JP7500091B2 - Method and computer program for generating aneurysm neck plane of cerebral aneurysm - Google Patents

Description

The present invention relates to a method and computer program for acquiring data showing the boundary plane (aneurysm neck plane) for measurement between a cerebral aneurysm and the parent blood vessel in which it is formed.

Cerebral aneurysms are dangerous vascular abnormalities. Their diagnosis is specialized and not easy. Therefore, a technology has been introduced that detects aneurysms by automatically analyzing three-dimensional image data taken of the head using CT (Computed Tomography) or MRI (Magnetic Resonance Imaging) (Patent Document 1). A technology has also been introduced that observes changes in the shape of an aneurysm (Patent Document 2). Furthermore, a technology has been introduced that determines the center lines of blood vessels in each location where an aneurysm has formed, in order to identify the shape of the aneurysm, and obtains accurate three-dimensional data of the blood vessels (Patent Document 3).

Patent No. 5496067 Patent Publication No. 5242235 Patent Publication No. 5890055

Conventionally, aneurysm areas are identified by detecting bulges and constrictions in blood vessels or by geometrically assuming the shape of the aneurysm, but unless the images showing the contours of the blood vessels and aneurysm are relatively smooth, it is difficult to obtain accurate results, and simple and stable measurement of aneurysms of various shapes is difficult. When the doctor's judgment is heavily added to the results of automatic computer processing, there are individual differences and the reproducibility of diagnoses varies. This makes it difficult to accurately measure the current state of the affected area and understand changes in its condition. It is also not easy to make a relative comparison with the affected area of a third party.

The present invention aims to provide a method for generating data showing the boundary plane (aneurysm neck plane) for measurement between a cerebral aneurysm and the parent blood vessel in which it is formed (the blood vessel most related to the formation of the aneurysm) using a relatively simple and reproducible method that is less susceptible to individual differences, and a computer program for executing data acquisition and calculation processing.

The following configurations are each a means for solving the above problems.

<Configuration 1>
A computer program that causes a computer to execute a process for detecting an aneurysm neck plane of an aneurysm, the process comprising:
1. A three-dimensional image showing the boundary surface of the aneurysm formed on the parent blood vessel and the surrounding blood vessels is displayed on a display.
2. Two designated points are input on the boundary surface on both sides of the portion of the parent blood vessel where an aneurysm has been formed, and the end points of the original center line of the parent blood vessel to be processed are determined on the center line of the parent blood vessel that is closest to these designated points.
3. Accept the specification of a landmark on the boundary surface of the aneurysm that indicates the direction of aneurysm growth.
4. Draw the original centerline of the parent vessel between the above-mentioned end points and the branching point where this original centerline of the parent vessel intersects with the original centerline of the aneurysm inside the aneurysm, and draw a virtual aneurysm centerline connecting the above-mentioned reference point, the original centerline of the aneurysm, and the branching point.
5. A virtual centerline of the parent vessel is drawn by flattening the original centerline of the parent vessel drawn between both end points of the parent vessel to a state not affected by the aneurysm or before the occurrence of the aneurysm.
6. Data showing vascular cross sections perpendicular to the center line at both ends of the parent vessel are generated, and image data showing a virtual mother vessel having the above-mentioned virtual mother vessel center line, in which the cross sections are connected by a smooth tubular surface, is generated.
7. Since the above-mentioned branching points move during the process of successively flattening the original centerline of the parent blood vessel, the virtual aneurysm centerline of the aneurysm is extended along that path.
8. The virtual aneurysm centerline of the aneurysm is flattened to generate data representing a virtual aneurysm cylinder with a diameter equal to or less than the outer diameter of the parent vessel.
9. Data representing a plane of the aneurysm neck is generated from image data of an image constituting a part of the virtual mother vessel at the intersection of the virtual mother vessel and the virtual aneurysm cylinder.

