A method and an auxiliary tool for reconstructing a digital model of a bone based on a scanned image

Abstract

The present invention discloses a method and an auxiliary tool for reconstructing a digital bone model based on scanned images. An inner component model is obtained by performing image scanning, image segmentation, and model reconstruction on the auxiliary tool; the reconstructed inner component model is imported into reverse engineering software or 3D printing support software, and the volume of the reconstructed inner component model is calculated. The volume of the reconstructed inner component model is divided by the volume of the original inner component to obtain the volume change rate of the reconstructed model caused by the entire technical process; the volume of the reconstructed digital bone model is corrected by using this volume change rate of the reconstructed model; it is possible to accurately understand the volume increase ratio of each scanning and model reconstruction, and then perform precise correction, effectively improving the accuracy of 3D model reconstruction. Through experimental verification, compared with the traditional method for reconstructing a digital bone model, the absolute average deviation value between the digital bone model reconstructed by the method provided by the present invention and the actual structure is 0.2 - 0.5 mm smaller than that of the traditional method.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a method and an auxiliary tool for reconstructing a bone digital model based on a scanned image. Background Art

[0002] At present, the application of 3D printing in medicine is in the ascendant. Common 3D printing technology applications in medicine mainly include: printing prostheses, implants, templates, guides, etc. 3D printing technology has its irreplaceable advantages in achieving personalized design. In order to achieve the goal of personalized design, these technologies are often inseparable from the use of CT and MR images of patients to reconstruct 3D digital models of patients' anatomical structures (such as bones).

[0003] For example, a Chinese invention patent application with publication number CN107320221A discloses a method for making a deformed knee joint bone model based on 3D printing, which mainly includes the following steps: (1) performing continuous CT scans on patients to obtain image data; (2) performing threshold differentiation and binarization processing in the medical software Mimics to obtain separate femur and tibia mask data and construct a three-dimensional model; (3) performing polygon processing and precise surface processing in reverse engineering software to obtain a NURBS surface model; (4) using FDM molding 3D printing technology to print a 1:1 scale pathological bone model.

[0004] Another example is a Chinese invention patent with publication number CN110223391A, which discloses a 3D printing method and device for a three-dimensional model of a bone. The method includes: obtaining target data, wherein the target data is relevant data obtained by performing a CT scan or an MRI scan on a patient's bone lesion; establishing a three-dimensional model of the bone based on the target data; and printing the three-dimensional model of the bone using a 3D printer.

[0005] However, in the prior art, the error between the reconstructed 3D model and the actual one is still at a relatively rough level compared to the international dimensional accuracy standard, and the reconstruction accuracy cannot meet the high-precision assembly requirements, thus restricting the clinical application of 3D printing technology. The inventors have found that there are many factors that cause this error, such as different brands and models of scanning equipment, partial volume effects of CT and MR scanning, dimensional errors of scanning machines, selection of specific scanning parameters, individual differences, body position factors, etc. However, the final result often leads to a larger volume of the reconstructed model than the actual structure, and the proportion of the volume increase varies depending on the specific anatomical structure. Taking the hip bone as an example, the reconstructed volume of the hip bone is generally 5-15% larger, and this volume increase often leads to a large deviation between the reconstructed model and the real structure. Summary of the invention

[0006] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a method for reconstructing a digital bone model based on a scanned image with small reconstruction model error and high reconstruction accuracy.

[0007] The present invention also provides an auxiliary tool used in the above method.

[0008] To achieve the above object, the present invention adopts the following technical solutions.

