CN109919913B

CN109919913B - Coronary artery radius calculation method, terminal and storage medium

Info

Publication number: CN109919913B
Application number: CN201910105746.1A
Authority: CN
Inventors: 高琪
Original assignee: Zhejiang University ZJU
Current assignee: HANGZHOU SHENGSHI TECHNOLOGY Co.,Ltd.
Priority date: 2019-02-01
Filing date: 2019-02-01
Publication date: 2020-12-08
Anticipated expiration: 2039-02-01
Also published as: CN109919913A

Abstract

The embodiment of the invention provides a method, a terminal and a storage medium for calculating the radius of a coronary artery, wherein the method for calculating the radius of the coronary artery comprises the following steps: acquiring point cloud data of coronary arteries, and determining a first point set based on the point cloud data; wherein the first set of points comprises points on a central axis of the coronary artery; establishing an index relation based on the first point set; wherein the index relationship represents a path formed by a plurality of points on the central axis; based on the point cloud data and the index relationship, a first radius of the coronary artery is calculated.

Description

Coronary artery radius calculation method, terminal and storage medium

Technical Field

The present invention relates to, but not limited to, the technical field of medical image processing, and in particular, to a method, a terminal, and a storage medium for calculating a radius of a coronary artery.

Background

For coronary artery diseases, the degree of lesion is measured mainly by microsurgery in the past in a manner of measuring the pressure difference between two ends of a guide wire at the coronary artery and the lesion at the anterior segment. With the development of medical technology, doctors currently accept to calculate the coefficient of coronary Flow Reserve (FFR) to measure the degree of lesion, and then provide appropriate advice to patients, such as whether to cure coronary artery disease through surgery. The FFR is calculated by assigning the blood supply amount of the branch according to the diameter of the coronary artery model, so that the normal radius of the coronary artery model needs to be calculated, however, the radius of the coronary artery cannot be accurately calculated in the related art.

Disclosure of Invention

The embodiment of the invention provides a method, a terminal and a storage medium for calculating the radius of a coronary artery, and aims to solve the problem that the radius of the coronary artery cannot be accurately calculated in the related art.

The technical scheme of the embodiment of the invention is realized as follows:

in a first aspect, an embodiment of the present invention provides a method for calculating a radius of a coronary artery, where the method includes:

acquiring point cloud data of coronary arteries, and determining a first point set based on the point cloud data; wherein the first set of points comprises points on a central axis of the coronary artery;

establishing an index relation based on the first point set; wherein the index relationship characterizes a path formed by a plurality of points on the central axis;

calculating a first radius of the coronary artery based on the point cloud data and the index relationship.

Optionally, the establishing an index relationship based on the first point set includes:

removing repeated points and discontinuous points in the first point set to obtain a second point set;

searching for exit and entry points of the coronary artery based on a first specific point in the second set of points;

establishing the index relationship based on the exit point and the entry point.

Optionally, before removing the repeated points and the discontinuous points in the first point set to obtain the second point set, the method further includes:

determining a point in the first point set, wherein the point is within a first preset distance range from the first point set to a first target point, and the point is the repeated point; wherein the first point set comprises the first target point, and the first target point is any point in the first point set;

acquiring a first direction of a tangent of a second target point, and determining the discontinuous point based on the first direction; wherein the second target point is any one point in a third point set, the third point set including points in the first point set other than the repeated points.

Optionally, the obtaining a first direction of a tangent of the second target point includes:

selecting a plurality of second specific points, the distances between the second specific points and the second target point are within a second preset distance range, from the third point set, and obtaining a fourth point set based on the plurality of second specific points;

acquiring a second direction of a tangent line of each second specific point in the fourth point set;

determining the first direction based on a plurality of the second directions.

Optionally, the determining the first direction based on the plurality of second directions includes:

and calculating a first average value of the plurality of second directions, and performing normalization processing on the first average value to obtain the first direction.

Optionally, the determining the discontinuous points based on the first direction includes:

determining the discontinuous points based on the first direction, the coordinates of the second target point, and a first threshold.

Optionally, the determining the discontinuous points based on the first direction, the coordinates of the second target point, and a first threshold includes:

constructing a first area by taking a point which is along the first direction and has a first distance with the second target point as a spherical center and the first distance as a radius;

constructing a second area by taking a point which is opposite to the first direction and has a first distance with the second target point as a spherical center and the first distance as a radius;

determining a number of points in a third set of points included in the first and second regions;

and if the number does not accord with the preset number range, determining the second target point as the discontinuous point.

Optionally, after removing the repeated points and the discontinuous points in the first point set to obtain a second point set, the method includes:

selecting a plurality of fourth target points with the distance between the fourth target points and the third target point within a third preset distance range on the basis of the second point set; wherein the third target point is any point in the second point set;

and smoothing the first direction of the third target point based on the first directions of the plurality of fourth target points to obtain a first target direction.

Optionally, the smoothing the first direction of the third target point based on the first direction of the plurality of fourth target points to obtain a first target direction includes:

projecting the first direction of each fourth target point to the first direction of the third target point to obtain each projected third direction;

unifying the directions of the third directions by using a symbolic function to obtain a plurality of fourth directions;

and calculating a plurality of second average values in the fourth direction, and performing normalization processing on the second average values to obtain the first target direction.

Optionally, the searching for the exit point and the entry point of the coronary artery based on the first specific point in the second set of points includes:

calculating a plurality of second distances between each point in the second set of points and the first particular point;

determining a point corresponding to the shortest distance in the plurality of second distances as an entry point of the coronary artery;

if one and only one of the first region and the second region includes a third specific point in the second point set, determining an exit point of the coronary artery based on the third specific point.

Optionally, the establishing the index relationship based on the exit point and the entry point includes:

determining a fifth target point from the second point set, wherein the distance between the fifth target point and the exit point is within a fourth preset distance range; the number of the fifth target points is at least one;

determining that a first target direction of a tangent of the fifth target point is not perpendicular to a first target direction of a tangent of the exit point from at least one fifth target point, and a fifth target point closest to the exit point is a parent node of the exit point;

establishing the index relationship based on a first target direction of a tangent of the exit point, a fifth direction of the exit point to the entry point, and a sixth direction of the exit point to the parent node.

Optionally, if one and only one of the first region and the second region includes a third specific point in the second point set, determining the exit point of the coronary artery based on the third specific point includes:

if one and only one of the first region and the second region includes a third specific point in the second point set, determining the third specific point as an initial exit point of the coronary artery;

if the target direction of the tangent of the initial exit point is perpendicular to the first target direction of the tangent of a specific target point in the fifth target points, replacing the initial exit point with the specific target point to obtain an exit point of the coronary artery; wherein the specific target point is a closest point to the initial exit point among the at least one fifth target point.

Optionally, the establishing the index relationship based on a first target direction of a tangent of the exit point, a fifth direction of the exit point to the entry point, and a sixth direction of the exit point to the parent node includes:

determining a path direction from the exit point to the entry point based on a first target direction, the fifth direction, the sixth direction of a tangent to the exit point;

and traversing the points in the second point set from the exit point along the path direction to obtain the index relationship.

Optionally, traversing the points in the second point set from the exit point along the path direction to obtain the index relationship, includes:

traversing points in the second set of points along the path direction from the exit point to the entry point, resulting in the index relationship.

Optionally, the number of the exit points is at least one, and the traversing the points in the second point set from the exit points along the path direction to obtain the index relationship includes:

traversing a first part of points in the second point set from each exit point along a path direction corresponding to each exit point, and traversing to a first exit point different from each exit point, and then backing to a first branch from the first exit point to obtain a first sub-path; wherein the first sub-path comprises a path from the each exit point to the first branch;

traversing a second part of points in the second point set from the first branch along the path direction corresponding to each exit point to obtain a second sub-path; wherein the second sub-path comprises a path from the first branch to the entry point corresponding to each exit point;

determining each path corresponding to the each exit point based on the first sub-path and the second sub-path;

determining the index relationship based on the each path corresponding to the each exit point.

