Refined reconstruction modeling and mechanical analysis method of the female pelvic floor system in the sagittal plane
Through the refined reconstruction modeling and mechanical analysis method of female pelvic floor system under the sagittal plane, the problem of lack of understanding of the morphological characteristics and biomechanical characteristics of the pelvic floor system in the prior art is solved, and more accurate analysis and treatment plans for pelvic floor stress dysfunction diseases are achieved.
Patent Information
- Application Number
- CN202111488338.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-12-08
- Publication Date
- 2025-03-25
- Estimated Expiration
- 2041-12-08
AI Technical Summary
The prior art is difficult to effectively analyze and solve the pelvic floor stress dysfunction diseases in women, especially due to the lack of understanding of the morphological characteristics and biomechanical characteristics of the pelvic floor system, resulting in poor treatment effect.
A refined reconstruction modeling and mechanical analysis method for female pelvic floor system under sagittal plane is proposed. Using nuclear magnetic resonance scanning and computer-aided design software, an accurate two-dimensional geometric model and finite element model is established, and the biomechanical characteristics of the pelvic floor system are analyzed through finite element simulation.
It has achieved a more accurate assessment and mechanical analysis of the female pelvic floor system, revealing the mechanical change mechanism of pelvic floor stress injury disease, providing a more scientific and accurate treatment plan, and has important clinical guiding significance.
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Figure CN114121290B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of female pelvic floor stress dysfunction analysis and research, mainly to the study of the mechanical action laws and injury mechanisms of the female pelvic floor system, and specifically to a refined reconstruction modeling and mechanical analysis method of the female pelvic floor system under the sagittal plane. Background Art
[0002] The incidence of female pelvic floor uterine prolapse combined with anterior or posterior vaginal wall prolapse is high. It is a common disease among multiparous women of all ages. The prevalence of POP is as high as 37%, which seriously affects the physical and mental health and quality of life of middle-aged and elderly women.
[0003] Pelvic floor stress dysfunction (urinary incontinence, pelvic organ prolapse, etc.) (PFSD) has the characteristics of high incidence, poor efficacy, and many controversial issues. The reason may be that there is a lack of understanding of the complex soft tissue shape and position characteristics and biomechanical properties of the pelvic floor system. Therefore, it is difficult to adopt scientific and accurate research methods and propose more targeted solutions. It is worth noting that the current surgical treatment methods are generally statistical clinical data, and rarely pay attention to the biomechanical principles and characteristics of the pelvic floor organs. There are also few reports on biomechanical surgical methods. Therefore, from the perspective of pelvic floor biomechanics, combined with physiology, pathology, and the relationship between disease and symptoms, analysis and research have important practical clinical significance.
[0004] Due to the soft tissue characteristics of the pelvic floor organs, especially the functional differences between static and dynamic, the biostress study of the pelvic floor system is extremely difficult. The finite element analysis method, which was first applied to engineering mechanics and bone and joint mechanics, has brought a ray of hope for the accurate biomechanical judgment of PFD. At present, most domestic experts and scholars focus on the three-dimensional digital reconstruction model of the organs, ligaments, pelvic floor muscles, etc. of the pelvic floor system based on MRI and its related parameter measurement and clinical case statistics, which are mainly used for digital demonstration, learning, training, and auxiliary diagnosis and treatment. A small number of literatures reconstruct three-dimensional models and finite element models of the organs, ligaments, pelvic floor muscles, etc. of the pelvic floor system based on MRI technology. These pelvic floor models are mostly rough expressions of some organs and tissues of the pelvic floor system, with incomplete structures and low accuracy. They lack a detailed description of the morphological position characteristics and biomechanical characteristics of the pelvic floor organs, which has a great impact on the mechanical results. In-depth analysis and evaluation of the overall mechanical balance principle, stress injury mechanism, and organ biomechanical effects of the pelvic floor system have not yet been conducted. Summary of the invention
[0005] This invention proposes a refined reconstruction modeling and mechanical analysis method of the female pelvic floor system under the sagittal plane in order to analyze and evaluate the overall mechanical balance principle, stress injury mechanism and organ biomechanical effects of the pelvic floor system, to more accurately evaluate POP and explore its occurrence mechanism before surgery, and to further guide the design of full pelvic floor stress repair and reconstruction surgery and optimize clinical treatment plans. This method can be used to explore the biological stress characteristics of the normal female pelvic floor, in order to reveal the mechanical change mechanism of pelvic floor stress injury diseases, and has important guiding significance for studying human pelvic floor diseases and proposing corresponding solutions.