<Configuration 2>
A method for detecting an aneurysm neck plane of an aneurysm, comprising: causing a computer to perform the following processes:
1. A three-dimensional image showing the boundary surface of the aneurysm formed on the parent blood vessel and the surrounding blood vessels is displayed on a display.
2. Two designated points are input on the boundary surface on both sides of the portion of the parent blood vessel where an aneurysm has been formed, and the end points of the original center line of the parent blood vessel to be processed are determined on the center line of the parent blood vessel that is closest to these designated points.
3. Accept the specification of a landmark on the boundary surface of the aneurysm that indicates the direction of aneurysm growth.
4. Draw the original centerline of the parent vessel between the above-mentioned end points and the branching point where this original centerline of the parent vessel intersects with the original centerline of the aneurysm inside the aneurysm, and draw a virtual aneurysm centerline connecting the above-mentioned reference point, the original centerline of the aneurysm, and the branching point.
5. A virtual centerline of the parent vessel is drawn by flattening the original centerline of the parent vessel drawn between both end points of the parent vessel to a state not affected by the aneurysm or before the occurrence of the aneurysm.
6. Data showing vascular cross sections perpendicular to the center line at both ends of the parent vessel are generated, and image data showing a virtual mother vessel having the above-mentioned virtual mother vessel center line, in which the cross sections are connected by a smooth tubular surface, is generated.
7. Since the above-mentioned branching points move during the process of successively flattening the original centerline of the parent blood vessel, the virtual aneurysm centerline of the aneurysm is extended along that path.
8. The virtual aneurysm centerline of the aneurysm is flattened to generate data representing a virtual aneurysm cylinder with a diameter equal to or less than the outer diameter of the parent vessel.
9. Data representing a plane of the aneurysm neck is generated from image data of an image constituting a part of the virtual mother vessel at the intersection of the virtual mother vessel and the virtual aneurysm cylinder.
10. To optimize the data showing the aneurysm neck plane, the aneurysm neck plane shown on the display is moved along the virtual aneurysm centerline of the aneurysm.

<Configuration 3>
The computer program according to configuration 1 or the method according to configuration 2, characterized in that a parameter indicating the degree to which the original center line of the parent blood vessel is to be flattened, a parameter indicating the degree to which the original center line of the aneurysm is to be flattened, and a parameter indicating the amount of movement of the generated aneurysm neck plane along the virtual aneurysm center line of the aneurysm are provided, and an operation screen for increasing or decreasing these parameters is displayed on the display while three-dimensional image data of the aneurysm and its surrounding blood vessels is displayed on the display.
<Configuration 4>
The computer program according to configuration 3, characterized in that the computer is endowed with a function of displaying target image data on a display, automatically inputting designated point A coordinate, designated point B coordinate, target point C coordinate, and each of the above parameters that have been stored in a memory unit as past history, and then executing a process of moving the designated point A coordinate, designated point B coordinate, and target point C coordinate, and accepting changes to each of the above parameters.

Data that accurately indicates the boundary plane (aneurysm neck plane) for measurement between an intracerebral aneurysm and the parent blood vessel can be easily obtained, and the results can be used to measure the area of the aneurysm neck flat on the boundary plane, as well as the Feret's diameter, and to obtain objective indicators for fluid calculations.
Furthermore, the aneurysm neck plane can be identified by simple, uniform operations, resulting in excellent measurement stability and reproducibility. This allows for highly accurate comparative observation of changes over time in the affected area of the same patient. In addition, there is little variation even in measurements from different patients, making it possible to collect a wide range of data and make relative comparisons.

FIG. 1 is an explanatory diagram (part 1) of a specific processing procedure of a computer program according to the present invention. FIG. 2 is an explanatory diagram (part 2) of a specific processing procedure of the computer program of the present invention. FIG. 2 is a functional block diagram of a computer for executing the above processes. Example data showing aneurysm structure using the aneurysm neck plane. 13 is an example of a screen displayed on a display during the process of detecting the aneurysm neck plane.

According to the present invention, a doctor can obtain data showing the aneurysm neck plane by manipulating the image displayed on a computer display in the following procedure. The following is a detailed description of an embodiment of the present invention.

The specific processing procedure of the computer program according to the present invention will be described with reference to Figures 1 and 2. For the structure of the computer used, refer to Figure 3 as appropriate. In Figures 1 and 2, the processing procedure is illustrated step by step, with indications S1 to S9. Note that these processing procedures are only an example, and the order of some steps may be changed as long as no contradictions are caused.

(Step S1)
A three-dimensional image showing the boundary surface of the aneurysm 48 formed on the parent blood vessel 50 and the surrounding blood vessels is displayed on the display.

Medical CT images and MRI images are collections of voxels (pixels in a three-dimensional image) with a resolution of about 0.2 mm. The outer diameter of the blood vessel in which the cerebral aneurysm 48 is formed is about 2 to 4 mm. The following examples show the results of operations performed under these conditions.