Optionally, the traversing a second partial point in the second point set from the first branch along the path direction corresponding to each exit point to obtain a second sub-path includes:

traversing a first sub-portion point of the second portion points from the first branch along the path direction corresponding to each exit point, and if the path direction is traversed to a second exit point different from the first exit point, returning to a second branch from the second exit point to obtain a third sub-path; wherein the third sub-path comprises a path from the first branch to the second branch;

traversing second sub-portion points of a second portion of points in the second set of points along the path direction corresponding to the each exit point from the second bifurcation to obtain a fourth sub-path; wherein the fourth sub-path comprises a path from the second bifurcation to the entry point corresponding to each exit point;

determining the second sub-path based on the third sub-path and the fourth sub-path.

Optionally, the determining the index relationship based on each path corresponding to each exit point includes:

determining a plurality of overlapped part paths and a plurality of non-overlapped part paths in a plurality of paths corresponding to a plurality of exit points; wherein the same overlapping portion of the paths of the plurality of overlapping portions has a unique path;

determining the index relationship based on the paths of the plurality of overlapping portions and the paths of the plurality of non-overlapping portions.

Optionally, the calculating a first radius of the coronary artery based on the point cloud data and the index relationship includes:

determining an outer contour boundary of the coronary artery based on the point cloud data;

determining a plurality of sixth target points, wherein the normal plane of the third target point is intersected with the outline boundary and the distance between the normal plane of the third target point and the third target point is smaller than a third distance, from the second point set; wherein the third target point is any point in the second point set;

acquiring each fourth distance between each sixth target point and the second target point;

calculating the first radius based on a plurality of the fourth distances.

Optionally, after calculating the first radius based on the plurality of fourth distances, the method further includes:

if a stenosis or plaque bulge exists in the branch section of the coronary artery, setting the radius of a third target point at a specific position of the branch section as a second radius based on the first radius; wherein the second radius is usable for blood flow distribution to the coronary arteries.

Optionally, if there is a stenosis or a plaque bulge in the branch section of the coronary artery, setting the radius of the third target point at the specific position of the branch section to be a second radius based on the first radius includes:

if a stenosis or plaque bulge exists in the branch section of the coronary artery and the length of the branch section belongs to a first length range, calculating a third average value of the first radius corresponding to all the third target points;

setting a radius of a third target point at a specific position of the branch segment as the second radius based on the third average value.

if a stenosis or plaque bulge exists in the branch section of the coronary artery and the length of the branch section belongs to a second length range, acquiring a plurality of specific radiuses in the first radiuses corresponding to all the third target points; the specific radii are larger than a preset radius;

calculating a fourth average of the plurality of specific radii;

setting a radius of a third target point at a specific position of the branch segment as the second radius based on the fourth average value.

In a second aspect, an embodiment of the present invention provides a terminal, where the terminal includes: a processor, a memory, and a communication bus;

the communication bus is used for realizing communication connection between the processor and the memory;

the processor is used for executing a coronary artery radius calculation program stored in the memory so as to realize the steps of the coronary artery radius calculation method.

In a third aspect, embodiments of the present invention provide a storage medium storing one or more programs, which are executable by one or more processors to implement the steps of the method for calculating a radius of a coronary artery described above.

The embodiment of the invention is applied to realize the following beneficial effects: based on the medical coronary artery model, keel information in the coronary artery model, namely points on the central axis of the coronary artery, is extracted, a basis is provided for calculating the radius of the coronary artery model, and then accurate blood flow distribution is provided for calculating FFR.

According to the method, the terminal and the storage medium for calculating the radius of the coronary artery, provided by the embodiment of the invention, the point cloud data of the coronary artery are obtained, and a first point set is determined based on the point cloud data; wherein the first set of points comprises points on a central axis of the coronary artery; establishing an index relation based on the first point set; wherein the index relationship represents a path formed by a plurality of points on the central axis; calculating a first radius of the coronary artery based on the point cloud data and the index relationship; that is to say, in the embodiment of the present invention, based on the acquired point cloud data of the coronary artery, a point on the central axis of the coronary artery is extracted first, then an index relationship characterizing a path formed between the points is established based on the point on the central axis, and finally, based on the point cloud data and the index relationship, a first radius corresponding to any one point on the central axis of the coronary artery can be calculated.

Drawings

Fig. 1 is a schematic flow chart of a method for calculating a radius of a coronary artery according to an embodiment of the present invention;

FIG. 2 is a schematic flow chart of another method for calculating a radius of a coronary artery according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a point cloud data of coronary arteries according to an embodiment of the present invention;

FIG. 4 is a schematic illustration of a point on the central axis of a coronary artery according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a coronary artery with a second target point and a tangent line thereof according to an embodiment of the present invention;

FIG. 6 is a schematic illustration of an access marker for coronary arteries according to an embodiment of the present invention;

FIG. 7 is a schematic cross-sectional radius view of a keel point of a coronary artery according to an embodiment of the invention;

FIG. 8 is a flow chart illustrating a method for calculating a radius of a coronary artery according to another embodiment of the present invention;

fig. 9 is a schematic structural diagram of a terminal according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail with reference to the accompanying drawings, the described embodiments should not be construed as limiting the present invention, and all other embodiments obtained by a person of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing embodiments of the invention only and is not intended to be limiting of the invention.

In the related technology, along with the outbreak of image big data, the image processing technology has the advantages of high processing precision, good reproducibility, high flexibility, strong universality and the like, and plays an increasingly important role in analyzing and identifying the shape of an object by depending on the image processing technology in various fields such as military industry, agriculture, medical treatment and the like. The main idea is to determine the object by key point positioning, and the rendering of an object shape must not leave the extraction of its skeleton.

Generally, the process of acquiring the skeleton of the image is a process of 'thinning' the image, which can effectively reflect the connectivity and topology of the original object shape. The current bone extraction algorithm is to repeat iterative computation from the boundary, uniformly strip the boundary of the graph layer by layer until the innermost one-dimensional bone is left.

The image skeleton extraction technology is a very important transformation in image analysis and shape description, and is an important topological description in image geometry. The skeleton extraction technology is applied to the shape analysis, the feature extraction, the pattern recognition and the like of an image target. The curve skeleton extraction algorithm has been a research hotspot in the fields of virtual navigation, form matching, fingerprint identification, medical image processing and the like.

In the field of medical Imaging, several technologies such as color ultrasound cardiovascular Imaging, Magnetic Resonance Imaging (MRI), and Digital Subtraction Angiography (DSA) are in succession. The medical image digitization degree is higher and higher, and the variety is more diversified. Medical imaging techniques have not only provided reconstructive models of various human organs, but also demonstrated hemodynamic changes through time-series blood flow velocity fields. The development of these techniques has greatly improved the efficiency and accuracy of doctor's diagnosis, while also reducing unnecessary surgical risks to the patient.

In the case of current coronary artery disease, the pressure difference across the guidewire at the anterior segment lesion of the coronary artery was previously measured primarily by microsurgery. Doctors now agree to calculate FFR to measure lesion size and give appropriate recommendations as to whether the patient needs to be cured by surgery. Since FFR is calculated by assigning the blood supply volume of the branch by the coronary artery model diameter, the normal radius of the coronary artery model needs to be calculated. In most cases, some patients develop stenosis, plaque bulge, or diffuse changes with long segments at the bifurcation, and these external uncontrollable factors affect the luminal blood flow distribution. Although there are many methods for vascular caliber, one of them is achieved by bone extraction. As above, extracting the coronary artery keel point becomes the first step of calculating the normal radius of the coronary artery model, which is an important step of calculating the coronary artery blood flow reserve coefficient; here, the normal radius may be understood as a radius at a blood vessel where no lesion occurs. However, the radius of the coronary artery cannot be accurately calculated in the related art.

An embodiment of the present invention provides a method for calculating a radius of a coronary artery, where the method is applied to a terminal, and as shown in fig. 1, the method includes:

step 101, point cloud data of a coronary artery is obtained, and a first point set is determined based on the point cloud data.

Wherein the first set of points includes points on a central axis of the coronary artery.

In the embodiment of the present invention, the point cloud data of the coronary artery may be obtained by the terminal performing three-dimensional reconstruction based on a plurality of Computed Tomography Angiography (CTA) images to obtain a coronary artery model and based on the coronary artery model. Here, the CTA image may be a coronary CTA image obtained by scanning a coronary artery with a multi-row spiral CT scanner after a suitable contrast medium is intravenously injected.

