Method for calculating localized narrowing of a conduit

Abstract

This invention provides a method for calculating localized stenosis from three-dimensional images of a conduit. [Solution] The method includes the steps of: determining the minimum diameter profile of the cross-section of the conduit along the length of the conduit (E3); defining at least one sliding window such that the minimum diameter of the conduit at both longitudinal ends of the window is known for each position of the window in the conduit (E4); and for each position of the at least one window, calculating the maximum reduction in the minimum diameter of the conduit within the window's range with respect to the interpolation of the diameter at both longitudinal ends of the window (E5).

Description

Technical Field

[0001] The present invention relates to imaging and acquisition of visual information of conduits such as blood vessels and around the conduits.

[0002] Specifically, the present invention relates to the identification of stenosis of blood vessel diameter.

[0003] Generally, the present invention is applicable to any mechanical conduit or physiological conduit for which a diameter profile inspection can be performed, for example, for medical purposes or maintenance purposes.

Background Art

[0004] In the field of cardiovascular imaging, current tools visualize blood vessels, measure blood vessel diameters, and enable manual placement of markers at different reference points in images of these blood vessels in order to infer certain features such as the presence of a particular stenosis in a blood vessel diameter that may be indicative of stenosis (e.g., stenosis of a coronary artery due to the presence of calcification in the coronary artery). Identifying stenosis is important because it can ultimately reduce the risk of a patient having a heart attack.

[0005] However, these manual methods are unreliable, time-consuming, non-reproducible, and introduce uncertainty into the measurements obtained.

[0006] Alternatively, tools developed using neural networks can also be used to identify stenosis of blood vessels. Still, this identification does not contain any quantifiable data based on facts that would allow agreement on the severity of the identified stenosis.

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, an object of the present invention is to provide a reliable and reproducible method for identifying and quantifying stenosis in conduits such as blood vessels, overcoming the above-mentioned drawbacks.

Means for Solving the Problems

[0008] This invention relates to a method for calculating local stenosis from a three-dimensional image of a conduit, and this method is A step of determining the minimum diameter profile of the conduit cross-section along the length of the conduit, A step of defining at least one sliding window for inspecting a conduit, wherein the minimum diameter of the conduit at both longitudinal ends of the window is known for each position of the window in the conduit; For each position of at least one window, the steps include calculating the maximum reduction in the minimum diameter of the conduit within the window's range with respect to interpolation of the diameter at both ends of the window's longitudinal direction, and It includes.

[0009] Thus, the solution of the present invention enables the automatic detection and quantification of conduit stenosis, such as vascular stenosis, through a simple method for the operator, without the operator having to manually select a reference. Clinical reliability is also enhanced.

[0010] Advantageously, this method also includes the step of recording the position of the window when the maximum reduction in the minimum diameter calculated for the window is greater than a predetermined threshold, preferably greater than a 50% reduction, and more preferably greater than a 70% reduction.

[0011] In a particular embodiment, the method further includes the step of evaluating, for each window whose position is recorded and which at least partially overlaps with another window whose position is recorded, the average reduction in the minimum diameter of the conduit within the scope of the window with respect to interpolation of the diameter at both longitudinal ends of the window.

[0012] Advantageously, the method includes the step of selecting, for each set of windows whose positions are recorded and which at least partially overlap, the window in which the average reduction of the evaluated minimum diameter is maximized in that set of windows.

[0013] Optionally, the method includes a preliminary step of acquiring a three-dimensional image of the xylem tree, and a step of processing this three-dimensional image by dividing the xylem tree into at least one three-dimensional image of a xylem.

[0014] Advantageously, the minimum diameter profile is determined with a measurement step between 0.1 mm and 1 mm, preferably between 0.2 mm and 0.5 mm, and more preferably between 0.3 mm, and the sliding inspection window slides along the conduit in increments equivalent to the measurement step of the minimum diameter profile.