[0006] This method is suitable for the reconstruction of sagittal two-dimensional geometric models and biomechanical analysis of the female pelvic floor system at different age stages, with different pelvic floor dysfunction diseases (healthy pelvic floor or pelvic organ prolapse (POP) and different types of women. It can be used to develop efficient mechanical analysis systems and intelligent auxiliary diagnosis systems for the pelvic floor system, and calculate the biomechanical characteristics of the pelvic floor organs such as mutual support, stress distribution, shape and position deformation characteristics, and the relationship between the sacral curvature and the mechanical axis under different abdominal pressure loads. It has low cost and high accuracy, and has important guiding significance for studying female pelvic floor diseases and proposing corresponding solutions.
[0007] The technical solution adopted by the present invention is: a refined reconstruction modeling and mechanical analysis method of the female pelvic floor system under the sagittal plane, the steps are as follows:
[0008] Step 1: Volunteers signed an informed consent form before the examination, and a mid-sagittal scan was performed on the female pelvic floor system of different age groups, different pelvic floor dysfunction diseases (healthy pelvic floor or pelvic organ prolapse (POP) etc.) and different types using a magnetic resonance imaging scanner to obtain mid-sagittal MRI images of the female pelvic floor system.
[0009] Step 2: Use Mimics software to open the midsagittal pelvic floor image, determine the shape, size, positional relationship and contour of the pelvic floor organs under the midsagittal plane, and measure the coordinate values of the key discrete feature data points marking the inner and outer contours of each pelvic floor organ.
[0010] Step 3: Use CAD computer-aided design software (such as Unigraphics, etc.) to read the coordinate values of the key discrete feature data points of the inner and outer contours of the pelvic floor organs, use accurate curve fitting methods to perform non-equidistant interpolation and approximation drawing on the key discrete feature data points of the inner and outer contours of the organs, and establish an accurate two-dimensional contour curve and solid geometric reconstruction model of the pelvic floor system in the sagittal plane ( Figure 3 ).
[0011] Step 4: According to Hooke's law and the principle of mechanical equilibrium, the mechanical projection and mechanical synthesis methods are used to obtain the mechanical projection relationship between the organs and ligaments of the pelvic floor system. The equivalent stiffness mechanical parameters of the ligaments and fascia of the female pelvic floor system under the sagittal plane are calculated respectively, and a set number of approximately parallel and uniformly distributed spring units are used to simulate the equivalent mechanical effects of each ligament, and the equivalent mechanical model of the pelvic floor system projected under the sagittal plane is obtained ( Figure 4 ).
[0012] Step 5: Based on the solid geometry reconstruction model of the female pelvic floor system obtained in the above step 3 and the simulation analysis method of the effective mechanical action in step 4, the method of the present invention uses finite element simulation software (such as ANSYS, etc.) to establish an accurate two-dimensional finite element model of the female pelvic floor system under the sagittal plane, and analyzes the biomechanical properties of the female pelvic floor system under the sagittal plane through finite element simulation.
[0013] Specifically, the specific method operation steps according to step 3 are:
[0014] 3.1) Using CAD computer-aided design software (such as Unigraphics, etc.), read the coordinate values of the key discrete feature data points of the inner and outer contours of each pelvic floor organ, and select a set number of key discrete feature data points of the inner and outer contours of each pelvic floor organ to describe the key shape and position features of the inner and outer contours of each organ under the sagittal plane.
[0015] 3.2) Using the cubic B-spline curve approximate fitting method, a cubic B-spline curve can be determined by fitting the selected four adjacent key discrete feature data points.
[0016] 3.3) By recursion, we can obtain cubic B-spline curves of multiple key discrete feature data points, thereby achieving accurate segmented fitting of the internal and external contours of the organ. The drawn segments of the curves are naturally connected, with C 2 Second order continuous ( Figure 2 ). The specific process is as follows:
[0017] Assume that the outer contour of a selected organ consists of n plane key discrete feature data points, denoted as P i ,i=1,2,.........n.
[0018] Draw the first cubic B-spline curve using P1, P2, P3, and P4;
[0019] Draw the second cubic B-spline curve using P2, P3, P4, and P5;
[0020]
[0021] P n-3 , P n-2 , P n-1 , Pn Draw the n-3th cubic B-spline curve.
[0022] 3.4) Perform non-equidistant interpolation calculation and approximation drawing on the fitting curve of the inner and outer contours of the organ. That is, according to the morphology and position characteristics of the organ, increase the number of interpolation points for the fitting curve with large curvature changes to ensure the natural connection and C of the interpolation curve. 1 First-order continuity, the precise contour curves of the pelvic floor organs obtained by fitting.