Here, the point cloud data may be stored as spatial coordinates (x, y, z) and may be an H × 3 dimensional array (H is the number of points included in the point cloud data). In the embodiment of the invention, after the terminal acquires the point cloud data, the point cloud array can be converted into the binary three-dimensional matrix Vol (337 multiplied by 412 multiplied by 231), and the connected domain of the point cloud with the number of the pixel points smaller than 100 in the connected domain is removed through the connected domain algorithm. Here, the connected component of the point cloud having the number of the element points smaller than 100 indicates that the position has a low possibility of coronary artery, and the points may be considered not to be points on the point cloud and may be removed to eliminate interference. And finally, directly extracting points on the central axis of the coronary artery by using a coronary artery skeleton extraction algorithm, wherein the points on the central axis of the coronary artery can also be called keel points forming the skeleton, and the positions of the keel points are recorded in 1-3 columns in the matrix A. Illustratively, the matrix a has 24 columns in total, but only a part of the columns are used in the embodiment of the present invention, and the index parameters related to the embodiment of the present invention are recorded in the part of the columns.

And 102, establishing an index relation based on the first point set.

Wherein the index relationship characterizes a path formed by a plurality of points on the central axis.

In an embodiment of the present invention, the first set of points includes the keel point, which is a point on the central axis of the coronary artery.

And 103, calculating a first radius of the coronary artery based on the point cloud data and the index relation.

In the embodiment of the invention, after the point cloud data and the index relationship are obtained, the terminal can calculate the first radius corresponding to any point on the central axis of the coronary artery based on the point cloud data and the index relationship.

According to the foregoing embodiment, an embodiment of the present invention provides a method for calculating a radius of a coronary artery, the method being applied to a terminal, and referring to fig. 2, the method includes:

step 201, point cloud data of coronary arteries are obtained, and a first point set is determined based on the point cloud data.

Illustratively, referring to fig. 3 and 4, in fig. 3, the terminal performs three-dimensional reconstruction based on a plurality of CTA pictures to obtain a coronary artery model, and the terminal can obtain point cloud data of a coronary artery based on the model, and further determines a first point set based on the point cloud data, where the first point set includes all points in fig. 4.

Step 202, determining that the point in the first point set, the distance between which and the first target point is within the first preset distance range, is a repeated point.

The first point set comprises a first target point, and the first target point is any point in the first point set.

In the embodiment of the invention, after the terminal acquires the first point set consisting of the points on the central axis of the coronary artery, the points in the first point set can be screened.

Here, the screening of the points in the first point set may include removing the keel points which are repeated in the first point set. The repeated keel points are points in the first point set, and the distance between the first point set and the first target point is within a first preset distance range.

For example, the first target point may be referred to as an ith keel point, and the distance d from all keel points (taking the jth keel point as an example) which are not calculated from the ith keel point to the ith keel point is traversed_ijTaking the distance d between the keel points smaller than 0.2 as a constraint condition, namely a mathematical expression: i X_j-X_iLess than 0.2, i belongs to (1, W-1), j belongs to (i +1, W), wherein W is the total number of keel points, X_jRepresenting the coordinates of the jth keel point. If the distance d from the ith keel point to the jth keel point_ijIf the number is less than 0.2, the jth keel point is considered as a repeat point and is also a keel point to be eliminated, and all the remaining keel points are traversed according to the method.

Step 203, a first direction of a tangent of the second target point is obtained, and discontinuous points are determined based on the first direction.

The second target point is any point in a third point set, and the third point set comprises points in the first point set except for repeated points.

Here, after the terminal determines the repeated keel point in the first point set, a third point set including points other than the repeated point in the first point set is obtained based on the first point set. Next, the terminal determines points discontinuous in the first direction based on the third point set.

Here, referring to fig. 5, after acquiring the third point set, the terminal may acquire the first direction of the tangent of each second target point in the third point set, and fig. 5 is a schematic diagram of the directions of the respective second target points and the tangents thereof.

In this embodiment of the present invention, the obtaining the first direction of the tangent of the second target point in step 203 includes:

step 203a, selecting a plurality of second specific points from the third point set, wherein the distances between the second specific points and the second target point are within a second preset distance range, and obtaining a fourth point set based on the plurality of second specific points.

Here, the terminal may select, after obtaining the third point set, a plurality of second specific points having a distance to the second target point within a second preset distance range from the third point set; here, the plurality of second specific points may serve as reference points for determining a direction of a tangent to the second target point. The plurality of second specific points constitute a fourth point set.

Step 203b, a second direction of the tangent line of each second specific point in the fourth point set is obtained.

Here, after the terminal obtains a plurality of second specific points, a second direction of a tangent line of each of the second specific points may be acquired.

Step 203c, determining the first direction based on the plurality of second directions.

In this embodiment of the present invention, the determining the first direction in step 203c based on the plurality of second directions includes: and calculating a first average value of the plurality of second directions, and carrying out normalization processing on the first average value to obtain the first direction.

Here, after the terminal determines the repeated keel points in the first point set, the first direction of the tangent to the second target point is determined based on the tangent directions of the plurality of second specific points in the fourth point set, so as to ensure the accuracy of the first direction of the tangent to the second target point.

Illustratively, Principal Component Analysis (PCA) is performed on the spatial coordinates of a plurality of keel points near a certain second target point, for example, within a second preset distance range, the first Principal Component is taken as a tangential direction, then an average value is obtained and normalized, the calculated value is the tangential direction of the keel, 4-6 columns in the matrix a are marked, and all keel points are traversed according to the above operation. Here, the first direction of the tangent line of the second target point may be calculated by using the spatial coordinates of 7 keel points near the second target point, and the first direction may be calculated more accurately by selecting 7 points, for example, when calculating the movement direction at the inflection point, the keel point at the inflection point and three keel points before and after itself may be selected, and the first direction of the tangent line at the inflection point may be calculated by using 7 keel points in total.

In this embodiment of the present invention, the determining discontinuous points based on the first direction in step 203 includes:

step 203d, determining discontinuous points based on the first direction, the coordinates of the second target point and the first threshold.

In the embodiment of the present invention, after the terminal acquires the first direction, the terminal may determine discontinuous points in the third point set based on the first direction, the coordinates of the second target point, and the first threshold, and use the determined discontinuous points as points to be removed.

In this embodiment of the present invention, the step 203d determines discontinuous points based on the first direction, the coordinates of the second target point, and the first threshold, and includes:

and A1, taking a point which is along the first direction and is away from the second target point by a first distance as a spherical center and taking the first distance as a radius, constructing a first area.

Here, the first region is a first sphere constructed with a point along the first direction and at a first distance from the second target point as a center of sphere and the first distance as a radius.

And A2, taking the point which is opposite to the first direction and is away from the second target point by the first distance as a spherical center and taking the first distance as a radius, constructing a second area.

Here, the second region is a second sphere constructed with a point in a direction opposite to the first direction and at a first distance from the second target point as a center of sphere and the first distance as a radius.

A3, determining the number of points in the third set of points included in the first and second regions.

Here, after constructing the first sphere and the second sphere, the terminal may obtain how many points in the third point set are included in total in the first sphere and the second sphere.

And A4, if the number does not meet the preset number range, determining the second target point as a discontinuous point.

Here, after acquiring the number of points in the third point set included in the first sphere and the second sphere, the terminal compares the number with a preset number range, and if the number meets the preset number range, determines that the second target point is a continuous point; and if the number does not accord with the preset number range, determining the second target point as a discontinuous point.

For example, assume that the first distance thre _ r is 3 and the position of the ith keel point is a_i＝(x_i，y_i，z_i) A 'corresponds to the first direction of the tangent line'_i＝(x′_i，y′_i，z′_i) Constructing a first sphere in the positive direction of the first direction of the tangent of the ith keel point; i.e. with (x)_i0，y_i0，z_i0) To mark the center of the sphere A_i0Calculating the expression of the center of the sphere as follows: a. the_i0＝A_i+thre_r*A′_iIn 1, with r₀0.99 × thre _ r is the radius (removing the self keel point). Calculating all keel points to the center of sphere A_i0D, with d < r₀The constraint condition is used for judging the number of keel points in the first sphere; based on the same principle, the opposite direction of the first direction of the tangent line of the ith keel point is equally executed once again to obtain a second sphere. Finally, the terminal determines that if the sum of the number of the keel points in the two balls is less than or equal to 2, the ith keel point is regarded as a point with discontinuous direction, namely the keel point to be removed.

