JPH1079034A - Method for measuring blood vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the through put of medical examination by calculating a vertical scanning line vertical to a straight line passing through the two central points of a blood vessel, and calculating the two edges of the blood vessel in the same way as a scanning line for the vertical scanning line. SOLUTION: The pixel value of each pixel on one scanning line set so as to be crossing a blood vessel at the position of the blood vessel measured in a living body picture stored as electronic data is calculated, and the edges of the blood vessel are calculated. A middle point between the both end points at which the edges and the scanning line are crossing each other is defined as the center point of the blood vessel. Then, more than each two scanning auxiliary lines are drawn before and behind the scanning line in parallel, the central points of the blood vessel corresponding to the scanning line and each scanning auxiliary line are calculated for the scanning line and more than four scanning auxiliary lines, and a straight line passing through the center point of the blood vessel corresponding to the scanning line which is vertical to an approximating straight line approximating a point column constituted of those calculated more than five central points of the blood vessel by a straight line is newly defined as a scanning line. Then, the both end points at which the new scanning line for the scanning line is crossing the blood vessel are calculated, and a distance between the both end points is defined as the width of the blood vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blood vessel measuring method for measuring a blood vessel width of a biological image such as a fundus image using image processing.

[0002]

2. Description of the Related Art A fundus image, which is one of medical information, allows non-invasive (non-invasive) observation of arterial blood vessels and venous blood vessels.
It is promising as one of the early detection methods for adult diseases because it can be used to diagnose not only eye diseases but also signs of important diseases of the circulatory system. An index of an important disease that can be diagnosed by a fundus examination is a ratio of a diameter of a blood vessel between an artery and a vein of the fundus, and is measured clinically.

[0003] It is important to measure this arteriovenous ratio during treatment or health examination, etc., to grasp the degree of progression of arteriosclerosis. In the past, when a doctor performed such an action, the output of a polaroid photograph or the like of a captured image was directly performed manually using a measuring tool such as a caliper.

[0004]

SUMMARY OF THE INVENTION The present inventor has found the following problems as a result of studying the above conventional technology.

[0005] In recent years, fundus examination items have been incorporated into medical examinations and health checkups, and it is expected that a large amount of data will be generated as the number of examinees increases. On the other hand, since diagnosis is performed by a small number of ophthalmologists, there is a problem that time, physical strength, and mental burden are increased.

When determining the ratio of the arterial to venous blood vessel diameters in order to examine the signs of arteriosclerosis from the fundus image, where to be examined (selection of the gaze position), the diameters of the arterial and venous blood vessels are specifically measured therefrom. Two operations of calculating the diameter ratio can be considered. The former is determined by the doctor based on experience,
A person looks at an image and can determine which position is better overall, faster and more accurately than when performing image processing with a computer. However, the latter requires a considerable amount of time when manually measuring the length or calculating the ratio of two values.

That is, when the doctor determines the arteriovenous blood vessel diameter ratio from the fundus image, the latter support is indispensable, and the former work result, the blood vessel position to be measured is more easily specified, and the latter is specified. It is necessary to perform image processing and interface.

As conventionally performed, a method of selecting a gaze position by a doctor and measuring the arteriovenous blood vessel diameter ratio in the region by a simple method has been known before the disclosure of the know-how according to the present invention. Instead, doctors used a caliper on a Polaroid photo and read it. Such a method can be used for a display (C
RT) is not sufficient in terms of accuracy and
There was a problem that it took time.

[0009] An object of the present invention is to provide a technique capable of increasing the number of subjects to be subjected to a medical examination.

[0010] Another object of the present invention is to provide a technique capable of improving the efficiency of medical examination work.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0012]

The following is a brief description of an outline of a typical invention among the inventions disclosed in the present application.

(1) In a blood vessel measuring method for measuring a blood vessel width from a biological image such as a fundus image using image processing, a step of selecting a position of a blood vessel to be measured from the biological image;
Setting one scan line so as to cross the blood vessel through the selected point, obtaining the pixel value of each pixel on the scan line, and obtaining two edges of the blood vessel on the scan line from each pixel value A step of determining the midpoint of the two edges as the center point of the blood vessel, a step of setting a scanning auxiliary line parallel to the scanning line near the scanning line, and Similarly, the process of obtaining the center point of the blood vessel,
Obtaining a vertical scanning line perpendicular to a straight line passing through the center point of the two blood vessels obtained from the scanning line and the scanning auxiliary line;
And a process of obtaining one edge.