[0009] A method for reconstructing a digital bone model based on a scanned image, characterized by comprising the following steps: 1) Making an auxiliary tool, which includes an inner component and an outer component, and the inner component is embedded or completely embedded in the outer component; the inner component is consistent with the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time, and the outer component is consistent with the human tissue outside the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time; 2) Scanning the target anatomical structure and the auxiliary tool to obtain images, and then performing image segmentation and model reconstruction on the target anatomical structure and the inner component using the same technical route; 3) Importing the reconstructed inner component model into reverse engineering software or 3D printing support software, calculating the volume of the reconstructed inner component model, and dividing the volume of the reconstructed model by the volume of the original inner component to obtain the volume change rate of the reconstructed model caused by the entire technical process; 4) Importing the reconstructed target anatomical structure model into reverse engineering software or 3D printing support software, measuring the volume of the reconstructed target anatomical structure model, and dividing the volume of the reconstructed target anatomical structure model by the volume change rate of the reconstructed model to obtain the corrected volume of the target anatomical structure model; 5) In reverse engineering software or 3D printing support software, using a surface offset algorithm to perform an inward surface offset on the reconstructed model of the target anatomical structure, and adjusting the surface offset distance to make the reconstructed model close to the corrected volume of the target anatomical structure.

[0010] More preferably, a plurality of inner components with different shapes are arranged on a single outer component, and each inner component is synchronously scanned when the auxiliary tool is scanned; the shape of the inner component is selected from a spherical shape, a cylindrical shape, a tubular shape, a free-form surface shape, and a shape completely consistent with the target anatomical structure; each inner component corresponds to the average value of the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time.

[0011] More preferably, a plurality of inner components with the same shape are arranged on a single outer component, and each inner component is synchronously scanned when the auxiliary tool is scanned; each inner component corresponds to the average value of the target anatomical structure of different populations in terms of CT gray scale or magnetic resonance relaxation time.

[0012] More preferably, the auxiliary tools are provided in sets, and each set of auxiliary tools has at least two outer components with different CT gray scales or magnetic resonance relaxation times to correspond to different populations.

[0013] More preferably, one of the inner components is provided on a single outer component, and the shape of the inner component is exactly the same as the shape of the target anatomical structure; the inner component corresponds to the average value of the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time, and the outer component corresponds to the average value of the human tissue outside the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time.

[0014] More preferably, the auxiliary tool is directly processed into a finished product by 3D printing.

[0015] Alternatively, the auxiliary tool first manufactures the inner component and then encapsulates it into the outer component to make a finished product; when manufacturing the inner component, 3D printing, mold curing or CNC machining is used; when encapsulating the outer component, one of the following two methods is adopted: a) placing the inner material into the uncured outer material and solidifying it to obtain a finished product, b) placing the inner component into the cavity of the outer material with holes or movable installation and installing and forming it.

[0016] More preferably, in step 2), the method of scanning the target anatomical structure and the auxiliary tool to obtain an image is: separately scanning twice before and after or scanning the auxiliary tool and the patient's target anatomical structure together.

[0017] More preferably, when the target anatomical structure and / or human tissue are multi-layered, the inner component and / or the outer component are correspondingly set to be multi-layered.

[0018] More preferably, the method for reconstructing a digital bone model based on a scanned image further includes a volume change rate correction step: registering the reconstructed model of the inner component and the original model of the inner component using algorithms such as least squares or using a 3D model registration tool in reverse engineering software to complete the registration of the reconstructed model and the original model of the inner component; after registration, offset the reconstructed model of the inner component inward by a surface offset algorithm or function, and by adjusting the surface offset distance, make the volume of the reconstructed model approximate to the volume of the original model, and obtain the absolute average deviation between the model and the original model at this time through deviation analysis, denoted as k 1 ; further adjust the surface offset distance to minimize the absolute average deviation between the processed reconstructed model and the original model, and denote this minimum value as k 2 ; compare k 1 and k 2 values. If the difference between k 1 and k 2 is not greater than the threshold, then select the correction ratio x 2 obtained by dividing the volume of the reconstructed model by the volume of the processed reconstructed model to correct the volume of the target anatomical structure model.

[0019] More preferably, it is determined whether to select the correction ratio x 2When calibrating the volume of the target anatomical structure model, the following steps are further included: Assume that the pixel size of the scanned image is L. If k 1 and k 2 are both greater than 0.301*L, then the calibration ratio x 2 is not used to calibrate the volume of the target anatomical structure model. If k 2 is not greater than 0.301*L, then the calibration ratio x 2 is selected to calibrate the volume of the target anatomical structure model.

