JP7225909B2 - How to calculate the gum health index - Google Patents

Description

The present invention relates to a method and apparatus for calculating a gingival health index from the state of gingival blood flow observed by laser speckle flowography.

Laser speckle flowgraphy (LSFG) captures speckles (spotted patterns) formed by the interference of scattered light caused by the scattering of laser light irradiated to living tissue by red blood cells, etc., and captures the speckle image. This is a method of obtaining temporal and spatial variations (MBR values) of pixels and forming an MBR image (so-called blood flow map).

As for fundus blood flow measurement by LSFG, a fundus blood flow imaging system (LSGF-NAVI, Softcare Co., Ltd.) is commercially available, and blood flow analysis and waveform analysis are performed based on MBR images. For example, evaluation items such as blowout time (hereinafter referred to as BOT) and blowout score (hereinafter referred to as BOS) calculated from the waveform of the MBR value of one heartbeat normalized by the heartbeat, and arteriosclerosis (Non-Patent Document 1, Non-Patent Document 2).

With regard to skin blood flow measurement by LSFG, the average MBR value obtained by averaging the MBR values for one heartbeat is very different from the skin blood flow measurement value by strain gauge plethysmography. Based on the knowledge that there is a high correlation, a method of obtaining the blood flow rate from the average MBR value has been proposed. An average MBR image obtained by two-dimensionally mapping this average MBR value shows the state of skin blood flow per heartbeat (Patent Document 1).

On the other hand, periodontal disease is an inflammatory disease caused by bacterial infection. The gingival margin becomes red and swollen due to inflammation, the periodontal pocket deepens, and the alveolar bone dissolves, requiring tooth extraction. become. In addition, it is known that causative bacteria of periodontal disease affect cardiovascular diseases such as arteriosclerosis (Non-Patent Document 3).

JP 2016-123689 A

Journal of Toho Medical Society, 62(3), p185, 2015 Journal of the Japanese Ophthalmological Society, 117, p110, 2013 National Cerebral and Cardiovascular Center, Periodontal Disease and Cardiovascular Disease, URL: http://www.ncvc.go.jp/cvdinfo/pamphlet/general/pamph105.html

In order to prevent periodontal disease, it is important to check the health of the gums regularly. However, it is difficult for ordinary people to check the health condition of gums. On the other hand, when LSFG is applied to the gingiva, it is possible to non-invasively observe the blood flow state of the gingiva in a short time using MBR images without relying on a dentist, and it is expected that some information about the health state of the gingiva can be obtained. be done. However, the relationship between the gingival blood flow image formed by LSFG and the health condition of the gingiva is unknown.

Accordingly, an object of the present invention is to form an MBR image of the gingiva using LSFG so that even ordinary people can check the health condition of the gingiva.

The present inventor formed an MBR image of the gingiva, formed an MBR image with an average of one heartbeat from the MBR image, and examined various evaluation items obtained from the waveform of the average one heartbeat for various parts of the gingiva and the state of health of the gingiva. As a result of investigating the relationship between the BOT and the falling rate calculated at the interdental papilla or the marginal gingiva are related to the health condition of the gingiva. The inventors have found that the rate of change between the value and the previous measured value serves as an index for mechanically determining the improvement or deterioration of the gingival health condition, and have completed the present invention.

That is, the present invention irradiates the gingiva of a subject with laser light, forms an MBR image by laser speckle flowography, normalizes the MBR image by the heartbeat to form an MBR image of an average of one heartbeat, and an average of one heartbeat. Measure BOT and Falling rate from the interdental papilla or marginal gingiva in the MBR image, calculate the rate of change between the measured value at a certain point and the measured value before that for each of BOT and Falling rate, Provided is a method for calculating a gingival health index using a rate of change as a gingival health index.