(2) The process of drawing two or more scanning auxiliary lines in parallel before and after the scanning line, and defining the scanning line and four or more scanning auxiliary lines as the scanning lines of the means (1), respectively. Assuming that the blood vessel measuring method of the means (1) is performed to obtain the center point of the blood vessel corresponding to each of the scanning line and the four or more scanning auxiliary lines, and the obtained center point of the five or more blood vessels. A process of obtaining an approximate straight line obtained by approximating a point sequence by a straight line, a process of newly forming a straight line passing through the center point of the blood vessel corresponding to the scan line and perpendicular to the approximate straight line, and a process of obtaining a new scan line. And a step of executing the blood vessel measuring method of the means (1) to obtain a point at both ends where a new scanning line and a blood vessel intersect, and a step of setting a distance between the points at both ends to a blood vessel width. .

That is, according to the blood vessel measuring method for a living body image such as a fundus image according to the present invention, one scanning line is set so as to intersect a blood vessel at a position of a blood vessel to be measured in a living body image stored as electronic data. , The pixel value of each pixel on the scanning line is determined, and the edge of the blood vessel is determined from each pixel value. A middle point between both ends where the obtained edge of the blood vessel intersects the scanning line is set as the center point of the blood vessel, and two or more scanning auxiliary lines are drawn in parallel before and after the scanning line. With respect to the scanning line and the four or more scanning auxiliary lines, the scanning line and the four or more scanning auxiliary lines respectively determine the center point of the corresponding blood vessel. An approximate straight line obtained by approximating a point sequence based on the obtained five or more blood vessel center points with a straight line is obtained, and a straight line perpendicular to the approximate straight line and passing through the center point of the blood vessel corresponding to the scan line is newly set as a scan line. For each scan line, the points at both ends where the new scan line and the blood vessel intersect are obtained. The distance between the two points is defined as the blood vessel width.

By performing the measurement support at that time and efficiently handling the health examination images, it is possible to target a larger number of subjects, and as a result, the number of subjects to be subjected to the health examination can be increased.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In all the drawings for describing the embodiments, parts having the same functions are given the same reference numerals, and their repeated explanation is omitted.

An embodiment of the blood vessel measuring method for a biological image according to the present invention will be described below.

FIG. 1 is a schematic diagram showing a fundus image, wherein 1 is an optic disc, 2 is a macula, 3 is a central retinal artery, and 4 is a central retinal vein.

As shown in FIG. 1, the components of the fundus image are an optic disc 1, a macula 2, a retina, a central retinal artery 3, and a central retinal vein 4. The macula 2 is substantially at the center of the fundus image, and the center has the best visual sensitivity. Central retinal artery 3 and central retinal vein 4 enter and exit from optic disc 1,
Four pairs of normal retinal central arteries 3 and central retinal veins 4 are branched in the vertical and horizontal directions with the optic disc 1 as a base point.

When there is a disease such as arteriosclerosis, it appears as a change in blood vessel diameter. When a stenosis occurs in an arterial blood vessel, the diameter of the blood vessel becomes small. When the diameters of the blood vessels of the central retinal artery 3 and the central retinal vein 4 running in pairs are measured, the ratio gradually becomes 1: 1. Come. Therefore,
Usually, the second segment (second blood vessel bifurcation from the nipple) to the third segment
An arteriovenous blood vessel diameter ratio (R artery / R vein) is determined between segments. FIG. 2 is a schematic diagram for explaining the arteriovenous blood vessel diameter ratio.

In such a case, the determination of where the arteriovenous blood vessel diameter ratio is to be measured (attention area) must depend on the doctor, but once the position is determined, the arteriovenous blood vessel diameter is determined by image processing. The ratio can be determined.

A method as shown in FIG. 3 is considered as an embodiment. That is, the position of the doctor is specified by a simple operation using a mouse on the fundus image displayed on the CRT by the doctor, and the blood vessel is extracted by image processing from the position.
Determine the arteriovenous vessel diameter ratio.

In this embodiment, a display (CRT)
Etc.), a straight line is traversed across the blood vessel to be measured on the fundus image displayed on the fundus image, and the doctor inputs the position by clicking the position using a mouse which is one of the input interfaces of the computer (FIG. 4). From the position information on the image thus input, the blood vessel diameter is measured by software on a computer as follows, and the arteriovenous blood vessel diameter ratio is obtained.