[0015] Advantageously, the longitudinal ends of the window are spaced apart by a distance between 1.8 mm and 14.1 mm.

[0016] Advantageously, multiple windows are defined such that each window includes a different distance between its longitudinal ends than the others.

[0017] In certain embodiments, the recording step is performed only if the maximum reduction in the minimum diameter of the conduit within the window range with respect to the minimum diameter at the longitudinal end of the window having the smallest minimum diameter is greater than a predetermined threshold, preferably a 40% reduction.

[0018] Advantageously, the method is implemented only for portions of the conduit whose minimum diameter is greater than a value between 1 mm and 3 mm, preferably greater than a value between 1.5 mm and 2 mm, and more preferably greater than a value of 1.6 mm.

[0019] In certain embodiments, the conduit is a physiological conduit such as a blood vessel, preferably a coronary artery.

[0020] The present invention also relates to a computer program including instructions, which, when the program is executed by a computer, cause the computer to implement each step of the method defined above.

[0021] The present invention also relates to a system comprising means for implementing each step of the method defined above.

[0022] This system includes, for example, a computer and a computer-readable data medium, and the computer program defined above is stored in the data medium.

Brief Description of the Drawings

[0023] Still other objects, features, and advantages of the invention will become apparent from the following description. The description is given by way of non-limiting examples only and is described with reference to the accompanying drawings. [Figure 1] It is a schematic diagram of various steps implemented in the method according to the invention. [Figure 2] It is a diagram of a three-dimensional conduit tree. [Figure 3] It is a schematic two-dimensional diagram of a conduit including stenosis.

Embodiments for Carrying Out the Invention

[0024] FIG. 1 schematically illustrates various steps in a method for calculating local stenosis from a three-dimensional image of a conduit ① shown in FIGS. 2 and 3.

[0025] For example, the conduit ① is a physiological conduit ① of a human body such as a blood vessel. The conduit ① may be, for example, a coronary artery, and at the tip P of this coronary artery, it may consist of a single branch of the aorta and does not include a bifurcation B.

[0026] This method can be started by a step E1 of acquiring a three-dimensional image of the tree ③ of the conduit ①.

[0027] This tree 3 is schematically illustrated in Figure 2. In Figure 2, reference numeral 1 indicates the path of what is referred to as a vessel in this application within tree 3. Clearly, tree 3 contains multiple vessels 1, and the bases of these vessels 1 on the left side of Figure 2 are common.

[0028] Next, step E2 may be performed to process the three-dimensional image by dividing the tree 3 of the conduit 1 into at least one three-dimensional image of the conduit 1.

[0029] Figure 3 shows a schematic enlarged view of the portion of conduit 1 that includes the constriction 5.

[0030] To implement the method, step E3 is performed to determine the minimum diameter profile D of the cross-section of conduit 1 along the length of conduit 1. Conduit 1 can be pre-selected by the operator from a tree 3 of conduits 1. Since conduit 1 is three-dimensional, it is actually necessary to determine the smallest diameter of each cross-section of conduit 1 by, for example, image processing. The image processing performed includes, for example, tracing the centerline L of the center of conduit 1 and tracing the radius that virtually extends from this centerline L to the wall of conduit 1, that is, to the lumen if conduit 1 is a coronary artery.

[0031] The position of the diameter along the length of conduit 1 is represented by x, that is, the position of the cross-section perpendicular to the longitudinal axis of conduit 1 defined by the center line L.

[0032] The minimum diameter profile D is optional, and the measurement increment is determined to be between 0.1 mm and 1 mm, preferably between 0.2 mm and 0.5 mm, and more preferably between 0.3 mm. Thus, in the latter example, the minimum diameter 1 of the conduit is known every 0.3 mm along the longitudinal axis of the conduit.

