JPH05264232A - Device for measuring diameter of contrasted blood vessel with high accuracy - Google Patents

Abstract

PURPOSE:To facilitate measuring of blood vessel diameter with high accuracy by enlarging a required area of a contrasted image of the coronary artenary, etc., to a high degree, and extracting the side edges of the blood vessel by means of an entropy filter. CONSTITUTION:A film 1 on which contrasted images are recorded is run on a stage 3 by a film running mechanism 2. The images are picked up by a monitor camera 5 and are displayed in a monitor 7 and a frame to be picked up is selected so as to determine a measuring range. An image of the range is picked up by a high resolution(digital) camera 10 and is sent to a data processing portion 11 and then a measuring portion 31 performs predetermined arithmetic and the range is displayed on a high resolution monitor 13 and output by an output device 14. The entropy filter of the measuring portion 31 performs entropy operations as to the range sandwiched by side edges obtained through first and second differentiations, for data subjected to load moving average operations. The measuring portion 31 adds the upper and lower side edges due to entropy to a blood vessel extracting circuit, and performs arithmetic for extracting a blood vessel and other arithmetic, thereby extracting the side edges and the axis, etc., of a blood vessel. Highly accurate measurement of the diameter of the blood vessel is thus made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-accuracy vessel diameter measuring device for contrast vessels. More specifically, the present invention is useful in clinical research and clinical treatment of heart disease,
The present invention relates to a new tube diameter measuring device that enables highly accurate blood vessel measurement from a contrasted blood vessel image.

[0002]

BACKGROUND OF THE INVENTION The incidence of heart disease in Japan is gradually increasing, and in 1985, it became the second leading cause of death after cancer, surpassing cerebrovascular disease. From such a social background, methods for evaluating coronary stenosis have been actively promoted. However, until the computer-aided image processing method was introduced to evaluate the stenosis of blood vessels for coronary angiograms, the evaluation was left to the interpretation of radiologists. Therefore, the actual situation is that different radiologists produce different results, and even the same radiologist obtained different results on different interpretation days.
Although this was a global situation, most hospitals in Japan evaluate coronary artery stenosis by such a method.

However, in Western countries where the prevalence of heart disease is much higher than in Japan, it has recently been noticed that radiologists have a large error in image interpretation, and a coronary artery measuring apparatus using an image processing method has been introduced. Development has been advanced.
At present, practical devices have been put on the market. Most of these devices adopt a method of adopting an input signal of which the number of horizontal and vertical pixels is 512 × 480 by a TV camera, but the blood vessel diameter is approximately 10 to 10 at a large diameter.
It has 20 pixels. Considering that the blood vessel wall is determined pixel by pixel at this resolution, an error of one pixel is unavoidable on one wall, and the error due to this is 10 to 20%. It was difficult to improve the accuracy by adding other errors to this. The enlargement ratio of the contrast image according to the related art is within 4 times.
In addition, the enlargement ratio referred to here is the above 512 × 4.
It is a multiple of the number of horizontal and vertical pixels when the screen of 80 pixels is used as a reference.

As an input image, for example, as shown in FIG. 1, a straight line perpendicular to the blood vessel axis (hereinafter referred to as "section axis") is assumed, the horizontal axis is the position on the cross section axis, and the vertical axis is the vertical axis. An angiographic image with the concentration of the contrast agent on the cross-sectional axis is subjected to smoothing processing to remove the influence of noise to obtain the concentration curve of the contrast agent, and the first derivative and the second derivative are applied to this. Often, a procedure for obtaining the edge of a blood vessel from these data is used.

In the smoothing process, the position on the horizontal axis in FIG. 1 is represented by a pixel i, and the density value on the vertical axis at this point is d (i).
And the width of the window to be smoothed is w,
The smoothed density value a (i) is expressed by the following equation.

[0006]

[Equation 1]

The first derivative g ₁ (i) of the smoothed contrast agent concentration curve represents the concentration gradient of the curve and is defined as follows.

[0008]

[Equation 2]

This g₁(I) Absolute of (i = 1, ...)
The maximum value, that is, the coordinate value i that gives the maximum gradient
Obtained in the left and right regions of the pipe cross-section axis, this position (f in Fig. 1₁
And f ₂) Is defined as the edge of the blood vessel and the first derivative filter
Is the law. Second derivative of contrast agent concentration curve g₂(I) (i =
1, ...) represents the rate of change of the gradient of the curve.
Is defined as

[0010]

[Equation 3]

The absolute value of this g ₂ (i) (i = 1, ...) Is the maximum, that is, the coordinate value i at which the curvature changes from convex upward to concave downward is found in the left and right regions of the blood vessel axis. The second-order differential filter method defines this position (s ₁ and s _{2 in} FIG. 1) as the edge of the blood vessel. From experience, it is normal that the blood vessel edge given by the first derivative filter is inside the actual edge and the result of the second derivative filter is the outer edge.
In practice, a margin is often defined between the two. This is called the mixing method.

The density value g ₃ obtained by the mixing method is obtained by applying a weighted sum to the first derivative and the second derivative, for example, by the following calculation.

[0013]

[Equation 4]

Here, it is assumed that a + b = 1. The above-described conventional method for obtaining the approximate position of the blood vessel margin is effective in clinical application and has no practical problems. However, from the standpoint of clinical research, there may be a problem in measurement accuracy. For example, when observing the change over time in the degree of stenosis of a coronary artery of a patient or determining the effect of a drug, it is often difficult to make the determination by the above-mentioned conventional measurement method.

Therefore, it has been desired to realize a method which can be used for detailed clinical research and can measure a blood vessel diameter with high accuracy, and a device therefor.

[0016]

The present invention has been made in view of the circumstances as described above, and is intended to solve the drawbacks of the conventional methods and to enable more accurate measurement of blood vessel diameter. In addition, it has an image reading means for highly magnifying a required area of a contrast image such as a coronary artery and an extraction processing means for extracting a blood vessel margin by an entropy filter, and a blood vessel whose margin is extracted from the enlarged image by an entropy filter. Provided is a high-accuracy vessel diameter measuring device for contrast-enhanced blood vessels, which is characterized by highly accurately measuring the diameter.

