Research and application discussion of cranial bone model preparation method based on three-dimensional reconstruction and 3D printing technology

Research and application discussion of cranial bone model preparation method based on three-dimensional reconstruction and 3D printing technology | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Research and application discussion of cranial bone model preparation method based on three-dimensional reconstruction and 3D printing technology Jing Peng, Wenjie Guo, Deqin Yang, Guohui Yang, Yanhong Shu, Ying Li, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4203522/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 Aug, 2024 Read the published version in Surgical and Radiologic Anatomy → Version 1 posted 7 You are reading this latest preprint version Abstract Purpose The aim of this study was to find an alternative method to meet traditional human anatomy teaching and clinical needs in order to solve the problem of cranial specimen attrition and specimen resource shortage due to long-term use. Methods We performed a CT scan of a well-preserved male cranial specimen and used Mimics 19.0 software for 3D reconstruction and cranial block separation. Subsequently, we compared the recognition ability of the processed cranial digital model with that of the 3D body digital model and used 3D printing to create the cranial model and compare it with the physical specimen. Results Twenty-two cranial bone block models were obtained, excluding the hyoid bone. Their 3D reconstructed digital models had better bony landmark recognition than the 3D body human digital models, and the differences between the 3D printed models and the physical specimens were minimal. In addition, only one STL file was required to produce the cranial models, which facilitates repetitive printing at any time. Conclusion By isolating cranial bone blocks through 3D reconstruction techniques and preparing high-quality cranial models in combination with 3D printing techniques, this study solves the problem of shortage of cranial teaching specimens for the sustainable development of clinical and medical schools. 3D printing Cranial separation 3D reconstruction Teaching resource Scranial specimens Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction Human cranial specimens are important teaching and research tools in the fields of anatomy, biomedicine, and anthropology [1]. The traditional cranial isolation operation is divided into the following steps: collecting the cranial specimen, cleaning and handling the cranial specimen, determining the orientation and positioning of the specimen, determining the preservation method of the specimen, and performing the display and maintenance of the specimen. However, the shortage of human specimen resources has become a problem that most medical schools must consider in order to achieve long-term development [2, 3], and at the same time, the traditional cranial bone separation method is usually complicated, difficult to completely separate the anatomical parts of the skull that are weak in bone quality, and the separation effect is difficult to control and will be damaged with the prolongation of the use of time, which has prompted people to constantly search for a new method of separating cranial bones[4-6]. It is precisely because of the lack of a suitable method for separating fragile bones such as the sieve bone and the pterygoid bone that there is currently a gap in the morphological statistics and growth mechanisms of these bones. Cochinski mentions a systematic approach to understanding the sphenoid wings, a study that would be better served by isolating the sphenoid bone as a whole[7]. In addition, in recent years, the research of AI artificial intelligence to separate the whole body anatomical structure of the human body is gradually emerging, but there are fewer literatures for exploring the method of automatic segmentation of cranial bone block, which may also be a bottleneck in the separation method. We provide a preliminary basis for the study of automatic segmentation of cranial bone blocks by introducing the method of separating cranial bones [8]. In recent years, with the development of 3D reconstruction technology and 3D printing technology, the use of 3D reconstruction technology to separate the skull and create a digital model of the skull, followed by the use of 3D printing technology to obtain a 3D printed skull model has played a great role in the teaching of human anatomy [9, 10]. Because the accurate reproduction ability of 3D printing technology can reflect the morphological characteristics of specimens and their anatomical features extremely well, 3D printed anatomical models are gradually replacing specimens is becoming a trend [11-13].3D printed model solves the problems of time-consuming, difficult to make moulding and easy to damage of pneumatic-containing bone of traditional separation methods, and also solves the problems of virtual digital technology that requires the support of equipments [14]. In addition, 3D printed models only need a S.T.L. file to achieve many advantages such as easy access, easy storage, low cost of mass production, easy promotion, etc., which makes it easier to meet the application needs of anatomy teaching in clinical and medical schools[15]. Therefore, we use 3D reconstruction and 3D printing technology to separate the skull, explore the image boundaries of each bone block, to provide a pre-basis for the formation mechanism of cranial bone joints, cranial deep learning and AI artificial intelligence, etc. Materials And Methods Skull Specimen selection and processing: approval was obtained from the ethics committee of Hunan University of Medicine. The procedures used in this study adhere to the tenets of the Declaration of Helsinki. Adult male cranial specimens with complete bony integrity after local dissection in the specimen bank were selected, and horizontal saw cuts were made along the supraorbital notch at about 1.2 cm above the posterior superior collar line and about 1.0 cm above the posterior superior collar line at the two localization points, fully exposing the cranial base and facilitating observation of anatomical landmarks (Fig. 1 ). CT scanning and data acquisition: before processing the cranial specimens, the specimens were scanned by continuous tomography via a 64 row 128 layer GE Optima CT machine with a voltage of 120 kV, a current of 150 mA, and a layer thickness of 0.625 mm, and exported in DICOM format. Fig.1 Adult male cranial specimen (mechanically segmented into skull base and skull cap). Three Dimensional Reconstruction and Processing The CT data were imported into Mimics 19.0 software (http://biomedical.materialise.com/mimics, RRID:SCR_012153) for threshold segmentation with a threshold value of 226-3071Hu, and a mask was generated;In the process of bone fragment separation, based on the threshold value of 226-3071, bone fragments were divided into two types of high bone density and low bone density according to the integrity of bone fragment reconstruction, the existence of large holes, and the clarity of bone markers, etc. Crop Mask was used to narrow the boundary line to the edge of the target skull fragment; Lasso in the Edit Masks tool was used to separate the preliminary boundary between the target cranial block and the other bones around it: Bone blocks with high bone density could be separated based on obvious demarcation lines such as the coronal suture, sagittal suture, parietal mastoid suture, nasal incision, zygomaticomaxillary suture, and so forth. At the same time, the 2D window image layers were observed to see whether the bone block boundary was clear, and Boolean operations were used to separate the surrounding bone blocks with complete bone and clear boundary lines. For bone blocks with low bone density, such as sphenoid bone, ethmoid bone and palatine bone, it was necessary to make single and multi layer editing, such as painting and erases of 2D image window according to layers. Moreover, sphenoid sinus orifice, sphenoid ridge and ethmoid cell of sphenoid bone were difficult to distinguish, so