KR101427028B1 - System for analizing stent-implanted blood vessel - Google Patents

Abstract

A blood vessel analysis system having a stent inserted therein is disclosed. Wherein the stent-inserted blood vessel analysis system comprises: an image providing unit for photographing an inside of a blood vessel into which a stent is inserted to provide a plurality of tomographic images; A strut position calculation unit for calculating position coordinates of a stent strut on the plurality of tomographic images; A vein-boundary-distance calculation unit for calculating boundary information of the inner wall of the blood vessel on the plurality of tomographic images, and a vein-strut distance calculation unit for calculating the distance between the strut and the inner wall of the vein using the coordinates of the strut and the boundary information .

Description

TECHNICAL FIELD [0001] The present invention relates to a system for analyzing blood vessels inserted into a stent,

The present invention relates to a stent-inserted blood vessel analysis system, and more particularly , to a stent-inserted blood vessel analysis system including a stent strut in a blood vessel into which a stent is inserted, a stent for calculating a distance between the stent strut and an inner wall of the blood vessel, To a blood vessel analysis system.

 It is important to determine the stenosis of the stenosis of the stenosis in the case of intravascular stent insertion in cardiovascular interventions. To determine whether stenosis of the stent is well stuck after the procedure, laser coherence tomography (OCT), optical coherence tomography technique is used.

In addition, neoplastic endothelial cells grow on the strut after the procedure, and the overgrowth of these endothelial cells causes narrowing of the blood vessels again. Therefore, various clinical results according to the patient's condition, stent structure, and drug component displayed on the surface are read through optical coherence tomography. In order to analyze this, thickness of neointimal membrane due to growth of struts and endothelial cells in vascular section images is measured and quantified through statistical analysis.

However, this image analysis is being done through manual work by skilled workers. However, manual work is not only very slow, but also often leads to errors that lead to different results for each worker. Therefore, it is necessary to develop a system that automatically and precisely measures the distance between the stent strut and the inner wall of the vessel based on the cross-sectional image of the vessel.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to quickly calculate strut coordinates without segmentation of a stent region on an angiographic image, to accurately calculate inner wall coordinates of a vessel based on a local region, The present invention provides a blood vessel analysis system having a stent inserted therein that can quickly calculate the distance through inner wall coordinates.

According to an aspect of the present invention, there is provided an image providing apparatus, comprising: an image providing unit for photographing an inside of a blood vessel into which a stent is inserted to provide a plurality of tomographic images; A strut position calculation unit for calculating position coordinates of a stent strut on the plurality of tomographic images; A vein-boundary-distance calculation unit for calculating boundary information of the inner wall of the blood vessel on the plurality of tomographic images, and a vein-strut distance calculation unit for calculating the distance between the strut and the inner wall of the vein using the coordinates of the strut and the boundary information And the stent is inserted into the blood vessel analysis system.

Wherein the strut position calculating unit comprises: a polar coordinate transforming unit for performing polar coordinate transformation on the tomographic image; An average brightness calculating unit for calculating a mean intensity value of the tomographic image in the polar coordinate system; An angle coordinate calculation unit for calculating an angle axis coordinate of the strut using the average brightness value; And a distance coordinate calculation unit for calculating the distance (r) axis coordinates of the strut using the calculated slaughter axis coordinates.

The angular coordinate calculator performs a 2nd partial derivative with respect to the angle parameter with respect to the average brightness value and calculates a second partial derivative with respect to the angle? The angle? Of the corresponding point can be calculated as the angle? Of the strut.

Wherein the distance coordinate calculator calculates a second partial differentiation with respect to a distance r variable by substituting the calculated angular coordinates into a tomographic image transformed into a polar coordinate system, and if the second partial differential value with respect to the distance (r) (R) of the strut can be calculated by the distance (r) coordinates of the strut.

Wherein the blood vessel boundary information calculation unit comprises: a curve setting unit that sets a curve that bisects the tomographic image up and down with respect to the angle? Axis; A control point setting unit for setting control points at regular intervals along the angle axis in the curve; A local region setting unit for setting a local region having a predetermined size around each of the control points; And an inner vessel wall boundary coordinate calculator for calculating a boundary coordinate of the inner wall of the blood vessel along a distance axis using a difference between brightness values of the two regions divided by the curve in the local region.

