A pelvic registration method in a labor process navigation system

Abstract

The present invention provides a pelvic registration method in a labor process navigation system. By measuring the key points of the pelvis of the person to be measured and using a registration algorithm to achieve the registration of the pelvis of the person to be measured with a standard pelvic model, the required delivery parameters can be obtained, including automatically depicting the labor process diagram and dynamically displaying the fetal head-pelvis relationship, etc., so as to effectively support the decision-making of the labor process. This registration algorithm can register the pelvis of the person to be measured with the standard pelvic model even when there is a certain degree of mismatch between them, while ensuring the robustness of the registration and the accuracy of the estimation of key parameters, which is sufficient for clinical use.

Description

Technical Field

[0001] This application relates to a pelvic registration method in a labor navigation system. Background Art

[0002] A labor navigation system combines advanced B-ultrasound imaging technology with safe and reliable spatial positioning technology to accurately measure all delivery parameters such as cervical dilation, fetal head position and orientation, and pelvic dimensions, dynamically display the fetal head-pelvic relationship, automatically draw a labor graph, and effectively support the decision-making during labor.

[0003] A smaller pelvic volume, a too-large fetus, or both can cause an uneven fetal-pelvic ratio. Any contraction of the pelvic diameter that causes a smaller pelvic volume will result in dystocia during childbirth. The pelvic diameter contraction can be an inlet contraction, a mid-pelvis contraction, an outlet contraction, or a contraction caused by all three of them together. According to the American College of Obstetricians and Gynecologists (2003), approximately 60% of cesarean sections in the United States are due to being diagnosed with dystocia. During childbirth, the clinical pelvic measurement assessment of the bony birth canal is based on the examiner using finger measurement to judge the anteroposterior diameter of the pelvic inlet, the interspinous diameter of the mid-pelvis, and the intertubercular diameter of the pelvic outlet.

[0004] The process of monitoring childbirth intermittently assesses the fetal head position by calculating the pelvic inlet, fetal head position, and cervical dilation. It can also measure the size of the pelvic inlet and parameters that could only be measured by calipers in the past, such as the mother's cervical length and pelvic dimensions.

[0005] The labor navigation system mainly has two major functions:

[0006] 1. Accurate determination of fetal head position and orientation

[0007] By marking the pelvis (superior and inferior margins of the symphysis pubis) and fetal head feature points (BPD, orbits, etc.) on the ultrasound image, the labor navigation system can determine the spatial position and orientation of the fetal head relative to the pelvic inlet plane and the birth canal.

[0008] 2. Radiation-free internal and external pelvic measurements

[0009] Through the B-ultrasound image positioned by magnetic field or an independent B-ultrasound image, or by marking the feature points of the mother's pelvis with a "digital finger" (measurement sensor), the labor navigation system can measure the pubic arch angle and various pelvic diameters.

[0010] In an actual labor navigation system, it is necessary to register the pelvic measurement points of the person to be measured with the standard pelvic model data.

[0011] First, it is necessary to measure the key points of the pelvis or tissue of the person to be measured through space technology or B-ultrasound images. These key points are beneficial for the matching of the pelvic model. Secondly, after determining the key points of the pelvis or tissue of the person to be measured, it is necessary to find an effective technical means to register the key points with the key points on the standard pelvic model of women in this area. The registration needs to ensure the matching of the pelvis of the person to be measured and the standard pelvic model, and also have a certain degree of robustness: in the case of a certain degree of mismatch between the pelvis of the person to be measured and the standard pelvic model, the two can be registered while ensuring the robustness of the registration and the accuracy of the estimation of key parameters, which is sufficient for clinical use. The present invention provides a pelvic registration method in a labor navigation system to solve the registration problem between the pelvic measurement points of the person to be measured and the standard pelvic model data. [Summary of the Invention]

[0012] The present invention provides a pelvic registration method in a labor navigation system. By measuring the key points of the pelvis of the person to be measured and using a registration algorithm to realize the registration of the pelvis of the person to be measured and the standard pelvic model, the required delivery parameters can be obtained, including automatically depicting the labor graph and dynamically displaying the fetal head-pelvis relationship, etc., so as to effectively support the decision-making of the labor process.

[0013] A pelvic registration method in a labor navigation system is characterized by including the following steps:

[0014] Step 1: Establish a standard pelvic model based on the 3D measurement data of a large number of real pelves;

[0015] Step 2: Select a group of key position points on the standard pelvic model, denoted as M i , i = 0, 1,..., K,..., I - 1 (1);

[0016] Step 3: Use a labor monitor to perform three-dimensional measurement on the pelvis of the person to be measured, and measure the key position points on the pelvis of the person to be measured, denoted as R i , i = 0, 1,..., K,..., I - 1 (2);

[0017] Step 4: Use the coordinates of the key position points on the standard pelvic model and the pelvis of the person to be measured to register the standard pelvic model and the pelvis of the person to be measured, and obtain the registration relationship between the two;

[0018] Step 5: According to the registration relationship obtained in Step 4 and the position of the physiological parameters in the standard pelvic model, estimate the position of the physiological parameters of the pelvis of the person to be measured.