More specifically, the present invention is more specifically a means for retrieving a measurement frame of a contrast image film such as a coronary artery, a means for reading a measurement region from the retrieved measurement frame with high magnification and high resolution, and the reading. It is characterized in that it is constituted by means for extracting the edge of the blood vessel, blood vessel axis, and normal diameter from the data of the measurement region by an arithmetic circuit including an entropy filter and Hough transform, and means for calculating and outputting the stenosis rate. It is intended to provide a highly accurate contrast vessel diameter tube diameter measuring device.

That is, according to the present invention, when the blood vessel diameter is extracted from the angiographic image, the extraction accuracy is improved.
We believe that it is necessary to reexamine the method for determining the enlargement ratio and the edge of the blood vessel at the time of image reading. Therefore, various combinations of these two methods are used, and the image is read at an enlargement ratio of about 10 times the angiographic image to read the blood vessel side. The entropy filter is applied on the cross-sectional axis of the blood vessel to determine the edge, and the Hough transform is applied to determine the normal blood vessel diameter, whereby the measurement accuracy can be significantly improved.

More specifically, for example, this measuring device is basically a monitor device for <a> contrast image retrieval,
It can be configured by a <b> high-magnification high-resolution image reading device, a <c> film traveling mechanism, a <d> read data processing device, a <e> data output device, and a <f> control device. <a> The contrast image retrieval monitor device inputs data by a method such as reading an angiographic image from a contrast image recording film with a normal monitor camera having a resolution of about 512 × 480 pixels, and displays this data on the monitor. Then, the frame of the film which is the target of blood vessel measurement is searched, and the measurement region to be enlarged is displayed by the cursor.

<B> The high-magnification high-resolution image reading device is
It is composed of a camera device having a resolution of about 10 times and a high-resolution monitor, and captures the image of the measurement region displayed by the cursor and stores the read data in the memory. <C> The film traveling mechanism searches the frame to be imaged while traveling through the film, automatically moves the searched frame to the high-magnification high-resolution image reading device, and the relative position between the film stage and the high-magnification image reading device. Is automatically adjusted so that the imaging range of the high-magnification, high-resolution image reading device matches the measurement area displayed by the cursor.

<D> The read data processing device applies a weighted moving average to the read image data to remove the influence of noise,
In addition to the first derivative and second derivative filter processing, entropy filter processing is performed to find the position of each blood vessel edge, the blood vessel axis is obtained from this, and the density value on the cross-sectional axis is obtained by the Vilinian interpolation method. Again performing each of the above processes to obtain the position of each blood vessel margin, Hough transform is performed on the range of the blood vessel including the stenotic portion to obtain the normal blood vessel diameter, and the normal diameter and the blood vessel are calculated. The stenosis rate is calculated from the diameter, and other main data are calculated.

<E> The data output device prints out the personal information of the patient and the display for displaying the search frame of the film, the display of the control instruction and the measurement data, the display of the measurement screen and the like. In addition, various data relating to patient identification information and blood vessels are stored in an optical disc, and displayed on a display or output as a hard copy if necessary.

<F> The control device has an operation unit and a computer, and the operation unit operates in accordance with a predetermined procedure to give necessary instructions to each unit constituting the system by the corresponding software. More specifically, various configurations are possible, including the configurations illustrated in the embodiments described later. Here, the entropy is the average amount of information relating to the density on a straight line set on the image, and the entropy for the range of ± w in the angiographic image is defined by the following equation.

[0024]

[Equation 5]

In FIG. 1, at both ends of the cross-section axis, the edges f ₁ · s obtained by the primary and secondary differential filters
For g (i) (i = 1 ... N) obtained for the area surrounded by ₁ and f ₂ · s ₂ , the coordinate value giving the minimum value is obtained, and the position is defined as the edge.
This can be represented in FIG. 1 by e ₁ and e ₂ . Further, the Hough transform is performed by intercepting a point on the blood vessel edge curve along the blood vessel axis represented by m and D coordinates with the m axis of a straight line passing through this point and the intercept on the D axis as shown in FIG. A coordinate conversion method that performs conversion as represented by b. 1 on the edge at the m and D coordinates
The straight line is one point of θ and b coordinates. At each point on the blood vessel marginal difference curve in the m and D coordinates, a straight line passing through that point can be formed by the amount of change in θ, but these straight lines are expressed as corresponding points in the θ and b coordinates. In general, the point (θ _m , b _m ) to which the largest number of straight lines correspond on the m and D coordinates gives a straight line equation representing the normal blood vessel diameter.

Another method for obtaining the normal diameter is to draw a tangent line at each point on the blood vessel marginal difference curve, and use the most common two tangent lines.
The area between the contact points becomes the peripheral portion of the normal blood vessel. The area between A and B in FIG. 14 shows the edge of the normal diameter. When the normal blood vessel diameter is obtained, the stenosis rate, that is, the ratio between the diameter reduced by the stenosis and the normal diameter can be obtained, which can provide an important factor for coronary artery morphology diagnosis.

Comparing the result measured by such a method with the conventional method, that is, the result measured by the mixed method of the primary differential filter and the secondary differential filter for the image magnified 4 times, for example, the image magnified 10 times The size of the standard deviation when the entropy filter is applied to is less than one-third of the value obtained when the mixing method is applied to the 4-fold enlarged image. In other words, the measuring method of the present invention has less variation in measured values and is three times superior in precision.

In order to compare the accuracy of the difference between the average value and the true value of the measured values, the size of the gap when the entropy filter of the 10 × magnified image is applied is the mixture method applied to the 4 × magnified image. It is less than one-fourth of the size of the gap when it is done. That is, the gap of the present invention is more than four times that of the conventional method. When the diameter on the image corresponding to a unit diameter (for example, 1 mm diameter) is calibrated by a catheter, this diameter is represented by (number of pixels) × (length of one pixel). When calibrating the measured values in this way, the value when the entropy filter is applied to the 10 × magnified image is 10
When set to 0, the values due to the difference in the weighting coefficient when the mixing method was applied to the 4 × magnified image were 81 to 94. A large value means that the ability to detect a minute diameter change is high, and therefore it can be seen that the entropy method is superior.