The inner vessel wall boundary coordinate calculating unit may include a function calculating unit for calculating an energy function for distance axis coordinates of the control point in the local region using coordinates of the distance axis of the control point as a variable; A slope vector calculating unit for calculating a gradient vector of the energy function and a steepest descent method for the slope vector to detect the minimum value of the energy function to calculate the energy function of the inner wall And an inner vessel wall boundary coordinate calculation unit for calculating the boundary coordinates of the distance direction.

The inner vessel wall boundary coordinate calculator may calculate the coordinates of the entire inner wall boundary of the blood vessel by connecting each control point to which the boundary direction coordinates of the inner wall of the vessel are substituted by the spline.

The vein-strut distance calculator moves the strut coordinates and the boundary coordinates of the inner wall of the vessel to original Cartesian coordinates, forms a plurality of circles centered on the strut coordinates, The radius of the smallest circle in contact with the inner wall of the blood vessel can be calculated as the distance between the strut and the inner wall of the blood vessel.

The stent-inserted vessel analysis system of the present invention can quickly calculate strut coordinates without dividing the stent region on the blood vessel tomographic image, accurately calculate the inner vessel wall coordinates based on the local region, calculate the calculated strut coordinates And the distance can be quickly calculated through the inner wall coordinate of the blood vessel.

1 is a block diagram of a blood vessel analysis system having a stent inserted therein according to an embodiment of the present invention.
2 is a block diagram of a strut position calculating unit according to an embodiment of the present invention;
3 is a block diagram of a blood vessel boundary information calculation unit according to an embodiment of the present invention;
4 is a diagram for explaining polar coordinate transformation according to an embodiment of the present invention,
5 is a view for explaining a process of calculating angle coordinates of a strut according to an embodiment of the present invention;
6 is a view for explaining the calculation of distance coordinates of a strut according to an embodiment of the present invention;
FIG. 7 is a view for explaining a procedure of calculating a vessel boundary coordinate according to an embodiment of the present invention.

The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated and described in the drawings. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms including ordinal, such as second, first, etc., may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be referred to as a first component, and similarly, the first component may also be referred to as a second component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, wherein like or corresponding elements are denoted by the same reference numerals, and redundant description thereof will be omitted.

FIG. 2 is a block diagram of a strut position calculating unit according to an embodiment of the present invention. FIG. 3 is a block diagram of an embodiment of the present invention. FIG. 4 is a view for explaining polar coordinate transformation according to an embodiment of the present invention. FIG. 5 is a view for explaining a process of calculating angular coordinates of a strut according to an embodiment of the present invention. FIG. 6 is a view for explaining the calculation of distance coordinates of a strut according to an embodiment of the present invention, and FIG. 7 is a view for explaining a process of calculating a vessel boundary coordinate according to an embodiment of the present invention.

Referring to FIG. 1, a blood vessel analysis system with a stent according to an embodiment of the present invention includes an image providing unit 10 for photographing an inside of a blood vessel into which a stent is inserted to provide a plurality of tomographic images, A stent position calculation unit 20 for calculating the position coordinates of the stent strut, a blood vessel boundary information calculation unit 30 for calculating the boundary information of the inner wall of the blood vessel on the plurality of tomographic images, and the stent strut position coordinate and boundary information, And calculating a distance between the strut and the boundary information.

First, the image providing unit 10 may photograph and provide a plurality of tomographic images of a blood vessel into which a stent is inserted.

The image providing unit 10 may include a plurality of tomographic images using IVUS, intravascular ultrasound, or optical coherence tomography (OCT) to provide a tomographic image in a blood vessel, for example. Can be provided by photographing.

Intravascular ultrasound technique uses ultrasonic wave of 40MHz exceeding audible frequency 20kHz to image ultrasound reflected from cell tissue to analyze cell tissue and provide direct and detailed information on changes in vessel lumen, atherosclerotic plaque, and vessel wall do. The optical coherence tomography is a medical imaging technique that images light reflected from a cell tissue using light emitted from a laser, such as an ultrasound technique. Since the resolution is ~ 15 μm, a ~100 μm thick stent strut And provides a high-resolution cross-sectional image of whether the lesion is well stuck in the blood vessel.