And 204, removing repeated points and discontinuous points in the first point set to obtain a second point set.

Here, after the terminal identifies the overlapped points and the discontinuous points from the first point set, the overlapped points and the discontinuous points in the first point set are removed to obtain a second point set.

Step 205, based on the second point set, selecting a plurality of fourth target points whose distances to the third target point are within a third preset distance range.

The third target point is any point in the second point set. After the terminal acquires the second point set, a plurality of fourth target points, the distances between which and the third target point are within a third preset distance range, are selected as reference points for adjusting the first direction of the third target point, so that the direction of the tangent line of the third target point becomes a smoother point and a more real point, which is more approximate to the trend of the keel point.

And step 206, smoothing the first direction of the third target point based on the first directions of the plurality of fourth target points to obtain a first target direction.

In this embodiment of the present invention, the step 206, based on the first direction of the plurality of fourth target points, of smoothing the first direction of the third target point to obtain the first target direction, includes:

and B1, projecting the first direction of each fourth target point to the first direction of the third target point to obtain each projected third direction.

And B2, unifying the directions of the third directions by using a sign function to obtain a plurality of fourth directions.

Here, the unification of the directions of the plurality of third directions based on the sign function means unifying the plurality of third directions into a unified direction, and further obtaining a plurality of fourth directions.

And B3, calculating a plurality of second average values in the fourth direction, and carrying out normalization processing on the second average values to obtain the first target direction.

For example, in the process of performing the smoothing process on the tangential direction of the keel point, first, assuming that the third preset distance thre _ r is 4, the distance d between the third target point, for example, the ith keel point, and all keel points is calculated, the keel point where d is less than thre _ r is taken, and the tangential direction of the keel point within the threshold is denoted as B' (for example, the tangential direction of 7 keel points near the ith keel point is included within the threshold). Next, the tangential direction of the ith keel point is A'_iProjection of tangential direction B ' of these keel points to tangential direction A ' of the ith keel point '_iAnd using a sign function, i.e.

And updating the tangential direction B' of the keel point in the threshold. Finally, the tangential direction B ' of the keel point in the threshold value is averaged and normalized, and the tangential direction is updated to be the tangential direction A ' of the ith keel point '_iAnd obtaining a first target direction, and updating data in 4-6 columns in the matrix A.

Step 207, the exit point and the entry point of the coronary artery are searched based on the first specific point in the second set of points.

In an embodiment of the present invention, the first specific point may be a point at the entrance of the left coronary artery obtained by the terminal, and the point is included in the second set of points. The terminal searches for an exit point and an entry point of the coronary artery based on the first specific point.

In an embodiment of the present invention, step 207 searching for exit and entry points of the coronary artery based on the first specific point in the second set of points comprises:

step 207a, calculating a plurality of second distances between each point in the second set of points and the first specific point.

Here, after the terminal acquires the first specific point, a plurality of second distances between each point in the second point set and the first specific point may be calculated.

Step 207b, determining the point corresponding to the shortest distance in the plurality of second distances as the entry point of the coronary artery.

Illustratively, referring to fig. 6, the first specific point P₁For the left coronal portal position, according to P₁Come to determine all keel points to P₁The shortest keel point is taken as the coronary artery entry point. The entry point position index 2 is in 15 columns of matrix a. Here, since there are points in the operation flow where there is a culling discontinuity, the entry point needs to be updated.

And step 207c, if one and only one of the first region and the second region comprises a third specific point in the second point set, determining the exit point of the coronary artery based on the third specific point.

In the embodiment of the present invention, the ith keel point is taken as an example, a ball in the front and back tangential directions of the keel point is constructed, and whether the keel point exists in the ball is determined by using the ball constructed in the front and back tangential directions, which is consistent with the method for constructing the first ball and the second ball. If there is keel point in the ball, it is counted for 1 time, and if there is no keel point in the ball, it is counted for 0 time. Judging whether the number of times of the keel points is present or not by using the two spheres as a constraint condition, and if no keel point is present in the two spheres (the count is 0), indicating that the keel point is an isolated point, and rejecting the point. If twoIf any one of the balls has a keel point (count is 1) and only one ball has the keel point, the keel point is an exit, and the 15 columns of the matrix A are marked as 1; if a keel point (count 2) exists in both spheres, this point is an intermediate point and is marked as 0 in the 15 columns of the matrix a. As shown in FIG. 6, the large asterisk points M1 and M2 are entry points, (in FIG. 6, a given first specific point P is₁Closer to the location of the coronary entry point M1, appearing to be almost at the same location), the small asterisk point N is the exit point.

In an embodiment of the present invention, if one and only one of the first region and the second region includes a third specific point in the second point set, the step 207c may include the following steps:

step 207c1, if one and only one of the first region and the second region includes a third specific point of the second set of points, determining the third specific point as the initial exit point of the coronary artery.

And step 207c2, if the target direction of the tangent of the initial exit point is perpendicular to the first target direction of the tangent of the specific target point in the fifth target points, replacing the initial exit point with the specific target point to obtain the exit point of the coronary artery.

Wherein the specific target point is a point closest to the initial exit point among the at least one fifth target point. That is, in the embodiment of the present invention, if the target direction of the tangent of the initial exit point is perpendicular to the first target direction of the tangent of the specific target point of the fifth target points, the initial exit point is removed, and a new exit point is marked again, that is, the initial exit point is replaced by the specific target point, so as to obtain the exit point of the coronary artery.

Step 208, based on the exit point and the entry point, an index relationship is established.

In this embodiment of the present invention, step 208 establishes an index relationship based on the exit point and the entry point, including:

step 208a, determining a fifth target point from the second point set, wherein the distance between the fifth target point and the exit point is within a fourth preset distance range.

Wherein the number of the fifth target points is at least one.

Step 208b, determining that the first target direction of the tangent of the fifth target point is not perpendicular to the first target direction of the tangent of the exit point from the at least one fifth target point, and the fifth target point closest to the exit point is a parent node of the exit point.

In the embodiment of the present invention, illustratively, a first exit keel point is taken as a child node, a keel point with the shortest distance (excluding itself) is calculated and recorded as a parent node of the first exit keel point, and a parent node index of the keel point is established in 16 columns in a matrix a. First, calculating the inner product of the direction from the child node to the father node and the first target direction (the first exit keel point) of the child node, if the inner product is larger than a certain threshold tau₁(τ₁Eps), a first target direction representing a tangent to the first exit keel point (sub-node) remains unchanged; if the inner product is less than a threshold τ₂(τ₂-eps) representing a first target direction of the tangent to the first exit keel point, wherein eps is 10-22; if inner product is (tau)₂，τ₁) And (generally, the vertical condition is restricted), it indicates that the first exit keel point has a problem and is recorded as a dead spot. And secondly, calculating the keel point with the shortest distance from all keel points to the dead points in the first step, updating the keel point with the shortest distance to a new exit point, simultaneously eliminating the recorded dead points, and judging the father node of the new exit point in the first step again, wherein eps is infinitesimal epsilon. And thirdly, traversing all the export keel points according to the method and establishing the father indexes of all the export keel points.

And step 208c, establishing an index relationship based on the first target direction of the tangent of the exit point, the fifth direction from the exit point to the entry point and the sixth direction from the exit point to the parent node.

In this embodiment of the present invention, in step 208c, based on the first target direction of the tangent line of the exit point, the fifth direction from the exit point to the entry point, and the sixth direction from the exit point to the parent node, an index relationship is established, which includes:

a first step of determining a path direction from an exit point to an entry point based on a first target direction, a fifth direction, and a sixth direction of a tangent to the exit point;

illustratively, a first target direction dir passing through a tangent of the keel itself, for example, at a first exit keel point₁The keel point and a fifth direction dir corresponding to the entry point₂And a sixth direction dir of the keel point and the keel point closest to the keel point (closest to the entry point, i.e. the parent node of the keel point)₃And weighting and averaging the three directions of the first target direction, the fifth direction and the sixth direction to obtain the driving direction from the outlet to the inlet as follows: dir ═ m₁*dir₁+m₂*dir₂+m₃*dir₃Wherein (m)₁，m₂，m₃) For the scaling factor, the specific value of the scaling factor in the embodiment of the present invention may correspond to

And secondly, traversing points in the second point set from the exit point along the path direction to obtain an index relation.