the anatomical structure should be trimmed repeatedly in combination with Toggle mask 3D preview to ensure the simulation of digital model; The two types of edited masks were automated to obtain the 3D digital model through 3D calculate. And according to the above method, 22 skull blocks were reconstructed and separated from the model (Fig. 2 A-B); Since the skull itself lacked the mandible and some teeth of the maxilla, the data of another specimen’ s mandible and teeth of the maxilla were used, and the teeth and the mandible that corresponded to what were missing in this skull specimen were made to arrive at the proper position using Pan and Rotate commands (Fig. 3 A-B); The skull block model was imported into 3 matic 11.0 software (http://biomedical.materialise.com/mimics, RRID:SCR_012153), and the small protruding or concave Areas of the model surface were Smoothed by Local Smoothing. The area to be repaired on the model surface is selected by operations such as Area Mark, and the selected triangular surface is deleted. Then Fill Hole Freeform was used to automatically repair tiny holes on bone blocks to achieve local optimization effect.; In 3-matic11.0 software, the cranial block model was moved by Interactive Translate. Through the appearance of the cranial block and the distribution of the cranial block, the Lasso Area Mark was utilized to mark the mother plate surface of the stent rest, and the thickness of the mother plate surface was designed through Uniform Offset. And then bracket design was completed through New Sketch,Add Constraint,Extrude and Revolve operation for (Fig. 4 A-B); The model generated STL files were saved and imported into Magics 21.0 software(http://biomedical.materialise.com/mimics, RRID:SCR_012153) for print pre processing to generate ".slc " format file. Fig.2 (A-B) The 21 cranial bone block models (without hyoid bone and mandible) were obtained by separating them through Crop Mask, Edit Masks and Boolean operations in Mimics 19.0, and the frontal view (a) and lateral view (b) were shown in 3D preview. Fig.3 (A-B) Obtaining the mandible and some teeth of the maxilla from another specimen, adjusting the teeth and mandible to the corresponding position through Pan and Rotate, and completing the 22 pieces of cranial bone block model, showing the frontal view (a) and lateral view (b) in 3D preview. Fig.4 (A-B) In 3 matic 11.0, the distance between each bone block was adjusted, and according to the appearance of the bone block model and the distribution of the cranial bone blocks, the bottom master and bracket were generated (a), and the 22 cranial bone models were unfolded and lined up to ensure that the details of each bone block can be observed (b). Digital Model Effectiveness Evaluation The modeling effect of this skull model was evaluated by comparing the processed skull model with the digital model of 3Dbody (www.3dbody.com), a commonly used software for medical teaching (Fig. 5 A-B)(Fig. 6 A-B). Fig.5 (A-B) Comparison of frontal view between digital model and 3D body model (a: digital model; b: 3D body model) (① brow arch ② zygomatic arch ③ inferior turbinate ④ Chin hole). Fig.6 (A-B) Comparison between the bottom view of the digital model and the 3D body model (a: digital model; b: 3D body model) (① zygomatic arch ② foramen ovale ③ carotid canal external orifice ④ occipital foramen ⑤ mastoid process ⑥ extraoccipital convexity). 3D Printing Six Star Intelligent-Laser Curable Printer is selected, which prints on the principle of layer-by-layer stacking of photosensitive resin to obtain a 1:1 solid model. rinting steps were as follows: (1) the ".slc" format files were imported into the 3D Print software, and the laser control system was open ; (2) 3D printing molding was started, and through the control of computer layering information, the photosensitive resin liquid material was stacked and printed layer by layer through the equipment to obtain the model(Fig. 7 A-B); (3) After being printed, the model was taken out and soaked in anhydrous ethanol for 15 20 minutes to remove the liquid photocuring resin attached to the surface of the model. After soaking, the printing support was removed and the model was dried with absorbent paper; (4) the model was placed in a UV drying oven for drying treatment. Finally, the 3D printed skull model was taken out. Fig.7 (A-B) The "slc" file was imported into a laser curing printer for 3D printing of cranial bone blocks to obtain a 3D printed model (a). The 3D printed model was cleaned, and the brackets were removed, resulting in 22 cranial bone blocks (excluding the hyoid bone) with intact details and complete bony landmarks (b). 3D Printing Model Effect Evaluation (1) Compare 3D printed cranial models with cranial specimens to assess model reproduction. (2) Compare the 3D printed skull model with other cranial teaching aids models to assess the accuracy(Fig. 8 A-B)(Fig. 9 A-B). Fig.8 (A-B) The external comparison of the skull base includes a 3D printed model, a specimen model, and a teaching model (a: teaching model b: 3D printed model c: physical specimen) (① incisor holes ② palatine foramen ③ zygomatic arch ④ foramen ovale ⑤ rupture holes ⑥ carotid canal external orifice ⑦ occipital condyles ⑧ extraoccipital convexity). Fig.9 (A-B) The comparison of the internal surface of the skull base includes 3D printed models, specimen models, and teaching models (a: teaching model b: 3D printed model c: physical specimen) (① blind foramen ② optic nerve canal ③ pituitary fossa ④ foramen ovale ⑤ foramen spinosum ⑥ rupture holes ⑦ intra-occipital ridge ⑧ intra-occipital convexity). Discussion Introduction of a practical method of cranial separation In teaching the anatomy of the skull, fine separation of each bone block is crucial. Traditional separation techniques, however, are time-consuming and labour-intensive, especially when dealing with fragile bone fragments such as sieve bones, where fragmentation often occurs. This situation leads to the fact that anatomy teaching often bypasses these bone fragments or relies solely on 2D images for teaching, which in turn affects the students' accurate understanding of these structures, due to the fact that a vague impression of the anatomical structures will further increase the difficulty in differentiating the cranial images for students. We used CT scanning and 3D reconstruction techniques to reconstruct the skull and finely segment each bone block according to a detailed and complete separation method, a method that can effectively separate fragile bone blocks without damaging the overall skull structure. In addition, the isolated cranial files can be digitally preserved from the erosion of time. We compared 22 skull blocks (excluding the hyoid bone) produced after 3D reconstruction and 3D printing with real specimens and found that the skull model designed by our method was superior to that of anatomical software and more realistically presented the morphology of the skull. Providing methods for anatomical measurements and biomechanical analyses As the study of the mechanism of cranial suture formation in the current literature mainly stays at the two-dimensional level, there is a lack of in-depth discussion on three-dimensional morphometric measurements.Richtsmeier et al. elaborated on the mechanism of cartilage ossification and membranous ossification during cranial bone development, and demonstrated the morphology of the skulls of mammals and infants through three-dimensional reconstruction [16]. In addition, the mechanism of cranial suture ossification disorder was thoroughly investigated in the paper, and it was pointed out that the development of cranial suture has an important influence on the whole cranial structure. Therefore, the development of a method capable of complete and accurate separation of cranial bones is of positive significance for research in this field. In terms of biomechanical analyses of the cranium, the existing literature tends to treat the cranial bone fragments in a combined manner, resulting in the realism of the model being compromised. Although some studies attempted to separate the cranial bones, their