First, in order to simplify the processing target, the pixel values of the voxels in the part representing the parent blood vessel 50 and the aneurysm 48 in the 3D image data taken by CT or MRI are binarized so that they are (1) and the pixel values of the voxels in the surrounding parts other than that are (0). For example, the half-value method or Otsu's method is used for this processing.

From this binary image of the aneurysm 48 and parent blood vessel 50, boundary surface image data is obtained, leaving only the voxels on the outer surfaces of the aneurysm 48 and parent blood vessel 50. For example, the MarchingCube method is used for this process. In this way, unnecessary data other than the binary image showing the contours of the aneurysm 48 and parent blood vessel 50 is deleted. After these preparatory processes, the obtained binary image is displayed on a computer display.

(Step S2-4) Two specified points A and B are input on the boundary surface on both sides of the location where the aneurysm 48 of the parent blood vessel 50 has formed. The computer determines the end points P1 and P2 of the center line of the parent blood vessel to be processed on the center line of the parent blood vessel that is closest to the specified points A and B.

The structure of the computer will now be described with reference to FIG. 3. This drawing shows a display 12 and a mouse 14 provided on the computer. An image display section 16 and an operation screen 18 are displayed on the display 12. The above-mentioned three-dimensional image 20 is displayed on the image display section 16. Operation buttons 22 for operating parameters, which will be described later, are displayed on the operation screen 18. The processing of step S1 above is automatically executed by the image processing section 32.

In Figure 1, designated points A and B are shown in the image marked (S1-S2). These designated points A and B are used to identify the upstream and downstream parts of the blood vessels that are causing the aneurysm 48 to grow among the complexly branching blood vessels around the aneurysm 48, and are designated at the doctor's discretion.

That is, the doctor looks at the boundary surface image displayed on the display 12 and specifies it using a pointer such as a mouse. The computer accepts this specification. Here, the end points P1 and P2 of the center line of the parent blood vessel 50 to be processed are determined from the specified points A and B. The end points P1 and P2 and the parent blood vessel 50 are shown in the diagram labeled (S4) in Figure 1.

For example, according to centerline generation using the DistanceMap method, the original centerline 60 of the parent blood vessel 50 and the original centerline 62 of the aneurysm 48 can be automatically obtained from a binary image showing the contour of the parent blood vessel 50 as shown in this figure. This process is executed by the axis detection module 34 and centerline generation module 36 of the computer's arithmetic processing unit 25 shown in Figure 3. The obtained data is stored in the computer's memory unit 24 as the endpoint P1 coordinates 51 and the endpoint P2 coordinates 52, as shown in Figure 3.

(Step S3) Receive the specification of a reference point C on the boundary surface of the aneurysm 48, which indicates the growth direction of the aneurysm 48.

Based on the characteristics of the shape of the aneurysm 48, the doctor determines and specifies the growth direction of the aneurysm 48. As shown in the diagram labeled (S3) in FIG. 1, the three-dimensional image 20 is rotated to confirm the direction of the aneurysm 48, and then a reference point C is specified with a pointer such as the mouse 14. The specified data is stored as the reference point C coordinates 54 shown in FIG. 3.

(Step S4-5) Between the above-mentioned end points P1 and P2, an original center line 60 of the parent blood vessel 50 and a branch point D where this original center line 60 intersects with an original center line 62 of the aneurysm 48 inside the aneurysm 48 are generated and drawn on the image display unit 16. Furthermore, a virtual aneurysm center line 68 connecting the above-mentioned reference point C, the original center line of the aneurysm, and the branch point D is generated and drawn on the image display unit 16.

To the left and right of the diagram labeled (S4), diagrams are placed showing the cross section of the parent blood vessel 50, the specified points A and B, and the positional relationship between the end points P1 and P2. These processes are executed by the center line generation module 36 and the branch point detection module 38 shown in FIG. 3. The branch point D coordinates 55 are stored in the memory unit 24.

As shown in the figure labeled (S4-5), the original centerline 60 of the parent blood vessel 50 is drawn into the inside of the aneurysm 48 and branches off from the original centerline 62 of the aneurysm 48 and other blood vessels. By connecting this branching point D, the original centerline 62 of the aneurysm, and the reference point C, a virtual aneurysm centerline 68 of the aneurysm 48 can be generated.