The image providing unit 10 is inserted into a blood vessel and takes a plurality of tomographic images while moving in the longitudinal direction of the blood vessel using a monorail method. The image providing unit 10 may provide a plurality of tomographic images taken at intervals of 0.06 to 0.2 mm while moving in the longitudinal direction of the blood vessel using the monorail method.

2, the strut position calculating unit 20 includes a polar coordinate transforming unit 21 for performing polar coordinate transformation on the tomographic image, an average brightness calculating unit 23 for calculating a mean intensity value in the tomographic image on the polar coordinate system, An angle coordinate calculator 23 for calculating an angle axis of the strut by using the average brightness value, an angle calculator 23 for calculating a distance of the strut r And a distance coordinate calculation unit 24 for calculating the axis coordinates.

The polar coordinate conversion unit 21 can convert the inputted tomographic image into polar coordinates. The image provided from the image data providing unit 10 is generally based on Cartesian coordinates. The polar coordinate transforming unit 21 performs coordinate transformation on each of a plurality of inputted tomographic images, It can be converted into a tomographic image based on the reference.

Referring to FIG. 4, the image a provided from the image providing unit 10 shows an actual cross-section of the blood vessel based on the Cartesian coordinate system. The image b transformed by the polar coordinate conversion can be set with the coordinate axis as an angle? With respect to the distance r from the center point of the image and the reference line extending from the center point.

The average brightness calculator 22 may perform an average brightness value calculation on the tomographic image converted into the polar coordinate system. The average brightness calculator 22 may calculate an average brightness value according to the following equation (1).

는 각도 축의 하한과 상한,

는 거리 축의 하한과 상한,

는 극좌표상의 이미지, G_σ는 표준편차 σ의 가우스 커널(Gaussian kernel)이다. 초음파나 광간섭성 단층촬영 이미지는 스페클에 의해 1차 또는 2차 미분을 계산할 때, 심한 오차가 발생하므로 이미지를 부드럽게 하기 위해서 가우스 커널(G_σ)등을 이용한 영상 처리를 하여 영상 노이즈를 감소시킨다.here,

The lower limit and upper limit of the angle axis,

The lower limit and upper limit of the distance axis,

Is an image, _σ G on the polar coordinates is the Gaussian kernel (Gaussian kernel) of the standard deviation σ. In calculating ultrasound or optical coherence tomography images by primary or secondary differentials due to speckle, severe errors occur. Therefore, in order to smooth the image, image processing using Gaussian kernel (G _σ ) .

The angular coordinate calculation unit 23 performs a second partial derivative with respect to the angle? Variable with respect to the average brightness value according to the following Equations 2 to 3, If the second-order partial differential value is greater than the predetermined threshold value (Θ) and is local maximum, the angle (θ) of the corresponding point can be calculated as the angle (θ) axis of the strut.

Here, &thetas; can calculate a value experimentally optimized to a preset threshold value. Generally, the secondary partial differential value in the stent strut shows a tendency to be larger than a small value among the secondary partial differential values at both ends of the shadow generated by the guide wire. Therefore, it is possible to set a threshold value using this. ? denotes the number of pixels and can be set to a size of 1 to 3 according to the number of adjacent pixels for comparing the secondary partial differential value with the local maximum value.

The distance coordinate calculator 24 substitutes the calculated sphygmomanometer coordinates into a polar coordinate image subjected to image processing using a Gaussian kernel G _σ or the like according to the following equation (4) And the distance r at which the second-order partial differential value with respect to the distance (r) variable becomes minimum can be calculated as the distance (r) axis coordinates of the strut. In this case, various filter functions can be applied to reduce image noise before performing the second-order partial differentiation.

Referring to FIG. 5, it can be seen that the average brightness value at the location where the strut is located has the local minimum peak value, and the secondary partial differential value exceeds the preset threshold value. Accordingly, a point having a local maximum maximum differential value among the points exceeding a predetermined partial differential value can be calculated as angle coordinates of the strut.

As a method for detecting a strut in a blood vessel, a gradient is used, while a second derivative is used in the present invention. This makes it possible to more accurately detect the position of the narrower stent strut in the graph of the average brightness value by using the curvature of the curve.

6, the second partial differential value for the distance axis is calculated on the angular coordinate (? ₁ ) calculated by the angular coordinate calculator 23, and the point at which the secondary partial differential value becomes minimum is set as the distance coordinate (r ₁ ).