[0023] 3.5) Using CAD computer-aided design software (such as Unigraphics, etc.), reconstruct the sagittal solid geometric model of each organ through the precise contour curves of each pelvic organ ( Figure 3 ).
[0024] Specifically, the specific method operation steps of step 4 are:
[0025] 4.1) The three-dimensional mechanical effects of the suspensory ligaments and fascia in the pelvic floor system are projected onto the median sagittal plane to calculate the combined mechanical effects of the suspensory ligaments on the median sagittal plane.
[0026] 4.2) According to Hooke's law and the principle of mechanical equilibrium, the formula: F = -2 × K × cos (α / 2) × d is used to calculate the mechanical projection composite force of each suspension ligament in the pelvic floor system under the median sagittal plane. (F is the combined tensile load on the ligament (N); the negative sign indicates that the elastic force generated by the spring is opposite to its elongation direction; K is the stiffness of each ligament (N / mm); α is twice the projection angle between a single ligament and the median sagittal plane (°); d is the elastic deformation or tensile displacement (mm)).
[0027] 4.3) The size ratio coefficient ξ is introduced to describe the size effect of each organ in the width direction, using the formula K mw =m×ξ to obtain the proportional coefficient of the spring unit stiffness parameter (K mw ), size ratio coefficient ξ=L W ×L eq , where L W and L eq are the equivalent width and average width of each pelvic organ, respectively, and m is the number of approximately parallel and uniformly distributed spring units of the equivalent action of each ligament and fascia). Therefore, under the midsagittal plane, the equivalent mechanical action of each ligament and fascia of the pelvic floor system can be expressed by F E =F / K mw Indicates (F E is the equivalent effect of each ligament and fascia).
[0028] 4.4) From the above equations, we can get the equivalent stiffness of the spring unit of each ligament (K E ) parameter formula is:
[0029] K E =2×K×cos(α / 2) / K mw
[0030] Specifically, the specific method operation steps of step 5 are:
[0031] 5.1) Import the solid geometry reconstruction model of the subsagittal pelvic floor system described in step 3 into finite element simulation software (such as ANSYS, etc.).
[0032] 5.2) Use solid units (such as ANSYS / Solid185 units, etc.) to perform hexahedral mesh sweeping on the organs in the pelvic floor system. According to the mechanical projection relationship between the organs and ligaments of the pelvic floor system described in step 4, use a set number of approximately parallel and uniformly distributed spring damping units (such as ANSYS / Combination14 or ANSYS / Combination39 spring damping units, etc.) to establish the equivalent connection mechanical action between the organs and the ligaments and fascia under the sagittal plane ( Figure 5 ).
[0033] 5.3) According to the shape, size, positional relationship and contour of the pelvic floor organs under the midsagittal plane described in step 2, the surface contact method is used to set contact units (such as ANSYS / Contact174) and target units (such as ANSYS / Target170) to simulate the external surface contact support between the outer wall of the cervix and the anterior and posterior fornix of the vagina, between the outer surface of the posterior wall of the vagina and the perineal body and rectum, between the perineal body and rectum, and between the rectum and the levator ani muscles in the pelvic floor system, and the internal surface contact support of organs such as the uterus, cervix, vagina, and urethra bladder.
[0034] 5.4) Constraint definition: Fixed constraints on the pubic and sacral coccyx, added bottom constraints on the vagina, perineal body, rectum and levator ani muscles.
[0035] 5.5) Load definition: Add positive pressure perpendicular to the surface of the organs to the upper wall of the uterus and the anterior wall of the vagina to simulate the Valsalva abdominal pressure load, and add the vertical downward load of the organ's own weight.
[0036] 5.6) Set the linear elastic, hyperelastic or viscoelastic material properties, material density and Poisson's ratio of the uterus, vagina, perineal body, rectum and levator ani muscles; set the linear or nonlinear stiffness parameters of the ligament tissues such as the main ligament, uterosacral ligament, round ligament and paravaginal support, calculate the equivalent stiffness mechanical parameters of each ligament and fascia of the female pelvic floor system in the sagittal plane according to step 4, use a set number of approximately parallel and uniformly distributed spring units to simulate the equivalent mechanical action of each ligament, and set the equivalent stiffness mechanical parameters to the stiffness value of the spring damping unit.
[0037] 5.7) Use the solver of finite element simulation analysis software (such as ANSYS, etc.) to calculate and analyze the biomechanical equilibrium state and change law of the female pelvic floor system.
