MODELING METHOD FOR ORTHOPEDIC CASTS
20170262611 · 2017-09-14
Inventors
Cpc classification
G05B19/4099
PHYSICS
G16Z99/00
PHYSICS
G05B2219/49023
PHYSICS
International classification
G05B19/4099
PHYSICS
Abstract
A computer-implemented method for modeling an orthopedic cast, including scanning an injured limb to extract raw body data; determining, from the extracted raw body data, a target portion data of the injured limb, the determined data representing a fine cast surface for the orthopedic cast; patterning the fine cast surface to form a ventilation structure and a blank area thereon; forming an opening gap on the blank area for assembling and disassembling the orthopedic cast; and offsetting the cast surface in parallel to thicken the orthopedic cast.
Claims
1. A computer-implemented method for modeling an orthopedic cast, comprising: scanning an injured limb to extract raw body data; determining, from the extracted raw body data, target portion data of the injured limb, the determined target portion data representing a fine cast surface for the orthopedic cast; patterning the fine cast surface to form a blank area thereon; forming an opening gap on the blank area for assembling and disassembling the orthopedic cast; and offsetting the fine cast surface in parallel to thicken the orthopedic cast.
2. The method of claim 1, further comprising: stretching points on surface areas near opening ends of the fine cast surface to create flare edges at the opening ends.
3. The method of claim 1, further comprising: patterning the fine cast surface to form a ventilation structure having a plurality of ventilation holes.
4. The method of claim 2, wherein the offsetting further comprises: offsetting the fine cast surface to form two parallel cast surfaces without connection at the opening ends.
5. The method of claim 4, further comprising: linking the two parallel cast surfaces at the opening ends by connecting edge nodes on one of the two parallel cast surfaces with corresponding edge nodes on the other one of the two parallel cast surfaces.
6. The method of claim 3, wherein the fine cast surface has a longitudinal direction, and the method further comprises: determining a centerline of the fine cast surface along the longitudinal direction, wherein the centerline is geometrically defined as a shortest path to connect two endpoints of the orthopedic cast; and removing end portions of the surface, the end portions being outside of clipping planes and the clipping planes being normal to the centerline.
7. The method of claim 6, wherein the centerline is bounded on the Voronoi diagram of the orthopedic cast and is composed of points centered on the maximal inscribed sphere.
8. The method of claim 6, wherein the centerline is a spline line and comprises tangent vectors varied along the spline line.
9. The method of claim 8, wherein the clipping plane is defined by a normal vector, which averages a couple of successive tangent vectors from an endpoint of the centerline.
10. The method of claim 2, further comprising stretching the opening ends to create flare edges at the opening ends by applying different extending coefficients on a closest distance between the centerline and points on the surface areas near the opening ends.
11. The method of claim 8, wherein the fine cast surface is shaped with a polyline tube shape, and wherein the patterning comprises: cutting the fine cast surface along a longitudinal direction of the surface to form a plurality of polyline loops; determining a reference vector for each of the polyline loops to create a bundle of vector lines for locating centers of the ventilation holes along a circumferential direction of the orthopedic cast; determining the blank area in accordance with angles between the reference vector and a start vector line and a symmetric end vector line of the created vector lines; and generating the opening gap on the determined blank area of the cast surface.
12. The method of claim 11, wherein the patterning further comprises: determining centers of the ventilation holes in an area other than the blank area of the cast surface; and generating the ventilation holes on the cast surface based on the centers.
13. The method of claim 11, wherein the cutting further comprises: averaging the tangent vectors along the centerline resulting in an average, the average being employed as a normal line of the cutting planes; integrating all micro segments composing of the centerline to obtain a total length of the centerline; subtracting two marginal lengths from the total length to define an effective length of the centerline; and cutting, within the effective length, the cast surface along the longitudinal direction of the surface to form a plurality of surface segments with polyline loops, the plurality of surface segments having an identical extension length in the longitudinal direction.
14. The method of claim 11, wherein the reference vector is determined by: selecting a user specified point on the cast surface; selecting a mapping point of the user specified point on the centerline; and defining a reference point located on each of the polyline loops, wherein the reference point is selected from the polyline loops with the closest distance to a reference line from the mapping point to the user specified point; wherein the reference vector is formed by a line extending from the defined reference point and in parallel to the reference line.
