JP7489423B2 - Calculation method for vascular elasticity index - Google Patents

Description

The present invention relates to a method for calculating a vascular elasticity index.

There is a method for measuring the blood flow rate in the skin by a laser speckle method (Patent Document 1).
There is also a method for performing stress monitoring by creating a hemoglobin image using face image data captured by an RGB camera, and creating heart rate data from the hemoglobin image (Patent Document 2).

Japanese Patent No. 6507639 JP 2017-29318 A

In Patent Document 1, since the measurement is performed using a light intensity image captured by irradiating a laser beam, it is not suitable for a user to measure the blood flow rate in the skin in their daily lives.
In addition, in Patent Document 2, stress monitoring is performed using a hemoglobin image, but other bioindicators cannot be calculated, so there is room for further research.

The present invention has been made in consideration of the above problems, and relates to a method for calculating a vascular elasticity index, which calculates the amount of hemoglobin at each time from a moving image of a predetermined area of a subject's body surface, and calculates a vascular elasticity index based on the change in the amount of hemoglobin. In this specification, the terms "method for calculating a vascular elasticity index" and "method for evaluating blood vessels and blood flow" refer to calculating a vascular elasticity index and evaluating blood vessels and blood flow of a subject for non-medical purposes, and include a calculation method and a method for evaluating blood vessels and blood flow that can be used by anyone other than a specialist. Specifically, the method for evaluating blood vessels and blood flow includes a method for advising on the prevention of lifestyle-related diseases and a method for estimating age.

The present invention relates to a method for calculating a blood vessel elasticity index, which includes an image acquisition step for acquiring time-series images of a predetermined area of the body surface, a hemoglobin amount calculation step for calculating the hemoglobin amount at each time of the time-series images, a period calculation step for calculating one heartbeat period based on the calculated change in the hemoglobin amount, and a blood vessel elasticity index calculation step for calculating a blood vessel elasticity index based on the change in the hemoglobin amount and the calculated period.

The present invention also relates to a vascular elasticity index calculation system including an image acquisition unit that acquires time-series images of a predetermined area of the body surface, a hemoglobin amount calculation unit that calculates the amount of hemoglobin at each time in the time-series images, a cycle calculation unit that calculates one cycle of the heartbeat based on the calculated change in the hemoglobin amount, and a vascular elasticity index calculation unit that calculates a vascular elasticity index based on the change in the hemoglobin amount.

The present invention also relates to a vascular elasticity index calculation device that includes at least a processor and a memory, the processor including an image acquisition means for acquiring time-series images of a predetermined area of the body surface, a hemoglobin amount calculation means for calculating the hemoglobin amount at each time of the time-series images, a period calculation means for calculating one heartbeat period based on the calculated change in the hemoglobin amount, and a vascular elasticity index calculation means for calculating a vascular elasticity index based on the change in the hemoglobin amount.

The method provided by the present invention allows the blood vessel elasticity index to be calculated based on the change in hemoglobin amount at each time calculated from the acquired time-series images (moving images), making it easy to calculate the blood vessel elasticity index and useful for daily health management.

FIG. 1 is a conceptual diagram of a method for calculating a vascular elasticity index. FIG. 13 is a diagram showing a comparison result between a case where the blood vessel elasticity index is calculated by LSFG and a case where the blood vessel elasticity index is calculated by a method for calculating the blood vessel elasticity index. FIG. 13 is a diagram showing a comparison result between a case where the blood vessel elasticity index is calculated by LSFG and a case where the blood vessel elasticity index is calculated by a method for calculating the blood vessel elasticity index. FIG. 2 is a diagram explaining each vascular elasticity index. 13 is a flowchart showing a method for calculating a blood vessel elasticity index. 13 is a flowchart showing a hemoglobin amount calculation process. 13 is a flowchart showing a period calculation process. 13 is a flowchart showing a blood vessel elasticity index calculation process. FIG. 13 is a diagram for explaining the calculation process of a vascular elasticity index. FIG. FIG. FIG. FIG. 1 is a conceptual diagram of a blood vessel elasticity index calculation system. 1 is a conceptual diagram of a blood vessel elasticity index calculation device. FIG.

Below, examples of preferred embodiments of the present invention will be described with reference to the drawings. Note that the drawings of the present embodiment are all intended to explain the technical concept, configuration, and operation of the present invention, and do not specifically limit the configuration. In addition, in all drawings, similar components are given similar reference numerals, and duplicate explanations will be omitted as appropriate.

＜Overview＞
An outline of a method for calculating a blood vessel elasticity index in this embodiment will be described.
The method for calculating a vascular elasticity index of this embodiment (hereinafter sometimes referred to as this method) is characterized by including an image acquisition step of acquiring time-series images of a specified area of the body surface, a hemoglobin amount calculation step of calculating the hemoglobin amount at each time in the time-series images, a period calculation step of calculating one heartbeat period based on the change in the calculated hemoglobin amount, and a vascular elasticity index calculation step of calculating a vascular elasticity index based on the change in the hemoglobin amount and the calculated period.

Until now, when calculating the vascular elasticity index of the body surface, for example, as in Patent Document 1, LSFG (Laser Speckle Flowgraphy), a technology that visualizes blood flow distribution using reflected and scattered laser light, has been used. However, since LSFG requires a device that irradiates laser light, it has been difficult for general users to calculate the vascular elasticity index on a daily basis at home, etc. Therefore, the inventors propose a calculation method that can calculate the vascular elasticity index on a daily basis by calculating the amount of hemoglobin from video image data captured on the body surface and calculating the vascular elasticity index.