[0038] The beneficial effects of the present invention are:
[0039] (1) The method of the present invention takes the organs and ligament fascia tissues of the female pelvic floor system as the research objects, obtains two-dimensional images of the organs in the female pelvic floor system based on magnetic resonance imaging technology (MRI), and uses computer-aided design (CAD) and curve fitting methods to accurately reconstruct the contour curves and geometric models of the organs in the female pelvic floor structure system under the sagittal plane. The shape and position characteristics of the organs under the sagittal plane and the two-dimensional reconstructed geometric model obtained by the method of the present invention are more accurate than the three-dimensional model reconstructed by the traditional method.
[0040] (2) The equivalent mechanical calculation formulas for the ligamentous fascia tissues such as the cardinal ligament and sacral ligament in the sagittal plane are given. The two-dimensional finite element model of the pelvic floor system in the sagittal plane is established. The accurate equivalent stiffness mechanical formula is used to describe the suspension effect of each ligamentous fascia tissue, which provides an effective and convenient processing method and greatly shortens the calculation time.
[0041] (3) This method is applicable to the reconstruction and biomechanical analysis of the sagittal two-dimensional geometric model of women of different ages and different degrees of pelvic floor dysfunction (healthy pelvic floor or pelvic organ prolapse (POP)). It is universal and extensive. It can be used to develop an efficient mechanical analysis system and intelligent auxiliary diagnosis system for the pelvic floor system, and calculate the biomechanical characteristics of the female pelvic floor system under different negative pressure loads. It is low-cost and high-precision, and has important guiding significance for studying female pelvic floor diseases and proposing corresponding solutions. BRIEF DESCRIPTION OF THE DRAWINGS
[0042] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present application, but do not constitute an improper limitation of the present invention. In the drawings:
[0043] Figure 1 It is a flow chart of the implementation of the present invention;
[0044] Figure 2 It is a curve fitting model for different types of pelvic floor systems based on key feature points;
[0045] Figure 3 It is a refined reconstructed geometric model of different types of pelvic floor systems;
[0046] Figure 4 It is an equivalent model of the female pelvic floor system in the midsagittal plane;
[0047] Figure 5There are different types of female pelvic floor systems, mesh models and spring suspension models;
[0048] Figure 6 It is the deformation result of different types of pelvic floor systems under 168cmH2O abdominal pressure load;
[0049] Figure 7 These are the stress results of different types of pelvic floor systems under 168cmH2O abdominal pressure load.
[0050] Note: Figure (a) and Figure (b) represent the pelvic floor support systems of two different women. DETAILED DESCRIPTION
[0051] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
[0052] Example 1: Figure 1-7 As shown, a refined reconstruction modeling and mechanical analysis method of the female pelvic floor system in the sagittal plane is shown, and the steps are as follows:
[0053] Step 1: A healthy, well-proportioned, married, childless female volunteer was recruited and signed an informed consent form before the examination. A midsagittal scan was performed on the female patient using a magnetic resonance imaging scanner to obtain a midsagittal axial image of the pelvis.
[0054] Step 2: Use Mimics software to open the female midsagittal pelvic floor image, determine the morphology, size, positional relationship with surrounding tissues and organs, and contours of the pelvic floor organs under the midsagittal plane, and measure the coordinate values of the key discrete feature data points marking the inner and outer contours of each pelvic floor organ.
[0055] Step 3: Using Unigraphics (UG) 3D design software, read the coordinate values of the key discrete feature data points of the inner and outer contours of the female pelvic floor organs, use accurate curve fitting methods to perform non-equidistant interpolation and approximation drawing on the key discrete feature data points of the inner and outer contours of the organs, and establish an accurate two-dimensional contour curve and solid geometric reconstruction model of the pelvic floor system in the sagittal plane ( Figure 3 ). The specific implementation steps are:
[0056] 3.1) Using Unigraphics (UG) three-dimensional design software, read the coordinate values of the key discrete feature data points of the inner and outer contours of each organ of the female pelvic floor, and select a set number of key discrete feature data points of the inner and outer contours of each organ of the pelvic floor to describe the key shape and position features of the inner and outer contours of each organ under the sagittal plane.
[0057] 3.2) Using the cubic B-spline curve approximate fitting method, the selected four adjacent key discrete feature data points are fitted and calculated to determine a cubic B-spline curve. By recursion, the cubic B-spline curves of multiple key discrete feature data points can be obtained, thereby achieving accurate segmented fitting of the internal and external contours of the organ. The drawn segments of the curves are naturally connected, with C 2 Second order continuous ( Figure 2 ).