(Step S5) As described above, the original center line 60 of the parent blood vessel 50 is generated between the two end points P1 and P2 of the parent blood vessel 50. This original center line 60 is flattened to a state not affected by the aneurysm 48 or before the aneurysm occurs to generate a virtual parent blood vessel center line 64, which is then drawn on the image display unit 16.

As shown in the figure labeled (S4), the original center line 60 of the parent blood vessel 50 is influenced by the shape of the aneurysm 48 and is drawn to the location of the branching point D inside the aneurysm 48. Here, the shape of the parent blood vessel 50 not influenced by the aneurysm 48 or in the state before the aneurysm occurs is restored. To this end, the original center line 60 of the parent blood vessel is flattened, and a virtual parent blood vessel center line 64 is generated and displayed.

The flattening of the original center line 60 of the parent blood vessel is performed by the flattening module 40 shown in FIG. 3. For example, if the original center line 60 of the parent blood vessel is a collection of line segments connecting many voxels, the angle between adjacent line segments is reduced by a certain percentage. This makes it possible to flatten the entire original center line 60 of the parent blood vessel while leaving elements of large bends and twists in the original center line 60 of the parent blood vessel.

The operation screen 18 in Figure 3 displays boxes that display numerical values so that each of the three types of parameters can be specified numerically, along with buttons to increase or decrease the values. In either case, the numerical values can be increased or decreased by operating the mouse 14 or keyboard.

The degree of this flattening can be increased or decreased by the doctor operating the operation buttons 22 on the computer operation screen 18. A virtual mother vessel centerline 64 is also displayed in addition to the original centerline 60 of the mother vessel so that the degree of flattening can be visually confirmed. The result of the adjustment is stored in the memory unit 24 as a mother vessel centerline flattening parameter 26. By storing this parameter, the virtual mother vessel centerline 64 that the doctor judges to be optimal can be regenerated and drawn at any time.

(Step S6) Data is generated showing vascular cross sections perpendicular to the original center line 60 at both end points P1 and P2 of the parent blood vessel 50, and the cross sections are connected with a smooth tubular surface. This generates image data showing a virtual mother blood vessel 66 having a virtual mother blood vessel center line 64.

The cross sections of the blood vessels at both end points P1 and P2 are shown in (S4). The cross sections of the aneurysm 48 and parent blood vessel 50 are generally not circular due to the influence of the surrounding tissue. In other words, they have a variety of shapes. If the cross sections at the end points P1 and P2 are swept along the virtual center line 64, a virtual parent blood vessel 66 as shown in (S6) of Figure 2 can be generated. At this time, in order to simplify the cross section of the virtual parent blood vessel 66, it is also possible to approximate it with a circle or ellipse of the same area as the cross section.

For example, if the blood vessel cross-sectional shape of the original image is used, the torsion (twist) of the parent blood vessel 50 can be taken into account when sweeping. This makes it possible to generate a virtual parent blood vessel 66 having a flattened virtual parent blood vessel centerline 64 that takes the twist into account. As a result, it is possible to generate a virtual parent blood vessel 66 with a shape close to the state of the parent blood vessel 50 when the aneurysm 48 does not exist. This process is executed by the virtual parent blood vessel generation module 42 in FIG. 3.

(Step S7) In the process of successively flattening the original center line 60 of the parent blood vessel 50, the branch point D moves, so the original center line 62 of the aneurysm 48 is extended along the path of this movement. In the diagram of (S7), the extended portion is shown in bold. This extended portion may be approximated by a broken line that represents the movement position of point D, or may be simplified to a straight line.

By adjusting the parent vessel centerline flattening parameters and gradually flattening the original centerline 60 of the parent vessel 50, the branch point D gradually moves from its original position toward the outside of the aneurysm 48. Following this movement, the virtual aneurysm centerline 68 of the aneurysm 48 is extended.

The aneurysm 48 can be seen as having branched off from the location where branch point D5 was previously located on the original center line 60 of the flattened parent vessel. Therefore, the virtual aneurysm center line 68 is extended by connecting that location with the original branch point D.

Now, an original centerline 62 of the aneurysm 48 has been generated, extending from the reference point C, which indicates the growth direction of the aneurysm 48, to the flattened virtual parent vessel centerline 64.