In this embodiment of the present invention, the second step traverses points in the second point set from the exit point along the path direction to obtain an index relationship, including:

c1, traversing a first part of points in the second point set from each exit point along the path direction corresponding to each exit point, and traversing to a first exit point different from each exit point, and then backing to the first branch from the first exit point to obtain a first sub-path.

Wherein the first sub-path comprises a path from each exit point to a first branch.

And C2, traversing a second part of points in the second point set from the first branch along the path direction corresponding to each exit point to obtain a second sub-path.

Wherein the second sub-path comprises a path from the first branch to an entry point corresponding to each exit point.

In this embodiment of the present invention, the C2 traversing the second partial point in the second point set from the first branch along the path direction corresponding to each exit point to obtain the second sub-path, may include the following steps:

and C21, traversing the first sub-part point in the second part point from the first branch along the path direction corresponding to each exit point, and traversing to a second exit point different from the first exit point, and then backing to the second branch from the second exit point to obtain a third sub-path.

Wherein the third sub-path comprises a path from the first branch to the second branch;

c22, traversing a second sub-portion point of the second portion of points in the second set of points from the second bifurcation along the path direction corresponding to each exit point, resulting in a fourth sub-path.

Wherein the fourth sub-path comprises a path from the second bifurcation to an entry point corresponding to each exit point.

It should be noted that, in the process of traversing a second sub-portion point in a second portion point of the second point set from the second bifurcation along the path direction corresponding to each exit point to obtain a fourth sub-path, it is still possible to traverse a portion of points in the second sub-portion point in the second portion point of the second point set from the second bifurcation along the path direction corresponding to each exit point, and traverse to another exit point, and then go back to the third bifurcation from another exit point to obtain a fifth sub-path; wherein the fifth sub-path comprises a path from the second branch to the third branch; traversing remaining ones of the second sub-portion points in the second set of points along the path direction corresponding to each exit point from the third bifurcation to obtain a sixth sub-path; the sixth sub-path includes a path from the third branch to an entry point corresponding to each exit point. Further, a fourth sub-path is determined based on the fifth sub-path and the sixth sub-path. That is, in the course of traversal, whenever traversal occurs from one branch F1 to another exit point different from the starting exit point of traversal, it is necessary to go back to another branch F2 between the other exit point and the branch F1, and continue traversing the remaining points along the path direction from another branch F2.

And C23, determining a second sub-path based on the third sub-path and the fourth sub-path.

And C3, based on the first sub-path and the second sub-path, determining each path corresponding to each exit point.

C4, determining an index relationship based on each path corresponding to each exit point.

In this embodiment of the present invention, the determining, by C4, an index relationship based on each path corresponding to each exit point may include the following steps:

and C41, determining a plurality of overlapped part paths and a plurality of non-overlapped part paths in the plurality of paths corresponding to the plurality of exit points.

Wherein the same overlapping part in the paths of the plurality of overlapping parts has a unique path;

and C42, determining an index relation based on the paths of the multiple overlapped parts and the paths of the multiple non-overlapped parts.

As can be seen from the above, in the embodiment of the present invention, in the process of traversing from an exit point to an entry point, if the exit point is traversed to another exit point, the branch point is returned to, and a new path is continuously searched until the entry point is traversed, so as to obtain the first sub-path. Similarly, a second sub-path may be obtained. If the paths from the bifurcation to the entrance in the second sub-path and the first sub-path are overlapped, determining the index relation based on the paths of a plurality of overlapped parts and the paths of a plurality of non-overlapped parts.

For example, the terminal may traverse the first sub-path first and then traverse the second sub-path, and when it is determined that the second sub-path and the first sub-path have an overlapping portion, update the index relationship based on the overlapping portion corresponding to the second sub-path.

In the embodiment of the invention, a traversal keel point (in the case of the embodiment, the driving direction dir on a keel point and the sixth direction dir of the nearest keel point of the keel point are searched in a given angle_sIs greater than 0.2, traversal from exit to entrance driving direction dir, at the bifurcation, traversal from one exit to another exit often occurs due to the driving direction dir may not be accurate enoughThe situation is. For such problems, depth-first is adopted, that is, a rollback strategy is adopted after a direction error, and the following ideas can be referred to: when traversing from an exit to an entry, if the exit or a dead point is encountered (the current keel point does not find a possible parent node, the dead point is a dead point), a keel point needs to be rolled back. And (3) the retreated path is regarded as a dead pixel, the walking is not carried out until the retreated path is retreated to the bifurcation, a new path is obtained, the new path reaches the entrance, the steps are repeated, the path is traversed to the entrance from the exit in sequence, the father indexes of all the keel points are established, and the father indexes are recorded in 16 columns in the matrix A.

Further, there will always be misjudged small branch exits at the entrance, such as the framed entrance point in fig. 6, which is typically within 10 keel points. Correcting the misjudged small branch only by assuming that the branch point is directly traversed from the exit ii, stopping traversing the keel of the branch to indicate that the branch is normal; and if the number of the keel points on the branch is within 10 points after the branch is directly traversed to the entry point from the exit ii, the small branch is judged by mistake, and the whole small branch is removed.

Step 209, calculating a first radius of the coronary artery based on the point cloud data and the index relationship.

In this embodiment of the present invention, step 209, calculating a first radius of the coronary artery based on the point cloud data and the index relationship, includes:

step 209a, determining the outline boundary of the coronary artery based on the point cloud data.

Here, before the terminal determines the outer contour boundary of the coronary artery based on the point cloud data, the following steps may also be performed based on the second point set:

first, all paths from exit to entry in the second set of points are traversed.

Secondly, the keel point spatial position distribution x, y and z coordinates are respectively subjected to N times of smoothing spline interpolation to smooth the positions of keel points in the second point set.

Thirdly, performing polynomial fitting on each path for N times, calculating a first derivative and a second derivative corresponding to each keel point, and calculating the curvature and the curvature radius of each keel point by combining a curvature formula.

Here, the terminal may calculate the curvature and the radius of curvature through N-th order polynomial data fitting based on the keel point spatial position. The curvature and the curvature radius can be calculated by the following steps: first, all path routes from the exit to the entry are described (for example, the index of 16 columns in the matrix a is described), in the embodiment of the present invention, the k-th path route is taken as an example, and according to the spatial coordinates (x, y, z) of the keel point, the coordinates (x) of the keel point are smoothed by 5 times of smoothing spline interpolation method through the function fit (t, m 'smoothing spline') respectively₅，y₅，z₅) Wherein t is the total number of the keel points in each path, and m is the coordinate value of x, y or z represented by the keel points in each path.

Secondly, each path route is subjected to quadratic polynomial fitting, and a mathematical expression is as follows: y ═ a × x²+ b × x + c, in this case, taking the kth path routes as an example, the function plotfit (t1, M, 2) is used to directly smooth the coordinates (x) of all keel points on the kth path₅，y₅，z₅) And carrying out quadratic polynomial numerical fitting in the directions of x, y and z respectively, recording a first-order coefficient b and a second-order coefficient a of each keel point, and marking the second-order coefficient a in 7-9 columns of the matrix A.

Wherein, t1 mathematical expression is:

N₁is the total number of keel points in each path route, and M is the coordinate (x) of t1 keel points near the jth keel point after smoothing₅，y₅，z₅)。

Finally, the mathematical expression of curvature is:

where v' is the value of the second order polynomial first derivative coefficient b and v "is the value of the second order polynomial second derivative coefficient a. Calculating the curvature, recording in the 10 th column of the matrix A, and the mathematical expression of the curvature radius is as follows:

the calculated radius of curvature is recorded in column 11 of matrix a.