separation boundaries were vague and far from the real form[17]. For example, in clinical practice, separating surgery on the upper jaw requires analysing the forces on the mid-jaw and pterygopalatine sutures; however, there is a lack of effective separation methods in the literature for irregular cranial sutures, which restricts in-depth finite element analyses of these areas[18]. Our proposed separation method can accurately separate the cranial boundaries in a near-real situation, which leads to a more accurate and improved force analysis of the bone blocks between the cranial sutures. Exploring the degree of bone block reconstruction in conventional ct scans After comparing the cranial model of 3Dbody, a widely used anatomical software in China, the purchased cranial teaching aids model and the cranial model prepared based on the combination of 3D reconstruction and 3D printing technology proposed in this study, it can be concluded that the cranial model in the 3Dbody software [19] is able to accurately display obvious bony landmarks such as the pterygoid point, mastoid process, and pennate process. However, for some detailed bony landmarks such as the saddle dorsum of the pterygoid, the sinusoidal groove of the medial temporal bone, and the trigeminal nerve indentation, there is a certain degree of ambiguity in the portrayal of the 3Dbody software model, and some of the detailed bony landmarks lacked clear labelling, which is of limited use as an aid to beginners. The defects of the cranial teaching aids model include: the cranial teaching aids model is formed by moulding and pressing, which leads to the expensive cost, lack of precision, and not easy to clean and store. Compared with the above, the digital model prepared in this study is able to more accurately reproduce the morphological features of the human skull by using the CT scan data of the skull specimen for reconstruction and focusing on overcoming the tiny bony landmarks that were difficult to determine in the previous software model. In addition, in terms of detail processing, the digital model is closer to the real specimen, and can better show the structures such as the winglets of the pterygoid, the supraorbital fissure, the carotid artery sulcus, the sieve labyrinth, the supraorbital foramen of the frontal bone, and the glochids of the sieve bone. It should be emphasised that the final result of the digital model is limited by factors such as the resolution of the CT data and the thickness of the scanned layers. Certain structures that cannot be easily reconstructed, such as the sieve foramen of the sieve bone, cannot be fully restored. In addition, there may be substandard rendering of holes, sutures, notches, fissures, grooves, channels, nodules, thin-walled structures, sharp peaks and crests in a few parts during the reconstruction process [20]. However, the present method has advantages in the separation of cranial bone sutures, separation of cranial bones with weak bone, and separation of air-containing bones, which can preserve the original morphological structure of cranial specimens without causing damage to them. Compared with other teaching aids models and anatomy teaching software, the digital model prepared in this study has high accuracy, high characterisation and high efficiency. Despite some limitations, the methodology of this study provides insights into the degree of reduction of conventional CT reconstruction models, and provides a more accurate and high-quality digital model resource for human anatomy education and pathology diagnosis, among other fields. Clinical and anatomical applications The advantage of 3D printed cranial models over traditional cranial specimens in daily teaching is the reduction of model wear and tear. Traditional skull specimens in the process of long-term use, due to the use of specimen receptacle is not reasonable and students observe and turn the process of the operation of the problem, easy to lead to the damage of air-containing bone, especially the butterfly bone, nasal bone and sieve bone defect is more common. In contrast, 3D printed models are printed with photosensitive resin material, which has good hardness and texture, and has less or even better differences with the use of real cranial specimens, especially in terms of separation difficulty, service life, storage conditions and display effect. In clinical teaching, 3D digital skull models and 3D printed skull models can often be used in combination. 3D digital models presented through visualisation platforms can provide clinicians with different angles or cross-sections of the cranial anatomy to observe, and present important anatomical structures that are difficult to observe in a digital and 3D printed form [21].3D printed models have the advantages of being designed according to the needs, easy to be adjusted, and printed in a short period of time, and they can also provide doctors with preoperative planning and the development of surgical protocols with precise anatomical preparation. Currently, anatomy teaching and image information acquisition mainly rely on tomographic images or observation of solid specimens, both of which have obvious limitations. The former requires rich anatomical experience and spatial imagination, while the latter can only obtain superficial anatomical structure information. However, the 3D reconstruction visualisation platform provides a novel approach to image learning [22]. This method corresponds each pixel point of the 2D image to the 3D model by acquiring 2D image data and performing 3D reconstruction using the image post-processing software Mimics. By combining 2D and 3D information acquisition, a new level of understanding of anatomical structures and boundaries can be achieved. Looking to the future, we hope to further improve the accuracy of 3D reconstruction techniques and separation of cranial bones to better apply digital and 3D printed models to assist clinicians and medical schools in teaching anatomy [23]. Limitations The quality of CT data affects the modelling effect: the quality of CT data has an important impact on the establishment of the skull model. If the layer thickness of CT data is too large, it will lead to a decrease in the accuracy of the model and will not be able to accurately reconstruct some fine bony structures; if the resolution of CT data is low, it will introduce more signal noise in the modelling process, thus affecting the quality of the model. Therefore, it is necessary to select CT data of appropriate quality when performing cranial bone separation to ensure the accuracy of the model. Consideration of the characteristics of cranial bone mass: The characteristics of cranial bone mass can also have some impact on the modelling. For example, regions with air-containing bone and thin bone have lower resolution in CT imaging, which increases the difficulty of modelling; and bone blocks with defects need to be artificially repaired to ensure the integrity and accuracy of the model. Conclusion In this study, 22 high-reduction 3D digital models of the skull (excluding the hyoid bone) were successfully separated and reconstructed using 3D reconstruction technology, which enriched the database of cranial models and provided useful resources for online teaching. In addition, the use of 3D printing technology to create a solid model of the skull has the advantages of low separation difficulty, convenient storage of the model, long time of use, and better presentation compared with traditional specimens, which is especially suitable for offline teaching. There are some limitations in this study, only a single sample to explore the separation and printing of cranial specimens, the future needs to expand the sample size in-depth study. In the future, thin-layer CT devices with smaller layer thicknesses will be introduced for skull scanning to improve the accuracy of 3D reconstruction technology on the skull and to assist in the teaching of human anatomy by accurately displaying bony landmarks. Declarations Funding This study was supported by Hunan Provincial Natural Science Foundation of China (2022JJ50292); A Project Supported by Scientific Research Fund of Hunan Provincial Education Department (23A0728); Research Project on Teaching Reform of Ordinary Higher Education Institutions in Hunan Province (HNJG-20231510); Hunan Province Social Science Outcome Review Committee Project (XSP24YBC004); Project of Key Laboratory of Digital Anatomy and 3D Printing Clinical Translational Research in Huaihua City (2020R2201); Huaihua Science and Technology Innovation Plan Project (2021R3105); Horizontal Projects (1. Research on "open + bridge-based" 3D guide in intracerebral hemorrhage puncture. 