Method for quickly calculating virtual acetabulum center

Abstract

The invention relates to a method for quickly calculating the center of a virtual acetabulum. The method for quickly calculating the virtual acetabulum center can be applied to a medical image registration step of hip replacement, and further can be applied to a computer-assisted bone surgery, specifically, a preoperative scanning image of a patient is obtained before the surgery; recognizing the instrument position through a camera to obtain the coordinate position of the real feature point; the method comprises the following steps: simulating free fall of a small ball to obtain virtual coordinates of a ball center when an instrument is in contact with an acetabulum, and taking the virtual coordinates as coordinate positions of virtual feature points; registration can be completed and an operation can be carried out with the assistance of other feature points. The method for quickly calculating the center of the virtual acetabulum, provided by the invention, has an optimization step, and is short in calculation time and high in precision.

Description

Technical Field

[0001] The invention relates to the technical field of medical image registration, in particular to a method for quickly calculating a virtual acetabulum center. Background Art

[0002] In the field of medical image processing and bone and joint disease treatment, accurate calculation of the acetabulum center is crucial. The acetabulum is part of the human hip joint and is essential for normal movement function and life activities. Knowing the patient's acetabulum center position is important for surgical planning, disease diagnosis and treatment monitoring.

[0003] Traditional methods of calculating the center of the acetabulum typically rely on medical imaging, such as X-rays, CT scans, or MRIs. These images provide valuable anatomical information, but often require complex image analysis techniques and time-consuming processes to determine the center of the acetabulum. This can increase patient wait times, increase surgical risks, and place an additional burden on medical equipment and resources. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method for quickly calculating the center of the virtual acetabulum, which does not require frequent imaging examinations, nor does it require fitting the acetabulum surface to simulate the calculation center. The calculation complexity is low, the calculation time is short, and the accuracy is high. It provides accurate feature points for registration in hip replacement, which can not only be used for registration in hip replacement, but also provide doctors with faster and more efficient anatomical information, and provide key support for the treatment and surgical planning of bone and joint diseases. It can also be applied to the retrieval of similar spherical area centers.

[0005] To achieve the above object, the present invention adopts the following technical solution: a method for quickly calculating the virtual acetabulum center, comprising the following steps: Step 1: Take the preoperative scanned acetabulum image as input; Step 2: Convert the preoperative acetabulum scan image into a three-dimensional point set P; Step 3: Using the incident vector as the z-axis of the virtual coordinate system, the acetabulum (2) is oriented upward; Step 4: Calculate the centroid m of the virtual point set P on the surface of the acetabulum (2) and rise to a set height h; Step 5: Take the centroid m' of the ascending point set as the center to generate the sampling point set Q; Step 6: Set each point q in the sampling point set as the center of the simulated falling ball, and find the lowest landing point k and the corresponding ball center o; Step 7: Iteratively optimize the sampling point q, and calculate the lowest landing point k and the corresponding sphere center o; the sphere center o corresponding to the lowest landing point is the center point of the virtual acetabulum.

[0006] In a preferred embodiment, the method for generating sampling points generates a sampling point set Q according to the input grid spacing step and grid number num.

[0007] In a preferred embodiment, the method for calculating the lowest point is Based on kd-tree search implementation; calculate the falling distance L between the sampling point q and the contact point p on the acetabulum (2) surface; find the point with the smallest falling distance L and record it as the lowest falling point k, and calculate the corresponding ball center o.

[0008] In a preferred embodiment, the distance between the lowest falling point k and the center o of the acetabulum (2) is calculated as the radius r of the screening circle; the falling distance L between the sampling point q and the contact point p on the surface of the acetabulum (2) is calculated; Calculate whether the sampling point q is within the radius r of the screening circle; if not, generate a new sampling point q' from the point outside the screening circle.

[0009] Compared with the prior art, the present invention has the following beneficial effects: The present invention relates to a method for quickly calculating the virtual acetabulum center. Traditional acetabulum center calculation methods are usually based on image processing technology, but due to the complexity of the image and the existence of a variety of possible interference factors, these methods often have low calculation accuracy, long operation time, and strong dependence on the doctor's subjective judgment. The purpose of the present invention is to provide a fast, accurate and automated acetabulum center calculation method. The method simulates the fall of a small ball in a virtual space to find the lowest landing point, and calculates the acetabulum center point based on the lowest landing point. It does not need to simulate the surface equation of the acetabulum surface, simplifies the calculation process and improves the calculation accuracy. The acetabulum center fast calculation method of the present invention can be widely used in the fields of diagnosis of hip joint diseases, surgical navigation and efficacy evaluation, etc., providing doctors with a more accurate and efficient acetabulum center calculation method, saving doctors' time and energy, and greatly improving doctors' surgical efficiency. At the same time, it also provides a feasible and accurate technical solution for the retrieval of similar spherical area centers. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Attached Figure 1 is a flow chart of a method for quickly calculating a virtual acetabulum center provided by an embodiment of the present invention; Attached Figure 2 It is a flow chart of finding the lowest point of the calculation method for quickly calculating the virtual acetabulum center provided by an embodiment of the present invention; Attached Figure 3 It is a flow chart of optimizing sampling points of a calculation method for quickly calculating a virtual acetabulum center provided by an embodiment of the present invention; Attached Figure 4 is a schematic diagram of generating sampling points provided by an embodiment of the present invention; Attached Figure 5 FIG. 4 is a schematic diagram of an embodiment of the present invention showing an instrument in contact with a spherical surface of a patient's acetabulum. DETAILED DESCRIPTION

[0011] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0012] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0013] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations.