First, when a change in pixel value is examined along a straight line that crosses the blood vessel specified by the doctor, the pixel value changes more rapidly near the contour of the blood vessel than in other portions. It is obtained as the extreme value of the gradient of the change. Therefore, the center coordinates of two places corresponding to the blood vessel contour can be considered to be substantially the center of the blood vessel.

The method of determining both end points where a straight line and a blood vessel intersect is determined by various edge detection methods such as an edge detection using a gradient, an edge detection operator using a weight matrix, and a method using a place where Laplacian becomes zero crossing. It can be used.

In a similar procedure, the center point of a blood vessel on a plurality of straight lines in parallel with the straight line designated by the doctor is determined.

An approximate straight line obtained by linearly approximating the point sequence of the center point (FIG. 5) by a method such as least squares approximation is estimated as a blood vessel running direction near a position designated by a doctor, and a straight line perpendicular to this is defined as a straight line designated by the doctor. Is drawn so as to pass through the center point of the blood vessel, and the length of the section where this straight line intersects the blood vessel is defined as the blood vessel width (FIG. 6).

A plurality of the blood vessel widths are generated in parallel with a straight line passing through the center point of the blood vessel obtained from the straight line specified by the doctor, and the blood vessel width is obtained from each of them. Should be the measurement width.

Here, the direction of travel of the blood vessel is determined, or
Regarding the parallel straight line group at the time of averaging the blood vessel width, in the position where the linearity of the blood vessel is high, the interval between the lines is long and it is better that the number is large, but the position where the curve is high such as the blood vessel is bent In, the shorter the distance between lines and the smaller the number, the more accurate the blood vessel width is obtained.

The processing flow of the blood vessel measuring method of the above embodiment is as follows.

(1) Instructing process near the measurement target location As shown in FIG. 7, first, the position of the blood vessel for measuring the thickness of the artery is designated by clicking the mouse (S1).
Next, the position of the blood vessel for measuring the thickness of the vein is designated by clicking the mouse (S2).

(2) Estimating Process of Traveling Direction of Blood Vessel to be Measured As shown in FIG. 8, a pixel value on a straight line connecting end points specified manually is obtained (S3), and a gradient of the pixel value is obtained (S3).
4) A point at which the absolute value of the gradient becomes maximum is obtained (S5).
Next, the maximum two points among the maximum points are set as points where a straight line connecting the blood vessel and the end point designated manually is intersected (S6), and an intermediate point between the two maximum points is set as the center point of the blood vessel (S7). Next, a plurality of lines are respectively drawn before and after in parallel with a straight line connecting the end points designated manually (S8), a blood vessel is extracted from each line to obtain a center point of the blood vessel (S9), and a center point of the obtained blood vessel is obtained. An approximate straight line for the group is determined and set as the direction of the blood vessel (S10).

(3) Calculation of Arteriovenous Blood Vessel Diameter Ratio As shown in FIG. 9, a straight line perpendicular to the estimated blood vessel running direction is obtained (S11), and pixel values on the obtained straight line are obtained (S11). S12), the gradient of the pixel value is obtained (S1).
3) Find the point where the absolute value of the gradient becomes maximum (S1)
4). Next, the maximum two points among the maximum points are defined as points where a straight line connecting the blood vessel and the end point designated manually is intersected (S15), and the distance between the two maximum points is defined as the cross-sectional diameter of the blood vessel (S1).
6). Next, the cross-sectional diameter of the blood vessel is obtained at a plurality of positions in the estimated blood vessel running direction, and the average value is used as the estimated diameter of the blood vessel (S17). Then, the ratio between the estimated diameters of the blood vessels obtained for the artery and the vein is determined as the arteriovenous blood vessel diameter ratio (S18).

As can be understood from the above description, according to the present embodiment, one scan line is set at the position of a blood vessel to be measured in a biological image stored as electronic data so as to intersect with the blood vessel. The pixel value of each pixel on the scanning line is obtained, the edge of the blood vessel is obtained from each pixel value, the midpoint between both ends where the obtained blood vessel edge intersects the scanning line is set as the center point of the blood vessel, Two or more scanning auxiliary lines are drawn before and after each other in parallel, and the above-mentioned scanning line and four or more scanning auxiliary lines correspond to the center point of the corresponding blood vessel with respect to the scanning line and four or more scanning auxiliary lines, respectively. Is obtained, an approximate straight line obtained by approximating a point sequence based on the obtained center points of five or more blood vessels with a straight line is obtained, and a straight line perpendicular to the approximate line and passing through the center point of the blood vessel corresponding to the scan line is newly added to the scan line. And a new scanning line for the new scanning line By finding the points at both ends where the blood vessels intersect and using the distance between the two points as the blood vessel width, the fundus examination measures the arteriovenous blood vessel diameter ratio and grasps the degree of progression of arteriosclerosis. The output of a polaroid photograph or the like can be supported by a computer without using a measuring tool such as a vernier caliper directly by hand, and a medical examination image can be handled efficiently. This allows
The number of health check recipients can be increased, and the efficiency of the screening work can be increased. As a ripple effect, it can contribute to the spread of medical examinations.