(Step S8) The original center line 62 of the aneurysm 48 is flattened to generate data representing a virtual aneurysm cylinder 72 with a diameter equal to or smaller than the outer diameter of the parent blood vessel 50.

Normally, inside the aneurysm 48, the original centerline 62 of the aneurysm 48 is bent in a complex manner due to Blebs, microvessels, and the like. Therefore, the original centerline 62 is flattened using the same method as for the parent blood vessel 50. The degree of this flattening is increased or decreased by the doctor on the computer operation screen 18, as in the case of the parent blood vessel 50. The result is stored in the memory unit 24 as the aneurysm centerline flattening parameter 28.

As shown in (S8), a virtual aneurysm cylinder 72 having a virtual aneurysm centerline 68 of the aneurysm 48 thus obtained is generated. Since it is a blood vessel branching off from the parent blood vessel 50, it is natural that the virtual aneurysm cylinder 72 is equal to or smaller than the outer diameter of the parent blood vessel 50, but for convenience of calculation, it is set to a certain thickness. The outer diameter can be any value as long as it is large enough to allow the following processing.

Empirically, good results can be obtained, for example, by calculating the cross-sectional area of the virtual parent vessel 66 at the portion where the original center line 62 of the aneurysm branches off from the virtual parent vessel 66, and selecting a diameter that is approximately 1/4 to 1/2 of the diameter of a circle with the same area. These processes are performed by the flattening module 40 and virtual aneurysm cylinder generation module 44 in Figure 3.

(Step S9) Image data of the detection surface 74 constituting part of the virtual mother vessel 66 at the intersection of the virtual mother vessel 66 and the virtual aneurysm cylinder 72 is acquired. This is a collection of voxels each having position coordinates on a curved surface. By performing a three-dimensional principal component analysis of these position coordinates, data showing the aneurysm neck plane 76 is generated from the plane created by the first and second principal component axes. This process is performed by the neck plane calculation module 46 in Figure 3.

The intersection plane between the virtual parent blood vessel 66 and the virtual aneurysm cylinder 72 extending in the direction in which the aneurysm 48 grows should be the boundary plane between the parent blood vessel 50 and the aneurysm 48, but when this is superimposed on the image displayed on the image display unit 16, it may be found to be slightly tilted or misaligned. This is because both the parent blood vessel 50 and the aneurysm 48 have complex shapes that are curved, twisted, tilted, etc. For this reason, an image showing the position of the aneurysm neck plane 76 is displayed to request the doctor to adjust the position.

(Step S10) To optimize the data representing the aneurysm neck plane 76, the aneurysm neck plane 76 displayed on the display 12 is moved along the original centerline 62 of the aneurysm.

As a result of the above processing, the storage unit 24 stores the parent vessel centerline flattening parameter 26, the aneurysm centerline flattening parameter 28, the neck plane position adjustment parameter 30, the designated point A coordinate 56, the end point P1 coordinate 51, the designated point B coordinate 57, the end point P2 coordinate 52, the reference point C coordinate 54, and the branch point D coordinate 55, which are saved together with the corresponding image data.

When the position adjustment of the aneurysm neck plane 76 is completed, the result is stored in the memory unit 24 as the neck plane position adjustment parameter 30. Figure 4 shows an example of using the aneurysm neck plane 76 thus obtained to obtain data showing the structure of the aneurysm. A cross section of the aneurysm 48 that intersects with the aneurysm neck plane 76 can be obtained, and its Feret diameter can be obtained.

As an example, the aneurysm height can be obtained by drawing a line 80 perpendicular to the aneurysm neck plane 76. Furthermore, the semi-aneurysm height width can be obtained at a position halfway along the line 80. The volume and surface area of the aneurysm on the aneurysm neck plane 76 can be obtained.

In the above process, the computer automatically performs all operations except for the doctor's operation of specifying points A, B, and C, adjusting the degree of flattening of the virtual parent vessel center line 64 and the virtual aneurysm center line 68, and fine-tuning the position of the aneurysm neck plane 76. Once the parameters are set, they can be stored and used for follow-up observation. By slightly changing these values, a new aneurysm neck plane 76 can be obtained.

Because the work is patterned, for example, there is little variation in the results even if different doctors or analysts use the same 3D images to perform analysis. Almost identical results are obtained. In addition, when photographs of the same affected area are continuously observed, there is no variation in the analysis conditions, so changes in the aneurysm can be confirmed accurately and efficiently.