FIG. 1 shows a conceptual diagram of this method.
As shown in Fig. 1, in this method, the subject's body surface (facial skin in this embodiment) is photographed using a visible light camera such as a webcam attached to a personal computer, a camera built into a tablet terminal, a camera built into a smartphone, a digital video camera, etc. In this method, the photographed images need to be time-series images (moving images) in order to calculate the amount of change in hemoglobin and extract the blood flow waveform.
The captured time-series images contain, in addition to the blood flow (signal) required for this method, noise such as the subject's movement and uneven lighting during capture. Therefore, the RGB waveforms of each pixel in the time-series images are subjected to independent component analysis, separated into hemoglobin, melanin, and shadow components, and a predetermined filter process is performed to extract the waveform of only the hemoglobin component (blood flow waveform). In this embodiment, a known technique (for example, a pigment component analysis method from a skin color image (Reference: Norimichi Tsumura, Nobutoshi Ojima, Kayoko Sato, Mitsuhiro Shiraishi, Hideto Shimizu, Hirohide Nabeshima, Syuuichi Akazaki, Kimihiko Hori, Yoichi Miyake, Image-based skin color and texture analysis/synthesis by extracting hemoglobin and melanin information in the skin, acm Transactions on Graphics, Vol. 22, No. 3. pp. 770-779(2003). (Proceedings of ACM SIGGRAPH 2003))) is used to extract the waveform of only the hemoglobin component.

2 and 3 show the results of a comparison between the blood vessel elasticity index calculated by LSFG and the blood vessel elasticity index calculated by the present method. The measurement conditions are as follows:
Subjects: 7 people in their 30s to 50s (total of men and women)
Method: Measure facial skin blood flow at rest for 10 seconds Camera shooting conditions: 30 [fps], 10 seconds shooting Image compression: None Lighting: LED (5000K)
Measurement area: left cheek Measurement area: approximately ⁴ cm2 (2 cm x 2 cm)
Number of pixels: Approximately 5000 pixels. Although FIGS. 2 and 3 show BOT (Blowout Time) among the blood vessel elasticity indices, similar results can be obtained with other blood vessel elasticity indices as described later.
As shown in Fig. 2, when the blood flow value calculated using LSFG and the hemoglobin amount value calculated by the present method are displayed on top of each other, the waveforms of the two are in good agreement, and as a result, it is understood that the BOT value calculated by the present method can be calculated to have a waveform close to that calculated by LSFG. Also, as shown in Fig. 3, it is understood that there is a high correlation between the BOT value calculated by the present method and the BOT value calculated by LSFG.
As described above, the results of calculating the vascular elasticity index using this method and the results of calculating the vascular elasticity index using LSFG are close to each other, so that it is possible to measure (calculate) the vascular elasticity index on a daily basis and to manage health using the vascular elasticity index.

<Calculation method of vascular elasticity index>
A method for calculating the vascular elasticity index will now be described.
"Body surface" refers to the surface of the body, including the skin, lips, etc. Also, parts such as the eyeballs, palpebral conjunctiva, and gums that are not visible (cannot be touched) when the eyes or mouth are closed, but are visible when the eyes or mouth are opened, in other words, parts that can be observed from the outside without medical procedures such as surgery, are considered to be included in the body surface. The "predetermined area of the body surface" may be any area of the body surface, and in this embodiment, the predetermined area is set on the cheek or forehead of the face.
A "time-series image" is an image obtained by photographing a predetermined area of a body surface for a predetermined period of time. The number of frames per second of a time-series image may be 5 [fps] or more, and preferably 30 [fps] or more. The photographing time of a time-series image may be 2 seconds or more, and preferably 10 seconds or more. A time-series image may be said to be a moving image composed of a plurality of images.
The "image acquisition process" refers to a process of acquiring time-series images of a specified area of the body surface, and the source of the time-series images can be anything, such as acquiring them from a specified medium, acquiring them via a network, or acquiring them directly from an imaging device (importing them directly from the imaging device).
The "amount of hemoglobin at each time" refers to a value obtained by extracting only the hemoglobin component for each frame of the acquired time-series images and calculating the amount of hemoglobin for each pixel, and the "step of calculating the amount of hemoglobin" refers to the step of calculating the amount of hemoglobin. The calculation method will be described later.
"Changes in hemoglobin amount" refers to the changes in hemoglobin amount from time to time, and the changes are understood based on values calculated for each frame of the time-series images.
"One cycle of a heartbeat" refers to one cycle of a heartbeat, which is the pulsation of the heart, and is the period from contraction to expansion to the next contraction (or the period from expansion to contraction to the next expansion) when the heart periodically contracts and expands. "Calculating one cycle of a heartbeat" refers to cutting out one cycle of a heartbeat based on the change in the amount of hemoglobin, since the amount of hemoglobin changes according to the pulsation of the heart. Specifically, one cycle is cut out by identifying the start and end points of the cycle based on a predetermined criterion (e.g., selecting the rising time when the amount of hemoglobin changes from a decrease to an increase) from the waveform information of the amount of hemoglobin, which is repeated approximately periodically. At this time, the length of one cycle of a heartbeat may be acquired as real time, or the length of one cycle may be acquired as a predetermined dimensionless time (e.g., 100). The "cycle calculation process" is a process of cutting out one cycle of a heartbeat.
The "vascular elasticity index" may be any information that can serve as an index regarding the flow (flow velocity or flow rate) of body fluids (mainly blood) in the skin tissue of the body surface, such as Fluctuation, Skew (bias of blood flow waveform), Blowout Score (BOS) (steady flow index of blood flow), BOT (Blowout Time), Rising rate (rising rate of blood flow), Falling rate, Flow Acceleration Index (FAI), Acceleration Time Index (ATI), and RI (Resistivity Index). Although details will be described later, by evaluating the vascular elasticity indices, particularly the BOT, falling rate, or ATI, it is possible to grasp (estimate) the state of the blood vessels (whether the blood vessels are flexible (can expand and contract) or stiff (cannot expand and contract)). The "vascular elasticity index calculation process" is a process of calculating at least one of the vascular elasticity indices.