2. Study on the application of digital "triple fixed" guide in endoscopic foraminal surgery). Author Contribution Concept and design: JP, WJG, GHY; model construction: JP, WJG, DQY, LL, PHY; drafting of the manuscript: JP, WJG, DQY, GHY, YHS, YL; manuscript editing: LBR, LL, PHY, JP; submission of the manuscript: YHS, YL. Acknowledgements The authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind's overall knowledge that can then improve patient care. Therefore, these donors and their families deserve our highest gratitude. References Bolino G, Fineschi V, Cecannecchia C, D’Antonio G, Frati P (2023) The Practice of Teaching and Scientific Research on Cadaveric Material Remains Crucial for Medical Education. 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Cite Share Download PDF Status: Published Journal Publication published 09 Aug, 2024 Read the published version in Surgical and Radiologic Anatomy → Version 1 posted Editorial decision: Revision requested 10 Jun, 2024 Reviews received at journal 04 Jun, 2024 Reviewers agreed at journal 25 May, 2024 Reviewers invited by journal 12 Apr, 2024 Editor assigned by journal 03 Apr, 2024 Submission checks completed at journal 02 Apr, 2024 First submitted to journal 01 Apr, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4203522","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":287259317,"identity":"ae3138df-11dc-4082-b8e6-e6f39931b26f","order_by":0,"name":"Jing Peng","email":"","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Jing","middleName":"","lastName":"Peng","suffix":""},{"id":287259318,"identity":"f2a28dc9-c240-4c38-b3de-3f36bb29aece","order_by":1,"name":"Wenjie Guo","email":"","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Wenjie","middleName":"","lastName":"Guo","suffix":""},{"id":287259319,"identity":"7fe8a979-5064-4b1a-b893-973af4641356","order_by":2,"name":"Deqin Yang","email":"","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Deqin","middleName":"","lastName":"Yang","suffix":""},{"id":287259320,"identity":"1142bb90-64ea-41db-9bfb-7aea652c7e2c","order_by":3,"name":"Guohui Yang","email":"","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Guohui","middleName":"","lastName":"Yang","suffix":""},{"id":287259321,"identity":"8522998d-a9df-4c22-8f32-2b651791646f","order_by":4,"name":"Yanhong Shu","email":"","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Yanhong","middleName":"","lastName":"Shu","suffix":""},{"id":287259322,"identity":"8c79ce06-4551-402f-8ee0-72b1f15897a9","order_by":5,"name":"Ying Li","email":"","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Ying","middleName":"","lastName":"Li","suffix":""},{"id":287259323,"identity":"f7ea5b63-bf4d-48e4-8a38-757595294ce2","order_by":6,"name":"Libing Rao","email":"","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Libing","middleName":"","lastName":"Rao","suffix":""},{"id":287259324,"identity":"33b85963-c167-4900-9bb0-5e5a756191ca","order_by":7,"name":"Penghui Yu","email":"","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Penghui","middleName":"","lastName":"Yu","suffix":""},{"id":287259325,"identity":"956c3891-27c5-41c4-aa9d-31fb09efcc86","order_by":8,"name":"Li Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIie3RsQrCMBCA4SuBurRkkxaHvsKVroKv0iL4DN2MKF1dK76Eo+OFQKdzFxwUXB0KroLWVYTGzSHfdEN+uCMAjvOHUAhFLY6FD4aoLa0ST+m6nA2k1xS6ZpsEPCUCNjJecmbClU0y8BYUVmKEDbcUKkjkkPoXo7jyM+TDjuI9pJttbpGkVTDFY5ekDDmebJKiiua78+3SDbYJMYpYMZC2TbQqcyGhQa046r9lsjbm/sDn+yuv90c5TuSoJ/kU/fbccRzH+e4FmRVOfrmuV74AAAAASUVORK5CYII=","orcid":"","institution":"Hunan University of Medicine","correspondingAuthor":true,"prefix":"","firstName":"Li","middleName":"","lastName":"Li","suffix":""}],"badges":[],"createdAt":"2024-04-02 03:29:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4203522/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4203522/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00276-024-03455-1","type":"published","date":"2024-08-09T15:57:09+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":54368371,"identity":"e8450c5a-c69f-4399-bcb5-ae54a66dd6b0","added_by":"auto","created_at":"2024-04-09 12:54:56","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":185187,"visible":true,"origin":"","legend":"\u003cp\u003eAdult male cranial specimen (mechanically segmented into skull base and skull cap).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/0d7ce053b1ba0f12ac9c9634.png"},{"id":54368370,"identity":"e9322f62-880c-4488-b7dd-5fbd30bd92ea","added_by":"auto","created_at":"2024-04-09 12:54:56","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":171361,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A-B) \u003c/strong\u003eThe 21 cranial bone block models (without hyoid bone and mandible) were obtained by separating them through Crop Mask, Edit Masks and Boolean operations in Mimics 19.0, and the frontal view (a) and lateral view (b) were shown in 3D preview.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/d7c6270a53c83fbfac6a3e9f.png"},{"id":54368369,"identity":"ec276ef0-ccec-4c7c-91bd-e573448beef4","added_by":"auto","created_at":"2024-04-09 12:54:56","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":184023,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A-B) \u003c/strong\u003eObtaining the mandible and some teeth of the maxilla from another specimen, adjusting the teeth and mandible to the corresponding position through Pan and Rotate, and completing the 22 pieces of cranial bone block model, showing the frontal view (a) and lateral view (b) in 3D preview.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/eb6d9dbe9a29cf621dbb48bf.png"},{"id":54368372,"identity":"8a5f134d-41b9-4249-82b2-760853b35d57","added_by":"auto","created_at":"2024-04-09 12:54:56","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":190088,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A-B) \u003c/strong\u003eIn 3 matic 11.0, the distance between each bone block was adjusted, and according to the appearance of the bone block model and the distribution of the cranial bone blocks, the bottom master and bracket were generated (a), and the 22 cranial bone models were unfolded and lined up to ensure that the details of each bone block can be observed (b).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/4e3ade86bbcd7a926165a6f7.png"},{"id":54369341,"identity":"d539ea54-e6be-4696-8cf8-8c13d0ccaa33","added_by":"auto","created_at":"2024-04-09 13:02:56","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":222076,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A-B) \u003c/strong\u003eComparison of frontal view between digital model and 3D body model (a: digital model; b: 3D body model) (① brow arch ② zygomatic arch ③ inferior turbinate ④ Chin hole).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/2527de77aa0492562f62e7f9.png"},{"id":54368375,"identity":"a27e2069-d0a4-4118-a9d4-ad6f37f8e916","added_by":"auto","created_at":"2024-04-09 12:54:56","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":232106,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A-B) \u003c/strong\u003eComparison between the bottom view of the digital model and the 3D body model (a: digital model; b: 3D body model) (① zygomatic arch ② foramen ovale ③ carotid canal external orifice ④ occipital foramen ⑤ mastoid process ⑥ extraoccipital convexity).