3, a blood vessel boundary information calculation unit 30 according to an embodiment of the present invention includes a curve setting unit 31 for setting a curve that bisects a tomographic image with respect to an angle axis, , A local region setting unit (33) for setting a local region having a predetermined size centered on each of the control points, a control point setting unit (32) for setting a control point at regular intervals along an angle axis, And an inner vessel wall boundary coordinate calculator 35 for calculating a boundary coordinate of the inner wall of the blood vessel along the distance axis using a difference between the brightness values of the two regions.

First, the stent strut on the image should be removed to extract the vascular boundary. This can be achieved by masking the coordinates on the tomographic image using the strut position coordinates calculated by the strut position calculation unit 20. [

The curve setting unit 31 can set a continuous curve C that bisects the tomographic image with respect to the angle? Axis. The tomographic image is divided by the curve setting section 31 into the upper region and the lower region of the curve C. [ The curve setting unit 31 can set a curve by forming an arbitrary curve C on the tomographic image based on, for example, the blood flow region and the blood vessel wall region.

The control point setting unit 32 can set a plurality of control points formed at equal intervals along the angle axis. The interval at which the control points are formed can be changed by setting. At this time, the coordinates of the respective slaughter axes of the control points are expressed by (? ₁ , ...,? _N ).

The local area setting unit 33 can set a local area centered on each set control point. The local region for control point p can be expressed as _Rp (p), and the local region _Rp (p) can be circular or rectangular, and the radius, or the length of the rectangle, Can be changed by setting.

The inner vessel wall boundary calculating unit may calculate the boundary coordinates of the inner wall of the vessel using the distance axis coordinates of the control point as a variable and the difference between the brightness values of the two regions, Can be calculated.

With reference to Fig. 7, when any of the control points (P _i) a local region in the center (R _ρ (p _i)) a difference value of the brightness values of the two regions separated by the boundary curve (C) inside the negative And the smallest point was calculated as the coordinates of the distance axis of blood flow and vessel wall boundary.

The process of calculating the inner wall boundary of the blood vessel will be described in detail.

First, the energy function E (C) of the curve divided by the curve on the tomographic image can be calculated according to the following equation (5).

Where | C | is the arc length (arc length) of the curve, λ is the correction parameter (fitting parameter), A_ (p ) is a local region (R _ρ (p)) curve (C) the average brightness of the upper area of the inside Value, A + (p) means the average brightness value in the region below the curve C in the local region R _? (P). Here, the correction parameter (?) Matches the numerical balance between the first and second terms in [Equation 5], and the average value calculated through the extraction of the inner wall of the image vessel can be used.

F (p) in the equation (5) is defined as a slope vector function according to the following equation (6).

Assuming that the angle axis coordinate of arbitrary control points is fixed and the distance axis coordinate of the inner wall of the blood vessel is calculated with respect to the control point to which each slaughter axis coordinate is fixed, when the local area R _? (P) is square , The function calculating unit 36 can calculate an energy function for the distance axis coordinates of the control point in the local region according to the following Equation (7) using the distance axis coordinates of the control point as a variable.

That is, the angle axis coordinates of the control point are fixed, and the distance axis coordinates of the control point formed discontinuously are used as variables, so that Equation (5) is replaced with Equation (7).

The slope vector calculator 37 can calculate the slope vector for the energy function calculated according to the following equation (8).

The inner vessel wall boundary coordinate calculator 35 detects the minimum value of the energy function by applying a steepest descent method according to the following equation (9) to calculate the distance axis coordinate of the inner wall of the vessel with respect to each control point After calculation, the calculated boundaries of the inner wall of the blood vessel can be calculated by connecting the calculated control points with splines.

When detecting the (local) minimum value of the energy function using the lowest drop method, the coordinates of the distance axes of each control point are updated repeatedly according to Equation (9), and the distances in the k- When the change between the axis coordinates falls within the tolerance range, it stops the iteration.

The vessel-strut distance calculating unit 40 may calculate the distance between the strut and the inner wall of the blood vessel using the position coordinates and boundary information of the strut.

The vein-strut distance calculating unit 40 may convert the position coordinates of the strut and the boundary coordinates of the inner wall of the vessel into the Cartesian coordinate system, and calculate the straight line distance between the two coordinates.

