JP2006271815A - Method and system for measuring oxygen saturation of skin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To execute both of a visual observation of the surface state of the skin and a measurement of the oxygen saturation of the skin using a skin magnified image pickup device. <P>SOLUTION: This method for measuring the oxygen saturation of the skin acquires an internal reflecting light image of a subject's skin, extracts a hemoglobin component image from the internal reflecting light image by an independent componential analysis, calculates a standard deviation or an average value of the concentration for every pixel of the hemoglobin component image, and evaluates the oxygen saturation of the skin using the standard deviation or the average value. Alternatively, a relational expression between the standard deviation or the average value of the concentration for every pixel of the hemoglobin component image and the oxygen saturation measured by spectrometry is acquired previously from the measurement of a plurality of skins and the oxygen saturation of the skin is measured from the hemoglobin component image of an arbitrary skin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method and system for measuring oxygen saturation of skin from a skin image.

  2. Description of the Related Art Conventionally, in order to visually observe and evaluate surface conditions such as skin roughness, pores, and color unevenness, a magnified skin imaging apparatus that magnifies and observes the skin surface has been used (Patent Document 1). ).

  On the other hand, a method of calculating the concentration of melanin pigment, oxidized hemoglobin or reduced hemoglobin, which is an indicator of the blood circulation state of the skin, by measuring the absorbance at a specific wavelength in the region from the skin surface to the microcirculatory system (Patent Document) 2) and an apparatus (Patent Document 3) that performs such measurement using a cordless probe has been proposed.

  According to the method described in Patent Document 2, optical characteristics based on the oxygen saturation of hemoglobin can be obtained.

  However, the conventional spectroscopic measurement performed for measuring the oxygen saturation of the skin or calculating the concentration of oxidized or reduced hemoglobin is mainly point measurement. On the other hand, a skin magnified image photographing apparatus that performs magnified observation of the skin surface has a certain area as a measurement target. Therefore, with the conventional method, it is not possible to measure the oxygen saturation level of the skin from the image obtained by the skin magnified image photographing device. Therefore, in order to perform both surface magnification observation and oxygen saturation measurement, and to comprehensively evaluate the skin, both the skin magnification image capturing device and the spectroscopic measurement device must be provided separately. In addition, it is not possible to search for a part to be subjected to spectroscopic measurement with a skin magnified image photographing device.

JP-A-6-313708 Japanese Patent Laid-Open No. 10-127585 JP 2001-70251 A

  In contrast to the above-described conventional technology, the present invention enables both visual observation of the skin surface state and measurement of the oxygen saturation of the skin using the skin enlargement image photographing device, and observes the skin surface state. An object is to enable measurement of oxygen saturation at a desired site while searching.

  The present inventors reflected density unevenness in a hemoglobin component image extracted from the internal reflection light image of the skin reflecting a congested region having a high reduced hemoglobin concentration, and the density unevenness of the hemoglobin component image was quantified as a statistic. Then, it discovered that the numerical value obtained had high correlation with the oxygen saturation degree of the skin measured by the conventional spectroscopic measurement method.

That is, the present invention acquires an internally reflected light image of the subject's skin,
Extracting a hemoglobin component image from the internally reflected light image by independent component analysis,
Calculate the standard deviation or average value of the density for each pixel of the hemoglobin component image,
Provided is an oxygen saturation evaluation method for evaluating skin oxygen saturation using the standard deviation or average value.

In addition, the present invention measures oxygen saturation by spectrophotometry for a plurality of skins,
Calculate the standard deviation or average value of the density for each pixel of the hemoglobin component image by the above method,
Obtain a relational expression between the standard deviation or average value and the oxygen saturation,
For any skin, extract the hemoglobin component image from the internal reflection image by independent component analysis,
Calculate the standard deviation or average value of the density for each pixel of the hemoglobin component image,
Provided is an oxygen saturation measurement method for calculating the oxygen saturation of an arbitrary skin from the standard deviation or average value using the relational expression.