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/8d8fd7e1e63c10079e6a6220.png"},{"id":54368378,"identity":"930c1cd4-02a2-4541-880e-ae6f261f34c2","added_by":"auto","created_at":"2024-04-09 12:54:56","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":236826,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A-B) \u003c/strong\u003eThe \"slc\" file was imported into a laser curing printer for 3D printing of cranial bone blocks to obtain a 3D printed model (a). The 3D printed model was cleaned, and the brackets were removed, resulting in 22 cranial bone blocks (excluding the hyoid bone) with intact details and complete bony landmarks (b).\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/f24ba078ec1fbcaf8c75b2fc.png"},{"id":54368373,"identity":"68d4b29c-7165-46d4-aa51-eb2298457170","added_by":"auto","created_at":"2024-04-09 12:54:56","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":298756,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A-B) \u003c/strong\u003eThe external comparison of the skull base includes a 3D printed model, a specimen model, and a teaching model (a: teaching model b: 3D printed model c: physical specimen) (① incisor holes ② palatine foramen ③ zygomatic arch ④ foramen ovale ⑤ rupture holes ⑥ carotid canal external orifice ⑦ occipital condyles ⑧ extraoccipital convexity).\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/7108cd3578fc9529bec23ca4.png"},{"id":54368377,"identity":"2b0dd088-db8a-4118-a256-19b52d7190d0","added_by":"auto","created_at":"2024-04-09 12:54:56","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":311188,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A-B) \u003c/strong\u003eThe comparison of the internal surface of the skull base includes 3D printed models, specimen models, and teaching models (a: teaching model b: 3D printed model c: physical specimen) (① blind foramen ② optic nerve canal ③ pituitary fossa ④ foramen ovale ⑤ foramen spinosum ⑥ rupture holes ⑦ intra-occipital ridge ⑧ intra-occipital convexity).\u003c/p\u003e","description":"","filename":"floatimage9.png","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/85331ebe578a88c408c81b9d.png"},{"id":62298266,"identity":"fccc1734-6843-409f-917c-578c1fac8e11","added_by":"auto","created_at":"2024-08-12 16:11:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2464351,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4203522/v1/58394a6f-508c-42d5-8827-a6ca4b1b38ce.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Research and application discussion of cranial bone model preparation method based on three-dimensional reconstruction and 3D printing technology","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHuman cranial specimens are important teaching and research tools in the fields of anatomy, biomedicine, and anthropology [1]. The traditional cranial isolation operation is divided into the following steps: collecting the cranial specimen, cleaning and handling the cranial specimen, determining the orientation and positioning of the specimen, determining the preservation method of the specimen, and performing the display and maintenance of the specimen. However, the shortage of human specimen resources has become a problem that most medical schools must consider in order to achieve long-term development [2, 3], and at the same time, the traditional cranial bone separation method is usually complicated, difficult to completely separate the anatomical parts of the skull that are weak in bone quality, and the separation effect is difficult to control and will be damaged with the prolongation of the use of time, which has prompted people to constantly search for a new method of separating cranial bones[4-6].\u003c/p\u003e\n\u003cp\u003eIt is precisely because of the lack of a suitable method for separating fragile bones such as the sieve bone and the pterygoid bone that there is currently a gap in the morphological statistics and growth mechanisms of these bones. Cochinski mentions a systematic approach to understanding the sphenoid wings, a study that would be better served by isolating the sphenoid bone as a whole[7]. In addition, in recent years, the research of AI artificial intelligence to separate the whole body anatomical structure of the human body is gradually emerging, but there are fewer literatures for exploring the method of automatic segmentation of cranial bone block, which may also be a bottleneck in the separation method. We provide a preliminary basis for the study of automatic segmentation of cranial bone blocks by introducing the method of separating cranial bones [8].\u003c/p\u003e\n\u003cp\u003eIn recent years, with the development of 3D reconstruction technology and 3D printing technology, the use of 3D reconstruction technology to separate the skull and create a digital model of the skull, followed by the use of 3D printing technology to obtain a 3D printed skull model has played a great role in the teaching of human anatomy [9, 10]. Because the accurate reproduction ability of 3D printing technology can reflect the morphological characteristics of specimens and their anatomical features extremely well, 3D printed anatomical models are gradually replacing specimens is becoming a trend [11-13].3D printed model solves the problems of time-consuming, difficult to make moulding and easy to damage of pneumatic-containing bone of traditional separation methods, and also solves the problems of virtual digital technology that requires the support of equipments [14]. In addition, 3D printed models only need a S.T.L. file to achieve many advantages such as easy access, easy storage, low cost of mass production, easy promotion, etc., which makes it easier to meet the application needs of anatomy teaching in clinical and medical schools[15].\u003c/p\u003e\n\u003cp\u003eTherefore, we use 3D reconstruction and 3D printing technology to separate the skull, explore the image boundaries of each bone block, to provide a pre-basis for the formation mechanism of cranial bone joints, cranial deep learning and AI artificial intelligence, etc.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003e\u003cstrong\u003eSkull\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSpecimen selection and processing: approval was obtained from the ethics committee of Hunan University of Medicine. The procedures used in this study adhere to the tenets of the Declaration of Helsinki. Adult male cranial specimens with complete bony integrity after local dissection in the specimen bank were selected, and horizontal saw cuts were made along the supraorbital notch at about 1.2 cm above the posterior superior collar line and about 1.0 cm above the posterior superior collar line at the two localization points, fully exposing the cranial base and facilitating observation of anatomical landmarks (Fig.\u0026nbsp;\u003ca href=\"#图1\"\u003e1\u003c/a\u003e). CT scanning and data acquisition: before processing the cranial specimens, the specimens were scanned by continuous tomography via a 64 row 128 layer GE Optima CT machine with a voltage of 120 kV, a current of 150 mA, and a layer thickness of 0.625 mm, and exported in DICOM format.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig.1\u003c/strong\u003e Adult male cranial specimen (mechanically segmented into skull base and skull cap).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eThree Dimensional Reconstruction and Processing\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe CT data were imported into Mimics 19.0 software (http://biomedical.materialise.com/mimics, RRID:SCR_012153) for threshold segmentation with a threshold value of 226-3071Hu, and a mask was generated;In the process of bone fragment separation, based on the threshold value of 226-3071, bone fragments were divided into two types of high bone density and low bone density according to the integrity of bone fragment reconstruction, the existence of large holes, and the clarity of bone markers, etc. Crop Mask was used to narrow the boundary line to the edge of the target skull fragment; Lasso in the Edit Masks tool was used to separate the preliminary boundary between the target cranial block and the other bones around it: Bone blocks with high bone density could be separated based on obvious demarcation lines such as the coronal suture, sagittal suture, parietal mastoid suture, nasal incision, zygomaticomaxillary suture, and so forth. At the same time, the 2D window image layers were observed to see whether the bone block boundary was clear, and Boolean operations were used to separate the surrounding bone blocks with complete bone and clear boundary lines. For bone blocks with low bone density, such as sphenoid bone, ethmoid bone and palatine bone, it was necessary to make single and multi layer editing, such as painting and erases of 2D image window according to layers. Moreover, sphenoid sinus orifice, sphenoid ridge and ethmoid cell of sphenoid bone were difficult to distinguish, so the anatomical structure should be trimmed repeatedly in combination with Toggle mask 3D preview to ensure the simulation of digital model; The two types of edited masks were automated to obtain the 3D digital model through 3D calculate. And according to the above method, 22 skull blocks were reconstructed and separated from the model (Fig.