Finally, Figure 5 shows an example of a characteristic screen that appears on the display during the process of actually using this computer to generate a neck plane.

The narrower of the two blood vessels branching from the left to the right is set as the parent blood vessel, and end points P1 and P2 are defined. The original center line 60 of the parent blood vessel that was initially generated is significantly curved, but has been sufficiently flattened as shown in the virtual aneurysm center line 68. The virtual parent blood vessel 66 and virtual aneurysm cylinder 72 are generated and drawn as shown in the image. The aneurysm neck plane 76 is also displayed at their intersection.

The above program waits for the input of specified points, reference points, and parameters each time during the processing process, and then performs calculations. However, there are times when you may want to retrieve image data that has been processed in the past and reconfirm the processing process or results. For example, this can be used when requesting a second opinion.

As shown in FIG. 3, the target image data 58, the designated point A coordinate 56, the designated point B coordinate 57, the target point C coordinate 54, and the three types of parameters 26, 28, and 30 are stored together in history data 59. It is advisable to store this data in history data 59 in a state where it can be retrieved together.

When reproducing the above process, the computer automatically inputs the target image data 58 stored in the history data 59, the designated point A coordinate 56, the designated point B coordinate 57, the target point C coordinate 54, and the three types of parameters 26, 28, and 30, and executes the process of generating the neck plane.

For example, it would be good to display the processing process step by step and allow the positions of specified points A and B and reference point C, as well as the values of each parameter, to be changed midway through. This would make it possible to specifically verify the processing process.

When observing the same patient over time, the photographing conditions may differ slightly from the previous time, so after automatically inputting the saved history data, it becomes necessary to adjust the positions and parameters of the designated points, etc. Even so, since there are not many differences from the previous processing, adjustments are easy. Moreover, by processing while checking the differences, information that is useful for follow-up observation can be obtained.

In either case, the computer should be provided with a function to display target image data 58 on the display 12 shown in FIG. 3, automatically input designated point A coordinate 56, designated point B coordinate 57, reference point C coordinate 54, and three types of parameters 26, 28, and 30 that have been stored in the memory unit as past history, and then move designated point A coordinate 56, designated point B coordinate 57, and reference point C coordinate 54, and execute processing to accept changes to each of the above parameters.

Reference Signs List 12 Display 14 Mouse 16 Image display unit 18 Operation screen 20 Three-dimensional image 22 Operation button 24 Memory unit 25 Calculation processing unit 26 Parent vessel centerline flattening parameter 28 Aneurysm centerline flattening parameter 30 Neck plane position adjustment parameter 32 Image processing unit 34 Axis center detection module 36 Centerline generation module 38 Branch point detection module 40 Flattening module 42 Virtual parent vessel generation module 44 Virtual aneurysm cylinder generation module 46 Neck plane calculation module 48 Aneurysm 50 Parent vessel 51 End point P1 coordinate 52 End point P2 coordinate 54 Reference point C coordinate 55 Branch point D coordinate 56 Designated point A coordinate 57 Designated point B coordinate 58 Target image data 59 History data 60 Original centerline of parent vessel 62 Original centerline of aneurysm 64 Virtual parent vessel centerline 66 Virtual parent vessel 68 Virtual aneurysm centerline 72 Virtual aneurysm cylinder 74 Detection surface 76 Aneurysm neck plane A, B Designated point C Point D Branch point

Claims (5)