15. The method of claim 12, wherein the centers of the ventilation holes are located on each of the polyline loops with a closest distance to the bundle of vector lines.
16. The method of claim 15, wherein the ventilation holes are formed by: modeling a plurality of spheres with identical diameter based on the centers; and removing portions of the cast surface intersecting with the spheres to form the ventilation holes.
17. The method of claim 14, wherein the opening gap is formed by: creating a path of the opening gap along the reference points and two end points on the flare edges; modeling a tube along the path, the tube being centered with the path; and removing portions of the cast surface intersecting with the tube to form the opening gap.
18. The method of claim 4, further comprising: creating an enclosed cast model by linking nodes on the opening ends on both parallel surfaces.
19. A system for modeling an orthopedic cast from raw body data of an injured limb, comprising: a memory storing executable instructions; a processor electrically coupled to the memory executing the executable instructions to perform operations of the system, wherein the executable instructions are configured to: digitize the raw body data and transfer the same as specific type of file; determine, from the digitized raw body data, target portion data of the injured limb, the determined target portion data representing a fine cast surface for the orthopedic cast; pattern the fine cast surface to form a blank area thereon; form an opening gap on the blank area for assembling and disassembling the orthopedic cast; and offset the cast surface in parallel to thicken the orthopedic cast.
20. The system of claim 19, wherein the executable instructions are configured to stretch points on surface areas near opening ends of the fine cast surface to create flare edges at the opening ends.
21. The system of claim 19, wherein the executable instructions are configured to pattern the fine cast surface to form a ventilation structure having a plurality of ventilation holes.
22. An orthopedic cast, comprising: a cast surface with a tube like shape; flare edges at opening ends of the cast surface; and a surface pattern formed on the cast surface and including a ventilation area and a blank area.
23. The orthopedic cast of claim 23, wherein the ventilation area comprises a number of ventilation holes.
24. The orthopedic cast of claim 23, wherein the blank area comprises an opening gap for assembling and disassembling the cast.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Exemplary non-limiting embodiments of the present application are described below with reference to the attached drawings. The drawings are illustrative and generally not made according to an exact scale. The same or similar elements on different figures are referenced with the same reference numbers.
[0024]
[0025]
[0026]
[0027]
[0028]
[0029]
[0030]
[0031]
[0032]
[0033]
[0034]
[0035]
[0036]
[0037]
DETAILED DESCRIPTION
[0038] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When appropriate, the same reference numbers are used throughout the drawings to refer to the same or like parts.
[0039]
[0040] The scanned data of an injured limb may be obtained by, for example, a photometric scanner, Artec Eva and Artec Space Spider (Luxembourg). Patients should be placed in an appropriate position for obtaining the adequate data for reconstructing an image of the injured limb. For example, the surface geometry of limb may be digitized and transferred as a polygonal STL (Standard Template Library) file with over a plurality of points and triangle elements (for example, 200,000 points and 400,000 triangle elements). The number of the points and the elements may vary widely from one anatomic site to another. The initial cast surface model may be generated from clipping the raw body data as shown in
[0041] At step S102, the target portion data for a fine cast surface is determined by clipping the raw body data. The determined data represents a fine cast surface for the orthopedic cast. The cast surface has tube like flare openings at the opening ends, which are formed by stretching points on surface areas near opening ends of the fine cast surface. In this step, a computation of centerline L is proposed to create a fine cast model with a visually perpendicular end plane. After the centerline L is determined, the end portions of the cast surface, which are outside of clipping planes normal to the centerline, will be removed. The clipping location may be determined by orthopedic technicians in accordance with the injury site. It should be noticed that the clipping plane 102 may not be visually perpendicular to the cast surface 101.