The blood vessel elasticity index will be described with reference to FIG.
BOT (Blowout Time): The continuity of high blood flow is an index showing the continuity of high MBR value, and the BOT value is expressed by the following formula using the half width (time) (W) of the MBR value and the heartbeat width (time) (F) shown in FIG. 4, and a proportional constant "C".
(BOT) = C * (W) / (F)
Rising rate: A value indicating the time variation of the rate of increase in blood flow, and is expressed by the following formula ("C" is a constant, and "S ₁ " and "Sall" are areas shown in FIG. 4).
Rising rate = C x ( _S1 /Sall)
Falling rate: The time variation of the blood flow falling speed is an index showing the time variation of the falling speed from the maximum MBR value in the time waveform of the MBR value per heartbeat. Using (Sall) and (S2) shown in Figure 4, the falling rate can be expressed by the following formula. In the following, "C" is a proportionality constant.
(Falling rate)=C·(S2)/(Sall)
FAI: The maximum upward acceleration during blood flow increase indicates the instantaneous maximum blood flow rate during blood flow increase.
ATI: The blood flow peak position is the proportion of the time during which the MBR time waveform reaches the maximum MBR value (MBRmax in FIG. 4) in one heartbeat.
RI (Resistivity Index): Peripheral vascular resistance is an index indicating peripheral vascular resistance, and the RI value is obtained by dividing the difference between the maximum MBR value (MBRmax in FIG. 4) and the minimum MBR value (MBRmin in FIG. 4) by the maximum MBR value.

Flowcharts of the present method are shown in Figures 5 to 8. Note that Figures 5 to 8 only show characteristic steps of the present method.
5 is a main flow chart of the present method, which comprises an image acquisition step, a hemoglobin amount calculation step, a period calculation step, and a blood vessel elasticity calculation step.

The image acquisition process (step S100) is a process for acquiring time-series images of a specific area of the body surface photographed for a specific period of time. In this process, the time-series images can be acquired from any source, such as from a specific medium, via a network, or from an imaging device.

The hemoglobin amount calculation process (step S200) is a process for calculating the hemoglobin amount of each pixel from the acquired time-series image data. Figure 6 shows a flowchart of the hemoglobin amount calculation process.

In step S210, the Red, Green, and Blue information of each pixel is calculated for each frame of the acquired time-series image data. This method uses images taken by a visible light camera, such as a webcam attached to a personal computer, a camera built into a tablet terminal, a camera built into a smartphone, or a digital video camera, so it is possible to calculate the RGB information of each pixel and extract the RGB waveform.

Step S220 is a process of extracting hemoglobin component values from the RGB waveform (extracting the waveform of the hemoglobin amount).
Here, a method for calculating the hemoglobin component in this method will be described. Oxygenated hemoglobin present in blood in a blood vessel (artery) has a characteristic of absorbing a specific incident light, and this characteristic can be used to monitor the blood flow rate that changes with the pulsation of the heart. The extracted RGB waveform contains melanin components, shadow components, and other components in addition to the hemoglobin component, and in this method, components other than the hemoglobin component are noise. Therefore, the RGB waveform is subjected to independent component analysis to extract only the hemoglobin component. By extracting only the hemoglobin component in this way (creating a waveform containing only the hemoglobin component), the blood flow rate can be monitored and the blood vessel elasticity index can be calculated. In this embodiment, as described above, the pigment component analysis method from a skin color image is used to extract only the hemoglobin component from the RGB waveform.

Step S230 performs an inversion process (positive/negative inversion process) of the waveform of the extracted hemoglobin amount. When blood flow is monitored using LSFG, reflected light is observed, whereas when blood flow is monitored using an image captured by a visible light camera as in this method, hemoglobin absorbance is observed. Because the relationship between reflected light and absorbance must be inverted, accurate evaluation cannot be performed by comparing the vascular elasticity index calculated using the extracted waveform as is. In this embodiment, a comparison process is performed between the vascular elasticity index calculated by this method and the vascular elasticity index calculated using LSFG, and the extracted waveform is inverted to evaluate the effectiveness of the method for calculating the vascular elasticity index using this method.

Returning to FIG. 5, the cycle calculation process (step S300) is a process of extracting one heartbeat cycle using the hemoglobin amount waveform and calculating the average one heartbeat waveform. FIG. 7 shows a flowchart of the cycle calculation process. The processing content of the cycle calculation process will be explained together with the graph shown in FIG. 9.