Furthermore, the present invention provides
(i) image forming means capable of forming an internally reflected light image of the skin,
(ii) means for storing a relational expression between a standard deviation or an average value of the concentration for each pixel calculated from a hemoglobin component image and oxygen saturation by a spectroscopic measurement method for a plurality of skins;
Means for extracting a hemoglobin component image from an internally reflected light image by independent component analysis for any skin;
Arithmetic unit comprising means for calculating standard deviation or average value of density of each pixel of hemoglobin component image, and means for calculating oxygen saturation of arbitrary skin from the standard deviation or average value using the relational expression ,
(iii) Provided is an oxygen saturation measurement system provided with display means for displaying the oxygen saturation of an arbitrary skin calculated by an arithmetic device.

  According to the oxygen saturation evaluation method of the present invention, a hemoglobin component image is extracted from the internal reflection light image of the skin by independent component analysis, and a standard deviation or an average value of the concentration of each pixel of the hemoglobin component image is calculated and calculated. Since the oxygen saturation of the skin is evaluated using the standard deviation or the average value, it is possible to use the enlarged skin image capturing device without using the spectroscopic measurement device that has been conventionally required for measuring the oxygen saturation. While observing an enlarged image of the skin, it is possible to evaluate a change in oxygen saturation at a desired site.

  Moreover, according to the oxygen saturation measurement method of the present invention, since the relational expression between the standard deviation or average value of the concentration of each pixel of the hemoglobin component image and the oxygen saturation measured by the spectrometer is used, any It is possible to measure the oxygen saturation of the skin from the hemoglobin component image of the skin.

  Furthermore, according to the oxygen saturation measurement system of the present invention, the skin internal reflection light image is obtained from the subject using the skin enlargement image capturing device, and the skin oxygen saturation is calculated from the image and shown to the subject. In addition to the observation results of the normal surface condition obtained using the skin enlargement imaging device, the oxygen saturation measurement result is shown to the subject, and the congestion state is observed and presented to effectively provide skin care advice. Can do.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a flow sheet of one aspect of the oxygen saturation evaluation method and oxygen saturation measurement method of the present invention, and FIG. 2 is a system configuration diagram of one aspect of an oxygen saturation measurement system that implements these methods. is there.

  The system 10 is obtained by the image forming unit 1 and the image forming unit 1 that can take a normal image of the skin and can form an internal reflection light image and a surface reflection light image of the skin using polarized light. A calculation device 2 that calculates the oxygen saturation level of the skin from the internally reflected light image, a display 3 that displays the oxygen saturation level of the skin calculated by the calculation device 2, and a printer 4 are provided.

  As the image forming means 1, a light source for projection, a digital camera, and a light source and a front surface of the digital camera each provided with a polarizing plate provided detachably can be used. As a more compact configuration, for example, A device provided with a polarizing filter to the skin surface observation device described in JP-A-6-313708 can be used. Here, an LED may be used as the light source.

  The digital camera that forms the image forming unit 1 is preferably one that can obtain a magnification of 20 to 200 times, a pixel number of 200 to 2000 pixels on one side, and a dot density of 200 to 10000 DPI in consideration of the photographing range.

  As the calculation means 2, a personal computer having an image processing function described later can be used. On the display 3 and the printer 4 connected to the personal computer, a normal image up to a magnification of about 200 times, an internally reflected light image, a hemoglobin component image, a measurement result of oxygen saturation, and the like can be appropriately switched or simultaneously displayed. To do. Moreover, you may enable it to display a melanin component image.

  When a beauty advisor, a cosmetics development researcher, or the like uses this system to evaluate the oxygen saturation of a subject's skin, first, the beauty advisor or the like acquires an internal reflection image of the subject's bare skin. The internally reflected light image can be formed by mounting a polarizing plate on the front surface of the digital camera so that the polarization direction is orthogonal to the polarizing plate on the front surface of the light source, and removing the surface reflected light component.

  Next, the calculation device 2 performs independent component analysis on the internally reflected light image, and extracts a hemoglobin component image from the internally reflected light image. Here, independent component analysis refers to the skin layer structure, the epidermal layer containing melanin as the main pigment component, the dermis layer containing hemoglobin as the main pigment component, and the subcutaneous tissue containing other pigment components. This is an analysis method that separates and extracts the signals of each layer from the image signal, considering that the signal is emitted independently from each layer and the mixture of them is an image signal.