[0020] An auxiliary tool for reconstructing a digital bone model based on a scanned image, characterized in that it includes: an inner component and an outer component, and the inner component is embedded or completely embedded in the outer component; the inner component is consistent with the target anatomical structure in terms of CT gray level or magnetic resonance relaxation time, and the outer component is consistent with the human tissue outside the target anatomical structure in terms of CT gray level or magnetic resonance relaxation time.

[0021] During application, an inner component model is obtained by performing image scanning, image segmentation, and model reconstruction on the auxiliary tool; the reconstructed inner component model is imported into reverse engineering software or 3D printing support software, and the volume of the reconstructed inner component model is calculated. The volume change rate of the reconstructed model caused by the entire technical process is obtained by dividing the volume of the reconstructed inner component model by the volume of the original inner component; the volume of the reconstructed digital bone model is calibrated using this volume change rate of the reconstructed model.

[0022] The beneficial effects of the present invention are as follows: Due to individual differences and differences in digital reconstruction methods, for the reconstruction of a specific anatomical structure under specific scanning parameters for a specific individual, this final volume increase ratio is often unknown. The auxiliary tool and reconstruction method adopted by the present invention can accurately understand the volume increase ratio of each scan and model reconstruction, and then perform precise correction, effectively improving the accuracy of 3D model reconstruction.

[0023] Verified by experiments, compared with the traditional method for reconstructing a digital bone model, the absolute average deviation value between the digital bone model reconstructed by the method provided by the present invention and the actual structure is 0.2 - 0.5 mm smaller than the traditional method. Description of the Drawings

[0024] Figure 1 Shown is a schematic structural diagram of a type I auxiliary tool.

[0025] Figure 2 Shown is a schematic structural diagram of a type II auxiliary tool.

[0026] Figure 3 Shown is a schematic structural diagram of a type III auxiliary tool.

[0027] Explanation of the reference numerals in the drawings.

[0028] 1: Inner component, 2: Outer component. Detailed implementation mode

[0029] In the description of the present invention, it should be noted that for orientation terms, such as the terms "center", "horizontal", "vertical", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the indicated orientation and positional relationship are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of the present invention.

[0030] In addition, such terms as "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "at least" is one or more than one, unless otherwise clearly and specifically defined.

[0031] In the present invention, unless otherwise clearly specified and defined, such terms as "assembled", "connected", and "joined" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may also be a mechanical connection; it may be directly connected, or connected through an intermediate medium, and may be internally connected and communicated between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the invention, unless otherwise specified and defined, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through other features therebetween. Moreover, the first feature being "above", "below", and "on top of" the second feature includes the first feature being directly above and diagonally above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "above", "below", and "beneath" the second feature includes the first feature being directly below or diagonally below the second feature, or merely indicating that the horizontal height of the first feature is lower than that of the second feature.

[0033] The following further describes the specific implementation mode of the present invention in conjunction with the drawings of the specification, making the technical solution and its beneficial effects of the present invention clearer and more definite. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0034] Additional aspects and advantages of the present invention will become apparent in the following description section or be learned through the practice of the present invention.

[0035] A method for reconstructing a digital model of a bone based on a scanned image, characterized by comprising the following steps.

[0036] 1) Fabricate an auxiliary tool, which includes an inner component and an outer component, and the inner component is embedded or completely encapsulated in the outer component; the inner component is consistent with the target anatomical structure in terms of CT gray level or magnetic resonance relaxation time, and the outer component is consistent with the human tissue outside the target anatomical structure in terms of CT gray level or magnetic resonance relaxation time.

[0037] 2) Scan the target anatomical structure and the auxiliary tool to obtain images, and then perform image segmentation and model reconstruction on the target anatomical structure and the inner component using the same technical route.

[0038] 3) Import the reconstructed inner component model into reverse engineering software or 3D printing support software, calculate the volume of the reconstructed inner component model, and divide the volume of the reconstructed model by the volume of the original inner component to obtain the volume change rate of the reconstructed model caused by the entire technical process.