Step S310 detects peaks in the waveform and performs processing to cut out each cardiac waveform.
FIG. 9(1) shows the hemoglobin amount waveform (waveform after inversion processing in step S230). The negative peak position of the hemoglobin amount waveform is detected as a minimum value and cut out for each heartbeat. In the case of FIG. 9(1), a waveform for 11 heartbeats can be cut out. In this embodiment, only values within a predetermined value of 20% of the median number of frames constituting one heartbeat are used. This is to eliminate waveforms that are disturbed due to measurement errors and determine the blood vessel elasticity index. The data range used for processing (predetermined value of 20%) can be set appropriately.

In step S320, normalization processing is performed for each heartbeat waveform extracted in step S310. The normalization processing may be performed on both the hemoglobin component amount (vertical axis) and the time (horizontal axis) for each heartbeat waveform, or on either one of them. In this embodiment, normalization processing is performed on the hemoglobin component amount (vertical axis).
FIG. 9(2) shows a graph in which waveforms extracted for each heartbeat are superimposed after normalization processing.

Step S330 is a process for calculating the average one heartbeat waveform. Since normalization processing is performed for each heartbeat waveform in step S320, the average is calculated for each time.

Step S340 performs a process of normalizing the calculated average one heartbeat waveform. In this embodiment, the normalization process in this step performs normalization on the hemoglobin component amount (vertical axis) and time (horizontal axis). Figure 9 (3) shows the calculated average one heartbeat waveform.

In this way, the cycle calculation process (e.g., step S300) includes a waveform normalization process (e.g., step S320) that calculates multiple cycles of the heartbeat (e.g., step S310), normalizes a waveform showing the change in the hemoglobin amount over the calculated multiple cycles of the heartbeat by the hemoglobin amount, and calculates one cycle of the heartbeat based on the normalized waveform (e.g., step S310). The cycle calculation process (e.g., step S300) also includes an average waveform calculation process (e.g., step S330) that averages the normalized waveforms over the multiple cycles to obtain an average waveform of the hemoglobin amount.

Returning to Fig. 5, the blood vessel elasticity calculation step (step S400) is a step of calculating a blood vessel elasticity index from the acquired average one-heartbeat waveform. The indexes shown in Fig. 4 are calculated. Note that although it is possible to calculate all the indexes, it is not necessary to calculate all the indexes. It is sufficient to calculate the necessary index depending on the evaluation content.
A flowchart of the blood vessel elasticity calculation process is shown in Fig. 8. Steps S410 to S470 in Fig. 8 differ in the types of feature values related to changes in hemoglobin amount extracted from one heartbeat cycle, and only the necessary feature values need to be calculated depending on the blood vessel elasticity index to be calculated (only the necessary processes from steps S410 to S470 need to be performed), and it is not necessary to perform all the processes.

Step S410 is a process of calculating a first time, which is the half-width of the maximum value of the hemoglobin amount, based on the average one heartbeat waveform.
Step S420 is a process of calculating a second time period, which is the total length from the rising edge to the falling edge of the hemoglobin amount, based on the average one heartbeat waveform.
Step S430 is a process of calculating a third time from the rising time of the hemoglobin amount to the peak time when the hemoglobin amount reaches a maximum value, based on the average one heartbeat waveform.
Step S440 is a process for calculating a fourth time from the peak time to the fall time of the hemoglobin amount based on the average one heartbeat waveform.
Step S450 is a process for calculating the maximum amount of hemoglobin based on the average one heartbeat waveform.
Step S460 is a process for calculating the minimum value of the hemoglobin amount based on the average one heartbeat waveform.
Step S470 is a process for calculating the maximum increase in the amount of hemoglobin per predetermined time based on the average one heartbeat waveform.
Step S480 is a process of calculating a blood vessel elasticity index (for example, at least one of BOT, ATI, falling rate, RI, and FAI).
The BOT is calculated using the first time and the second time.
The ATI is calculated using the second and third times.
The falling rate is calculated using the fourth time and the maximum value.
The RI is calculated using the maximum and minimum values.
The FAI is calculated using the maximum increase.

In this way, the method further includes a feature calculation step (e.g., step S410 to step S440) for calculating feature amounts related to changes in the hemoglobin amount from one cycle of the hemoglobin amount and the heart rate. The feature calculation step calculates as feature amounts one or more of a first time, which is the half-width of the maximum value of the hemoglobin amount (e.g., step S410), a second time, which is the total length from the rising edge of the hemoglobin amount to the falling edge (e.g., step S420), a third time from the rising edge of the hemoglobin amount to the peak time at which the maximum value is reached (e.g., step S430), and a fourth time from the peak time to the falling edge of the hemoglobin amount (e.g., step S440). The vascular elasticity index calculation step calculates a vascular elasticity index (e.g., BOT, ATI, falling rate) using one or more of the first time, the second time, the third time, and the fourth time (e.g., step S480).
The method further includes a feature calculation process (e.g., step S450 to step S470) for calculating feature amounts related to changes in the hemoglobin amount from the hemoglobin amount and one heartbeat cycle. The feature calculation process calculates one or more of the maximum hemoglobin amount (e.g., step S450), the minimum hemoglobin amount (e.g., step S460), and the maximum increase among the increases in the hemoglobin amount per a predetermined time (e.g., step S470) as feature amounts. The vascular elasticity index calculation process calculates a vascular elasticity index (e.g., RI, FAI) using one or more of the maximum hemoglobin amount, the minimum hemoglobin amount, and the maximum increase in the hemoglobin amount (e.g., step S480).