The present invention also provides a gingival health index calculator that uses laser speckle flowography,
a laser light irradiation device for irradiating the gingiva with a laser light,
A digital video camera that forms a speckle image by receiving scattered light of a laser beam irradiated on the gums through a polarizing filter,
Equipped with an arithmetic device and an image display device that displays an image formed by a digital video camera or arithmetic device,
Arithmetic device
the ability to form an MBR image from a speckle image;
A function of forming an MBR image with an average of one heartbeat by normalizing the MBR image by the heartbeat;
A function of forming an average MBR image by averaging MBR values for one heartbeat in an average one-heartbeat MBR image;
A function to extract the interdental papilla or marginal gingiva from the MBR image of one heart beat on average,
A function to measure BOT and falling rate from the waveform of the MBR value of the extracted interdental papilla or marginal gingiva for an average of one heartbeat,
A function to store BOT and falling rate and their measurement date and time for each subject, and for each of BOT and falling rate, calculate the rate of change between the measured value at a certain point and the measured value before that, and calculate these rate of change as a gingival health index.

According to the calculation method of the gingival health index of the present invention, the BOT and the falling rate measured from the interdental papilla or the marginal gingiva of the MBR image of one heart beat on average by LSFG are measured values at a certain point in time. Since the rate of change between the measured value and the previous measured value is calculated as the gingival health index, improvement or deterioration of the gingival health condition can be mechanically determined based on the gingival health index. Therefore, it is possible to check the health condition of the gums noninvasively, and it is possible for even ordinary people to check the health condition of the gums.

In addition, since this gingival health index is the rate of change between the measured values of BOT and Falling rate at a certain point in an individual subject and these measured values before that, there is no inter-individual disparity in BOT or Falling rate itself. is reduced or eliminated. Therefore, this determination index serves as a good guideline for determining whether the subject's gingival health condition has improved or deteriorated during the current measurement compared to the previous measurement.

Furthermore, if the gingival region for which the gingival health index is measured is the interdental papilla or marginal gingival region of the front tooth, a speckle image can be easily taken. In addition, even when the speckle image of the anterior teeth is taken, the entire gingiva in the oral cavity is subject to determination, and the health condition of the gingiva of the posterior teeth can also be checked, which significantly reduces the burden on the subject.

On the other hand, according to the gingival health index calculator of the present invention, the gingival health index of the present invention can be easily obtained.

FIG. 1 is a schematic configuration diagram of a gingival health index calculation device according to an embodiment. FIG. 2 is a front view of the mouth of a subject wearing the corner hook. FIG. 3 is a flowchart of processing in the gingival health index calculation device of the embodiment. FIG. 4 is an explanatory diagram of a method of obtaining the MBR value for one average heartbeat. FIG. 5 is an explanatory diagram of a method for obtaining an average MBR value. FIG. 6 is an explanatory diagram of BOT. FIG. 7 is an explanatory diagram of Falling Rate. FIG. 8A is a superimposed image of an average MBR image and a two-dimensional color image. FIG. 8B is a diagram showing contour lines of tooth regions in the average MBR image. FIG. 8C is a diagram showing the analysis range on the average MBR image. FIG. 9 is an explanatory diagram of a gingival blood flow measurement site and a gingival condition evaluation site. FIG. 10 is an explanatory diagram of gingival evaluation points in each tooth. FIG. 11A is a diagram showing the relationship between the rate of change in BOT and the rate of change in Falling Rate, and those with deteriorating and improving gingival health conditions in subjects in their twenties and thirties. FIG. 11B is a diagram showing the relationship between the rate of change in BOT and the rate of change in Falling Rate, and those with deteriorating and improving gingival health conditions, with subjects in their 50s and 60s.

The present invention will be described in detail below. In each figure, the same reference numerals denote the same or equivalent components.

FIG. 1 is a schematic configuration diagram of a gingival health index calculator 1 according to an embodiment of the present invention. This calculation device calculates a gingival health index using laser speckle flowography. A digital video camera 3 for forming a speckle image, a polarizing filter 4, an arithmetic device 5, and an image display device 6 are provided. The laser beam exit 2a is located near the light receiving portion of the digital video camera 3. As shown in FIG. A light-receiving portion of a digital camera that forms a two-dimensional color image of the gingiva is also provided, and the light-receiving portion of the digital camera is also located near the light-receiving portion of the digital video camera 3 .

The laser beam irradiation device 2 and the digital video camera 3 can be the same as those described in Patent Document 1. It is preferable that the camera platform or arm on which the video camera 3 is attached is capable of adjusting the fixing angle of the video camera 3 so that the video camera 3 does not receive specular reflection light and surface reflection light.