[0029]

【Example】

(System Configuration) FIG. 2 is a block diagram showing the outline of the present invention. The film (1) on which a contrast image is recorded is run on the stage (3) by the film running mechanism (2) controlled by the imaging position controller (4), and the image taken by the monitor camera (5) is interfaced ( A frame to be imaged is displayed on the monitor (7) via 6) and a region to be measured is determined. This area is imaged by the high resolution camera (10) and sent to the data processing unit (11) to perform a predetermined calculation, and commands and data are displayed on the monitor (12) and images are displayed on the high resolution monitor (13). And output by the output device (14).

Imaging position controller (4), interface (6), data processing unit (11) and output device (14)
Are controlled by the CPU (8), and the operation of each unit is performed by the operation unit (9) via the CPU (8). Next, the outline of the operation of each block will be described in more detail with reference to FIG.
That is, the imaging position controller (4) is composed of a film traveling controller (20) and a stage controller (21). By the operation of the operation section (9), the film traveling controller (20) is used to control the traveling mechanism (2) of the film, so that the film is fed back and forth at a normally used feed speed of 1 frame per second, and back and forth. Fast-forward / slow-forward, 1 frame or 1 perforation feed, and can be sent from the imaging position of the monitor camera (5) to the imaging position of a high-resolution monitor camera (hereinafter abbreviated as “digital camera”) (10).

The output of the monitor camera (5) is temporarily stored in the frame memory (22) of the interface (6), and the ITV monitor (7) is sent through the OR gate (24) together with the cursor generated by the cursor generator (23). To display. The operator operates the feed button of the operation unit (9) while looking at the screen of the monitor (7) to search for a frame on the desired screen. FIG. 4 shows this search screen (61), in which the screen generated by the monitor camera (5) is overlaid with a box-shaped cursor (63) of a long rectangle shown by a dotted line, which is created by the cursor generator (23). Will be displayed. The range of the box cursor (63) indicates the range captured by the digital camera (10). The operator operates the box cursor position adjustment button of the operation unit (9) to move the box cursor to a position centered on the place where the stenosis occurs, and adjusts the angle to change the longitudinal direction of the blood vessel (62) to be imaged. Make it almost orthogonal to the long side of the box cursor. At this time, the memory (1
In 5), the coordinates X _S , Y _S of the upper left corner of the box cursor and the angle γ are recorded.

When the position of the box cursor is inappropriate, fine adjustment of X, Y, and γ can be performed again to set it at a desired position. When the move button of the operation unit (9) is pressed in this state, the film (1) is automatically fed to the image pickup position of the high resolution digital camera (10) by the film feed controller (20).

The stage (3) is a moving table for precisely setting the film at the image pickup positions of the monitor camera (5) and the digital camera (10), and is controlled by the stage controller (21). It has the function of finely moving and rotating the film in the x direction (long side direction) and y direction (short side direction). This movement / rotation may be performed only by the stage, but may be performed together with the film feeding mechanism (2).

However, this movement fixes the stage,
It goes without saying that the digital camera (10) may be moved. By the above operation, the switch (2
Since the monitor (7) is automatically switched from the monitor camera (5) to the digital camera (10) by 5), the image pickup screen of the digital camera (10) is displayed on the screen.

As the digital camera (10), for example, a known multi-element CCD line sensor that employs a method of mechanically precise sub-operation can be used. Further, as the digital camera (10), a high-definition camera or the like can be used as it is. However, although a high-definition camera has an advantage of being capable of high-speed image pickup, it has a drawback that the resolution in the vertical direction is slightly inferior and that there is no need for moving image pickup, and in the case of the present invention in which there is little need for color image pickup, it is wasteful. is there.

In the image pickup by the digital camera (10),
Although the image quality may be inferior, the imaging screen can be fixed in a short time by high-speed scanning, and this finalized screen can be imaged by low-speed scanning to obtain a target final high-quality screen.
The high-speed scanning is performed by, for example, pressing a push button of the operation unit (9), and as shown in FIG. 3, the signal captured by the digital camera (10) is once written in the buffer memory (26), The read data is displayed on the high resolution monitor (13) via the frame memory (27), the cursor generator (28) and the overlay memory (29), and the OR gate (30).

As the monitor (13), for example, 2,
It is necessary to have a resolution of 048 pixels × 3,000 lines. It is possible to use a high-definition monitor for broadcasting, but it may not be possible to display all of the vertical direction because the number of lines is insufficient. The screen (64) displayed on the monitor (13) is, as shown in FIG. 5, the entire screen (65) reduced to the left end, the cursor (67) shown by a dotted line inside thereof, and the zoom screen (66) to the right. ) Is formed of a multi-screen.

The whole screen (65) is the CP of FIGS. 2 and 3.
Under the control of U (8), writing is performed from the buffer memory (26) to the left end of the frame memory (27) while thinning out, for example, every four lines, and the zoom screen (6
6) indicates the range of the box cursor (67) generated by the cursor generator (28), for example, 1.2.4.8.
The data is written in the right end of the frame memory (27) by performing interpolation enlargement at the magnification of. On the other hand, the box cursor (67) is written at the position of the entire screen of the overlay memory (29). This frame memory (27) and overlay memory (29) are monitored (1) via an OR gate (30).
The above-mentioned multi-screen is displayed in 3).

The cursor (67) can freely change the coordinates X _Z , Y _Z of the upper left end thereof by the control of the operation unit (9), so that the cursor can be set at any position on the whole screen (65). You can move. Further, since the zoom screen (66) can be enlarged and displayed at a magnification of, for example, 1, 2, 4, 8 times as described above, it is possible to display any position of the entire screen (65) in any size. ..

When the confirmation screen of the angiographic image is obtained by the above operation, the zoom mode button of the operation unit (9) is pressed to further enlarge the zoom screen (66) of FIG. It can be expanded to the whole surface of the monitor like 6. In this state, when it is necessary to correct the position of the measurement frame or the box cursor, the correction can be performed by returning to the original state. When that is not necessary, the quick scan is stopped, and thereafter, the slow scan is performed.