[0033] For the remainder of the method, condition C1 is optionally applied so that the subsequent steps are implemented only in portions of the conduit 1 where the minimum diameter D is greater than a value between 1 mm and 3 mm, preferably greater than a value between 1.5 mm and 2 mm, and more preferably greater than a value of 1.6 mm. In fact, if the conduit 1 is a blood vessel, this blood vessel does not have a constant minimum diameter D, and the tip P of the conduit 1 is extremely thin, for example, with a minimum diameter of less than 1 mm, so the implementation of this method is not relevant to this type of minimum diameter D.

[0034] Next, step E4 is performed to define at least one sliding window for inspecting the conduit 1, such that the minimum diameter D of the conduit 1 at both longitudinal ends of the window is known for each position of the conduit 1 within the window.

[0035] In practice, x1 and x2 are the positions at the longitudinal ends of each window, and x2 generally corresponds to a position where the minimum diameter D is smaller than that of position x1, and is generally closer to the tip P.

[0036] For example, the longitudinal ends of the window are spaced apart by a distance known as the window width, which is between 1.8 mm and 14.1 mm, allowing for proper inspection of foreign matter in conduits 1 of similar dimensions.

[0037] Each examination window is designed to slide along the conduit 1 to examine the localized stenosis 5 of the conduit 1, which may be an indication of the presence of stenosis.

[0038] For example, the window slides along the conduit 1 with displacement increments equivalent to the steps used to measure the minimum diameter profile D.

[0039] Multiple windows are defined, at the discretion of the user, such that each window includes a different distance between its longitudinal ends. In certain embodiments, a number of windows are defined to cover a wide range of window widths, for example, from 1.8 mm to 14.1 mm.

[0040] For example, the windows are defined such that there is one window for each possible width between 1.8 mm and 14.1 mm, with each different width increment being 0.3 mm.

[0041] Next, step E5 is performed to calculate, for each position of at least one window, the maximum decrease in the minimum diameter D of the conduit 1 within the window's range, with respect to the interpolation of the diameter at both ends of the window in the longitudinal direction.

[0042] Thus, for each x between x1 and x2, the minimum diameter reduction D of conduit 1 within the window range is calculated with respect to the interpolation of the diameter at both longitudinal ends of the window. Then, the maximum values ​​of these reductions are calculated according to the following comprehensive formula.

[0043]

number

[0044] Thus, this calculation provides particularly relevant data regarding the presence of stenosis 5 in conduit 1, with a larger maximum decrease indicating narrowing of conduit 1 in its cross-sectional direction, which is a sign of severe stenosis, for example, if conduit 1 is a coronary artery.

[0045] For example, step E6 may be performed to record the window position according to the conditions of C2 when the maximum reduction in the minimum diameter calculated for a certain window exceeds a predetermined threshold, preferably a 50% reduction, and more preferably a 70% reduction. These percentages correspond to stenosis 5 that may potentially indicate the presence of severe stenosis, or stenosis 5 that in any case require investigation into the cause.

[0046] Step E6, which involves recording, includes, for example, writing the window's position, its width, and the maximum decrease in the minimum diameter D calculated for that window to memory.

[0047] Optionally, recording step E6 is further performed according to condition C3 only if the maximum reduction in the minimum diameter D of conduit 1 within the window range with respect to the minimum diameter D at the longitudinal end of the window having the smallest minimum diameter D exceeds a predetermined threshold, preferably a 40% reduction. These dual conditions C2 and C3 avoid confusing the undesirable constriction 5 with the presence of a bifurcation B from conduit 1.

[0048] Next, for each window whose position was recorded in the preceding step E6 and which at least partially overlaps with another window whose position was recorded, step E7 can be performed to evaluate the average decrease in the minimum diameter D of the conduit 1 within the range of that window with respect to the interpolation of the minimum diameter D at both ends of the longitudinal direction of the window. The average of these decreases is evaluated according to the following comprehensive formula.

[0049]

number

[0050] Finally, for each set of windows whose positions are recorded and which at least partially overlap, step E8 may be performed to select the window such that the evaluated mean minimum diameter reduction D is the largest in that set of windows.