\u0026nbsp;\u003ca href=\"#图2\"\u003e2\u003c/a\u003eA-B); Since the skull itself lacked the mandible and some teeth of the maxilla, the data of another specimen\u0026rsquo; s mandible and teeth of the maxilla were used, and the teeth and the mandible that corresponded to what were missing in this skull specimen were made to arrive at the proper position using Pan and Rotate commands (Fig.\u0026nbsp;\u003ca href=\"#图3\"\u003e3\u003c/a\u003eA-B); The skull block model was imported into 3 matic 11.0 software (http://biomedical.materialise.com/mimics, RRID:SCR_012153), and the small protruding or concave Areas of the model surface were Smoothed by Local Smoothing. The area to be repaired on the model surface is selected by operations such as Area Mark, and the selected triangular surface is deleted. Then Fill Hole Freeform was used to automatically repair tiny holes on bone blocks to achieve local optimization effect.; In 3-matic11.0 software, the cranial block model was moved by Interactive Translate. Through the appearance of the cranial block and the distribution of the cranial block, the Lasso Area Mark was utilized to mark the mother plate surface of the stent rest, and the thickness of the mother plate surface was designed through Uniform Offset. And then bracket design was completed through New Sketch,Add Constraint,Extrude and Revolve operation for (Fig.\u0026nbsp;\u003ca href=\"#图4\"\u003e4\u003c/a\u003eA-B); The model generated STL files were saved and imported into Magics 21.0 software(http://biomedical.materialise.com/mimics, RRID:SCR_012153) for print pre processing to generate \".slc \" format file.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig.2 (A-B) \u003c/strong\u003eThe 21 cranial bone block models (without hyoid bone and mandible) were obtained by separating them through Crop Mask, Edit Masks and Boolean operations in Mimics 19.0, and the frontal view (a) and lateral view (b) were shown in 3D preview.\u003c/p\u003e\n\u003cp\u003e\u003cbr /\u003e\u003cstrong\u003eFig.3 (A-B) \u003c/strong\u003eObtaining the mandible and some teeth of the maxilla from another specimen, adjusting the teeth and mandible to the corresponding position through Pan and Rotate, and completing the 22 pieces of cranial bone block model, showing the frontal view (a) and lateral view (b) in 3D preview.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig.4 (A-B) \u003c/strong\u003eIn 3 matic 11.0, the distance between each bone block was adjusted, and according to the appearance of the bone block model and the distribution of the cranial bone blocks, the bottom master and bracket were generated (a), and the 22 cranial bone models were unfolded and lined up to ensure that the details of each bone block can be observed (b).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDigital Model Effectiveness Evaluation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe modeling effect of this skull model was evaluated by comparing the processed skull model with the digital model of 3Dbody (www.3dbody.com), a commonly used software for medical teaching (Fig.\u0026nbsp;\u003ca href=\"#图5\"\u003e5\u003c/a\u003eA-B)(Fig.\u0026nbsp;\u003ca href=\"#图6\"\u003e6\u003c/a\u003eA-B).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig.5 (A-B) \u003c/strong\u003eComparison of frontal view between digital model and 3D body model (a: digital model; b: 3D body model) (① brow arch ② zygomatic arch ③ inferior turbinate ④ Chin hole).\u003c/p\u003e\n\u003cp\u003e\u003cbr /\u003e\u003cstrong\u003eFig.6 (A-B) \u003c/strong\u003eComparison between the bottom view of the digital model and the 3D body model (a: digital model; b: 3D body model) (① zygomatic arch ② foramen ovale ③ carotid canal external orifice ④ occipital foramen ⑤ mastoid process ⑥ extraoccipital convexity).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3D Printing\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSix Star Intelligent-Laser Curable Printer is selected, which prints on the principle of layer-by-layer stacking of photosensitive resin to obtain a 1:1 solid model. rinting steps were as follows: (1) the \".slc\" format files were imported into the 3D Print software, and the laser control system was open ; (2) 3D printing molding was started, and through the control of computer layering information, the photosensitive resin liquid material was stacked and printed layer by layer through the equipment to obtain the model(Fig.\u0026nbsp;\u003ca href=\"#图7\"\u003e7\u003c/a\u003eA-B); (3) After being printed, the model was taken out and soaked in anhydrous ethanol for 15 20 minutes to remove the liquid photocuring resin attached to the surface of the model. After soaking, the printing support was removed and the model was dried with absorbent paper; (4) the model was placed in a UV drying oven for drying treatment. Finally, the 3D printed skull model was taken out.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig.7 (A-B) \u003c/strong\u003eThe \"slc\" file was imported into a laser curing printer for 3D printing of cranial bone blocks to obtain a 3D printed model (a). The 3D printed model was cleaned, and the brackets were removed, resulting in 22 cranial bone blocks (excluding the hyoid bone) with intact details and complete bony landmarks (b).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3D Printing Model Effect Evaluation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e(1) Compare 3D printed cranial models with cranial specimens to assess model reproduction. (2) Compare the 3D printed skull model with other cranial teaching aids models to assess the accuracy(Fig.\u0026nbsp;\u003ca href=\"#图8\"\u003e8\u003c/a\u003eA-B)(Fig.\u0026nbsp;\u003ca href=\"#图9\"\u003e9\u003c/a\u003eA-B).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig.8 (A-B) \u003c/strong\u003eThe external comparison of the skull base includes a 3D printed model, a specimen model, and a teaching model (a: teaching model b: 3D printed model c: physical specimen) (① incisor holes ② palatine foramen ③ zygomatic arch ④ foramen ovale ⑤ rupture holes ⑥ carotid canal external orifice ⑦ occipital condyles ⑧ extraoccipital convexity).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFig.9 (A-B) \u003c/strong\u003eThe comparison of the internal surface of the skull base includes 3D printed models, specimen models, and teaching models (a: teaching model b: 3D printed model c: physical specimen) (① blind foramen ② optic nerve canal ③ pituitary fossa ④ foramen ovale ⑤ foramen spinosum ⑥ rupture holes ⑦ intra-occipital ridge ⑧ intra-occipital convexity).