The measurement area setting method described above is shown in FIG.
As shown in, the digital camera (1
A box cursor (63) indicating the imaging range of (0) is superimposed and displayed, and when the range of this cursor (63) is imaged by the digital camera (10), the blood vessel (62) is displayed horizontally. In addition, the film was moved, the position of the camera and the stage in the x and y directions, and the angle were adjusted, and the screen was confirmed using the multi-screen shown in FIG. It goes without saying that it is good.

For example, in FIG. 4, a + mark is displayed on a portion to be enlarged and an optical axis position of the digital camera (10) is displayed by a circle mark, and a + mark portion to be imaged is displayed by pressing the move button. It is also possible to move to the position of 10), rotate the angle found by the angle scale superimposed on the screen of the high-magnification image, and fix the final screen with the box cursor when necessary.

Hereinafter, further, the measurement of the front stage, the measurement of the rear stage,
The calculation by the concentration area method, the calibration by the catheter, the calculation and display of the final data, the color display of the screen, and the application will be described in detail. Measurement at the previous stage By pressing the measurement start button of the operation unit (9) shown in FIGS. 2 and 3, the digital camera (10) captures an image of the determined area, and the obtained data is stored in the buffer memory (26). Store.

Next, the operation item (9) is used to specify the measurement item. The items that can be designated include, for example, the following various types, and are appropriately selected according to the purpose. Note that other items can be added as necessary. (1) Whether the edge of the blood vessel is detected by the weighted sum method of the first derivative and second derivative filters or the entropy filter method.

(2) Necessity of printing (3) Necessity of storage on the magneto-optical disk (4) Necessity of concentration area display (5) Object to be processed is blood vessel or catheter (6) Blood vessel and catheter are in the same frame Or select to display in another frame. These designated items can be displayed from the operation unit (9) to the CPU.
It is written in (8) and displayed on the monitor (12).

The measuring section (31) in FIG. 3 receives the pixel data supplied from the frame memory (27) and performs the calculations necessary for the above various measurements. These operations are performed by hardware
Software or a combination thereof can be selected, but in the present invention, hardware is used to increase the processing speed. Figure 7: Measuring unit (31)
It is a block diagram of.

Since most of the hardware can be constructed by a known technique if the calculation formula is known, most of the calculation formulas are presented below. However, the characteristic parts of the entropy filter and the Hough transform circuit are A concrete circuit is presented. It should be noted that each circuit in the measurement unit (31) is controlled by the CPU (8) according to the processing item written in the operation unit (9).
Operate under the control of.

In FIG. 7, the switches (41) and (42) are switched to the (41-1) and (42-2) sides, respectively, and the weighted moving average calculation circuit (43) calculates
Is calculated to remove noise. At this time, the window is set to 22, for example. The calculation result calculated pixel by pixel is sequentially stored in the frame memory (44), and when the calculation is completed, the switch (42) is switched to the (42-2) side.

With the switch (45) set to the (45-1) side, the signal for which the weighted moving average has been completed is sent to the first derivative filter (46) and the second derivative filter (47), and the concentration of the signal is plotted on a line perpendicular to the blood vessel axis. The change is examined to find the position i _maxd on the cross-sectional axis that gives the maximum value maxd (i, m), and the first and second derivatives of the above equation 2 and the second derivative of the above equation 3 are performed above and below it to obtain g ₁ ( i) and g ₂
Find (i).

The outputs of the primary differential filter (46) and the secondary differential filter (47) are the maximum value extraction arithmetic circuit (4
In addition to 8), as shown in FIG. 8, the coordinates f ₁ and f ₂ that give the maximum value by the first derivative are obtained, and the coordinates s that give the first edge by the first derivative and the maximum value by the second derivative are obtained.
₁ and s ₂ are obtained and used as the second edge by the second derivative.

This screen is displayed on the monitor (13). The processing range designation circuit (4
In addition to 9), specify the ranges of f ₁ and s ₁ and f ₂ and s ₂ , respectively. The switch (45) is set to the (45-2) side. At this time, the entropy filter (50) includes a weighted moving average circuit (4) stored in the frame memory (44).
The output of 3) and the output of the processing range designation circuit (49) are added, and for the range sandwiched by the edges by the first derivative and the second derivative with respect to the data subjected to the weighted moving average calculation, Entropy calculation is performed using the formula.

FIG. 9 is a block diagram of the entropy calculation circuit. The coordinate value i on a straight line perpendicular to the blood vessel axis is added to the terminal (71), and the auxiliary variable j is separately added to the terminal (72). j is increased from -w by the incrementer (74)
The data is changed to w, and (i + j) is obtained by an adder (73) with i, and this data is added to the memory (75).
The density value d (i + j) of the zoom screen is stored in the memory (75).
Is stored, and the corresponding pixel is read by the (i + j) signal from the adder (73). As the memory (75), the frame memory (27) can be used as it is.

The data read from the memory (75) is output P obtained by summing from -w to + w by the adder (76), logP by the logarithm unit (79) constituted by the ROM, and 1 by the reciprocal unit (80). / P is obtained. On the other hand, the output d (i + j) of the memory (75) is added to the logarithmic circuit (77) constituted by the ROM to logd (i
+ J), the multiplier (78) calculates the product d (i + j) logd (i + j) of d (i + j) and its logarithm, and the multiplier (81) calculates the product 1 / P * 1 / (P * d (i +)).
j) logd (i + j) is taken, and the subtracter (82) finds the difference from logP.

D (i + j) is integrated as j increases. On the other hand, when the output of the incrementer (74) of j is added to the comparator (84) and j becomes w, the output is added to the latch (85) and the operation of the equation 2 is completed. Output g
(I) is output from the terminal (86) to the minimum value extraction circuit 51. The above calculation is performed in the ranges of f ₁ and s ₁ and f ₂ and s ₂ , respectively, and the minimum value extraction circuit (5
In 1), the minimum values e ₁ and e ₂ are calculated,
This is the third edge of the entropy filter (50). These relative positions are shown in FIG. 8 above.
These edges are displayed on the monitor (13).