[0042] Computing centerline L of the raw cast surface 101 is used not only for creating desired edges of the fine cast model 103, but also for subsequent modeling steps. The centerline computation and fine edge clipping process may be implemented as follows. [0043] a) There are many mathematical descriptions of the centerline which is an intuitive central path. The centerline L may be geometrically defined as the shortest path to connect two endpoints of a tube like cast. It should be noted that the centerline L may be bounded on, for example, the Voronoi diagram of the cast and may be composed of points centered the maximal inscribed sphere. In the present embodiment, the centerline L may be calculated by the conventional technical means, such as the Vascular Modeling Toolkit (VMTK, Orobixsrl). [0044] b) Once the centerline L is determined, it may be used to define reference planes to perform a fine clipping. The centerline L may be a spline line and the tangent vectors may vary along the spline line. The clipping plane may be defined by a normal vector, which averages a couple of successive tangent vectors from an endpoint of the centerline L. In this connection, it may use tangent vectors of 5 (as an example) successive points started from an endpoint to calculate the normal vector. However, the number of the successive points is not limited thereto. Two new clipping planes are generated in this step. [0045] c) Two new clipping planes may be applied to the unclipped raw body surface, e.g. body data acquired from 3D scanner, to perform a re-clipping process. The two clipping planes may be located at two endpoints of the centerline and a fine cast surface model 103 may be obtained by re-clipping data.
[0046] At step S103, flare openings are generated by stretching points on surface areas near opening ends of the fine cast surface.
[0047] The flare opening for tube-like cast geometry may create a funnel-shaped end. Flare edges are required by orthopedists and are modeled in both end sides of the fine cast model to ensure the wearing comfort and safety. The funnel-shaped geometry with round corners may produce a smooth touching surface and thus may prevent injuries from the usual movement of part (such as the wrist) of the injury limbs. Points on the surface areas near the opening edges may be stretched by extending vectors. Referring to
{right arrow over (A)}.sub.i−{right arrow over (C)}.sub.i=b.sub.i({right arrow over (A)}.sub.i−{right arrow over (C)}.sub.i) (1)
[0048] Where C.sub.i (i=0, 1, . . . , n) are central points on the centerline. C.sub.i is the point with the closest distance to the original surface vertex point A.sub.i. {right arrow over (A)}.sub.i′ is the new vertex point stretched from A.sub.i.Math.b.sub.i is the extending coefficient with respect to points same layer as A.sub.i. Values of coefficient b.sub.i may lineally vary along the centerline.
[0049] The maximal extending coefficients may be applied on the opening ends of the tube-like cast. Not all surface points are applied with the extending factor. In this embodiment, surface points with a certain distance (for example, 3˜5 mm) to the clipping plane are applied with the extending coefficient. There is no exact standard to determine the values of the coefficients depending on the original geometry. For example, the maximal coefficient used in this embodiment may be 1.15, but the present application is not limited thereto. The funnel-shaped opening ends are more or less intuitive and different values of the maximal coefficient with orthopedic feasibility are acceptable. Flare shapes 104 and 105 may be generated in both sides of the cast 103 in this step.
[0050] The process now turns to step S104, in which the fine cast surface is patterned to form a ventilation area and a blank area.
[0051]
[0052] The process begins with step S201. In this step, the cast surface is cut along the longitudinal direction of the surface to form a plurality of polyline loops. An algorithm may be developed to perform this step automatically. For example, the algorithm may firstly average the tangent vectors along the centerline, which is a spline line. It then uses the average of the tangents as the normal vector of the cutting planes. For example, the total length of the centerline may be computed by integration of all micro segments that compose of the centerline. The effective length of the centerline may be defined by subtracting two marginal lengths from the total length as illustrated in
[0053] Then the process 2000 turns into step S202, in which a reference vector for each of the polyline loops is determined to create a bundle of vector lines for locating centers of the ventilation holes along a circumferential direction. In this step, a user specified point on the cast surface and a mapping point of the user specified point on the centerline is selected.
[0054]
[0055] Each reference vector L.sub.v may be used to create a bundle of vector lines L.sub.i for further locating the centers of holes. In terms of technical needs, the number of holes for each slice may be pre-defined. As shown in
Where β is the angle between two adjacent vectors and m is the number of holes for each slice. The centers of holes are located at the polyline loop 301 with the closest distance to the vector lines L.sub.i. Each vector line L.sub.i determines one hole center.