Next, the calculation results in this embodiment will be described.
<Measurement conditions>
Subjects: Healthy men and women in their 20s to 70s N = 100 (before exclusion) Analysis site: Cheeks Shooting conditions for this method: 30 [fps] 10-second shooting Image compression: None Lighting: LED (5000K)
Measurement area: forehead Measurement area: approx. ⁴ cm2 (2 cm x 2 cm)
Number of pixels at measurement site: Approximately 10,000 pixels Figure 10 (1-1) is a graph in which the BOT value calculated using LSFG is plotted on the vertical axis and the subject's age is plotted on the horizontal axis, and (1-2) is a graph in which the BOT value calculated using this method is plotted on the vertical axis and the subject's age is plotted on the horizontal axis.
In the case of (1-1), there was a negative correlation between the BOT value and age, and in the case of (1-2), there was also a negative correlation between the BOT value and age.
FIG. 10(2) shows the correlation coefficients between each index calculated using LSFG and the age of the subject, and the correlation coefficients between each index calculated using this method and the age of the subject.
In the case of (2-1), the content is the same as that shown in FIG. 10(1), so the explanation will be omitted.
(2-2) shows the rising rate. In the case of LSFG, there was a weak negative correlation between the rising rate and age, and in the case of the present method, there was a negative correlation between the rising rate and age.
(2-3) shows the falling rate. In the case of LSFG, there is a weak positive correlation between the falling rate and age, while in the case of the present method, there is a positive correlation between the falling rate and age.
(2-4) shows the RI, and in the case of LSFG, there was a positive correlation between RI and age, and in the case of the present method, there was a weak positive correlation between RI and age.
From these facts, it can be said that the vascular elasticity index obtained by this method corresponds to the vascular elasticity index obtained using LSFG.

Figure 11 shows the results of analysis of two measurement sites, the forehead and cheek, under the same measurement conditions and measurement sites as in Figure 10. In (1), the analysis target is the forehead, and in (2), the analysis target is the cheek. In the case of (1), there is a negative correlation between the BOT value and age, and in the case of (2), there is a negative correlation between the BOT value and age. In addition, the correlation coefficients of (1) and (2) are close to each other.
From these facts, it can be said that the blood vessel elasticity index can be calculated not only from the forehead but also from other parts of the face (e.g., the cheeks).

7, in this embodiment, when calculating the average one-heartbeat waveform in the period calculation step, normalization processing is performed on the hemoglobin component amount and time (see steps S320 to S340). This is because performing the normalization processing as described below provides a higher correlation coefficient than not performing the normalization processing.
FIG. 12 shows the calculation results of the BOT value when normalization processing is performed and when it is not performed under the same measurement conditions as FIG. 10. (1) is a graph showing the correlation between the case where the normalization processing is not performed on the hemoglobin component amount and time, and the BOT value is calculated by the present method and the case where the BOT value is calculated using LSFG, (2) is a graph showing the correlation between the case where the normalization processing is performed on the hemoglobin component amount (intensity), the case where the BOT value is calculated by the present method and the case where the BOT value is calculated using LSFG, and (3) is a graph showing the correlation between the case where the normalization processing is performed on the time, and the case where the BOT value is calculated by the present method and the case where the BOT value is calculated using LSFG. As is clear from (1) to (3), it can be said that there is a strong correlation between the case where the normalization processing is performed on the hemoglobin component amount and the case where the normalization processing is performed on the time and the case where the normalization processing is performed on the time. Also, as is clear from (2) and (3), it can be said that there is a strong correlation between the BOT value calculated using LSFG and the case where the normalization processing is performed on the hemoglobin component amount and the case where the normalization processing is performed on the time. For these reasons, in this method, the blood vessel elasticity index is calculated using the average one heartbeat waveform that has been normalized with respect to the hemoglobin amount and/or time.

<Blood vessel elasticity index calculation system>
The blood vessel elasticity index calculation system 200 will be described with reference to FIG.
The blood vessel elasticity index calculation system 200 in this embodiment is composed of an image acquisition unit 210, a hemoglobin amount calculation unit 220, a period calculation unit 230, and a blood vessel elasticity index calculation unit 240. In addition, an information processing terminal (not shown) capable of executing various processes is provided, and the image acquisition unit 210, the hemoglobin amount calculation unit 220, the period calculation unit 230, and the blood vessel elasticity index calculation unit 240 are provided in the information processing terminal. The information processing terminal is provided with an input device such as a keyboard or a pointing device, a processing unit, a storage unit, etc. In addition, the information processing terminal is preferably provided with a display device, but may be provided outside the information processing terminal and connected via a network. In addition, the information processing terminal may be provided with a built-in or external camera (visible light camera).

The image acquisition unit 210 is a means for acquiring time-series images of a predetermined area of the body surface, and the source of the time-series images does not matter, such as acquiring them from a predetermined medium, acquiring them via a network, acquiring them from an imaging device, etc. The image acquisition unit 210 also acquires time-series images of visible light captured by a digital camera or a camera provided in a mobile terminal.
The hemoglobin amount calculation unit 220 is a means for separating only the hemoglobin component for each frame of the acquired time-series image and calculating the amount of hemoglobin for each pixel.
The cycle calculation unit 230 is a means for calculating one heartbeat cycle based on the change in the amount of hemoglobin.
The blood vessel elasticity index calculation unit 240 is a means for calculating the blood vessel elasticity index.
The processes performed by the image acquisition section 210, the hemoglobin amount calculation section 220, the period calculation section 230, and the blood vessel elasticity index calculation section 240 are similar to those described above in the method for calculating the blood vessel elasticity index.