  More specifically, for RGB of the image signal, -log (R), -log (G), and -log (B) are assigned to the x-axis, y-axis, and z-axis, respectively, and the skin color of the flat portion of the skin is there. When color space mapping is performed, as shown in FIG. 3 (a), it is distributed in a substantially flat shape, so that it can be seen that two components contribute to the skin color. This independent two-component signal intensity is considered to correspond to the amount of melanin or hemoglobin, respectively, and as shown in FIG. 3 (b), the skin color is closer to the component vector of melanin (-log (B)) ) And the hemoglobin component vector (the one closer to -log (G)). Therefore, a signal representing the hemoglobin amount is extracted from the signal of the internally reflected light image of each subject, and a distribution image of the hemoglobin component amount is output. However, when there is unevenness or uneven illumination, the amount of hemoglobin component is obtained by projecting onto a plane containing both melanin and hemoglobin vectors along the direction of the vector of the light source component acquired in advance to remove the shadow component.

  Details of such analysis processing and image processing are described in Vol. 16, No. 9 / September 1999 / J. Opt. Soc. Am. A 2169, and commercially available image analysis software (for example, This can be done by installing Adobe Photoshop).

  FIG. 4 shows a normal enlarged image (a) of the skin of a cheek site of a subject and a hemoglobin component image (b) thereof. According to the knowledge of the present invention, the overall brightness of the hemoglobin component image, that is, the density average for each pixel is influenced by the quality of the overall blood flow of the skin, and the better the blood flow, the higher the oxidized hemoglobin concentration. , The concentration becomes thinner. The density unevenness of the hemoglobin component image reflects a congested state having a high reduced hemoglobin concentration. Usually, the greater the density unevenness, that is, the greater the standard deviation of the density for each pixel, the higher the reduced hemoglobin concentration.

  Therefore, in this system, the standard deviation or average value of the density for each pixel of the extracted hemoglobin component image is calculated. These calculations can also be performed by the above-described commercially available image analysis software.

  The change over time in the standard deviation and the average value obtained from the hemoglobin component image corresponds well with the change over time in the oxygen saturation measured using a conventional spectroscopic measurement device. Therefore, the change of the oxygen saturation degree of the skin can be easily known by tracking the change of the standard deviation or the average value of the density for each pixel of the hemoglobin component image for the subject.

  The standard deviation or average value calculated from the hemoglobin component image corresponds to the oxygen saturation value measured by the conventional spectroscopic method, and the oxygen saturation is measured from the standard deviation or average value calculated from the hemoglobin component image. In order to be able to do this, oxygen saturation is measured in advance for a plurality of skins by spectroscopic measurement, and the standard deviation or average value of the concentration for each pixel is calculated from the hemoglobin component image, and these relational expressions are obtained. Is preferably obtained by a regression method and stored in the arithmetic unit 2.

  As this relational expression, for example, the following expression (1) can be given.

（式中、σ：ヘモグロビン成分画像のピクセル毎の濃度の標準偏差
Ａ：ヘモグロビン成分画像のピクセル毎の濃度の平均値
ａ、ｂ、ｃ、ｄ：係数 ）

(Where, σ: standard deviation of density for each pixel of the hemoglobin component image A: average value of density for each pixel of the hemoglobin component image a, b, c, d: coefficient)

  In addition, in the arithmetic unit 2, a large number of standard deviations or average values of the concentrations for each pixel calculated from the hemoglobin component image of the skin and the oxygen saturation by the skin spectroscopic measurement device are accumulated to construct these databases. The above relational expression (1) may be calculated from this database, or a database is constructed in a management server 5 separate from the computing device 2, and the computing device 2 is appropriately connected to the management server 5 by communication means. You may make it possible to access and acquire the above-mentioned relational expression (1).

  The arithmetic device 2 uses the relational expression (1) and measures the oxygen saturation of the subject's skin from the standard deviation or average value of the concentration for each pixel calculated from the subject's hemoglobin component image.