[0056] Once the centers of the ventilation holes are determined, a plurality of spheres with same diameter will be modeled based on the centers. At step S203, the ventilation holes are formed by removing portions of the cast surface intersecting with the spheres.
[0057]
[0058] After the centers of holes are selected, a plurality of micro spheres 601 with those centers may be modeled as shown in
[0059] At step S204, the blank area is determined in accordance with angles between the reference vector and a start vector line and a symmetric end vector line of the created vector lines. Generally, the angles are same as each other. After the blank area is determined, a path of the opening gap is created along the reference points and two end points on the flare edges.
[0060] Once the ventilation area and the blank area are determined, an opening gap will be formed on the blank area for assembling and disassembling the orthopedic cast.
[0061]
[0062] The previous steps have created a marker specified to a user on the cast surface. Based on the marker point C.sub.r, the array of alpha points C.sub.ri may be selected in previous steps as illustrated in
[0063] Creating a smoothing curve as the path for opening gap 805 is developed in this embodiment. More points located at geodesics will be added into the control point set. The control point set multiplies the points for modeling an accurate and rational path line. A spline line passing through all points in the control point set is built and run through the cast surface 103. The spline line may be defined as the path of the opening gap 805.
[0064] At step S205, a tube 806 will be modeled for creating the opening gap 805. The opening gap is formed by removing portions of the cast surface intersecting with the tube. In this step, a circle may be created at one end point of the spline line and sweep along the path to generate the tube 806. The spline line is then served as the centerline of the tube 806. A small size of the tube will develop a small gap which would better enclose the injury limbs. The smaller size of the tube 806, the better cast structure will be modeled. For the consideration of the manufacturing feasibility, e.g. accuracy of 3D printing, the diameter may be set as around, for example, 2 mm. But the diameter of the tube is not limited thereto. A parametric tube may be created for adjustments of the gap space. Once the tube 806 is built, the opening gap 805 will be developed by performing Boolean subtraction between the tube and cast surface as displayed in
[0065] At step S105, the cast surface is offset in parallel so as to thicken the orthopedic cast.
{right arrow over (p)}′={right arrow over (p)}+t.Math.{right arrow over (n)}.sub.pi (3)
[0066] Where {right arrow over (p)} is an original vertex of an element; {right arrow over (p)}′ is the offset vertex. {right arrow over (n)}.sub.pi is the normalized direction vector of the element and t is the thickness. Due to the curve shape of the cast surface with concave shape in some regions, a relatively great thickness may result in wrapping element shapes on the cross section, where sides of two or more elements intersect. A small thickness (e.g. 1 mm) is suggested in each step of offsetting to avoid geometric error. Offsetting elements with a small thickness is able to technically smooth the surface and further reduce the occurrence of wrapping elements. The accumulation of thicknesses can generate the resulting thickness as required by users.
[0067]
[0068] The above steps and related algorithms may be developed by, for example, Visualization Toolkit (VTK, Kitware) and integrated into an intelligent designing system. The cast geometry is built from scanned data making an orthosis custom made.
[0069]
[0070] As will be appreciated by one skilled in the art, the present application may be embodied as a system, a method or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment and hardware aspects that may all generally be referred to herein as a “unit”, “circuit,” “module” or “system.” Much of the inventive functionality and many of the inventive principles when implemented, are best supported with or integrated circuits (ICs), such as a digital signal processor and software therefore or application specific ICs. It is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating ICs with minimal experimentation. Therefore, in the interest of brevity and minimization of any risk of obscuring the principles and concepts according to the present application, further discussion of such software and ICs, if any, will be limited to the essentials with respect to the principles and concepts used by the preferred embodiments.
[0071] In addition, the present application may take the form of an entirely software embodiment (including firmware, resident software, microcode, etc.) or an embodiment combining software. For example, the system may comprise a memory that stores executable components and a processor, electrically coupled to the memory to execute the executable components to perform operations of the system, as discussed in reference to
[0072] Although the preferred examples of the present application have been described, those skilled in the art can make variations or modifications to these examples upon knowing the basic inventive concept. The appended claims are intended to be considered as comprising the preferred examples and all the variations or modifications fell into the scope of the present application.