[0058] Assume that the outer contour of a selected organ consists of n plane key discrete feature data points, denoted as P i ,i=1,2,.........n.
[0059] Draw the first cubic B-spline curve using P1, P2, P3, and P4;
[0060] Draw the second cubic B-spline curve using P2, P3, P4, and P5;
[0061]
[0062] P n-3 , P n-2 , P n-1 , P n Draw the n-3th cubic B-spline curve.
[0063] 3.3) Perform non-equidistant interpolation calculation and approximation drawing on the fitting curves of the inner and outer contours of the organs. That is, according to the morphology and position characteristics of each organ, increase the number of interpolation points for some fitting curves with large curvature changes to ensure the natural connection and C of the interpolation curves. 1 First-order continuity, the precise contour curves of the pelvic floor organs obtained by fitting.
[0064] 3.4) Reconstruct the solid geometric model of each organ in the sagittal plane through the precise contour curves of each organ in the pelvic floor ( Figure 3 ).
[0065] Step 4: According to Hooke's law and the principle of mechanical equilibrium, the mechanical projection and mechanical synthesis methods are used to obtain the mechanical projection relationship between the organs and ligaments of the pelvic floor system. The equivalent stiffness mechanical parameters of the ligaments and fascia of the female pelvic floor system under the sagittal plane are calculated respectively, and a set number of approximately parallel and uniformly distributed spring units are used to simulate the equivalent mechanical effects of each ligament, and the equivalent mechanical model of the pelvic floor system projected under the sagittal plane is obtained ( Figure 4 ). The specific implementation process is:
[0066] 4.1) The three-dimensional mechanical effects of the suspensory ligaments in the pelvic floor system are projected onto the median sagittal plane to calculate the combined mechanical effects of the suspensory ligaments on the median sagittal plane.
[0067] 4.2) According to Hooke's law and the principle of mechanical equilibrium, the mechanical projection composite force of each suspension ligament in the pelvic floor system under the midsagittal plane is calculated. The formula for the mechanical projection composite force of each suspension ligament in the pelvic floor system is:
[0068] F CL = -2×K CL ×cos(α CL / 2)×d CL
[0069] F USL = -2×K USL ×cos(α USL / 2)×d USL
[0070] F APS = -2×K APS ×cos(α APS / 2)×d APS
[0071] F PPS = -2×K PPS ×cos(α PPS / 2)×d PPS
[0072] F RL = -2×K RL ×cos(α RL / 2)×d RL
[0073] F BL = -2×K BL ×cos(α BL / 2)×d BL
[0074] Among them: F CL 、F USL 、F APS 、F PPS 、F RL and F BL K is the combined tensile load (N) on the main ligaments of the pelvic floor system, the uterosacral ligament, the anterior and posterior paravaginal supporting fascia, the round ligament and the broad ligament. CL , K USL , K APS , K PPS , K RL and K BL These are the stiffness (N / mm) of the main ligaments of the pelvic floor system, the uterosacral ligament, the anterior and posterior paravaginal supporting fascia, the round ligament, and the broad ligament. CL d USL d APS dPPS d RL and d BL They are the elastic deformation or tensile displacement (mm) of the main ligaments of the pelvic floor support system, the uterosacral ligament, the anterior and posterior paravaginal supporting fascia, the round ligament and the broad ligament. CL , α USL , α APS , α PPS , α RL and α BL They are the average angles between the main ligaments of the pelvic floor support system, the uterosacral ligaments, the anterior and posterior paravaginal supporting fascia, the round ligament and the broad ligament. Half of the average angle is the projected angle (°) between a single ligament and the midsagittal plane.
[0075] 4.3) The size ratio coefficient ξ is introduced to describe the size effect in the width direction of the organ, using the formula K mw = m × ξ to obtain the proportional coefficient of the spring unit stiffness parameter. ξ is the size proportional coefficient, ξ = L W ×L eq , where L W and L eq are the equivalent width and average width of the pelvic organs in the ligament fascia action area, which is approximately equivalent to the plane strain action of the midsagittal plane. eq =0.1mm, taking the overall average width of the pelvic floor organs of healthy women as a reference, take L W =20mm. Therefore, under the midsagittal plane, the equivalent suspension mechanical action of each ligament of the pelvic floor system can be expressed as:
[0076] F ECL =F CL / K mw
[0077] F EUSL =F USL / K mw
[0078] F EAPS =F APS / K mw
[0079] F EPPS =F PPS / K mw
[0080] F ERL =F RL / K mw
[0081] F EBL =F BL / K mw
[0082] Among them, F ECL 、F EUSL 、F EAPS 、F EPPS 、F ERL and F EBL They are the equivalent suspension mechanical loads (N) of the main ligaments of the pelvic floor system, the uterosacral ligaments, the anterior and posterior paravaginal supporting fascia, the round ligament and the broad ligament.