Next, when the terminal performs step 209a to determine the outer contour boundary of the coronary artery based on the point cloud data, for example, the terminal converts the keel point volume pixel data into coordinates in physical coordinates (pixelsping is the pixel pitch in the x and y directions, and spacingweenslices is the layer pitch in the z direction, generally, the values in the x and y directions are multiplied by pixelsping values, and the values in the z direction are multiplied by spacingweenslices values), and the conversion of the point cloud into a three-dimensional matrix obtains the outer contour boundary by using a median plane generating function in Matlab.

Step 209b, determining a plurality of sixth target points from the second point set, wherein the normal plane of the third target point intersects the outline boundary and the distance between the sixth target points and the third target point is smaller than the third distance.

The third target point is any point in the second point set.

Here, the third distance may be referred to as an initial radius r₀. Here, the terminal may calculate the normal plane of the third target point through the physical coordinates and the tangential direction of a keel point, i.e., the third target point.

Step 209c, obtaining each fourth distance between each sixth target point and the second target point.

Here, the normal plane intersects the outer contour boundary and is less than r away from the keel point₀The points (a) are a plurality of sixth target points, and each fourth distance between each sixth target point and the second target point is further obtained, and r is updated based on the plurality of fourth distances₀。

Step 209d, calculating the first radius based on the plurality of fourth distances.

Here, after n iterations, r₀Will converge to a number r at this time₀Is the true radius of the model, i.e. the first radius.

Illustratively, an iso-surface function is performed by binarizing the three-dimensional matrix Vol (337 × 412 × 231) to generate outer contour points and surfaces, which are labeled FV. In the embodiment of the invention, firstly, the pixel spacing PixelSpacing in the x direction and the y direction is 0.3898, the interlayer spacing SpacingBetWeenSlces in the z direction is 0.5000, the numerical values in the x direction and the y direction of the coordinates (1-3 columns in the matrix A) of the body of the coronary keel point are multiplied by the pixel spacing PixelSpacing, and the numerical values in the z direction are multiplied by the interlayer spacing SpacingBetWeenSlces, and the numerical values are converted into the numerical values under the physical coordinate system.

Second, assume an initial radius r ₀4 cm. Taking the coordinate of the ith keel point as A_i＝(x_i，y_i，z_i) And the corresponding tangential direction is A'_i＝(x′_i，y′_i，z′_i) The mathematical expression of the normal plane is as follows:

x ' (X-X) + Y ' (Y-Y) + Z ' (Z-Z) ═ 0. Wherein x, y and z are the space physical coordinates of the keel point, and (x ', y ' and z ') are tangent vectors corresponding to the keel point (i.e. normal vectors of the normal plane). Calculating the intersection of the normal plane and the outer contour boundary and the distance between the normal plane and the keel point less than r₀The points of (1) are updated to the initial radius r after averaging all the keel points of the points₀(ii) a Passing through radius r n times₀After iteration, r₀Convergence to a constant value, and the iteration ends, then r₀Is recorded in column 13 of matrix a for the true radius of the model.

Then, all paths from exit to entry are traversed, and 5 times smoothing spline interpolation smoothing radius r is performed through the function fit (t, r 'smoothing spline') respectively₀Wherein t is the total number of keel points in each path, r₀The radius from the keel point to the boundary of the outer contour in each path.

In this embodiment of the present invention, the step 209d of calculating the first radius based on the plurality of fourth distances includes:

step 209d1, if there is a stenosis or plaque protrusion in the branch segment of the coronary artery, setting the radius of the third target point at the specific location of the branch segment to be the second radius based on the first radius.

Wherein the second radius can be used for blood flow distribution to the coronary arteries.

Finally, the blood flow reserve coefficient (FFR) is calculated, and the blood flow distribution is carried out on the coronary artery model according to the normal radius of the blood vessel bifurcation. At the true radius r of the calculation model₀The method is based on the outer contour boundary of the coronary artery, if there is a stenosis or plaque bulge at the bifurcation of the coronary artery, the FFR calculation will be affected by inaccurate blood flow distribution, so the real radius of the bifurcation of the coronary artery needs to be restored to the normal radius.

In an embodiment of the present invention, in step 209d1, if there is a stenosis or plaque protrusion in the branch segment of the coronary artery, setting the radius of the third target point at the specific position of the branch segment as the second radius based on the first radius, including:

and D11, if there is a stenosis or plaque bulge in the branch section of the coronary artery and the length of the branch section belongs to the first length range, calculating a third average value of the first radius corresponding to all the third target points.

D12, setting the radius of the third target point at the specific position of the branch segment to be the second radius based on the third average value.

Exemplarily, if the length of the keel point of the branch segment is 4 pixel points, the correction is not carried out; if the length of the keel point of the branch section is 4 to 70 pixel points, the length of the branch section is determined to belong to the first length range, and 1.2 times of the average value (removing 2 keel points at the head and the tail) of all radiuses is taken to correct the radius of the front 3 keel point models of the bifurcation.

In another embodiment of the present invention, if there is a stenosis or plaque protrusion in the branch segment of the coronary artery in step 209d1, setting the radius of the third target point at the specific position of the branch segment as the second radius based on the first radius, may include:

d21, if there is a stenosis or plaque bulge in the branch section of the coronary artery and the length of the branch section belongs to the second length range, acquiring a plurality of specific radiuses in the first radiuses corresponding to all the third target points.

Wherein the plurality of specific radii are larger than a preset radius.

D22, calculating a fourth average value of a plurality of specific radii.

D23, setting the radius of the third target point at the specific position of the branch segment to be the second radius based on the fourth average value.

Illustratively, if the keel point of the branch segment is greater than 70 pixel points, and the length of the branch segment is determined to belong to the second length range, 1.2 times of the average value of the first 40 keel point model radii of the maximum radius is taken to correct the first 3 keel point model radii of the bifurcation, and the corrected normal radius is recorded in the 22 th column in the matrix a.

Based on the steps executed by the terminal, the schematic cross-sectional radius diagram of the keel point of the coronary artery shown in fig. 7 can be obtained, and then the terminal can output keel model data. The keel model in figure 7 has coordinates in meters. The output files are in the formats of dat and ply. The dat format keel model relates to various information, such as the physical coordinates, curvature, radius of curvature, index, model radius, etc. of the keel. The ply format, provides a model for calculating FFR display.

The method for calculating the radius of the coronary artery provided by the embodiment of the invention can calculate the first radius corresponding to any central axis of the coronary artery, and by adopting the method provided by the embodiment of the invention, not only is minimally invasive surgery not needed, but also quantitative calculation can be realized for the radius of the coronary artery, so that the radius of the coronary artery can be accurately calculated, and accurate blood flow distribution can be provided for calculating FFR.

It should be noted that, for the descriptions of the same steps and the same contents in this embodiment as those in other embodiments, reference may be made to the descriptions in other embodiments, which are not described herein again.

According to the foregoing embodiment, with reference to fig. 8, a method for calculating a radius of a coronary artery according to an embodiment of the present invention is further described, where the method is applied to a terminal, and the method includes:

301: point cloud data of coronary arteries is acquired.

302: and extracting keel points based on the coronary artery point cloud data.

Here, the terminal converts the point cloud array of the coronary artery into a binary three-dimensional matrix, eliminates a smaller connected domain, and then directly extracts the keel point by using a skeleton extraction algorithm.

303: calculating the tangential direction of the keel points, and removing repeated and discontinuous keel points.

Here, the terminal calculates the tangential direction of the keel point. Taking a keel point as an example, selecting W keel points with the minimum distance to the keel point, performing principal component analysis on coordinates of the W keel points, and taking the direction of a first principal component as the tangential direction of the keel point. Traversing all the remaining keel points according to the method to obtain discontinuous keel points and removing the discontinuous keel points.

And removing repeated keel points by the terminal. Step 1, selecting a keel point, calculating the distance from the keel point to other keel points, and removing keel points (except the keel point) with the distance smaller than a certain threshold value; and 2, selecting the keel points which are not selected in the previous step, calculating the distance from the keel points which are not selected in the previous step to the keel points, and removing the keel points according to the rule in the step 1. And (5) repeating the step (2).

304: and searching the entrance and exit points of the coronary keel point according to the given entrance position.

Here, the terminal may acquire given two portal positions, and set the keel point closest to the two portal positions as the left and right coronary portals.