When a clear f ₁ · s ₁ · f ₂ · s ₂ cannot be obtained due to the unclearness of the original image, etc., as shown in FIG.
As shown in 0, the operator operates the operation unit (9) while looking at the screen of the monitor (13), inputs the position of each edge (x mark) at an appropriate point, and connects these points with a straight line. Is the processing range. Generally, the third edge by the entropy filter is often used, but when selecting the edge by the weighted sum of the first and second derivative filter data, the output of the maximum value extraction circuit (48) is weighted. In addition to the sum calculation circuit (52), the weighted sum g ₃
(I) is obtained, and its coordinates e ₁ ′ and e ₂ ′ are calculated as shown in FIG. 11, and this is taken as the fourth edge by the weighted sum of the first derivative and the second derivative.

The procedure when a clear edge cannot be obtained by the first derivative and the second derivative is the same as the manual operation in the entropy filter described above. Measurement of the latter stage Set the switch (53) shown in FIG. 7 to the (53-1) side,
The upper and lower edges e ₁ and e ₂ by entropy are added to the blood vessel axis extraction circuit (54), and the points at which the shortest distances to the upper and lower edges are equal are connected to form a blood vessel axis ax by the entropy method as shown in FIG.

Next, in the vertical gradient calculation circuit (59), a straight line perpendicular to the blood vessel axis is obtained as shown in FIG. This straight line is, for example, a straight line perpendicular to the average gradient of 5 pixels forming the blood vessel axis. In the mean gradient, with the position of the central pixel set to 0, the quantities S _XY · S _XX related to the linear regression equation obtained by using x (i) and y (i) as independent variables in the x direction and the y direction, respectively. If S _YS · S _YY ,
The calculated gradient γ of the perpendicular is given by the following equation.

[0058]

[Equation 6]

Next, in the perpendicular data creation circuit (60) shown in FIG. 7, the data in the frame memory (27) in FIG. 3 is referred to, and each pixel is directly on n perpendicular to the blood vessel axis. The density value is obtained by the vilinian interpolation method. Here, in the vilinian interpolation method, as shown in FIG. 13, the pixel value at the upper left corner of a square whose side length is 1 is f (u ′,
v ′), the pixel value f (u ₀ , v ₀ ) at the position (α, β) from the upper left corner is interpolated by the following equation.

[0060]

[Equation 7]

When the weighted sum of the edges e ₁ ′ and e ₂ ′ by the primary and two-dimensional filters is used as the edge, the switch (53) in FIG. 7 is switched to the (53-2) side, and the same calculation is performed thereafter. Then, as shown in FIG. 11, the blood vessel axis ax '
Then, the density value of each pixel on the line n'perpendicular to the blood vessel axis is calculated by the above-mentioned vilinian interpolation method. Next, the switch (41) in FIG. 7 is switched to the (41-2) side, and the following processing is performed by the same operation as described above by the density data f (u ₀ , v ₀ ) on the perpendicular line of the blood vessel axis.

(1) Weighted moving average calculation circuit (43) 's weighted moving average calculation (1) (2) Primary differential filter (46) and secondary differential filter (47): Of the first and second derivatives above and below (3) Coordinates F ₁ , F ₂ and S ₁ which give the maximum values of the first and second derivatives by the maximum value extraction calculation circuit (48)
- performs the operation of S _2, respectively obtains the fifth and sixth edge of the upper and lower vessel axis.

(4) Designation of the ranges of F ₁ and S ₁ and F ₂ and S ₂ by the processing range designation circuit (49) (5) Weighted moving average calculation in the weighted moving average circuit (43) in the range (6) ) Entropy calculation for the weighted moving average data by the entropy filter (50) and seventh edge E ₁ · E ₂ calculation by the minimum value extraction calculation circuit (51) (7) Switch (53) to (53-1) , The points at which the lengths of the perpendiculars to the upper and lower edges are equal are calculated to obtain the blood vessel axis AX.

(8) When the weighted sum of the first derivative and the second derivative is used as the edge, the output of the maximum value operation circuit (48) is added to the weighted sum operation circuit (52) and the eighth edge E ₁ is added. ′
· E ₂ 'seek, switching the switch (53) to (53-2), the same way the vessel axis AX' Request. Further, with the switch (53) of FIG. 7 set to the (53-1) side, the edge data of the entropy filter is added to the edge coordinate difference calculation circuit (56), and the difference between the upper and lower edges D = E ₁ -E ₂ Then, as shown in the figure, the horizontal axis represents the blood vessel axis direction m and the vertical axis represents the edge difference D, and the edge difference curve is displayed on the monitor 13.

Whether or not the Hough transformation can be performed is examined on the screen of FIG. 14 displayed on the monitor 13, and when the Hough transformation is possible, the normal diameter V can be obtained as follows by the definition, and the obtained normality can be obtained. The diameter is displayed on the monitor (13). Hough transform can not time end point _A (m _a, D _a) in the portion where there is no stenosis across the sections that cause constriction as shown in FIG. _{14 · B (m b, D} b) the input manual Then, linear interpolation is performed according to the following equation to obtain the normal diameter.

[0066]

[Equation 8]

One point on the edge difference curve shown in FIG. 15 (m,
The relational expression between the intercept b on the D axis of the straight line drawn in D) and the angle θ formed by the m axis is expressed by the following equation.

[0068]

[Equation 9]

Here, a specific value is given to θ, m and D are changed along the edge curve, and the value of b is obtained for each (m, D). This calculation is performed over the entire section of m. The same calculation is performed by changing the value of θ at a preferable interval, and (θ _m , b _m ) having the highest appearance frequency of (θ, b) is used to calculate the equation giving the normal diameter. FIG. 16 is a block diagram of a circuit for obtaining a normal diameter by the above method. (91) is a circuit that finds and saves b of each pixel when θ is changed by the above equation (8), and (92) detects b and takes the same value and detects and saves the number of repetitions thereof. Circuit (93) finds b that maximizes the number of repetitions, then performs a similar search except for this b and the number of repetitions, and repeats this for a predetermined n times to obtain n sets. This is a circuit for obtaining a combination of θ and b.