<Blood Vessel Elasticity Index Calculation Device>
The blood vessel elasticity index calculation device 300 will be described with reference to FIG.
The blood vessel elasticity index calculation device 300 in this embodiment includes a processor 301 and a memory 302, and the processor 301 includes an image acquisition unit 310, a hemoglobin amount calculation unit 320, a period calculation unit 330, and a blood vessel elasticity index calculation unit 340. The memory 302 stores data necessary for the processor 301 to perform processing (processing for calculating the blood vessel elasticity index), data necessary in the processing, etc. Although not shown, the blood vessel elasticity index calculation device 300 preferably includes an input unit such as a keyboard or a pointing device, an input/output unit for transmitting and receiving data to and from an external device, a display unit, etc. In addition, the blood vessel elasticity index calculation device 300 may be provided with a built-in or external camera (visible light camera).

The image acquisition unit 310 is a means for acquiring time-series images of a predetermined area of the body surface (corresponding to an image acquisition means), and the source of the time-series images does not matter, such as acquiring from a predetermined medium, acquiring via a network, acquiring from an imaging device, etc. The image acquisition unit 310 also acquires time-series images of visible light captured by a digital camera or a camera provided in a mobile terminal.
The hemoglobin amount calculation unit 320 is a means for separating only the hemoglobin component for each frame of the acquired time-series image and calculating the hemoglobin amount of each pixel (corresponding to a hemoglobin amount calculation means).
The cycle calculation unit 330 is a means (corresponding to a cycle calculation means) for calculating one heartbeat cycle based on a change in the amount of hemoglobin.
The blood vessel elasticity index calculation unit 340 is a means for calculating the blood vessel elasticity index (corresponding to a blood vessel elasticity index calculation means).
The processes performed by the image acquisition section 310, the hemoglobin amount calculation section 320, the period calculation section 330, and the blood vessel elasticity index calculation section 340 are similar to those described above in the method for calculating the blood vessel elasticity index.

<Method of evaluating blood vessels and blood flow>
The method for evaluating blood vessels and blood flow includes an image acquisition step, a hemoglobin amount calculation step, a period calculation step, a vascular elasticity index calculation step, and an evaluation step. The image acquisition step, the hemoglobin amount calculation step, the period calculation step, and the vascular elasticity index calculation step are the same as those described above in the method for calculating the vascular elasticity index.
The evaluation step evaluates the vascular elasticity or skin blood flow age based on the calculated vascular elasticity index. In order to facilitate the evaluation by the evaluator, it is preferable to display the calculated vascular elasticity index on a display device, such as by displaying a graph or comparing it with other subjects. FIG. 15 shows an example of the display of the calculated vascular elasticity index. As shown in FIG. 15, the value of the vascular elasticity index (BOT in the case of FIG. 15) used in the evaluation is displayed, and the position of the calculated BOT value compared to subjects of the same age as the subject (corresponding to the vascular elasticity index in FIG. 15), the skin blood flow age estimated based on the calculated BOT value (corresponding to the skin blood flow age in FIG. 15), etc. are displayed.
In general, by observing the change in the value of the vascular elasticity index, it is possible to grasp the risk of lifestyle-related diseases. For example, the value of the vascular elasticity index can grasp the inflow of blood into tissues, the continuity of blood flow into tissues, the outflow of blood from tissues, the variability of blood flow rate, etc., and therefore it is possible to grasp the reaction of blood vessels to the pulsation of blood flow. If the continuity of blood flow into tissues is high, it can be estimated that the blood vessels are flexible and can expand and contract, and if the continuity of blood flow into tissues is low, it can be estimated that the blood vessels are hard and cannot expand and contract. In addition, since it is known that there is a correlation between the continuity of blood flow into tissues and age, it is also possible to estimate whether the vascular age is appropriate for the actual age from the value of the vascular elasticity index. Therefore, by observing the change in the value of the vascular elasticity index, it can be used to predict the risk of lifestyle-related diseases associated with the deterioration of vascular conditions, to provide advice on lifestyle habits to improve vascular conditions, and to provide advice on lifestyle habits to improve vascular age, and it is possible to utilize it for preventing lifestyle-related diseases and promoting health.
In general, by observing the condition of blood vessels and blood flow on the surface of the body (just below the skin), it is possible to understand (evaluate) the moisture state of the skin, the elasticity of the skin, and the condition of the gums, and this can also be used to provide advice to improve these conditions.

<Modification>
In this embodiment, the RGB waveform is subjected to independent component analysis, and a process of extracting only the hemoglobin component is performed to extract the hemoglobin component value from the RGB waveform (the waveform of the hemoglobin amount is extracted) (see step S220), but this is not limited to the above. For example, since hemoglobin is said to strongly absorb green light with a wavelength of 540 nm, the blood flow rate can be monitored by using pixel information of the green waveform of the RGB waveform. Therefore, as a process of extracting only the hemoglobin component, only the green waveform may be extracted from the RGB waveform, and the hemoglobin component may be extracted (the waveform of the hemoglobin amount is extracted). Even in this way, the vascular elasticity index can be calculated in the same way as when the RGB waveform is subjected to independent component analysis and only the hemoglobin component is extracted.

In this embodiment, after each heartbeat waveform is cut out, normalization processing (see step S320) is performed for each heartbeat waveform, but this is not limited to the above. For example, after normalization processing is performed on the acquired hemoglobin component waveform, each heartbeat waveform may be cut out.