[0083] 4.4) Combining the above formulas, the equivalent stiffness parameter formula of the spring unit of each ligament can be obtained as follows:
[0084] K ECL =2×K CL ×cos(α CL / 2) / K mw
[0085] K EUSL =2×K USL ×cos(α USL / 2) / K mw
[0086] K EAPS =2×K APS ×cos(α APS / 2) / K mw
[0087] K EPPS =2×K PPS ×cos(α PPS / 2) / K mw
[0088] K ERL =2×K RL ×cos(α RL / 2) / K mw
[0089] K EBL =2×K BL ×cos(α BL / 2) / K mw
[0090] Among them, K ECL , K EUSL , K EAPS , K EPPS , K ERL and K EBL They are the equivalent stiffness parameters of the equivalent spring units of the main ligaments, uterosacral ligaments, anterior and posterior paravaginal supporting fascia, round ligament and broad ligament of the pelvic floor system.
[0091] Step 5: Based on the solid geometry reconstruction model of the female pelvic floor system obtained in step 3 and the simulation analysis method of the mechanical effect in step 4, the finite element simulation software ANSYS is used to establish an accurate two-dimensional finite element model of the female pelvic floor system in the sagittal plane, and the biomechanical characteristics of the female pelvic floor system in the sagittal plane are analyzed through finite element simulation. The specific steps are:
[0092] 5.1) Import the organ solid geometry model reconstructed using Unigraphics (UG) (3D design software) into ANSYS finite element analysis software.
[0093] 5.2) Using ANSYS Solid185 entity units to perform hexahedral mesh sweeping division on each organ in the pelvic floor system, according to the mechanical projection relationship between each organ and each ligament of the pelvic floor system as described in step 4 of claim 1, using a set number of approximately parallel and uniformly distributed ANSYS Combination14 spring damping units to simulate the equivalent connection mechanical effect between each organ and each ligament fascia under the sagittal plane ( Figure 5 ).
[0094] 5.3) According to the shape, size, positional relationship with surrounding tissues and organs and contours of the pelvic floor organs under the midsagittal plane as described in step 2 of claim 1, a surface contact method is adopted to set ANSYS Contact174 contact unit and ANSYSTarget170 target unit to simulate the external surface contact support effect between the outer wall of the cervix and the anterior and posterior fornix of the vagina, between the outer surface of the posterior wall of the vagina and the perineum and rectum, between the perineum and rectum, and between the rectum and the levator ani muscles in the pelvic floor system, and the internal surface contact support effect of organs such as the uterus, cervix, vagina, and urethra bladder.
[0095] 5.4) Constraint definition: Constrain the Z-direction displacement (perpendicular to the midsagittal plane) of all nodes in the finite element model of the pelvic floor system, fix the pubic bone and sacrum, and add bottom constraints of the vagina, perineal body, rectum and levator ani muscles.
[0096] 5.5) Load definition: Add a positive pressure simulation (168cmH2O) Valsalva abdominal pressure load perpendicular to the organ surface to the upper wall of the uterus and the anterior wall of the vagina, and add a vertical downward load of the organ's own weight.
[0097] 5.6) Set the elastic modulus of the uterus, vagina, perineum and rectum to 2 MPa, density to 1000 kg / m3, and Poisson's ratio to 0.45; the elastic modulus of the levator ani muscle to 1.41 MPa, density to 1000 kg / m3, and Poisson's ratio to 0.49, and define the linear stiffness parameter K of the left and right main ligaments CL =1260N / m, linear stiffness parameter K of the left and right uterosacral ligaments USL=630N / m, linear stiffness parameter K of ligamentous tissues such as round ligament and paravaginal support RL =K APS =K PPS =200N / m. According to the calculation of the equivalent stiffness mechanical parameters of each ligament and fascia of the female pelvic floor system in the sagittal plane as described in step 4 of claim 1, a set number of approximately parallel and uniformly distributed spring units are used to simulate the equivalent mechanical action of each ligament, and the equivalent stiffness mechanical parameter is set to the stiffness value of the spring damping unit.
[0098] 5.7) Use the large deformation statics solver of finite element simulation analysis software (such as ANSYS, etc.) to calculate and analyze the biomechanical equilibrium state and change law of the female pelvic floor system, and output the stress distribution and deformation cloud map of the pelvic floor equivalent model ( Figure 6 , Figure 7 ).