A polarizing filter 4 is placed in front of the light-receiving part of the video camera 3 in order to remove specular reflection light and surface reflection light of the laser beam irradiated to the gingiva S and to allow the video camera 3 to receive internally scattered light. are placed.

As the arithmetic unit 5, a personal computer capable of analyzing video signals and having a function of performing the processing shown in FIG. 3 can be used. As the image display device 6, a display capable of displaying an image formed by the digital video camera 3 or the arithmetic device 5 can be used. More specifically, the arithmetic unit 5 has a function of forming an MBR image from the speckle image taken by the digital video camera 3, and a function of forming an MBR image of one heartbeat on average by normalizing the MBR image by heartbeats. It has a function of forming an average MBR image by averaging MBR values for one heartbeat in an average one-heartbeat MBR image. Here, forming an MBR image of an average of one heartbeat by normalizing the MBR image by the heartbeat means that, as shown in FIG. It refers to forming an image in which the values are averaged over the number of frames for one heartbeat. Further, the average MBR image is a still image whose pixel value is the average MBR value obtained by averaging the MBR values of all frames constituting one average heartbeat at each pixel, as shown in FIG. The function of forming these images can be the same as that of the computer described in Patent Document 1.

Further, the computing device 5 has a function of extracting the interdental papilla or marginal gingiva from the MBR image of one heart beat on average. In order to facilitate this extraction, the arithmetic unit 5 has the function of superimposing a two-dimensional image of the gingiva, preferably a two-dimensional color image, taken with a digital camera and an average MBR image. The superimposition function itself can be the same as that of the computer described in Patent Document 1.

Extraction of the interdental papilla or the marginal gingiva may be performed by a known image processing method of identifying regions by hue or brightness in a superimposed image of a two-dimensional color image of the gingiva and an average MBR image. It is preferable to specify pixels belonging to teeth on this superimposed image and then extract them. If the tooth region and the gingival region are automatically recognized from the average MBR value on the superimposed image by image processing, there is a possibility that an object other than the tooth with no blood flow, such as the hook at the corner of the mouth, will be recognized as the tooth region. However, such erroneous recognition can be eliminated by the operator specifying pixels belonging to teeth. Extraction of the interdental papilla or marginal gingiva after the pixels belonging to the tooth are designated is preferably performed as follows. That is, the arithmetic unit identifies, as a tooth region, a region of pixels surrounding a pixel specified by the operator, where the difference between the average MBR value and the average MBR value of the specified pixels is within a predetermined range, It is preferable to extract a region of pixels adjacent to the tooth region as the interdental papilla or marginal gingival region, in which the difference between the average MBR value of the pixel and the average MBR value of the tooth region exceeds a predetermined range. , the area up to 2 mm from the boundary between the tooth area and the adjacent area is preferably extracted as the interdental papilla or marginal gingiva. In this way, a camera that measures gingival blood flow by distinguishing between tooth regions and interdental papilla or marginal gingiva by means of the average MBR value regardless of color information such as hue and brightness of superimposed images. The analysis process can be simplified because the measurement site can be identified only by the measurement.

The computing device 5 has a function of measuring the BOT and the falling rate from the extracted MBR image of the interdental papilla or marginal gingiva of one heartbeat on average. Here, as shown in FIG. 6, BOT is an evaluation calculated by multiplying the ratio (W/F) of the half width W and one heartbeat width F by a constant _C1 in the waveform of the MBR value of the average one heartbeat. The item indicates the ratio of the half-value width in one heartbeat. Also, as shown in FIG. 7, the falling rate is a constant C ₂ to the ratio ( _SF /Sall) of the area S _F of the falling region and the rectangular area Sall surrounding the falling region in the waveform of the MBR value for one average heartbeat. It is an evaluation item calculated by multiplying by

_Arithmetic device 5 has a function of storing the measured values of BOT and falling rate together with the date and time of measurement. It has a function of calculating the rate of change of the measured value _BOT2 and outputting the rate of change as a determination index of the state of health of the gums. Here, the rate of change is _{a numerical value calculated by BOT1/BOT2 , where BOT1} is the measured value at a certain time and BOT2 is the measured value before that time. Moreover, as the measurement date and time, the shooting date and time of the speckle image can be used.