In this embodiment, normalization processing is performed on the waveforms cut out for each heart beat waveform to calculate the average one heart beat waveform (see steps S320 to S340), but this is not limited to the above. For example, the average one heart beat waveform may be calculated from the waveforms cut out for each heart beat waveform, and then normalized. In this case, the time is aligned at the beginning to 0, and the maximum period of the target heart beat waveform is averaged as 100.

Also, the means constituting the blood vessel elasticity index calculation system may be provided at different locations. Specifically, in the blood vessel elasticity index calculation system, the captured time-series image data can be acquired by the information processing terminal included in the blood vessel elasticity index calculation system 200 via a network line, medium, etc., in the same way that the blood vessel elasticity index calculation system is configured so that the calculation results can be acquired by another information processing terminal (not shown) other than the information processing terminal included in the blood vessel elasticity index calculation system 200 via a network line, medium, etc. In this way, a user (subject) at a location other than the information processing terminal included in the blood vessel elasticity index calculation system 200 may take a picture of a specific area of himself/herself using a smartphone or the like, transmit the captured image to the information processing terminal included in the blood vessel elasticity index calculation system 200, calculate the blood vessel elasticity index at the information processing terminal, and transmit the calculation results (including the evaluation results) to the other information processing terminal via a network line, medium, etc. In this way, the user can easily grasp the blood vessel elasticity index and check the evaluation results, making it easier to use for daily health management.

200 Blood vessel elasticity index calculation system 210 Image acquisition section 220 Hemoglobin amount calculation section 230 Cycle calculation section 240 Blood vessel elasticity index calculation section 300 Blood vessel elasticity index calculation device 301 Processor 302 Memory 310 Image acquisition section 320 Hemoglobin amount calculation section 330 Cycle calculation section 340 Blood vessel elasticity index calculation section

Claims (12)