[0099] The present invention utilizes nuclear magnetic resonance imaging technology to obtain two-dimensional images of various organs in the female pelvic floor system, and uses computer-aided design and curve fitting methods to accurately reconstruct the contour curves and geometric models of various organs in different types of female pelvic floor structural systems under the sagittal plane, and provides the equivalent stiffness mechanical calculation formula of ligament fascia tissues such as the main ligament and sacral ligament under the sagittal plane, so as to calculate the biomechanical properties of the female pelvic floor system under the sagittal plane using finite element modeling.
[0100] The specific calculation method of the present invention is described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation mode. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.
Claims
1. A refined reconstruction modeling and mechanical analysis method for the female pelvic floor system in the sagittal plane, characterized by: The specific steps are as follows: Step 1: Use a magnetic resonance imaging scanner to perform a midsagittal scan of the female pelvic floor system of different age groups, different pelvic floor dysfunction diseases and different types to obtain a midsagittal MRI image of the female pelvic floor system; Step 2: Use Mimics software to open the midsagittal pelvic floor image, determine the shape, size, positional relationship and contour of the pelvic floor organs under the midsagittal plane, and measure the coordinate values of the key discrete feature data points marking the inner and outer contours of each pelvic floor organ; Step 3: Using CAD computer-aided design software, read the coordinate values of the key discrete feature data points of the inner and outer contours of each pelvic floor organ, use accurate curve fitting methods to perform non-equidistant interpolation and approximation drawing on the key discrete feature data points of the inner and outer contours of the organs, establish an accurate two-dimensional contour curve of the pelvic floor system under the sagittal plane, and obtain a two-dimensional refined reconstruction model and a solid geometry reconstruction model; Step 4: According to Hooke's law and the principle of mechanical equilibrium, the mechanical projection and mechanical synthesis methods are used to obtain the mechanical projection relationship between the organs and ligaments of the pelvic floor system, and the equivalent stiffness mechanical parameters of the ligaments and fascia of the female pelvic floor system under the sagittal plane are calculated respectively. A set number of approximately parallel and uniformly distributed spring units are used to simulate the equivalent mechanical action of each ligament, and the equivalent mechanical model of the pelvic floor system projected under the sagittal plane is obtained; Step 5: Based on the solid geometry reconstruction model of the female pelvic floor system obtained in step 3 and the simulation analysis method of the intermediate mechanical action in step 4, use finite element simulation software to establish an accurate two-dimensional finite element model of the female pelvic floor system in the sagittal plane, and analyze the biomechanical characteristics of the female pelvic floor system in the sagittal plane through finite element simulation.
2. The refined reconstruction modeling and mechanical analysis method of the female pelvic floor system in the sagittal plane according to claim 1 is characterized by: The specific steps in step 3 are: 3.1) Using CAD computer-aided design software, read the coordinate values of key discrete feature data points of the inner and outer contours of each organ of the pelvic floor, select a set number of key discrete feature data points of the inner and outer contours of each organ of the pelvic floor to describe the key shape and position features of the inner and outer contours of each organ under the sagittal plane; 3.2) Using the cubic B-spline curve approximate fitting method, the selected four adjacent key discrete feature data points are fitted and calculated to determine a cubic B-spline curve; 3.3) By recursion, the cubic B-spline curves of multiple key discrete feature data points can be obtained, thereby achieving accurate segmented fitting of the internal and external contours of the organ. The drawn segments of the curves are naturally connected, with C 2 Second-order continuous, the specific process is as follows: Assume that the outer contour of a selected organ consists of n plane key discrete feature data points, denoted as P i ,i=1,2,.........n, 3.4) Perform non-equidistant interpolation calculation and approximation drawing on the fitting curves of the inner and outer contours of the organs, that is, according to the morphology and position characteristics of the organs, increase the number of interpolation points for the fitting curves with large curvature changes to ensure the natural connection and C of the interpolation curves. 1 First-order continuity, the precise contour curves of the pelvic floor organs obtained by fitting; 3.5) Using CAD computer-aided design software, the solid geometric model of each organ in the sagittal plane was reconstructed through the precise contour curves of each organ in the pelvic floor.