Θ is input from the terminal 101 and is, for example, −9.
The range of 0 ° to + 90 ° is changed in 0.5 ° steps. m is a number representing a pixel in the direction of the blood vessel axis and is a terminal (10
3), and changes from 0 to the length of the blood vessel to be investigated by the incrementer (104). The first θ is the ROM (1 that stores the value of tan θ
02), and outputs -tan θ. Multiplier (10
5) ROM (102) and incrementer (104)
Then, take the product of each output of and add -tan θ * m to the adder (10
Output to 7). The memory (106) stores the edge difference D (m) for m, and outputs the edge difference D (m) for the designated m. As this memory, the frame memory (27) of FIG. 3 can be used as it is. Since m is output as m corresponding to the number of pixels corresponding to the length of the blood vessel to be investigated, the edge difference D (m) corresponding thereto is added to the adder (107). Therefore, the adder (107) is the multiplier (105) and the memory (106).
Then, the b of Equation 9 is calculated and the memory (10
Accumulate in 8). Next, change the value of θ by one step (0.5 °)
The matrix data of b is completed by enlarging the size, performing the same calculation, accumulating it in the memory (108), and repeating the same calculation over the entire range of θ. Memory (1
Of the matrix data stored in 08), one b is read out by the control of the address counter (109), and is input to the comparator (111) as the comparand through the selector (110). The other b value read out next is input to the comparator (111) as a comparison number by the selector, and those having the same value are counted by the counter (112).
The number of repetitions recorded in 2) is recorded in the latch (113). This operation is performed until the compared numbers read from the memory (108) have reached one cycle, and these count numbers are recorded in the latch (113). The determination of the completion of this round is made by comparing the output of the incrementer (104) with the comparator (9
In addition to 4), it is performed by sending an END signal when the number of b values input from the terminal (95) (total number of matrix data-1) matches, and the latch (113) stores the recorded data in a memory. It is stored in (114). Next, the numbers to be compared are changed one after another, and the same operation is performed to detect the number of repetitions having the same value as other b, and the result is stored in the memory (114). The maximum value of the data read from the memory (114) is detected by the comparator (115) and the maximum value calculation circuit (116), and the corresponding θ _m · b _m is output. Repeated maximum detection n times, b
It is possible to obtain n sets of θ · b in descending order of. These b are output from the terminal (117) and θ is output from the terminal (118).

These n sets of θ · b are monitored by the monitor (13).
The most appropriate normal diameter is selected by observing FIG. 14 output above. When neither of these is appropriate, the normal diameter is input by manual operation as described above. The above calculation is to obtain the normal diameter for the edge by the entropy filter (50). When it is appropriate to use the edge for the weighted sum of the first derivative and the second derivative, the switch (53) is turned on. As (53-2), the output of the weighted sum calculation circuit (52) is added to the edge coordinate difference calculation circuit (56) and the Hough conversion circuit (57), and the same operation is performed to calculate the normal diameter.

Calculation by Concentration Area Method Although each of the above-mentioned data expresses its function depending on the position of the edge, that is, the size of the blood vessel, it exists in the cross-sectional area of the blood vessel in the portion where stenosis is generated and the portion where it is not. The blood vessel diameter can be estimated by knowing the amount representing the total amount of the contrast agent. For that purpose, a method of comparing the area between the concentration curve on the cross-sectional axis as shown in FIG. 1 and the horizontal axis can be considered. In order to further clarify the difference due to the position of the blood vessel, in FIG. 17, for example, the concentration values a (i) _s1 and a (i) _s2 at the edge positions s ₁ and s _{2 obtained} by the second derivative are connected by a straight line. There is a method of using the areas of the edges e ₁ and e ₂ by the entropy filter between the straight line and the curved line. This area A
Is given by the following equation when the point on the straight line is y (i).

[0073]

[Equation 10]

In this embodiment, this method is used, and FIG.
The screen is displayed on the monitor 13. Also,
Instead of the edge by the entropy filter, the density value at the edge position by the weighted sum of the first derivative and the second derivative may be used. Further, the measurement area is plotted on the vertical axis and the measurement position (m coordinate) is plotted on the horizontal axis to create a graph similar to that shown in FIG. 14, and Hough transform is applied by the above method to obtain the normal diameter.
Using this normal diameter value, the stenosis rate can be calculated by applying the above equation (8).

Calibration by Catheter Since the angiographic images described above are not clear in absolute size, calibration is performed using a catheter of known size. Here, the catheter is a tube for injecting a contrast medium into a blood vessel for the purpose of imaging the blood vessel, and a material that is harmless to the human body and is safe is selected. However, the tube used for calibration may or may not be the one actually used.

The catheter is usually imaged together with an angiographic blood vessel at the time of angiography, but when the catheter image is not imaged at the same time, it is desirable to image only the catheter image on at least the same apparatus and under the same condition on the same film. For that purpose, water should be placed around the catheter to create the same environment as the inside of the human body as much as possible, and if possible, it should be placed near the measurement point of the patient and filmed on the film.

The film thus photographed is searched for a corresponding frame in the same manner as described above, a measurement region of the catheter is selected and a series of measurement processing is performed, and the entropy filter or the first derivative and second derivative filters are weighted. If the marginal difference based on the sum is obtained, the number of pixels of the digital camera (10) corresponding to this marginal difference can be known. Therefore, the absolute value per pixel can be known by dividing the inner diameter of the catheter by this number of pixels. .. The absolute value of the edge difference of the blood vessel to be measured can be obtained by multiplying the number of pixels of the edge difference of the blood vessel obtained by the same operation by the absolute value of the pixel.

The calculation of the final data and the normal diameter for display are considered to have a fluctuation of 10%,
The normal diameter obtained by the above calculation is taken as an average normal diameter,
The blood vessel diameter at a concentration value 10% lower than this is set as a virtual lower limit normal diameter. Figure 18 shows these relationships,
Edge difference curve / straight line showing normal diameter position and 10 from this
The straight line at the position where the percentage is lowered is the monitor (1
Display in 3).

Diameter data of a value equal to or larger than the virtual lower limit normal diameter is
It is used to calculate the standard deviation of blood vessel diameter in the normal diameter range.
Blood vessel diameter D (m) and normal diameter V (m) decreased due to stenosis
And the stenosis rate S _tThe following equation can be obtained by expressing (m).