In this case, the blood-strut distance calculation unit 40 forms a plurality of circles around the strut coordinates, calculates the radius of the smallest circle in contact with the inner wall of the plurality of circles using the boundary coordinates of the inner wall of the blood vessel, The distance from the inner wall of the blood vessel can be calculated.

As used in this embodiment, the term " portion " refers to a hardware component such as software or an FPGA (field-programmable gate array) or ASIC, and 'part' performs certain roles. However, 'part' is not meant to be limited to software or hardware. &Quot; to " may be configured to reside on an addressable storage medium and may be configured to play one or more processors. Thus, by way of example, 'parts' may refer to components such as software components, object-oriented software components, class components and task components, and processes, functions, , Subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functions provided in the components and components may be further combined with a smaller number of components and components or further components and components. In addition, the components and components may be implemented to play back one or more CPUs in a device or a secure multimedia card.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims It can be understood that

100: Vascular analysis system with stent inserted
10: image offerer
20: Strut position calculating section
30: blood vessel boundary information calculation unit
40: blood vessel-strut distance calculating unit

Claims (8)

An image providing unit for photographing an inside of a blood vessel into which a stent is inserted to provide a plurality of tomographic images;
A strut position calculation unit for calculating position coordinates of a stent strut on the plurality of tomographic images;
A blood vessel boundary information calculation unit for calculating boundary information of the inner wall of the blood vessel on the plurality of tomographic images;
Strut distance calculating unit for calculating a distance between the strut and the inner wall of the blood vessel using the coordinates of the strut and the boundary information,
The blood vessel boundary information calculation unit calculates,
A curve setting unit for setting a curve that bisects the tomographic image up and down with respect to the angle? Axis;
A control point setting unit for setting control points at regular intervals along the angle axis in the curve;
A local region setting unit for setting a local region having a predetermined size around the control point;
And an inner vessel wall boundary coordinate calculation unit for calculating a boundary coordinate of the inner wall of the blood vessel along the distance axis using a difference between brightness values of two regions divided by the curve in the local region, .
The method of claim 1,
Wherein the strut position calculating unit
A polar coordinate transformation unit for performing polar coordinate transformation on the tomographic image;
An average brightness calculating unit for calculating a mean intensity value of the tomographic image in the polar coordinate system;
An angle coordinate calculator for calculating an angle axis coordinate of the strut using the average brightness value;
And a distance coordinate calculator for calculating distance (r) axis coordinates of the strut using the calculated sphygmor coordinates.
3. The method of claim 2,
Wherein the angle coordinate calculation unit performs a second partial derivative with respect to the angle parameter with respect to the average brightness value, and when the second partial differential value with respect to the angle parameter is larger than a predetermined threshold value, A stent for calculating a value of an angle (?) Of the point at an angle (?) Axis of the strut when the local maximum is obtained.
3. The method of claim 2,
The distance coordinate calculator calculates,
A second partial differentiation is performed on a distance r variable by substituting the calculated slaughter axis coordinates into a tomogram transformed into polar coordinates and a distance r to which the second partial differential value with respect to the distance r variable is minimum, (R) axis coordinate of the strut.
delete The method according to claim 1,
The vessel inner wall boundary coordinate calculator calculates,
A function calculating unit for calculating an energy function with respect to the coordinates of the distance axis of the control point, using the distance axis coordinates of the control point as a variable in the local region;
A gradient vector calculating unit for calculating a gradient vector of the energy function;
And an inner vessel wall boundary coordinate calculation unit for calculating a distance direction boundary coordinate of the inner wall of the blood vessel by detecting a minimum value of the energy function by applying a steepest descent method to the slope vector, Blood vessel analysis system.
The method according to claim 6,
Wherein the inner vessel wall boundary coordinate calculation unit includes a stent inserted into the inner wall boundary coordinates of the inner wall of the blood vessel and spline each control point having the distance boundary coordinate assigned thereto by spline to calculate the coordinates of the entire inner wall wall boundary.
The method according to claim 1,
The vein-strut distance calculator may convert the strut coordinates and the boundary coordinates of the inner wall of the vessel into Cartesian coordinates, form a plurality of circles centered on the strut coordinates, and calculate, using the boundary information, And a stent for calculating a radius of the smallest circle in contact with the inner wall as a distance between the strut and the inner wall of the blood vessel.

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