[0014] Traditional methods for calculating the center of the acetabulum in virtual space are mostly based on medical imaging, such as X-rays, CT scans or MRI. These images provide valuable anatomical information, but usually require complex image analysis techniques and time-consuming processes to determine the center of the acetabulum, such as image processing or fitting the surface equation of the acetabulum surface point set. It is highly dependent on the doctor's subjective judgment, the calculation process is complex, and the accuracy cannot be guaranteed.

[0015] The present invention proposes a method for quickly calculating the virtual acetabulum center. Figure 1 As shown, the following steps are included: The patient's acetabulum image scanned before surgery is converted into a three-dimensional point set P; The incident angle of the instrument is taken as the incident vector 1 and the z axis of the virtual coordinate system. The coordinate system in the virtual space is transformed by rotation, and the acetabulum 2 in the virtual space is oriented upward. Calculate the centroid m of the virtual point set P on the surface of the acetabulum 2; Raise the center of mass m to a height h; Take the centroid m' of the ascending point set as the center, and step as the grid spacing to construct a sampling point set Q with a grid number of num; Simulate the sampling point q as a small ball, assume that the small ball falls, and calculate the lowest point k that contacts the acetabulum surface point p and the corresponding center o of the ball at the time of contact; Iterate multiple times, optimize the sampling points, and repeat the above steps until there is no new lowest point k.

[0016] The ball center o corresponding to the lowest landing point is the center point of the virtual acetabulum.

[0017] The method for determining the lowest landing point k in the method for quickly calculating the virtual acetabulum center is as follows: Figure 2 As shown, the steps are as follows: According to the generated sampling point set Q, the kd-tree method is used to generate the columnar point cloud coverage area; Calculate the distance L between all points in the covered area and the acetabulum surface point set p; The point with the smallest distance L is the lowest landing point.

[0018] The method for optimizing sampling points in the method for quickly calculating the virtual acetabulum center is as follows: Figure 3 As shown, the steps are as follows: Calculate the distance between the lowest landing point k and the center o of the acetabulum 2 as the radius r of the screening circle; Calculate the falling distance L between the sampling point q and the contact point p on the surface of the acetabulum 2; Calculate whether the sampling point q is within the radius r of the screening circle; If not, the points outside the screening circle will be generated as new sampling points q'.

[0019] Example: A method for quickly calculating the virtual acetabulum center, such as Figures 1 to 3 As shown, the following steps are included: Obtain images of the acetabulum from the patient's preoperative scans; The preoperative scanned acetabulum image is converted into a virtual point set P; According to the incident angle of the instrument, set the incident vector 1; Rotate the z-axis of the virtual coordinate system to be parallel to the incident vector 1, with the acetabulum facing upward; Calculate the centroid m of the virtual point set P; Raise the mass center m to a height h, where h = 2.5 * the radius of the instrument ball head; Take the centroid m' after the rise as the center of the grid, set the step size step=8, the number of grids num=4, generate the grid, take the intersection of the grids as the center of the ball, simulate the ball falling, and find the virtual coordinates of the center of the ball when it touches the ground; Set the number of iterations to 10, the error to 10-5, and set a new step size step = step / 2 for each iteration; The center of the ball calculated in the previous iteration is used as the new grid center until the number of iterations is completed or the error requirement is met; The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. All technical solutions belonging to the principle of the present invention belong to the protection scope of the present invention. For those skilled in the art, several improvements made without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for quickly calculating a virtual acetabulum center, characterized in that: The following steps are involved: Step 1: Take the preoperative scanned acetabulum image as input; Step 2: Convert the preoperative acetabulum scan image into a three-dimensional point set P; Step 3: Using the incident vector as the z-axis of the virtual coordinate system, the acetabulum (2) is oriented upward; Step 4: Calculate the centroid m of the virtual point set P on the surface of the acetabulum (2) and rise to a set height h; Step 5: Take the centroid m' of the ascending point set as the center to generate the sampling point set Q; Step 6: Set each point q in the sampling point set as the center of the simulated falling ball, and find the lowest landing point k and the corresponding ball center o; Step 7: Iteratively optimize the sampling point q, and calculate the lowest landing point k and the corresponding sphere center o; the sphere center o corresponding to the lowest landing point is the center point of the virtual acetabulum.

2. A method for quickly calculating a virtual acetabulum center according to claim 1, characterized in that: The sampling point generation method generates a sampling point set Q according to the input grid spacing step and grid number num.

3. A method for quickly calculating a virtual acetabulum center according to claim 1, characterized in that: Method for calculating the lowest point Based on kd-tree search implementation; calculate the falling distance L between the sampling point q and the contact point p on the acetabulum (2) surface; find the point with the smallest falling distance L and record it as the lowest falling point k, and calculate the corresponding ball center o.

4. The method for quickly calculating the virtual acetabulum center according to claim 1, characterized in that: Calculate the distance between the lowest falling point k and the center o of the acetabulum (2) as the radius r of the screening circle; calculate the falling distance L between the sampling point q and the contact point p on the surface of the acetabulum (2); Calculate whether the sampling point q is within the radius r of the screening circle; If not, the points outside the screening circle will be generated as new sampling points q'.

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