[0019] Among them, the registration in Step 4 specifically includes the following steps:

[0020] a. Respectively perform average value correction on the coordinates of the key position points on the standard pelvic model and the pelvis of the person to be measured, where:

[0021] The average points at key positions on the standard pelvic model are

[0022] The average points at key positions of the subject to be measured are

[0023] The corrected average model is M i (A) = M i - EM + ER, i = 0, 1, …, K, …, I - 1;

[0024] b. Perform standard deviation correction on the average points at key positions on the standard pelvic model and those of the subject to be measured:

[0025] The standard deviation of the standard pelvic model is

[0026] The standard deviation of the subject to be measured is

[0027] The corrected STD model is

[0028] c. Geometric matching. Rotate the corrected STD model with a rotation matrix, and the rotation matrix is obtained by the following formula:

[0029]

[0030] The rotated model is:

[0031] M i (C) = CC α,β,γ M i (B) i = 0, 1, …, K, …, I - 1 (9).

[0032] Preferably, the rotation matrix is obtained by the following formula:

[0033]

[0034] The rotated model is:

[0035] Among them, for the calculation of CC α,β,γ the following method is adopted:

[0036] Assume that the covariance matrix of each point after centering is:

[0037]

[0038] Construct matrix N. To achieve less computational effort in implementation, the covariance matrix C can be calculated cor to construct matrix N. Then matrix N can be constructed as follows:

[0039]

[0040] where Δ = [A 23 A 32 A 12 T , and tr represents the trace of the matrix. Among them, matrix A is represented as:

[0041] A = C cor - C cor T (12)

[0042] Use singular value decomposition or numerical methods to solve the eigenvectors q of matrix N, corresponding to the rotation matrix:

[0043]

[0044] In this way, the registration of the pelvis of the person to be measured and the pelvis of the standard model is achieved, while ensuring the robustness of the registration and the accuracy of the estimation of key parameters.

[0045] Preferably, the position of the physiological parameter is the birth axis.

[0046] Preferably, three-dimensional measurement is performed on the pelvis of the person to be measured by using the method of direct measurement by touch positioning or the method of indirect measurement by ultrasonic imaging technology.

[0047] This patent obtains the required delivery parameters by measuring the key points of the pelvis of the person to be measured and achieving registration with the standard pelvis model, including automatically depicting the partogram and dynamically displaying the fetal head-pelvis relationship, etc., thereby effectively supporting the decision-making of the labor process. [Description of the Drawings]

[0048] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0049] Figure 1 shows a standard pelvis model;

[0050] Figure 2 shows the stretched pelvis model;

[0051] Figure 3 shows the schematic diagram of the side and key planes of the pelvis;

[0052] Figure 4 shows the schematic diagram of the triangular description of the 3D pelvis model;

[0053] Figure 5 ​The registration result obtained by using this method is shown, where '+' represents the measurement points and '*' represents the calculated points after matching. [Specific Embodiment]

[0054] The labor process navigation system is a product for digitizing the delivery of pregnant women, and is used to quantitatively evaluate the status of pregnant women and fetuses in the uterus. The pelvic registration method in the embodiments of the present invention is as follows:

[0055] The basic idea is as follows: For Figure 1 the standard pelvic model, by measuring some parameters of the pelvic bone of the person to be measured and registering them with the standard pelvic model, and then performing matching according to certain registration principles, the registration of the two pelvic bones can be achieved. After registration, the position of the physiological parameters of the person to be measured can be estimated through the position of the physiological parameters in the standard model. For example, the theoretical parturition axis, etc.

[0056] Among them, the standard pelvic model is modeled based on 3D measurement data of a large number of real pelvic bones, as Figure 2 shown.

[0057] Key points in the pelvic model:

[0058] Select a set of key points on the standard pelvic model. Each point is represented by a three-dimensional vector (x, y, z). These key points are used to transform a pelvic module into the pelvic model of the person to be measured. A set of key points on the pelvic bone is represented as:

[0059] M i , i = 0, 1,..., K,..., I - 1 (1) Key points of the pelvic bone of the person to be measured:

[0060] Perform three-dimensional measurement on the pelvic bone of the person to be measured through a delivery monitor. These key points of the pelvic bone of the person to be measured correspond to the key points of the standard pelvic model. The measurement process includes direct touch positioning or other indirect methods (imaging techniques such as ultrasound). The key points of the pelvic bone of the person to be measured are represented as:

[0061] R i , i = 0, 1,..., K,..., I - 1 (2)

[0062] Use the key points in the standard pelvic model and the key points of the pelvic bone of the person to be measured to perform pelvic matching between the two according to the following method. Thus, the position of the physiological parameters of the pelvic bone of the person to be measured can be estimated based on the registration relationship and the position of the physiological parameters in the standard pelvic model.