[0039] 4) Import the reconstructed target anatomical structure model into reverse engineering software or 3D printing support software, measure the volume of the reconstructed target anatomical structure model, and divide the volume of the reconstructed target anatomical structure model by the volume change rate of the reconstructed model to obtain the corrected volume of the target anatomical structure model.

[0040] 5) In reverse engineering software or 3D printing support software, use the surface offset algorithm to perform an inward surface offset on the reconstructed model of the target anatomical structure, and adjust the surface offset distance to make the reconstructed model approach the corrected volume of the target anatomical structure.

[0041] Wherein, the auxiliary tool is a two-layer or multi-layer structure. When the target anatomical structure and / or human tissue is multi-layer, the inner component and / or the outer component are correspondingly set to be multi-layer. The following takes the two-layer structure as an example for illustration. In the two-layer structure, the inner component is embedded or completely encapsulated in the outer material.

[0042] As Figure 1 shown, the outer component 2 is made of a material that is basically consistent with the human tissue outside the target anatomical structure in terms of the gray level of the CT scan image or the relaxation time of the MR scan image. The inner component 1 is a dimension standard part, and the standard parts enclosed therein are basic shapes with various forms, which can be spheres, cylinders, tubes, free-form surfaces, or forms that are completely consistent with the target anatomical structure, etc. The material used is basically consistent with the average value of the target anatomical structure in terms of the gray level of the CT scan image or the relaxation time of the MR scan image.

[0043] As Figure 2As shown, in some embodiments, the range of variation of the image gray level or relaxation time of the target anatomical structure in the population is segmented, and different average values of different segments correspond to different image gray levels and relaxation time materials. Similarly, the range of variation of the image gray level or relaxation time of the human tissue outside the target anatomical structure in the population is also segmented, and different average values of different segments correspond to different image gray levels and relaxation time materials. When making the auxiliary tool, it can be designed in sets. Each set of auxiliary tools has at least two outer components 2 with different CT gray levels or magnetic resonance relaxation times to correspond to different populations; a plurality of inner components 1 with the same shape are arranged on each outer component 2, and the CT gray level or magnetic resonance relaxation time of each inner component 1 corresponds to the average value of the target anatomical structure of different populations.

[0044] Since the CT gray levels or magnetic resonance relaxation times of the inner components 1 are different, it is best to arrange the inner components 1 in a stepped manner according to different CT gray levels or magnetic resonance relaxation times on the same outer component 2.

[0045] As Figure 3 shown, in some embodiments, the inner component 1 having the same shape as the target anatomical structure can also be encapsulated or embedded in a single outer component 2.

[0046] To facilitate those skilled in the art to better understand the bone model reconstruction method of the present invention, the following takes the reconstruction of the hip bone digital model based on GE 16-slice or 32-slice CT in South China as an example for illustration. In the following description, Type I represents the Figure 1 auxiliary tool shown, Type II represents the Figure 2 auxiliary tool shown, and Type III represents the Figure 3 auxiliary tool shown.

[0047] In the hip bone scan images based on GE 16-slice or 32-slice CT in South China, the average CT gray value of the soft tissue around the bones of a single individual generally ranges from 40 to 70 Hu, with an average value of about 55 Hu. The average gray value of the hip bone is between 300 and 560 Hu, with an average value of 405 Hu. The type I outer layer structure is made of a material with a CT gray value of 55 Hu, such as high molecular resin material, high molecular gel or latex, etc., with appropriate addition of inorganic salts such as calcium sulfate. The inner layer material is made of inorganic salts such as gypsum and adhesive gypsum, or a mixture of inorganic salts and high molecular materials (such as polyvinyl alcohol and polyvinyl acetate emulsion) with a CT gray value of 405 Hu. For type II, the CT gray value of the material can be adjusted by adjusting the ratio of inorganic salts to high molecular materials to obtain various outer and inner layer materials with stepped CT gray values, such as 3 kinds of outer layer materials with CT gray values of 45 Hu, 55 Hu, and 65 Hu, and 6 kinds of inner layer materials with CT gray values of 300 Hu, 350 Hu, 400 Hu, 450 Hu, 500 Hu, and 550 Hu. Using 6 kinds of inner layer materials, 18 spheres with the same diameter are made and respectively sealed into 3 kinds of inner layer materials to form a set of tools. For type III, the materials are the same as those of type I, except that the standard parts sealed or embedded in it are components consistent with the target shape.