[0080]

[Equation 11]

By changing m, S _t (m) corresponding to this is obtained, and a stenosis rate curve as shown in FIG. 19 is displayed on the monitor (13). A plurality of cursors (1, 2, ..., N) are displayed on the stenosis rate curve of FIG. 19, and the data of, for example, FIG. 20 at this point is calculated and displayed on the monitor (12). In addition, average stenosis rate (%), average absolute diameter (μm),
The average normal diameter including the stenosis and the standard deviation of the blood vessel diameter in the normal diameter range are calculated and displayed on the monitor (13).

In order to be able to list the relational positions between the edge of the blood vessel and the normal diameter, for example, the upper and lower edges E ₁ (m) and E ₂ (m) and the normal diameter V (m) by the entropy filter are displayed on the monitor (13). Is displayed as shown in FIG. And the difference between the equation density area A _a in the range of normal size as (m) and density area of a portion occurring stenosis A _b (m), the ratio of the concentration area of the normal diameter, by concentration area Stenosis rate S _n (m).

[0083]

[Equation 12]

This stenosis rate is to be determined as necessary. At this time, the stenosis rate in each part where stenosis has occurred is calculated, and a stenosis rate curve similar to that shown in FIG. 19 is monitored (13).
To display. Also, A _a (m) · A _b (m) and S _n (m) for a plurality of points designated by the cursor can be tabulated, and data such as the average stenosis rate (%) can be obtained.

In the printer (32) shown in FIG. 3, for example, the patient name, the date of birth, the date of coronary angiography, the photographing device, the photographing angle, the distance between the X-ray source and the bed, and the blood vessel diameter are obtained. It outputs the blood vessel name and maximum stenosis rate and prints personal data. Since a large amount of each screen data and related data are stored, it is desirable to store them in a large capacity memory such as a magneto-optical disk (33) if necessary. Examples of these data include the following.

(1) Personal data mentioned above (2) Image data taken by the monitor camera 1 (3) Edge difference curve in FIG. 14 (4) Upper and lower edges and normal blood vessel diameter in FIG. 21 are displayed Image (5) A high resolution color cathode ray tube is used as the color display monitor (13) of the data screen of FIG. 20, and the frame memory (27) is R as shown in FIG.
In the case of the G / B memory plate, for example, in FIG. 21, the space between the edges corresponding to the inside of the blood vessel can be filled with a light red color, and the normal diameter can be displayed with a blue color or the like. 1/3/5/6/8/10/11/12 /
Similarly, in 14, 17, 18, and 19 as well, various colors can be selectively used to make it easy to see and identify each part.

When the film (1) is a color film, a screen with a complete color display can be obtained, a more realistic feeling can be obtained, and another effect can be expected. However, at this time, it is necessary to change the filter and perform imaging three times with the digital camera (10). The configuration of this system, each unit constituting the system, data calculation method, data collection method, data storage method and its display method have the same technical concept. Not a thing.

[0088] While the foregoing description Applications: those that target coronary artery will be obvious that the same may be applied to other vessels, for example carotid artery. Further, it can be applied to the precise measurement of the stenosis situation in the bile duct and urethra. In addition, if the film is a tubular image, the deformed state such as stenosis can be observed and measured, and thus it can be widely applied industrially.

[0089]

As described in detail above, according to the present invention, a frame to be measured can be searched from a film contrast image by an extremely simple operation, and the selection operation of the measurement region from the searched frame is automatically performed by using the cursor. Since the measurement area can be displayed horizontally, the operation is extremely simple and easy.

In this invention, since the entropy filter is applied by using the camera of high magnification and high resolution, the precision is three times as high as that of the prior art and the precision is four times or more better, and the minute diameter is small. It has the advantage of high change detection capability. Further, in the present invention, the central axis is calculated from the edge detected by the entropy filter, and the entropy filter is further applied on the line perpendicular to the central axis, so that the edge which is extremely close to the actual value can be obtained. .. Further, in the present invention, the accurate normal diameter is calculated by the Hough transform, so that the stenosis rate with reliability can be obtained.

Moreover, in the present invention, since a huge amount of time-consuming calculations are processed by the hardware circuit, there is an advantage that the processing speed is extremely fast, and the edge by the entropy filter and the edge by the weighted sum of the first derivative and the second derivative are obtained. An appropriate edge can be selected depending on the state of the image. A method of calculating the stenosis rate from the normal diameter obtained by the Hough transform and a method of calculating the stenosis rate by the concentration area method can be freely selected.

As described above, the present invention enables highly accurate blood vessel diameter measurement. Therefore, it is useful for various clinical studies to obtain the diameter of the vascular branch of interest from the angiographic image using this device, quantify it, and record it.As a result, the pathological condition of heart disease and arteriosclerosis becomes clear As a result, improvements in diagnostic treatment methods can be expected. For example, various treatment methods for cardiovascular stenosis are currently proposed and implemented, but the relationship between disease state and prognosis is not always clear. Therefore, a detailed examination of the tube diameter measurement on the contrast image before treatment and the condition of the patient after the treatment may reveal a method of selecting a treatment with a favorable prognosis for the patient based on the tube diameter measurement result before the treatment. Be expected. Further, as a result of these studies, it is considered that if the use of this device enables the selection of an effective treatment method, it will be effectively used for daily diagnostic treatment. When these points are combined, this device is considered to be a device that should be introduced to core medical facilities nationwide.

[Brief description of drawings]

FIG. 1 is a concentration curve of a contrast agent on a line perpendicular to the blood vessel axis.

FIG. 2 is a principal block diagram showing an outline of the apparatus of the present invention.

FIG. 3 is an overall block diagram showing an outline of the apparatus of the present invention.

FIG. 4 is a search screen for a film frame imaged by a monitor camera.

FIG. 5 is a multi-screen view of an entire screen and a zoom screen.

FIG. 6 is an enlarged zoom screen view which is spread over the entire monitor screen.

FIG. 7 is a block diagram of a measuring unit that performs various calculations.

FIG. 8 is a drawing showing the positions of edges detected by a first derivative / second derivative and an entropy filter.

FIG. 9 is a block diagram showing a configuration of an entropy filter.