an image acquisition step of acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation step of calculating the hemoglobin amount at each time of the time-series images;
a period calculation step of calculating one period of a heartbeat based on the calculated change in the amount of hemoglobin;
and calculating a blood vessel elasticity index based on the change in the hemoglobin amount and one cycle of the calculated heartbeat ,
The period calculation step calculates a plurality of periods of a heartbeat,
a waveform normalization step of normalizing a waveform indicating the calculated change in the hemoglobin amount over a plurality of heartbeat periods by the hemoglobin amount;
A method for calculating a vascular elasticity index , comprising the steps of: calculating one heartbeat cycle based on a normalized waveform . an image acquisition step of acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation step of calculating the hemoglobin amount at each time of the time-series images;
a period calculation step of calculating one period of a heartbeat based on the calculated change in the amount of hemoglobin;
and calculating a blood vessel elasticity index based on the change in the hemoglobin amount and one cycle of the calculated heartbeat ,
the cycle calculation step includes a step of calculating a plurality of cycles of the heartbeat and averaging the waveforms of the plurality of cycles to obtain an average waveform of the hemoglobin amount;
The method for calculating a vascular elasticity index, wherein the vascular elasticity index calculation step calculates the vascular elasticity index from an average waveform of the hemoglobin amount . an image acquisition step of acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation step of calculating the hemoglobin amount at each time of the time-series images;
a period calculation step of calculating one period of a heartbeat based on the calculated change in the amount of hemoglobin;
a blood vessel elasticity index calculation step of calculating a blood vessel elasticity index based on the change in the hemoglobin amount and one cycle of the calculated heartbeat ;
a feature amount calculation step of calculating a feature amount relating to a change in the hemoglobin amount from the hemoglobin amount and one cycle of the heartbeat,
The feature amount calculation step includes:
A first time that is a half-width of the maximum value of the hemoglobin amount;
A second time which is a total length from the rise time to the fall time of the hemoglobin amount;
a third time from the rise of the hemoglobin amount to the peak time at which the hemoglobin amount reaches a maximum value;
and a fourth time from the peak time to the fall time of the hemoglobin amount as the feature amount,
A method for calculating a vascular elasticity index, characterized in that the vascular elasticity index calculation step calculates the vascular elasticity index using one or more of the first time, the second time, the third time, or the fourth time . a feature amount calculation step of calculating a feature amount relating to a change in the hemoglobin amount from the hemoglobin amount and one cycle of the heartbeat,
The feature amount calculation step includes:
the maximum value of the hemoglobin amount; and the minimum value of the hemoglobin amount.
a maximum increase in the amount of increase in the amount of hemoglobin per a predetermined time period; and
A method for calculating a vascular elasticity index according to any one of claims 1 to 3, characterized in that the vascular elasticity index calculation step calculates the vascular elasticity index using one or more of the maximum value of the hemoglobin amount, the minimum value of the hemoglobin amount , or the maximum increase in the hemoglobin amount. an image acquisition unit for acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation unit for calculating the amount of hemoglobin at each time of the time-series images;
a period calculation unit that calculates one period of a heartbeat based on the calculated change in the amount of hemoglobin;
a blood vessel elasticity index calculation unit that calculates a blood vessel elasticity index based on the change in the hemoglobin amount and one cycle of the calculated heartbeat ;
Including,
The period calculation unit calculates a plurality of periods of a heartbeat,
a waveform normalization unit that normalizes a waveform indicating the calculated change in the hemoglobin amount over multiple heartbeat periods by the hemoglobin amount;
A system for calculating a blood vessel elasticity index , comprising: calculating one heartbeat cycle based on a normalized waveform . an image acquisition unit for acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation unit for calculating the amount of hemoglobin at each time of the time-series images;
a period calculation unit that calculates one period of a heartbeat based on the calculated change in the amount of hemoglobin;
a blood vessel elasticity index calculation unit that calculates a blood vessel elasticity index based on the change in the hemoglobin amount and one cycle of the calculated heartbeat ;
Including,
the cycle calculation unit includes an average waveform calculation unit that calculates multiple cycles of heartbeats and averages the waveforms of the multiple cycles to obtain an average waveform of the hemoglobin amount;
The blood vessel elasticity index calculation system is characterized in that the blood vessel elasticity index calculation unit calculates the blood vessel elasticity index from an average waveform of the hemoglobin amount . an image acquisition unit for acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation unit for calculating the amount of hemoglobin at each time of the time-series images;
a period calculation unit that calculates one period of a heartbeat based on the calculated change in the amount of hemoglobin;
a blood vessel elasticity index calculation unit that calculates a blood vessel elasticity index based on the change in the hemoglobin amount and one cycle of the calculated heartbeat ;
a feature amount calculation unit that calculates a feature amount related to the amount of hemoglobin and a change in the amount of hemoglobin from one cycle of the heartbeat,
The feature amount calculation unit
A first time that is a half-width of the maximum value of the hemoglobin amount;
A second time which is a total length from the rise time to the fall time of the hemoglobin amount;
a third time from the rise of the hemoglobin amount to the peak time at which the hemoglobin amount reaches a maximum value;
and a fourth time from the peak time to the fall time of the hemoglobin amount as the feature amount,
A vascular elasticity index calculation system characterized in that the vascular elasticity index calculation unit calculates the vascular elasticity index using one or more of the first time, the second time, the third time, or the fourth time . a feature amount calculation unit that calculates a feature amount relating to a change in the hemoglobin amount from the hemoglobin amount and one cycle of the heartbeat,
The feature amount calculation unit
the maximum value of the hemoglobin amount; and the minimum value of the hemoglobin amount.
a maximum increase in the amount of increase in the amount of hemoglobin per a predetermined time period; and
The vascular elasticity index calculation system according to any one of claims 5 to 7, characterized in that the vascular elasticity index calculation unit calculates the vascular elasticity index using one or more of the maximum value of the hemoglobin amount, the minimum value of the hemoglobin amount , or the maximum increase in the hemoglobin amount. The device includes at least a processor and a memory,
The processor,
an image acquisition means for acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation means for calculating the hemoglobin amount at each time of the time series images;
a period calculation means for calculating one period of a heartbeat based on the calculated change in the amount of hemoglobin;
a blood vessel elasticity index calculation means for calculating a blood vessel elasticity index based on the change in the hemoglobin amount and one calculated cycle of the heartbeat ,
The period calculation means calculates a plurality of periods of the heartbeat,
a waveform normalization means for normalizing a waveform indicating the calculated change in the hemoglobin amount over a plurality of heartbeat periods by the hemoglobin amount;
A blood vessel elasticity index calculation device , which calculates one heartbeat cycle based on a normalized waveform . The device includes at least a processor and a memory,
The processor,
an image acquisition means for acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation means for calculating the hemoglobin amount at each time of the time series images;
a period calculation means for calculating one period of a heartbeat based on the calculated change in the amount of hemoglobin;
a blood vessel elasticity index calculation means for calculating a blood vessel elasticity index based on the change in the hemoglobin amount and one calculated cycle of the heartbeat ,
the period calculation means includes an average waveform calculation means for calculating a plurality of periods of the heartbeat and averaging the waveforms of the plurality of periods to obtain an average waveform of the hemoglobin amount;
The blood vessel elasticity index calculation means calculates the blood vessel elasticity index from the average waveform of the hemoglobin amount.
A blood vessel elasticity index calculation device comprising: The device includes at least a processor and a memory,
The processor,
an image acquisition means for acquiring time-series images of a predetermined area of a body surface;
a hemoglobin amount calculation means for calculating the hemoglobin amount at each time of the time series images;
a period calculation means for calculating one period of a heartbeat based on the calculated change in the amount of hemoglobin;
a blood vessel elasticity index calculation means for calculating a blood vessel elasticity index based on the change in the hemoglobin amount and one calculated cycle of the heartbeat ;
a feature calculation means for calculating a feature relating to the amount of hemoglobin and a change in the amount of hemoglobin from one cycle of the heartbeat,
The feature amount calculation means,
A first time that is a half-width of the maximum value of the hemoglobin amount;
A second time which is a total length from the rise time to the fall time of the hemoglobin amount;
a third time from the rising time of the hemoglobin amount to the peak time at which the hemoglobin amount reaches a maximum value;
and a fourth time from the peak time to the fall time of the hemoglobin amount as the feature amount,
A vascular elasticity index calculation device characterized in that the vascular elasticity index calculation means calculates the vascular elasticity index using one or more of the first time, the second time, the third time, or the fourth time . a feature amount calculation means for calculating a feature amount relating to a change in the hemoglobin amount from the hemoglobin amount and one cycle of the heartbeat,
The feature amount calculation means
the maximum value of the hemoglobin amount; and the minimum value of the hemoglobin amount.
a maximum increase in the amount of increase in the amount of hemoglobin per a predetermined time period; and
The vascular elasticity index calculation device according to any one of claims 9 to 11, characterized in that the vascular elasticity index calculation means calculates the vascular elasticity index using one or more of the maximum value of the hemoglobin amount, the minimum value of the hemoglobin amount , or the maximum increase in the hemoglobin amount.

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