The calculation method of the gingival health index of the present invention can be performed as follows using the calculation device 1 described above. First, as shown in FIG. 1, the chin of the subject P is fixed by the chinrest 11 . In this case, as shown in FIG. 2, it is preferable to have the subject P wear the hook 10 at the corner of the mouth so that the image of the gingiva S can be easily taken. Next, the gingiva S of the subject P is irradiated with laser light from the laser light irradiation device 2 and a speckle image is captured by the digital video camera 3 . The imaging conditions in this case can be the same as those described in Patent Document 1. For example, it is preferable to irradiate with a laser beam having a wavelength of 800 to 950 nm and an intensity of JISC6802 class 1M. Imaging can be performed for 3 to 150 seconds, preferably 3 to 30 seconds in order to reduce the burden on the subject. Also, a two-dimensional color image of the subject P is taken with a digital camera.

When a speckle image is input to the arithmetic device 5, the arithmetic device 5 calculates an MBR value, which is the temporal and spatial fluctuation amount of the speckle for each pixel, and forms an MBR image. Next, an MBR image of one heartbeat on average is formed from the MBR images, and the MBR values of one heartbeat on average are averaged at each pixel to form an average MBR image.

Next, in order to extract the analysis site, first, the average MBR image and the two-dimensional color image taken with a digital camera are superimposed. FIG. 8A is an example of a superimposed image thus obtained.

Next, when the operator designates a point belonging to a tooth in the superimposed image, the arithmetic unit 5 detects a region, for example, light intensity, of pixels surrounding the designated pixel whose average MBR value is smaller than a predetermined value A region with less than 150 gradations expressed in 254 gradations is identified as a tooth region. In this case, the MBR average value is calculated with 0.05 to 0.2 mm ² as one unit in the average MBR image, and the tooth region is determined by detecting the difference between the average MBR value and the designated point for each unit. good too. As a result, it is possible to automatically identify even the boundary region between the tooth and the gingiva where the difference between the average MBR values of adjacent pixels is small. FIG. 8B shows the contour lines of the tooth regions thus identified. The gingiva is an area adjacent to the tooth area, and when the light intensity is represented by 254 gradations as described above, the average MBR value of the pixels of the gingiva is a predetermined value or more, for example, 150 or more. , it is preferable to extract a region having such an average MBR value and extending from the boundary between the tooth and the gingiva to 1 to 2 mm on the gingival side. FIG. 8C shows the analysis range thus extracted. The analysis range is the interdental papilla and marginal gingiva where inflammation is likely to occur.

After extracting the interdental papilla or marginal gingiva from the average MBR image, the computing device 5 measures the BOT and the falling rate in the MBR image of one average heartbeat, and stores the values together with the date and time of measurement. When the speckle images of the same subject at different measurement dates are taken in the same manner and the BOT and the falling rate are measured, the computing device calculates the rate of change of the BOT and the rate of change of the falling rate.

In the gingival health index calculation method of the present invention, improvement or deterioration of the gingival health condition is determined, for example, as follows, using the thus calculated BOT change rate and falling rate change rate as health indices.
If the rate of change of BOT is less than 1 and the rate of change of Falling rate is less than 1, the health of the gums is definitely deteriorating.
If the rate of change in BOT is less than 1 and the rate of change in Falling rate is greater than or equal to 1, there is a high possibility that the health condition of the gums is deteriorating.
If the rate of change in BOT is 1 or more and the rate of change in Falling rate is less than 1, the health of the gums may be improved.
If the rate of change of BOT is 1 or more and the rate of change of Falling rate is 1 or more, it is highly likely that the health condition of the gums is deteriorating.

This determination result relates to the state of the entire gingiva in the oral cavity, and not only to the gingiva of the anterior tooth for which the speckle image was taken. This is presumed to be due to the fact that when inflammation occurs in any gingiva in the oral cavity, its influence affects the hardened state of blood vessels in the entire gingiva. Therefore, according to the present invention, by taking speckle images of the front teeth, it is determined that the health condition of the gums is deteriorating even when there is inflammation in the gums of the back teeth. be attached.