[0048] Auxiliary tool processing method: First, design the digital model of the standard part of the inner layer component. The shape of the outer layer material is not limited. Then, the finished product can be obtained through one of the two technical routes: 1) Additive manufacturing (3D printing) of various materials to directly process the finished product. 2) First, make a high-precision inner layer component and seal it into the outer layer material to make the finished product: The inner layer component can be made by: a) Additive manufacturing (3D printing), b) Making a mold and pouring the inner layer material into the mold for curing and forming, c) CNC machining to cut and mill the solidified block. According to the different outer layer materials, the outer layer material can be sealed in the following ways: a) Place the inner layer material into the non-solidified outer layer material, and the finished product is obtained after the outer layer material solidifies, b) Drill holes or install the inner layer component in the cavity of the movable outer layer material component for installation and forming.

[0049] Usage method: Types I and II are relatively small in size and are generally scanned together with the patient's target anatomical structure to obtain an image containing the target anatomical structure and the Type I or II tool. Using the same technical route, image segmentation and model reconstruction are performed on the target anatomical structure and the inner components of the Type I or II tool. In the reconstructed inner component model of the Type I tool, select the component with a topological shape similar to the anatomical structure. In the Type II tool, select the inner and outer layer materials with gray levels similar to those of the target anatomical structure and the surrounding tissues. The selected inner component model is imported into reverse engineering software or 3D printing support software to calculate the volume of the reconstructed model. The volume of the reconstructed model divided by the volume of the original component is the ratio of the reconstructed model volume caused by the entire technical process (volume change rate). Dividing the volume of the reconstructed model of the anatomical structure measured in the software by this ratio can calculate the corrected volume of the target anatomical structure. Use the surface offset algorithm or perform an inward surface offset on the reconstructed model of the target anatomical structure in the software. By adjusting the surface offset distance, the processed model is made to approach the corrected volume of the target anatomical structure. At this time, the corrected model eliminates model magnification and is closer to the real anatomical structure.

[0050] The Type III tool needs to be scanned separately before and after the anatomical structure scan (the scan parameters are the same as those for the anatomical structure scan). Using the same technical route, image segmentation and model reconstruction are performed on the target anatomical structure and the inner components of the Type III tool. The inner component model is imported into reverse engineering software or 3D printing support software to calculate the volume of the reconstructed model. The volume of the reconstructed model divided by the volume of the original component is the ratio of the reconstructed model volume caused by the entire technical process (volume change rate). Dividing the volume of the reconstructed model of the anatomical structure measured in the software by this ratio can calculate the corrected volume of the target anatomical structure. Use the surface offset algorithm or perform an inward surface offset on the reconstructed model of the target anatomical structure in the software. By adjusting the surface offset distance, the processed model is made to approach the corrected volume of the target anatomical structure. At this time, the corrected model eliminates model magnification and is closer to the real anatomical structure.

[0051] Verification.

[0052] In the above process, a verification method can also be selected to verify the ratio (let this ratio be x) involved in the subsequent calculations 1Proper correction is carried out. The digital model of the inner layer component of the selected type I or type II tool is registered with the digital model of the original standard part using the least squares algorithm to complete the registration of the 3D model, or the 3D model registration tool in reverse engineering software (such as Geomagic, etc.) is used to complete the registration of the reconstructed inner layer component with the original digital model. After registration, the average deviation between the reconstructed model and the original digital model is understood using the software's 3D deviation analysis function (or calculating the average Hausdorff distance using algorithms such as the isosurface extraction algorithm as the absolute average deviation). The reconstructed model is offset inward by the surface offset algorithm or function. By adjusting the surface offset distance, the volume of the reconstructed component model is approximated to the volume of the original component. The absolute average deviation between the processed model and the original model is understood through deviation analysis (set as k 1 ); further adjust the surface offset distance to minimize the absolute average deviation between the processed reconstructed component model and the original component (set this minimum value as k 2 ); if k 1 and k 2 differ greatly, it is necessary to check whether the reconstruction technical process is affected by noise and whether the reconstruction technical route needs to be changed to reconstruct the model; if k 1 and k 2 have a difference that meets expectations, the ratio of the volume of the reconstructed component model divided by the volume of the processed reconstructed component model can be selected (set this ratio as x 2 , the correction ratio) to further correct the volume of the target anatomical structure.