  The beauty advisor compares the measured oxygen saturation of the subject's skin with a general desired oxygen saturation, and gives beauty advice such as a method for improving skin blood flow to the subject as necessary. Alternatively, if the oxygen saturation of the subject is measured over time, the effect of the previous beauty advice can be judged from the change, and it can be used for future beauty advice. Can be explained based on numerical data of oxygen saturation of the skin. Furthermore, the beauty advice regarding the oxygen saturation of the skin can be given together with the observation result of the normal enlarged image of the skin obtained by the image forming means 1.

  Hereinafter, the present invention will be specifically described based on examples.

Example 1
A Japanese female 20 was a subject, and the oxygen saturation of the cheek and arm was measured by the system shown in FIG.

  In this case, the magnification of the image forming unit is set to 20 times, and an internal reflected light image of the pixel 640 × 480 is acquired for 1 cm on one side of the photographing range, and the standard deviation and average value for each pixel of the obtained internal reflected light image are obtained. Was calculated.

  On the other hand, the skin oxygen saturation (IS) calculated by the method of Patent Document 2 is measured for the measurement site of the same subject, and the equation (1) (a = 0.1) obtained from the standard deviation and average value described above is measured. , b = 0.001, c = 0.001, d = 0.001), and plotted to obtain the correlation diagram of FIG.

  From the result of FIG. 5, it can be seen that there is a high correlation between the oxygen saturation of the formula (1) of this method and the oxygen saturation obtained by the conventional spectroscopic measurement apparatus.

  INDUSTRIAL APPLICABILITY The present invention is useful when developing a cosmetic product, observing and presenting a customer's blood stasis state at a store, etc., and explaining the blood flow improvement effect of the cosmetic product and the accompanying oxygen saturation improvement state.

It is a flow sheet of the oxygen saturation measuring method of the present invention. It is a system configuration diagram of the present invention. It is explanatory drawing of independent component analysis. An enlarged image (a) of a normal skin and a hemoglobin component image (b) thereof. It is a related figure of the oxygen saturation (IS) of the skin by the conventional spectrometer, and the standard deviation / average value of the density | concentration for every pixel of the hemoglobin component image of skin.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image formation means 2 Arithmetic apparatus 3 Display 4 Printer 5 Management server 10 Oxygen saturation measuring system

Claims (5)

Acquire an internal reflection image of the subject's skin,
Extracting a hemoglobin component image from the internally reflected light image by independent component analysis,
Calculate the standard deviation or average value of the density for each pixel of the hemoglobin component image,
An oxygen saturation evaluation method for evaluating oxygen saturation of skin using the standard deviation or average value.   The evaluation method according to claim 1, wherein an internal reflection light image of skin having a magnification of 20 to 200 times is acquired using a skin enlargement image photographing device. For multiple skins, measure oxygen saturation by spectroscopic methods,
The standard deviation or average value of the density for each pixel of the hemoglobin component image is calculated by the method according to claim 1 or 2,
Obtain a relational expression between the standard deviation or average value and the oxygen saturation,
For any skin, extract the hemoglobin component image from the internal reflection image by independent component analysis,
Calculate the standard deviation or average value of the density for each pixel of the hemoglobin component image,
An oxygen saturation measurement method for calculating the oxygen saturation of the arbitrary skin from the standard deviation or average value using the relational expression. (i) image forming means capable of forming an internally reflected light image of the skin,
(ii) means for storing a relational expression between a standard deviation or an average value of the concentration for each pixel calculated from a hemoglobin component image and oxygen saturation by a spectroscopic measurement method for a plurality of skins;
Means for extracting a hemoglobin component image from an internally reflected light image by independent component analysis for any skin;
Means for calculating a standard deviation or average value of the density of each pixel of the hemoglobin component image, and a means for calculating oxygen saturation of the arbitrary skin from the standard deviation or average value using the relational expression apparatus,
(iii) An oxygen saturation measuring system comprising display means for displaying the oxygen saturation of any skin calculated by the arithmetic device. The arithmetic unit constructed a database that correlates the standard deviation or average value of the concentration for each pixel calculated from the hemoglobin component image and the oxygen saturation by the spectroscopic measurement method for a plurality of skins, and calculated from the hemoglobin component image 5. The oxygen saturation measurement system according to claim 4, further comprising means for calculating a relational expression between a standard deviation or an average value of the concentration for each pixel and an oxygen saturation obtained by a spectroscopic measurement method.

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