305: and searching disconnected points from the outlet to the inlet in sequence, and establishing a keel point index relation.

Here, the terminal is respectively constructed into a ball along the positive and negative tangential directions of the first keel point (not counting the entrance keel point); if there is a keel point in the ball, it is marked 1 time, and if there is no keel point in the ball, it is marked 0 time. If the keel points exist in the two balls, the first keel point is the middle point; if the keel point exists in one of the two balls and only one of the two balls, the first keel point is an outlet; if no keel point exists in the two spheres, the first keel point is an independent point, namely a point which is not connected, and the point is removed. And finally, traversing the rest keel points according to the method.

Further, a keel point index (child node and parent node) relationship is established. Taking the first export keel point (child node) as an example, the keel point (excluding itself) corresponding to the shortest distance is calculated as the father node of the first export keel point. First, calculating the direction dir of the child node and the father node_{f_s}Then recalculate dir_{f_s}And the direction dir of the sub-node (first exit keel point)_sThe inner product of (d). If the inner product is greater thanA certain threshold τ₁Tangential direction dir of the sub-node (first exit keel point)_sThe change is not changed; if the inner product is less than a threshold τ₂The tangential direction of the first outlet keel point is reversed-dir_s(ii) a If the inner product is at the threshold value (tau)₂，τ₁) Indicate dir_{f_s}，dir_sThe included angle between the two is too large), the first outlet keel point is a disconnected point and is recorded as a dead point. And secondly, calculating the keel points with the shortest distance from all keel points to the dead points in the first step, updating the keel points with the shortest distance to new exit points, simultaneously eliminating recorded dead points, and judging father nodes of the new exit points in the first step again. And thirdly, traversing all the export keel points according to the method and establishing the father indexes of all the export keel points.

Further, the terminal weights and averages the three directions through the tangential direction of a keel point, the direction from the keel point to the corresponding entry point, and the direction from the keel point to the keel point (and the point closest to the entry) which is the sequentially traversed direction dir of the keel point.

Further, the terminal searches and traverses keel points in a given angle, and traverses from the exit to the entry according to the sequentially traversed direction dir of the keel points. The traversal mode adopts depth priority, namely a backspacing strategy is adopted after the direction is wrong.

306: and calculating the curvature and the curvature radius through N-degree polynomial data fitting based on the keel point space position.

Here, the terminal first traverses all paths from exit to entry; secondly, smoothing the positions of the keel points by respectively performing N times of smoothing spline interpolation on x, y and z coordinates of the keel point spatial position distribution; and finally, performing polynomial fitting on each path for N times, calculating a first derivative and a second derivative corresponding to each keel point, and calculating the curvature and the curvature radius of each keel point by combining a curvature formula.

307: and re-establishing the index, and further outputting keel voxel data.

308: and (5) coordinate conversion.

309: and calculating the radius of the cross section based on the point and the surface corresponding to the point cloud data of the coronary artery, and further outputting a keel model.

Here, the terminal acquires an outer contour boundary, namely an isosurface, and then calculates the section radius based on the outer contour boundary and an index relation; further, the radius is smoothed by an N-th order smoothing spline interpolation on the section radius. It should be noted that the radius of the bifurcation may not be accurate, and the data of the radius of the bifurcation is repaired, so as to output the keel model.

Based on the foregoing embodiments, an embodiment of the present invention provides a terminal, which may be applied to a method for calculating a radius of a coronary artery according to the embodiments corresponding to fig. 1-2, and referring to fig. 9, the terminal 4 includes: a processor 41, a memory 42, and a communication bus 43, wherein:

the communication bus 43 is used to realize a communication connection between the processor 41 and the memory 42.

The processor 41 is configured to execute a coronary artery radius calculation program stored in the memory 42 to implement the following steps:

establishing an index relation based on the first point set; wherein the index relationship represents a path formed by a plurality of points on the central axis;

based on the point cloud data and the index relationship, a first radius of the coronary artery is calculated.

In other embodiments of the present invention, when processor 41 is configured to execute the index relationship established in memory 42 based on the first point set, the method may include the following steps:

based on the exit point and the entry point, an index relationship is established.

In other embodiments of the present invention, processor 41 is configured to execute a coronary artery radius calculation program in memory 42 to implement the following steps:

determining a point in the first point set, wherein the point, the distance between the point and the first target point is within a first preset distance range, is a repeated point; the first point set comprises a first target point, and the first target point is any point in the first point set;

acquiring a first direction of a tangent of a second target point, and determining discontinuous points based on the first direction; the second target point is any point in a third point set, and the third point set comprises points in the first point set except for repeated points.

In other embodiments of the present invention, when the processor 41 is configured to execute the first direction of the tangent of the second target point in the memory 42, the following steps may be implemented:

based on the plurality of second directions, a first direction is determined.

In other embodiments of the present invention, the processor 41 is configured to execute the following steps when determining the first direction based on the plurality of second directions in the memory 42:

and calculating a first average value of the plurality of second directions, and carrying out normalization processing on the first average value to obtain the first direction.

In other embodiments of the present invention, when processor 41 is configured to execute the step of determining the point of discontinuity based on the first direction in memory 42, the step of:

based on the first direction, the coordinates of the second target point and the first threshold, the discontinuous points are determined.

In other embodiments of the present invention, when the processor 41 is configured to execute the step of determining the discontinuous points in the memory 42 based on the first direction, the coordinates of the second target point and the first threshold, the step of:

and if the number does not accord with the preset number range, determining the second target point as a discontinuous point.

selecting a plurality of fourth target points with the distance to the third target point within a third preset distance range based on the second point set; the third target point is any point in the second point set;

In another embodiment of the present invention, when the processor 41 is configured to execute the smoothing process on the first direction of the third target point based on the first directions of the plurality of fourth target points in the memory 42, to obtain the first target direction, the following steps may be performed:

unifying the directions of the plurality of third directions by using a symbolic function to obtain a plurality of fourth directions;

and calculating second average values of the plurality of fourth directions, and performing normalization processing on the second average values to obtain the first target direction.

In other embodiments of the present invention, processor 41, when executing search in memory 42 for exit and entry points of the coronary artery based on a first specific point in the second set of points, may be implemented by:

calculating a plurality of second distances between each point in the second point set and the first specific point;

if one and only one of the first region and the second region includes a third specific point of the second set of points, determining an exit point of the coronary artery based on the third specific point.

In other embodiments of the present invention, processor 41 is configured to execute the following steps in establishing the index relationship in memory 42 based on the exit point and the entry point:

determining that the first target direction of the tangent of the fifth target point is not perpendicular to the first target direction of the tangent of the exit point from at least one fifth target point, and the fifth target point closest to the exit point is a parent node of the exit point;

based on the first target direction of the tangent of the exit point, the fifth direction from the exit point to the entry point, and the sixth direction from the exit point to the parent node, an index relationship is established.

In other embodiments of the present invention, the processor 41 is configured to execute the following steps when determining the exit point of the coronary artery based on a third specific point in the second point set included in only one of the first region and the second region in the memory 42, if the third specific point is included in the first region and the second region:

if one and only one of the first region and the second region comprises a third specific point in the second point set, determining the third specific point as an initial exit point of the coronary artery;

if the target direction of the tangent line of the initial exit point is perpendicular to the first target direction of the tangent line of the specific target point in the fifth target points, replacing the initial exit point with the specific target point to obtain an exit point of the coronary artery; wherein the specific target point is a point closest to the initial exit point among the at least one fifth target point.

In other embodiments of the present invention, processor 41 is configured to execute the following steps when establishing the index relationship in memory 42 based on a first target direction of a tangent line of the exit point, a fifth direction from the exit point to the entry point, and a sixth direction from the exit point to the parent node:

determining a path direction from the exit point to the entry point based on a first target direction, a fifth direction, and a sixth direction of a tangent to the exit point;

and traversing the points in the second point set along the path direction from the exit point to obtain an index relation.

In other embodiments of the present invention, the processor 41 is configured to execute the following steps when traversing the points in the second point set from the exit point along the path direction in the memory 42 to obtain the index relationship:

the index relationship is obtained by traversing the points in the second set of points from the exit point along the path direction to the entry point.