[0053] Verification criteria.

[0054] During the verification process, the following method can also be used to determine whether the correction ratio should be selected to participate in the calculation of the corrected volume of the anatomical structure. Let the pixel size of the scanned image be L. First, understand whether k 1 and k 2 are close to or less than 0.301*L, that is, if both k 1 and k 2 are significantly greater than 0.301*L, it indicates that the technical process of the model reconstruction method needs to be improved. If k 2 is close to or less than 0.301*L, then select x 2 to enter the subsequent correction calculation. The principle is that it can be mathematically proven that in the ideal state, using the slice-level reconstruction method to reconstruct an irregular anatomical structure infinitely many times, the average deviation of all reconstructed models will approach 0.301*L. Based on this standard, it can be judged that the reconstruction error of a certain reconstruction method has reached an ideal level. If the corrected reconstruction error is still significantly greater than 0.301*L, it indicates that there is a problem with the model reconstruction technical process.

[0055] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0056] Through the description of the above structures and principles, those skilled in the art should understand that the present invention is not limited to the above specific embodiments. Improvements and substitutions using well-known techniques in the art based on the present invention fall within the protection scope of the present invention, and the protection scope of the present invention shall be defined by each claim item and its equivalents. Those parts not described in the specific embodiments are all prior art or common general knowledge.

Claims

1. A method for reconstructing a digital model of bone based on a scanned image, characterized in that, it comprises the following steps: 1) Making an auxiliary tool, which includes an inner component and an outer component, and the inner component is completely embedded or inserted into the outer component; the inner component is consistent with the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time, and the outer component is consistent with the human tissue outside the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time; 2) Scanning the target anatomical structure and the auxiliary tool to obtain images, and then performing image segmentation and model reconstruction on the target anatomical structure and the inner component using the same technical route; 3) Importing the reconstructed inner component model into reverse engineering software or 3D printing support software, calculating the volume of the reconstructed inner component model, and dividing the volume of the reconstructed model by the volume of the original inner component to obtain the volume change rate of the reconstructed model caused by the entire technical process; 4) Importing the reconstructed target anatomical structure model into reverse engineering software or 3D printing support software, measuring the volume of the reconstructed target anatomical structure model, and dividing the volume of the reconstructed target anatomical structure model by the volume change rate of the reconstructed model to obtain the corrected volume of the target anatomical structure model; 5) In reverse engineering software or 3D printing support software, using a surface offset algorithm to perform an inward surface offset on the reconstructed model of the target anatomical structure, and adjusting the surface offset distance to make the reconstructed model approach the corrected volume of the target anatomical structure.

2. The method for reconstructing a digital model of bone based on a scanned image according to claim 1, characterized in that, a plurality of inner components with different shapes are arranged on a single outer component, and each inner component is synchronously scanned when the auxiliary tool is scanned; the shape of the inner component is selected from a spherical shape, a cylindrical shape, a tubular shape, a free-form surface shape, and a shape completely consistent with the target anatomical structure; each inner component corresponds to the average value of the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time.

3. The method for reconstructing a digital model of bone based on a scanned image according to claim 1, characterized in that, a plurality of inner components with the same shape are arranged on a single outer component, and each inner component is synchronously scanned when the auxiliary tool is scanned; each inner component corresponds to the average value of the target anatomical structure of different populations in terms of CT gray scale or magnetic resonance relaxation time.