[0051] These two final steps, E7 and E8, prevent the same stenosis 5 from being included in calculations multiple times for different windows, and allow for filtering to evaluate the window that provides the best reference for identifying stenosis 5, for example, stenosis. The best reference here is an equivalent of the latest manual reference, but obtained in an automated, reproducible, optimized, and reliable manner.

[0052] In this way, the window's position, width, and the maximum and average decrease in the minimum diameter D are calculated and evaluated, and the corresponding window is selected and stored, for example, in memory.

[0053] The invention also relates to a system comprising means for carrying out each step of the illustrated method, the means including, for example, a computer. [Explanation of symbols]

[0054] 1 conduit 3 trees 5 Stenosis

Claims

1. A method for calculating local stenosis from a three-dimensional image of a conduit (1), Step (E3) of determining the minimum diameter profile (D) of the cross-section of the conduit (1) along the length of the conduit (1), Step (E4) of defining at least one sliding window for inspecting the conduit (1), wherein the minimum diameter (D) of the conduit (1) at both longitudinal ends of the window is known for each position of the window in the conduit (1), Step (E5) for each position of the at least one window, calculate the maximum reduction in the minimum diameter of the conduit (1) within the range of the window with respect to interpolation of the diameter (D) at both ends of the window in the longitudinal direction. A method characterized by comprising:

2. The method according to claim 1, further comprising the step (E6) of recording the position of the window when the maximum reduction of the minimum diameter (D) calculated for the window is greater than a predetermined threshold, preferably greater than a 50% reduction, and more preferably greater than a 70% reduction.

3. The method according to claim 2, further comprising the step (E7) of evaluating, for each window in which the position is recorded and which at least partially overlaps with another window in which the position is recorded, the average reduction in the minimum diameter (D) of the conduit (1) within the range of the window with respect to the interpolation of the diameter (D) at both longitudinal ends of the window.

4. The method according to claim 3, wherein the positions are recorded, and for each set of at least partially overlapping windows, the step (E8) of selecting a window such that the average decrease in the evaluated minimum diameter (D) is greatest in the set of windows.

5. The method according to any one of claims 1 to 4, comprising: a preliminary step (E1) of acquiring a three-dimensional image of the tree (3) of the conduit (1); and a step (E2) of processing the three-dimensional image by dividing the tree (3) of the conduit (1) into at least one three-dimensional image of the conduit (1).

6. The method according to any one of claims 1 to 5, wherein the minimum diameter profile (D) is determined to have a measurement step between 0.1 mm and 1 mm, preferably between 0.2 mm and 0.5 mm, more preferably between 0.3 mm, and the sliding inspection window slides along the conduit (1) in increments equivalent to the measurement step of the minimum diameter profile (D).

7. The method according to any one of claims 1 to 6, wherein the longitudinal ends of the window are provided separated by a distance between 1.8 mm and 14.1 mm.

8. The method according to claim 7, wherein a plurality of windows are defined such that each window includes a distance between its longitudinal ends that is different from the others.

9. The method according to any one of claims 1 to 8, wherein the recording step (E6) is performed only if the maximum decrease in the minimum diameter (D) of the conduit (1) within the range of the window with respect to the minimum diameter at the longitudinal end of the window having the smallest minimum diameter is greater than a predetermined threshold, preferably greater than a 40% decrease.

10. The method according to any one of claims 1 to 9, which is embodied only in the portion of the conduit (1) in which the minimum diameter (D) is greater than a value between 1 mm and 3 mm, preferably greater than a value between 1.5 mm and 2 mm, and more preferably greater than a value of 1.6 mm.

11. The method according to any one of claims 1 to 10, wherein the conduit (1) is a physiological conduit (1) such as a blood vessel, and preferably a coronary artery.

12. A system comprising means for implementing each step of the method according to any one of claims 1 to 11.

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