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cstrong\u003eIntroduction of a practical method of cranial separation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn teaching the anatomy of the skull, fine separation of each bone block is crucial. Traditional separation techniques, however, are time-consuming and labour-intensive, especially when dealing with fragile bone fragments such as sieve bones, where fragmentation often occurs. This situation leads to the fact that anatomy teaching often bypasses these bone fragments or relies solely on 2D images for teaching, which in turn affects the students\u0026apos; accurate understanding of these structures, due to the fact that a vague impression of the anatomical structures will further increase the difficulty in differentiating the cranial images for students. We used CT scanning and 3D reconstruction techniques to reconstruct the skull and finely segment each bone block according to a detailed and complete separation method, a method that can effectively separate fragile bone blocks without damaging the overall skull structure. In addition, the isolated cranial files can be digitally preserved from the erosion of time. We compared 22 skull blocks (excluding the hyoid bone) produced after 3D reconstruction and 3D printing with real specimens and found that the skull model designed by our method was superior to that of anatomical software and more realistically presented the morphology of the skull.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eProviding methods for anatomical measurements and biomechanical analyses\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs the study of the mechanism of cranial suture formation in the current literature mainly stays at the two-dimensional level, there is a lack of in-depth discussion on three-dimensional morphometric measurements.Richtsmeier et al. elaborated on the mechanism of cartilage ossification and membranous ossification during cranial bone development, and demonstrated the morphology of the skulls of mammals and infants through three-dimensional reconstruction [16]. In addition, the mechanism of cranial suture ossification disorder was thoroughly investigated in the paper, and it was pointed out that the development of cranial suture has an important influence on the whole cranial structure. Therefore, the development of a method capable of complete and accurate separation of cranial bones is of positive significance for research in this field.\u003c/p\u003e\n\u003cp\u003eIn terms of biomechanical analyses of the cranium, the existing literature tends to treat the cranial bone fragments in a combined manner, resulting in the realism of the model being compromised. Although some studies attempted to separate the cranial bones, their separation boundaries were vague and far from the real form[17]. For example, in clinical practice, separating surgery on the upper jaw requires analysing the forces on the mid-jaw and pterygopalatine sutures; however, there is a lack of effective separation methods in the literature for irregular cranial sutures, which restricts in-depth finite element analyses of these areas[18]. Our proposed separation method can accurately separate the cranial boundaries in a near-real situation, which leads to a more accurate and improved force analysis of the bone blocks between the cranial sutures.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExploring the degree of bone block reconstruction in conventional ct scans\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAfter comparing the cranial model of 3Dbody, a widely used anatomical software in China, the purchased cranial teaching aids model and the cranial model prepared based on the combination of 3D reconstruction and 3D printing technology proposed in this study, it can be concluded that the cranial model in the 3Dbody software [19] is able to accurately display obvious bony landmarks such as the pterygoid point, mastoid process, and pennate process. However, for some detailed bony landmarks such as the saddle dorsum of the pterygoid, the sinusoidal groove of the medial temporal bone, and the trigeminal nerve indentation, there is a certain degree of ambiguity in the portrayal of the 3Dbody software model, and some of the detailed bony landmarks lacked clear labelling, which is of limited use as an aid to beginners. The defects of the cranial teaching aids model include: the cranial teaching aids model is formed by moulding and pressing, which leads to the expensive cost, lack of precision, and not easy to clean and store. Compared with the above, the digital model prepared in this study is able to more accurately reproduce the morphological features of the human skull by using the CT scan data of the skull specimen for reconstruction and focusing on overcoming the tiny bony landmarks that were difficult to determine in the previous software model. In addition, in terms of detail processing, the digital model is closer to the real specimen, and can better show the structures such as the winglets of the pterygoid, the supraorbital fissure, the carotid artery sulcus, the sieve labyrinth, the supraorbital foramen of the frontal bone, and the glochids of the sieve bone.\u003c/p\u003e\n\u003cp\u003eIt should be emphasised that the final result of the digital model is limited by factors such as the resolution of the CT data and the thickness of the scanned layers. Certain structures that cannot be easily reconstructed, such as the sieve foramen of the sieve bone, cannot be fully restored. In addition, there may be substandard rendering of holes, sutures, notches, fissures, grooves, channels, nodules, thin-walled structures, sharp peaks and crests in a few parts during the reconstruction process [20]. However, the present method has advantages in the separation of cranial bone sutures, separation of cranial bones with weak bone, and separation of air-containing bones, which can preserve the original morphological structure of cranial specimens without causing damage to them.\u003c/p\u003e\n\u003cp\u003eCompared with other teaching aids models and anatomy teaching software, the digital model prepared in this study has high accuracy, high characterisation and high efficiency. Despite some limitations, the methodology of this study provides insights into the degree of reduction of conventional CT reconstruction models, and provides a more accurate and high-quality digital model resource for human anatomy education and pathology diagnosis, among other fields.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical and anatomical applications\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe advantage of 3D printed cranial models over traditional cranial specimens in daily teaching is the reduction of model wear and tear. Traditional skull specimens in the process of long-term use, due to the use of specimen receptacle is not reasonable and students observe and turn the process of the operation of the problem, easy to lead to the damage of air-containing bone, especially the butterfly bone, nasal bone and sieve bone defect is more common. In contrast, 3D printed models are printed with photosensitive resin material, which has good hardness and texture, and has less or even better differences with the use of real cranial specimens, especially in terms of separation difficulty, service life, storage conditions and display effect.\u003c/p\u003e\n\u003cp\u003eIn clinical teaching, 3D digital skull models and 3D printed skull models can often be used in combination. 3D digital models presented through visualisation platforms can provide clinicians with different angles or cross-sections of the cranial anatomy to observe, and present important anatomical structures that are difficult to observe in a digital and 3D printed form [21].3D printed models have the advantages of being designed according to the needs, easy to be adjusted, and printed in a short period of time, and they can also provide doctors with preoperative planning and the development of surgical protocols with precise anatomical preparation.\u003c/p\u003e\n\u003cp\u003eCurrently, anatomy teaching and image information acquisition mainly rely on tomographic images or observation of solid specimens, both of which have obvious limitations. The former requires rich anatomical experience and spatial imagination, while the latter can only obtain superficial anatomical structure information. However, the 3D reconstruction visualisation platform provides a novel approach to image learning [22]. This method corresponds each pixel point of the 2D image to the 3D model by acquiring 2D image data and performing 3D reconstruction using the image post-processing software Mimics. By combining 2D and 3D information acquisition, a new level of understanding of anatomical structures and boundaries can be achieved.