The fundus is the only site where human blood vessels can be observed in a non-invasive (non-invasive) manner. By diagnosing the image, not only the fundus disease but also the circulatory system such as hypertension and diabetes can be observed. Serious illness can be found. Therefore, if the computer can assist the comparative projection of the fundus image and improve the efficiency of the diagnosis work by the doctor, the significance is significant.

As described above, the invention made by the present inventor is:
Although specifically described based on the embodiment, the present invention
It is needless to say that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the scope of the invention.

[0039]

The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.

(1) It is possible to increase the number of persons who undergo medical examinations by doctors.

(2) It is possible to improve the efficiency of medical examination work by doctors.

(3) An adult disease can be detected early by a fundus examination or the like.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a fundus image for explaining a blood vessel measurement method according to an embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining an arteriovenous blood vessel diameter ratio to be measured in the present embodiment.

FIG. 3 is a diagram showing an embodiment in which a traveling direction of a blood vessel designated by image processing by a computer in the blood vessel measurement method of the present embodiment is estimated, a diameter of the blood vessel is obtained, and an arteriovenous blood vessel diameter ratio is obtained as a ratio thereof. It is.

FIG. 4 is a diagram showing an example of a method of giving the position of an artery (or vein) with a mouse when the doctor of the present embodiment indicates a blood vessel desired to be measured.

FIG. 5 is a diagram illustrating an example of a method of estimating a traveling direction of a blood vessel designated by a doctor according to the present embodiment by image processing.

FIG. 6 is a diagram illustrating an example of a case where a computer according to the present embodiment obtains a diameter of a blood vessel as a direction perpendicular to a traveling direction of the blood vessel estimated by image processing.

FIG. 7 is a flowchart of an instruction process near a measurement target portion in the blood vessel measurement method according to the embodiment.

FIG. 8 is a flowchart of a process of estimating a traveling direction of a blood vessel to be measured in the blood vessel measuring method according to the embodiment.

FIG. 9 is a flowchart of a calculation process of an arteriovenous blood vessel diameter ratio in the blood vessel measuring method according to the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optic disc, 2 ... Macular area, 3 ... Central retinal artery, 4 ...
Central retinal vein.

Claims (2)

[Claims] In a blood vessel measuring method for measuring a blood vessel width from a biological image such as a fundus image using image processing, a step of selecting a position of a blood vessel to be measured from the biological image and intersecting the blood vessel through the selected point. Setting one scanning line as described above, obtaining a pixel value of each pixel on the scanning line,
A step of obtaining two edges of the blood vessel on the scanning line from each pixel value, a step of obtaining a midpoint of the two edges as a center point of the blood vessel, and a scanning auxiliary line near the scanning line and parallel to the scanning line Setting the scanning auxiliary line as the center point of the blood vessel in the same manner as the scanning line, and perpendicular to a straight line passing through the scanning line and the central point of the two blood vessels obtained from the scanning auxiliary line. Finding a vertical scanning line,
Obtaining two edges of a blood vessel with respect to the vertical scanning line in the same manner as the scanning line. 2. A process of drawing two or more scanning auxiliary lines in parallel before and after the scanning line, and the scanning line and four or more scanning auxiliary lines are regarded as the scanning line according to claim 1, respectively. 2. A step of executing the blood vessel measuring method according to claim 1 to obtain a center point of a blood vessel corresponding to each of the scanning line and the four or more scanning auxiliary lines, and a point sequence based on the obtained center points of the five or more blood vessels. A process of obtaining an approximate straight line that approximates a straight line, a process of making a new scan line a straight line perpendicular to the approximate straight line and passing through the center point of the blood vessel corresponding to the scan line,
2. A blood vessel, comprising: a step of performing the blood vessel measurement method according to claim 1 to obtain a point at both ends where a new scanning line intersects a blood vessel; and a step of setting a distance between the two points to a blood vessel width. Measurement method.