FIG. 10 is an explanatory diagram of detecting a blood vessel axis from the edge by the entropy filter and inputting the edge by the first-order and second-order differentials by manual.

FIG. 11 is an explanatory diagram for detecting a blood vessel axis from a margin based on a weighted sum of primary and secondary differential filters.

FIG. 12 is an explanatory diagram of a perpendicular line to a blood vessel axis.

FIG. 13 is an explanatory diagram of a vilinian interpolation method.

FIG. 14 is an explanatory diagram of a normal diameter interpolation method.

FIG. 15 is an explanatory diagram of Hough transform.

FIG. 16 is a block diagram of a Hough transform circuit.

FIG. 17 is an explanatory diagram of a concentration area method.

FIG. 18 is an explanatory diagram of a virtual lower limit normal diameter.

FIG. 19 is a drawing showing a stenosis rate curve and a calculation position of stenosis rate relation data by a cursor.

FIG. 20 is a diagram showing a display example of calculation results.

FIG. 21 is a screen view showing upper and lower edges and a normal blood vessel diameter.

[Explanation of symbols]

 1 film 2 film traveling mechanism 3 stage 4 imaging position controller 5 ITV camera 6 interface 7 ITV monitor 8 CPU 9 operation unit 10 high resolution camera (digital camera) 11 data processing unit 12 data monitor 13 high resolution monitor 14 output device 15 memory 20 film running controller 21 stage controller 22 frame memory 23 cursor generator 24, 30 OR gate 25, 34, 41, 42, 45, 53 switch 26 buffer memory 27, 44 frame memory 28 cursor generator 29 overlay memory 31 Measuring unit 32 Printer 33 Magneto-optical disk 43 Weighted moving average arithmetic circuit 44 Frame memory 46 First derivative filter 47 Second derivative filter 48 Maximum value extraction arithmetic circuit 49 Processing range finger Constant circuit 50 Entropy filter 51 Minimum value extraction circuit 52 Weighted sum calculation circuit 54 Center axis extraction circuit 55 Cross-sectional area calculation circuit 57 Hough conversion circuit 58 Tube deformation shape calculation circuit 59 Vertical gradient calculation circuit 60 Vertical line data creation circuit 61 Search Screen 62 Blood vessel 63 Cursor 64 Multi screen 65 Whole screen 66 Zoom screen 67 Cursor displayed on the whole screen 71 i Input terminal 72 j Input terminal 73, 76 Adder 74 Incrementer 75 Memory 77, 79 Log value ROM 78, 81 Multiplier 80 Inverse calculator 82 Subtractor 83 w Input terminal 84 Comparator 85 Latch 86 g (i) output terminal 91 b Calculation circuit 92 Maximum number calculation circuit of the same b when θ is changed 93 Maximum of the maximum number Value calculation circuit 94 Comparator 95 n Input terminal 101 θ input terminal 10 -tanθROM 103 i input terminals 104 incrementer 105 multiplier 106, 108 memory 107 adder 109 address counter 110 selector 111 comparator 112 counter 113 and 115 latch 114, 116 maximum value calculation circuit 117 b value output terminal 118 theta value output terminal

Claims (6)

[Claims] 1. An image reading means for highly magnifying and reading a required area of a contrast image such as a coronary artery, and an extraction processing means for extracting a blood vessel edge by an entropy filter, and a margin by an entropy filter from the enlarged image. A highly accurate contrast vessel diameter measuring device for measuring a blood vessel diameter by extracting the blood vessel with high accuracy. 2. A means for retrieving a measurement frame of a contrast image film such as a coronary artery, a means for reading a measurement region from the retrieved measurement frame with high magnification and high resolution, and an entropy filter from the data of the read measurement region. 2. The high-accuracy contrast vessel diameter measuring device according to claim 1, which is configured by means for extracting a marginal edge, a blood vessel axis, and a normal diameter of a blood vessel by an arithmetic circuit including Hough transform, and means for calculating and outputting a stenosis rate. 3. Angiographic image film is sequentially monitored.
Equipped with a contrast image display monitor for reading with a camera, displaying this on the monitor, selecting the film frame to be measured for the pipe diameter, displaying the measurement area to be highly magnified on the monitor screen and extracting it The high-accuracy vessel diameter measuring device for contrast-enhanced blood vessels according to claim 2. 4. The film traveling mechanism and the film, which are signals for the high-enlargement measurement region determined in claim 3, are transmitted.
3. The film is sent to a stage, and the selected frame is transferred onto a film stage of a high-magnification image reading device.
The high-accuracy contrast-enhanced blood vessel according to claim 3, wherein the relative position between the high-magnification reading device and the film stage can be automatically moved so that the imaging range of the high-magnification image reading device determined in step 3 coincides with the measurement range. Pipe diameter measuring device. 5. The entropy filter or the weighted sum of the first and second edges in the upper and lower first and second edge regions respectively obtained by the first-order differential filter and the second-order differential filter. The blood vessel axis is obtained from the upper and lower third or fourth edges, respectively, and the concentration values obtained by the Viliniya method on the vertical line of the blood vessel axis are again calculated by the above-mentioned calculation, and the first to fourth edges are respectively obtained. The upper and lower fifth to eighth edges corresponding to the above are obtained, and the upper and lower seventh or eighth edge differences are calculated, and the Hough transform is applied to the range of the blood vessel including the stenosis. 3. The high-accuracy contrast vessel diameter measuring device according to claim 2, wherein the normal diameter is calculated, and the stenosis rate is calculated from the normal diameter and the marginal difference. 6. A position m in the blood vessel axis direction is plotted on the abscissa, and a difference D (m) between positions of both edges of the blood vessel corresponding to this m is plotted on the ordinate at one point on a blood vessel marginal difference curve. When the angle between the drawn straight line and the horizontal axis is θ and the intercept on the vertical axis is b, when m and θ are changed, the number of b having the same value is detected from among the corresponding b, 6. The contrast blood vessel height according to claim 2, wherein a predetermined number of combinations of θ and b are detected in order from the maximum number b, and the normal diameter in the narrowed portion of the blood vessel is detected from this combination. Precision pipe diameter measuring device.