4. The method for reconstructing a digital model of bone based on a scanned image according to claim 2 or 3, characterized in that, the auxiliary tools are provided in sets, and each set of auxiliary tools has at least two outer components with different CT gray scales or magnetic resonance relaxation times to correspond to different populations.

5. The method for reconstructing a digital model of bone based on a scanned image according to claim 1, characterized in that, one inner component is arranged on a single outer component, and the shape of the inner component is completely consistent with the shape of the target anatomical structure; the inner component corresponds to the average value of the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time, and the outer component corresponds to the average value of the human tissue outside the target anatomical structure in terms of CT gray scale or magnetic resonance relaxation time.

6. A method for reconstructing a digital model of a bone based on a scanned image according to claim 1, characterized in that, the auxiliary tool is directly processed into a finished product by 3D printing; or, the auxiliary tool first manufactures an inner component and then seals it into an outer component to manufacture a finished product; when manufacturing the inner component, 3D printing, mold curing or CNC machining is used; when sealing the outer component, one of the following two methods is adopted: a) placing the inner material into the uncured outer material and solidifying it to obtain a finished product, b) placing the inner component into the outer material with cavities formed by punching or movable installation and installing it into shape.

7. A method for reconstructing a digital model of a bone based on a scanned image according to claim 1, characterized in that, in step 2), the target anatomical structure and the auxiliary tool are scanned to obtain images, which are scanned separately in two times before and after or the auxiliary tool and the patient's target anatomical structure are scanned together.

8. A method for reconstructing a digital model of a bone based on a scanned image according to claim 1, characterized in that, when the target anatomical structure and / or human tissue are multi-layered, the inner component and / or the outer component are correspondingly set to be multi-layered.

9. A method for reconstructing a digital model of a bone based on a scanned image according to claim 1, characterized in that, it further includes a volume change rate correction step: the registration of the 3D model of the reconstructed model of the inner component and the original model of the inner component is completed by using the least square algorithm or the registration of the reconstructed model of the inner component and the original model is completed by using a 3D model registration tool in reverse engineering software; After registration, the reconstructed model of the inner layer component is offset inward by a surface offset algorithm or function. By adjusting the surface offset distance, the volume of the reconstructed model is approximated to the volume of the original model. The absolute average deviation between the model and the original model at this time is obtained through deviation analysis and set as k 1 ; Further adjust the surface offset distance to minimize the absolute average deviation between the processed reconstructed model and the original model, and let this minimum value be k 2 ; Compare k 1 , k 2 values. If the difference between k 1 and k 2 is not greater than the threshold value, then select the correction ratio x 2 obtained by dividing the reconstructed model volume by the processed reconstructed model volume to correct the volume of the target anatomical structure model; Determine whether to select the correction ratio x 2 When correcting the volume of the target anatomical structure model, the following steps are further included: Assume the pixel size of the scanned image is L. If k 1 and k 2 are both greater than 0.301*L, then do not correct the volume of the target anatomical structure model through the correction ratio x 2 to correct the volume of the target anatomical structure model. If k 2 is not greater than 0.301*L, then select the correction ratio x 2 to correct the volume of the target anatomical structure model.

10. An auxiliary tool for reconstructing a digital model of a bone based on a scanned image, which is applied to a method for reconstructing a digital model of a bone based on a scanned image according to any one of claims 1-9, characterized in that, it includes: an inner component and an outer component, the inner component is embedded or completely embedded in the outer component; the inner component is consistent with the target anatomical structure in CT gray scale or magnetic resonance relaxation time, and the outer component is consistent with the human tissue outside the target anatomical structure in CT gray scale or magnetic resonance relaxation time; when in use, the inner component model is obtained by scanning the image of the auxiliary tool, segmenting the image and reconstructing the model; the reconstructed inner component model is imported into reverse engineering software or 3D printing support software, the volume of the reconstructed inner component model is calculated, and the volume change rate of the reconstructed model caused by the entire technical process is obtained by dividing the volume of the reconstructed inner component model by the volume of the original inner component; the volume of the reconstructed digital model of the bone is corrected by using the volume change rate of the reconstructed model.

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