In other embodiments of the present invention, processor 41 is configured to execute that the number of exit points in memory 42 is at least one, and when traversing the points in the second point set along the path direction from the exit point to obtain the index relationship, the following steps are performed:

traversing a first part of points in the second point set from each exit point along the path direction corresponding to each exit point, and traversing to a first exit point different from each exit point, and returning to a first branch from the first exit point to obtain a first sub-path; wherein the first sub-path comprises a path from each exit point to a first bifurcation;

traversing a second part of points in the second point set from the first branch along the path direction corresponding to each exit point to obtain a second sub-path; wherein the second sub-path comprises a path from the first branch to an entry point corresponding to each exit point;

determining each path corresponding to each exit point based on the first sub-path and the second sub-path;

an index relationship is determined based on each path corresponding to each exit point.

In other embodiments of the present invention, processor 41 is configured to execute the following steps when traversing a second part of points in the second point set from the first branch along the path direction corresponding to each exit point in memory 42 to obtain the second sub-path:

traversing a first sub-part point in the second part points from the first branch along the path direction corresponding to each exit point, and traversing to a second exit point different from the first exit point, and returning to the second branch from the second exit point to obtain a third sub-path; wherein the third sub-path comprises a path from the first branch to the second branch;

traversing second subpart points in the second part points in the second point set from the second bifurcation along the path direction corresponding to each exit point to obtain a fourth subpath; wherein the fourth sub-path comprises a path from the second bifurcation to an entry point corresponding to each exit point;

based on the third sub-path and the fourth sub-path, a second sub-path is determined.

In other embodiments of the present invention, when the processor 41 is configured to execute the index relationship determined in the memory 42 based on each path corresponding to each exit point, the following steps may be implemented:

determining a plurality of overlapped part paths and a plurality of non-overlapped part paths in a plurality of paths corresponding to a plurality of exit points; wherein the same overlapping part in the paths of the plurality of overlapping parts has a unique path;

an index relationship is determined based on the paths of the plurality of overlapping portions and the paths of the plurality of non-overlapping portions.

In other embodiments of the present invention, the processor 41 is configured to execute the step of calculating the first radius of the coronary artery in the memory 42 based on the point cloud data and the index relationship, and the step of:

determining a plurality of sixth target points, wherein the normal plane of the third target point intersects with the outline boundary and the distance between the sixth target points and the third target point is smaller than the third distance, from the second point set; the third target point is any point in the second point set;

based on the plurality of fourth distances, a first radius is calculated.

if the branch section of the coronary artery has a stenosis or a plaque bulge, setting the radius of a third target point at the specific position of the branch section as a second radius based on the first radius; wherein the second radius can be used for blood flow distribution to the coronary arteries.

In other embodiments of the present invention, the processor 41 is configured to execute the following steps when the radius of the third target point at the specific position of the branch segment is set to be the second radius based on the first radius if there is a stenosis or plaque protrusion in the branch segment of the coronary artery in the memory 42:

if the branch section of the coronary artery has a stenosis or a plaque bulge and the length of the branch section belongs to the first length range, calculating a third average value of the first radius corresponding to all the third target points;

setting a radius of a third target point at a specific position of the branch section to a second radius based on the third average value.

if the branch section of the coronary artery has a stenosis or a plaque bulge and the length of the branch section belongs to the second length range, acquiring a plurality of specific radiuses in the first radiuses corresponding to all the third target points; the specific radiuses are larger than the preset radiuses;

calculating a fourth average value of a plurality of specific radii;

setting the radius of the third target point at the specific position of the branch section as the second radius based on the fourth average value.

It should be noted that, for a specific implementation process of the steps executed by the processor in this embodiment, reference may be made to an implementation process in the method for calculating a radius of a coronary artery according to the embodiment corresponding to fig. 1-2, and details are not described here again.

Based on the foregoing embodiments, an embodiment of the present invention provides a storage medium storing one or more programs, the one or more programs being executable by one or more processors to implement the steps of:

In other embodiments of the invention, the one or more programs are executable by the one or more processors to perform the steps of:

based on the plurality of second directions, a first direction is determined.

In other embodiments of the invention, where the number of exit points is at least one, the one or more programs are executable by the one or more processors to perform the steps of:

based on the plurality of fourth distances, a first radius is calculated.

calculating a fourth average value of a plurality of specific radii;

The above description is only an example of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and scope of the present invention are included in the protection scope of the present invention.

Claims

1. A method of calculating a radius of a coronary artery, the method comprising:

establishing an index relation based on the first point set;

wherein the index relationship characterizes a path formed by a plurality of points on the central axis;

calculating a first radius of the coronary artery based on the point cloud data and the index relationship;

wherein the establishing an index relationship based on the first point set comprises:

searching for exit and entry points of the coronary artery based on a first specific point in the second set of points; wherein the first specific point is a point at the entrance of the left coronary artery of the second point concentration;

establishing the index relationship based on the exit point and the entry point;

wherein said calculating a first radius of the coronary artery based on the point cloud data and the index relationship comprises:

acquiring each fourth distance between each sixth target point and the second target point; wherein the second target point is any one point in a third point set, the third point set including points in the first point set other than the repeated points;

calculating the first radius based on a plurality of the fourth distances.

2. The method of claim 1, wherein before removing the repeated points and the discontinuous points in the first set of points to obtain a second set of points, the method further comprises:

acquiring a first direction of a tangent of the second target point, and determining the discontinuous point based on the first direction.

3. The method of claim 2, wherein obtaining the first direction of the tangent to the second target point comprises:

determining the first direction based on a plurality of the second directions.

4. The method of claim 3, wherein determining the first direction based on the plurality of second directions comprises:

5. The method of claim 2, wherein the determining the point of discontinuity based on the first direction comprises:

6. The method of claim 5, wherein determining the discrete point based on the first direction, the coordinates of the second target point, and a first threshold comprises:

constructing a first area by taking a point which is along the first direction and has a first distance from the second target point as a spherical center and the first distance as a radius;

7. The method of claim 6, wherein after removing the repeated points and the discontinuous points in the first set of points to obtain a second set of points, the method comprises:

8. The method of claim 7, wherein smoothing the first direction of the third target point based on the first direction of the fourth target points to obtain a first target direction comprises:

9. The method of claim 7, wherein said searching for exit and entry points of the coronary artery based on a first specific point in the second set of points comprises:

10. The method of claim 9, wherein establishing the index relationship based on the exit point and the entry point comprises:

11. The method of claim 10, wherein determining the exit point of the coronary artery based on a third specific point in the second set of points if one and only one of the first and second regions includes the third specific point comprises:

12. The method of claim 10, wherein establishing the index relationship based on a first target direction of a tangent line of the exit point, a fifth direction of the exit point to the entry point, and a sixth direction of the exit point to the parent node comprises:

13. The method of claim 12, wherein traversing points in the second set of points from the exit point along the path direction, resulting in the index relationship, comprises:

14. The method of claim 12, wherein the number of the exit points is at least one, and wherein traversing the points in the second set of points from the exit point along the path direction to obtain the index relationship comprises:

15. The method of claim 14, wherein traversing a second portion of the second set of points from the first branch along the path direction corresponding to the each exit point to obtain a second sub-path comprises:

16. The method according to claim 14 or 15, wherein said determining the index relationship based on said each path corresponding to said each exit point comprises:

17. The method of claim 1, wherein after calculating the first radius based on the plurality of fourth distances, the method further comprises:

18. The method of claim 17, wherein setting the radius of the third target point at the specific location of the branch segment to a second radius based on the first radius if the branch segment of the coronary artery has a stenosis or plaque bulge comprises:

19. The method of claim 17, wherein setting the radius of the third target point at the specific location of the branch segment to a second radius based on the first radius if the branch segment of the coronary artery has a stenosis or plaque bulge comprises:

calculating a fourth average of the plurality of specific radii;

20. A terminal, characterized in that the terminal comprises:

a memory for storing executable instructions;

a processor for executing executable instructions stored in the memory to implement the method of calculating a radius of a coronary artery according to any one of claims 1 to 19.

21. A storage medium having stored thereon executable instructions for causing a processor to perform the method of calculating a radius of a coronary artery of any one of claims 1 to 19 when the executable instructions are executed.