EXAMPLES The present invention will be specifically described below with reference to Examples.
14 subjects in their 50s to 60s and 15 subjects in their 20s to 30s were used as subjects, and the apparatus shown in FIG. Speckle images were taken, BOT and Falling rate were measured on different measurement days, and the rate of change of BOT and the rate of change of Falling rate on different measurement days were calculated. In this case, the measurement date is the first time, and 2 weeks, 1 month, and 2 months after the first measurement date. The rate of change from day to day, the rate of change from the date of measurement after 2 weeks and the date of measurement after 1 month and 2 months, the rate of change from the date of measurement after 1 month and the date of measurement after 2 months were obtained in 6 different rates. .

On the other hand, on each measurement day, the degree of gingival bleeding and the degree of gingival inflammation were evaluated by a dental hygienist as the health condition of a total of 16 gums from the first premolar to the second molar in the maxilla and mandible according to the following criteria. It was evaluated by giving a score of 0-3.

Extent of gingival bleeding Criteria based on the extent of bleeding immediately after inserting the pull orb into the periodontal pocket with light pressure (20-25 g) 0: No bleeding observed.
1: Punctate bleeding is observed.
2: Linear bleeding is observed.
3: Spontaneous bleeding is observed.

Degree of gingival inflammation 0: Clean gingiva. No inflammation observed.
1: Mild inflammation. There is a change in color tone such as redness. No bleeding on probing.
2: Moderate inflammation. Redness and edema are present. Bleeding on probing.
3: Severe inflammation. Significant redness, swelling, and ulceration. Tendency to spontaneous bleeding.

For these evaluations, six points around the tooth indicated by black circles in FIG. 10 were evaluated on each tooth. Then, the total score of 6 (points/line)×16=96 points was used as an evaluation point.

Those who scored higher on each measurement day for both the degree of gingival bleeding and gingival inflammation compared to the previous measurement day were those who scored worse, and the scores for both scored decreased. 11A and 11B show the relationship between the rate of change of BOT and the rate of change of Falling rate. From these figures, it can be seen that when both the rate of change in BOT and the rate of change in Falling rate are less than 1.0, the gingival inflammation is certainly exacerbated. Also, when the change rate of BOT is 1 or more and the change rate of Falling rate is less than 1, many improvers appear.

It should be noted that the use of BOS instead of BOT did not provide a good index of gingival inflammation.

1 Apparatus for calculating index for judging the state of health of gums 2 Laser light irradiation apparatus 2a Laser light emission port 3 Digital video camera 4 Polarizing filter 5 Arithmetic device 6 Image display device 10 Hook at corner of mouth 11 Chin rest P Test subject S Gingiva

Claims (1)

A device for calculating a gingival health index using laser speckle flowography,
a laser light irradiation device for irradiating the gingiva with a laser light,
A digital video camera that forms a speckle image by receiving scattered light of a laser beam irradiated on the gums through a polarizing filter,
a digital camera that forms a two-dimensional image of the gums ;
Equipped with an arithmetic device and an image display device that displays an image formed by a digital video camera or arithmetic device,
Arithmetic device
the ability to form an MBR image from a speckle image;
A function of forming an MBR image with an average of one heartbeat by normalizing the MBR image by the heartbeat;
A function of forming an average MBR image by averaging MBR values for one heartbeat in an average one-heartbeat MBR image;
A function to superimpose an average MBR image and a two-dimensional image,
When a pixel belonging to a tooth is specified in the superimposed image of the average MBR image and the two-dimensional color image, the computing device calculates the average MBR value of the pixels surrounding the specified pixel in the superimposed image. and the difference between the average MBR value of the specified pixel and the average MBR value of the specified pixel is within a predetermined range as the tooth area, and the pixel adjacent to the tooth area and the difference between the average MBR value of the tooth area and the average MBR value of the tooth area is specified A function of extracting the interdental papilla or the marginal gingiva from the MBR image of one heart beat on average by taking the area of pixels exceeding the range as the interdental papilla or the marginal gingiva;
Blowout from the waveform of the MBR value of the extracted interdental papilla or marginal gingiva for one average heartbeat
A function to measure time (hereinafter referred to as BOT) and falling rate,
A function to store BOT and falling rate and their measurement date and time for each subject, and for each of BOT and falling rate, calculate the rate of change between the measured value at a certain point and the measured value before that, and calculate these rate of change as a gingival health index.

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