3. The refined reconstruction modeling and mechanical analysis method of the female pelvic floor system under the sagittal plane according to claim 1 is characterized by: The specific steps of step 4 are: 4.1) The three-dimensional mechanical effects of the suspensory ligaments and fascia in the pelvic floor system are projected onto the median sagittal plane to calculate the combined mechanical effects of each suspensory ligament on the median sagittal plane; 4.2) According to Hooke's law and the principle of mechanical equilibrium, the formula: F = -2 × K × cos (α / 2) × d is used to calculate the mechanical projection composite force of each suspension ligament in the pelvic floor system under the median sagittal plane. F is the combined tensile load on the ligament, in N; the negative sign indicates that the elastic force generated by the spring is opposite to its elongation direction; K is the stiffness of each ligament, in N / mm; α is twice the projection angle between a single ligament and the median sagittal plane, in degrees; d is the elastic deformation or tensile displacement, in mm; 4.3) The size ratio coefficient ξ is introduced to describe the size effect of each organ in the width direction, using the formula K mw =m×ξ to obtain the proportional coefficient K of the spring unit stiffness parameter mw , size ratio coefficient ξ=L W ×L eq , where L W and L eq are the equivalent width and average width of each pelvic organ, respectively; m is the number of approximately parallel and uniformly distributed spring units of the equivalent action of each ligament and fascia; therefore, under the midsagittal plane, the equivalent mechanical action of each ligament and fascia of the pelvic floor system can be expressed by F E =F / K mw Indicates that F E It is the equivalent effect of each ligament and fascia; 4.4) From the above formulas, we can get the equivalent stiffness K of the spring unit of each ligament: E The parameter formula is: K E =2×K×cos(α / 2) / K mw 。 4. The refined reconstruction modeling and mechanical analysis method of the female pelvic floor system under the sagittal plane according to claim 1, characterized in that: The specific steps of step 5 are: 5.1) Importing the solid geometry reconstruction model of the subsagittal pelvic floor system obtained in step 3 into the finite element simulation software; 5.2) Using solid units to perform hexahedral mesh sweeping division on each organ in the pelvic floor system, according to the mechanical projection relationship between each organ and each ligament in the pelvic floor system described in step 4, using a set number of approximately parallel and uniformly distributed spring damping units, establish the equivalent connection mechanical action between each organ and each ligament fascia under the sagittal plane; 5.3) According to the shape, size, positional relationship and contour of the pelvic floor organs under the midsagittal plane described in step 2, a surface contact method is used to set contact units and target units to simulate the outer surface contact support between the outer wall of the cervix and the anterior and posterior fornix of the vagina, between the outer surface of the posterior wall of the vagina and the perineum and rectum, between the perineum and rectum, and between the rectum and the levator ani muscles in the pelvic floor system, and the inner surface contact support of organs such as the uterus, cervix, vagina, and urethra and bladder; 5.4) Constraint definition: constrain the Z-direction displacement of all nodes in the finite element model of the pelvic floor system, constrain the pubic bone and sacrum, and add bottom constraints of the vagina, perineal body, rectum and levator ani muscles; 5.5) Load definition: Add positive pressure perpendicular to the surface of the organ to the upper wall of the uterus and the anterior wall of the vagina to simulate the Valsalva abdominal pressure load, and add the vertical downward load of the organ's own weight; 5.6) setting the linear elastic or hyperelastic material properties, material density and Poisson's ratio of the uterus, vagina, perineal body, rectum and levator ani muscles; setting the linear or nonlinear stiffness parameters of the ligament tissues such as the main ligament, uterosacral ligament, round ligament and paravaginal support, calculating the equivalent stiffness mechanical parameters of each ligament fascia of the female pelvic floor system under the sagittal plane according to step 4, using a set number of approximately parallel and uniformly distributed spring units to simulate the equivalent mechanical action of each ligament, and setting the equivalent stiffness mechanical parameters to the stiffness value of the spring damping unit; 5.7) The large deformation statics solver of the finite element simulation analysis software is used to calculate and analyze the biomechanical equilibrium state and change law of the female pelvic floor system.
5. The refined reconstruction modeling and mechanical analysis method of the female pelvic floor system in the sagittal plane according to claim 1, characterized in that: In step 1, the different pelvic floor dysfunction diseases include healthy pelvic floor or pelvic organ prolapse POP.
6. The refined reconstruction modeling and mechanical analysis method of the female pelvic floor system in the sagittal plane according to claim 1, characterized in that: The CAD computer-aided design software in step 3 is Unigraphics, and the finite element simulation software in step 5 is ANSYS.
7. The refined reconstruction modeling and mechanical analysis method of the female pelvic floor system under the sagittal plane according to claim 4, characterized in that: The solid unit in 5.2) is ANSYS / Solid185 unit, the spring-damper unit is ANSYS / Combination14 or ANSYS / Combination39 spring-damper unit, the contact unit in 5.3) is ANSYS / Contact174, and the target unit is ANSYS / Target170.