[0063] Step 1 - Decentralization:

[0064] Perform average value correction on the coordinate values of the key position points on the standard pelvic model and the pelvic bone of the person to be measured respectively, where:

[0065] The average points at key positions on the standard pelvic model are

[0066] The average points at key positions of the subject to be measured are

[0067] The corrected average model is M i (A) = M i - EM + ER, i = 0, 1, ..., K, ..., I - 1;

[0068] Step 2 - Standard Deviation Correction

[0069] Perform standard deviation correction on the average points at key positions on the standard pelvic model and the subject to be measured:

[0070] The standard deviation of the standard pelvic model is

[0071] The standard deviation of the subject to be measured is

[0072] The corrected STD model is

[0073] Step 3 - Geometric Matching

[0074] For the measurement closest to real life, the next stage involves rotating the corrected STD model with a rotation matrix, and the rotation matrix is obtained by calculating the following formula:

[0075]

[0076] The rotated model is:

[0077] M i (C) = CC α,β,γ M i (B) i = 0, 1, ..., K, ..., I - 1 (9)

[0078] Among them, for the calculation of CC α,β,γ the following method is adopted:

[0079] Assume that the covariance matrix of each point after centering is:

[0080]

[0081] Construct matrix N. To achieve a smaller computational amount, matrix N can be constructed by calculating the covariance matrix C cor Then matrix N can be constructed as follows:

[0082]

[0083] where Δ = [A 23 A 32 A 12 T , and tr represents the trace of the matrix. The matrix A is represented as:

[0084] A = C cor -C cor T (12)

[0085] Use singular value decomposition or numerical methods to solve for the eigenvector q of matrix N, corresponding to the rotation matrix:

[0086]

[0087] In this way, the registration of the pelvis of the subject to be measured and the pelvis of the standard model is achieved.

[0088] The specific actual operation is as follows, as Figure 5 shown. The black cross in the figure represents the pelvis model parameters, and the circular markers are the vital parameters measured directly or indirectly. Through the registration of these points, the physiological curve marked by the cross in the middle is calculated for actual labor process assessment.​

Claims

1. A pelvic registration method in a labor process navigation system, characterized in that: It includes the following steps: Step 1: Establish a standard pelvic model based on a large amount of 3D measurement data of real pelves; Step 2: Select a set of key position points on the standard pelvic model, denoted as M i , where i = 0, 1, ..., K, ..., I - 1; Step 3: Use a parturition monitor to perform three-dimensional measurement on the pelvis of the person to be measured, and measure the key position points on the pelvis of the person to be measured, denoted as R i , i = 0, 1,..., k,..., I - 1; Step 4: Use the coordinates of the key position points on the standard pelvic model and the pelvis of the person to be measured to register the standard pelvic model and the pelvis of the person to be measured, and obtain the registration relationship between the two; Step 5: Estimate the positions of the physiological parameters of the pelvis of the person to be measured according to the registration relationship obtained in Step 4 and the positions of the physiological parameters in the standard pelvic model; Among them, the registration in Step 4 specifically includes the following steps: a. Respectively perform mean value correction on the coordinates of the key position points on the standard pelvic model and the pelvis of the person to be measured, where: The average points at key positions on the standard pelvic model are The average point of the key positions of the subject to be measured is The corrected average model is M i (A) = M i -EM + ER, i = 0, 1, ..., K, ..., I - 1; b. Perform standard deviation correction on the key position average points on the standard pelvic model and the person to be measured; The standard deviation of the standard pelvic model is The standard deviation of the subject is Calibrate the STD model to c. Geometric matching, rotating the calibrated STD model with a rotation matrix CC α,β,γ Obtained by calculating according to the following formula: The rotated model is: M i (C) = CC α,β,γ ·M i (B) i = 0, 1, ..., K, ..., I - 1 (9).

2. The pelvic registration method according to claim 1, wherein for the calculation of CC α,β,γ the following method is adopted: Assume that the covariance matrix of each point after centering is: Construct matrix N. To achieve less computational effort in implementation, matrix N can be constructed by calculating the covariance matrix C cor to construct matrix N, then matrix N can be constructed as follows: where Δ = [A 23 A 32 A 12 T , tr represents the trace of the matrix, where the matrix A is represented as:​ A = C cor -C cor T (12) Use singular value decomposition or numerical methods to solve the eigenvector q of matrix N, corresponding to the rotation matrix: In this way, the registration of the pelvis of the person to be measured and the standard model pelvis is achieved.

3. The pelvic registration method according to claim 1, wherein the position of the physiological parameter is the birth axis.

4. The pelvic registration method according to claim 1, wherein three-dimensional measurement is performed on the pelvis of the person to be measured by using a direct measurement method of touch positioning or an indirect measurement method of ultrasonic imaging technology.

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