\u003c/p\u003e\n\u003cp\u003eLooking to the future, we hope to further improve the accuracy of 3D reconstruction techniques and separation of cranial bones to better apply digital and 3D printed models to assist clinicians and medical schools in teaching anatomy [23].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe quality of CT data affects the modelling effect: the quality of CT data has an important impact on the establishment of the skull model. If the layer thickness of CT data is too large, it will lead to a decrease in the accuracy of the model and will not be able to accurately reconstruct some fine bony structures; if the resolution of CT data is low, it will introduce more signal noise in the modelling process, thus affecting the quality of the model. Therefore, it is necessary to select CT data of appropriate quality when performing cranial bone separation to ensure the accuracy of the model.\u003c/p\u003e\n\u003cp\u003eConsideration of the characteristics of cranial bone mass: The characteristics of cranial bone mass can also have some impact on the modelling. For example, regions with air-containing bone and thin bone have lower resolution in CT imaging, which increases the difficulty of modelling; and bone blocks with defects need to be artificially repaired to ensure the integrity and accuracy of the model.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this study, 22 high-reduction 3D digital models of the skull (excluding the hyoid bone) were successfully separated and reconstructed using 3D reconstruction technology, which enriched the database of cranial models and provided useful resources for online teaching. In addition, the use of 3D printing technology to create a solid model of the skull has the advantages of low separation difficulty, convenient storage of the model, long time of use, and better presentation compared with traditional specimens, which is especially suitable for offline teaching. There are some limitations in this study, only a single sample to explore the separation and printing of cranial specimens, the future needs to expand the sample size in-depth study. In the future, thin-layer CT devices with smaller layer thicknesses will be introduced for skull scanning to improve the accuracy of 3D reconstruction technology on the skull and to assist in the teaching of human anatomy by accurately displaying bony landmarks.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eThis study was supported by Hunan Provincial Natural Science Foundation of China (2022JJ50292); A Project Supported by Scientific Research Fund of Hunan Provincial Education Department (23A0728); Research Project on Teaching Reform of Ordinary Higher Education Institutions in Hunan Province (HNJG-20231510); Hunan Province Social Science Outcome Review Committee Project (XSP24YBC004); Project of Key Laboratory of Digital Anatomy and 3D Printing Clinical Translational Research in Huaihua City (2020R2201); Huaihua Science and Technology Innovation Plan Project (2021R3105); Horizontal Projects (1. Research on \"open\u0026thinsp;+\u0026thinsp;bridge-based\" 3D guide in intracerebral hemorrhage puncture. 2. Study on the application of digital \"triple fixed\" guide in endoscopic foraminal surgery).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConcept and design: JP, WJG, GHY; model construction: JP, WJG, DQY, LL, PHY; drafting of the manuscript: JP, WJG, DQY, GHY, YHS, YL; manuscript editing: LBR, LL, PHY, JP; submission of the manuscript: YHS, YL.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThe authors sincerely thank those who donated their bodies to science so that anatomical research could be performed. Results from such research can potentially increase mankind's overall knowledge that can then improve patient care. 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Methods\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"surgical-and-radiologic-anatomy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"sara","sideBox":"Learn more about [Surgical and Radiologic Anatomy](http://link.springer.com/journal/276)","snPcode":"276","submissionUrl":"https://submission.nature.com/new-submission/276/3","title":"Surgical and Radiologic Anatomy","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"3D printing, Cranial separation, 3D reconstruction, Teaching resource, Scranial specimens","lastPublishedDoi":"10.21203/rs.3.rs-4203522/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4203522/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e \u003cb\u003ePurpose\u003c/b\u003e The aim of this study was to find an alternative method to meet traditional human anatomy teaching and clinical needs in order to solve the problem of cranial specimen attrition and specimen resource shortage due to long-term use.\u003c/p\u003e \u003cp\u003e \u003cb\u003eMethods\u003c/b\u003e We performed a CT scan of a well-preserved male cranial specimen and used Mimics 19.0 software for 3D reconstruction and cranial block separation. Subsequently, we compared the recognition ability of the processed cranial digital model with that of the 3D body digital model and used 3D printing to create the cranial model and compare it with the physical specimen.\u003c/p\u003e \u003cp\u003e \u003cb\u003eResults\u003c/b\u003e Twenty-two cranial bone block models were obtained, excluding the hyoid bone. Their 3D reconstructed digital models had better bony landmark recognition than the 3D body human digital models, and the differences between the 3D printed models and the physical specimens were minimal. In addition, only one STL file was required to produce the cranial models, which facilitates repetitive printing at any time.\u003c/p\u003e \u003cp\u003e \u003cb\u003eConclusion\u003c/b\u003e By isolating cranial bone blocks through 3D reconstruction techniques and preparing high-quality cranial models in combination with 3D printing techniques, this study solves the problem of shortage of cranial teaching specimens for the sustainable development of clinical and medical schools.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e","manuscriptTitle":"Research and application discussion of cranial bone model preparation method based on three-dimensional reconstruction and 3D printing technology","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-09 12:54:51","doi":"10.21203/rs.3.rs-4203522/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-06-10T10:06:06+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-06-04T10:01:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"249868780243655339369975719668035242524","date":"2024-05-25T15:26:04+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-04-12T04:51:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-04-03T20:25:32+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-04-02T15:00:10+00:00","index":"","fulltext":""},{"type":"submitted","content":"Surgical and Radiologic Anatomy","date":"2024-04-02T03:26:05+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"surgical-and-radiologic-anatomy","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"sara","sideBox":"Learn more about [Surgical and Radiologic Anatomy](http://link.springer.com/journal/276)","snPcode":"276","submissionUrl":"https://submission.nature.com/new-submission/276/3","title":"Surgical and Radiologic Anatomy","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ed1a11c4-54bf-457f-b13b-36dabdc9df2a","owner":[],"postedDate":"April 9th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-08-12T16:00:20+00:00","versionOfRecord":{"articleIdentity":"rs-4203522","link":"https://doi.org/10.1007/s00276-024-03455-1","journal":{"identity":"surgical-and-radiologic-anatomy","isVorOnly":false,"title":"Surgical and Radiologic Anatomy"},"publishedOn":"2024-08-09 15:57:09","publishedOnDateReadable":"August 9th, 2024"},"versionCreatedAt":"2024-04-09 12:54:51","video":"","vorDoi":"10.1007/s00276-024-03455-1","vorDoiUrl":"https://doi.org/10.1007/s00276-024-03455-1","workflowStages":[]},"version":"v1","identity":"rs-4203522","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4203522","identity":"rs-4203522","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}