating to select from said table one of said different incident guides as corresponding to the identified group, enabling said selector to activate the selected incident guide to direct said NIR spectrum to said skin for calculation of said biological component density based upon the NIR spectrum irradiated through said selected incident path and reflected from said skin.

12. The device as set forth in claim 11, wherein

a plurality of said incident guides having the light projecting ends spaced by the same distance from said light receiving end are arrange about said single reflective guide to have the light projecting ends coaxial with said light receiving end.