A computer program that causes a computer to execute a process for detecting an aneurysm neck plane of an aneurysm, the process comprising:
1. A three-dimensional image showing the boundary surface of the aneurysm formed on the parent blood vessel and the surrounding blood vessels is displayed on a display.
2. Two designated points are input on the boundary surface on both sides of the portion of the parent blood vessel where an aneurysm has been formed, and the end points of the original center line of the parent blood vessel to be processed are determined on the center line of the parent blood vessel that is closest to these designated points.
3. Accept the specification of a landmark on the boundary surface of the aneurysm that indicates the direction of aneurysm growth.
4. Draw the original centerline of the parent vessel between the above-mentioned end points and the branching point where this original centerline of the parent vessel intersects with the original centerline of the aneurysm inside the aneurysm, and draw a virtual aneurysm centerline connecting the above-mentioned reference point, the original centerline of the aneurysm, and the branching point.
5. A virtual centerline of the parent vessel is drawn by flattening the original centerline of the parent vessel drawn between both end points of the parent vessel to a state not affected by the aneurysm or before the occurrence of the aneurysm.
6. Data showing vascular cross sections perpendicular to the center line at both ends of the parent vessel are generated, and image data showing a virtual mother vessel having the above-mentioned virtual mother vessel center line, in which the cross sections are connected by a smooth tubular surface, is generated.
7. Since the above-mentioned branching points move during the process of successively flattening the original centerline of the parent blood vessel, the virtual aneurysm centerline of the aneurysm is extended along that path.
8. The virtual aneurysm centerline of the aneurysm is flattened to generate data representing a virtual aneurysm cylinder with a diameter equal to or less than the outer diameter of the parent vessel.
9. Data representing a plane of the aneurysm neck is generated from image data of an image constituting a part of the virtual mother vessel at the intersection of the virtual mother vessel and the virtual aneurysm cylinder. A method for detecting an aneurysm neck plane of an aneurysm, comprising: causing a computer to perform the following processes:
1. A three-dimensional image showing the boundary surface of the aneurysm formed on the parent blood vessel and the surrounding blood vessels is displayed on a display.
2. Two designated points are input on the boundary surface on both sides of the portion of the parent blood vessel where an aneurysm has been formed, and the end points of the original center line of the parent blood vessel to be processed are determined on the center line of the parent blood vessel that is closest to these designated points.
3. Accept the specification of a landmark on the boundary surface of the aneurysm that indicates the direction of aneurysm growth.
4. Draw the original centerline of the parent vessel between the above-mentioned end points and the branching point where this original centerline of the parent vessel intersects with the original centerline of the aneurysm inside the aneurysm, and draw a virtual aneurysm centerline connecting the above-mentioned reference point, the original centerline of the aneurysm, and the branching point.
5. A virtual centerline of the parent vessel is drawn by flattening the original centerline of the parent vessel drawn between both end points of the parent vessel to a state not affected by the aneurysm or before the occurrence of the aneurysm.
6. Data showing vascular cross sections perpendicular to the center line at both ends of the parent vessel are generated, and image data showing a virtual mother vessel having the above-mentioned virtual mother vessel center line, in which the cross sections are connected by a smooth tubular surface, is generated.
7. Since the above-mentioned branching points move during the process of successively flattening the original centerline of the parent blood vessel, the virtual aneurysm centerline of the aneurysm is extended along that path.
8. The virtual aneurysm centerline of the aneurysm is flattened to generate data representing a virtual aneurysm cylinder with a diameter equal to or less than the outer diameter of the parent vessel.
9. Data representing a plane of the aneurysm neck is generated from image data of an image constituting a part of the virtual mother vessel at the intersection of the virtual mother vessel and the virtual aneurysm cylinder.
10. In order to optimize the data showing the aneurysm neck plane, the aneurysm neck plane shown on the display is moved along the virtual aneurysm centerline. The computer program according to claim 1, characterized in that a parameter indicating the degree to which the original center line of the parent blood vessel is to be flattened, a parameter indicating the degree to which the original center line of the aneurysm is to be flattened, and a parameter indicating the amount of movement of the generated aneurysm neck plane along the virtual aneurysm center line of the aneurysm are provided, and an operation screen for increasing and decreasing these parameters is displayed on the display while three-dimensional image data of the aneurysm and the blood vessels surrounding it are displayed on the display. The method according to claim 2, characterized in that a parameter indicating the degree to which the original center line of the parent blood vessel is to be flattened, a parameter indicating the degree to which the original center line of the aneurysm is to be flattened, and a parameter indicating the amount of movement of the generated aneurysm neck plane along the virtual aneurysm center line of the aneurysm are provided, and an operation screen for increasing and decreasing these parameters is displayed on the display while three-dimensional image data of the aneurysm and the blood vessels surrounding it are displayed on the display. The computer program according to claim 3, characterized in that the computer is endowed with a function of displaying target image data on a display, automatically inputting designated point A coordinate, designated point B coordinate, reference point C coordinate, and each of the above parameters that have been stored in a memory unit as past history, and then executing a process of moving designated point A coordinate, designated point B coordinate, and reference point C coordinate, and accepting changes to each of the above parameters.

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