Portal de Periódicos da CAPES

Three-dimensional portable document format: A simple way to present 3-dimensional data in an electronic publication

2011; Elsevier BV; Volume: 140; Issue: 2 Linguagem: Inglês

10.1016/j.ajodo.2011.04.010

1097-6752

Jan Christian Danz, Christos Katsaros,

Anatomy and Medical Technology

Three-dimensional (3D) models of teeth and soft and hard tissues are tessellated surfaces used for diagnosis, treatment planning, appliance fabrication, outcome evaluation, and research. In scientific publications or communications with colleagues, these 3D data are often reduced to 2-dimensional pictures or need special software for visualization. The portable document format (PDF) offers a simple way to interactively display 3D surface data without additional software other than a recent version of Adobe Reader (Adobe, San Jose, Calif). The purposes of this article were to give an example of how 3D data and their analyses can be interactively displayed in 3 dimensions in electronic publications, and to show how they can be exported from any software for diagnostic reports and communications among colleagues. Three-dimensional (3D) models of teeth and soft and hard tissues are tessellated surfaces used for diagnosis, treatment planning, appliance fabrication, outcome evaluation, and research. In scientific publications or communications with colleagues, these 3D data are often reduced to 2-dimensional pictures or need special software for visualization. The portable document format (PDF) offers a simple way to interactively display 3D surface data without additional software other than a recent version of Adobe Reader (Adobe, San Jose, Calif). The purposes of this article were to give an example of how 3D data and their analyses can be interactively displayed in 3 dimensions in electronic publications, and to show how they can be exported from any software for diagnostic reports and communications among colleagues. Tessellated surface models are used not only in orthodontics or maxillofacial surgery, but also in many other scientific fields such as astronomy, biology, engineering, architecture, and cartography.1Swennen G.R. Mommaerts M.Y. Abeloos J. De Clercq C. Lamoral P. Neyt N. et al.A cone-beam CT based technique to augment the 3D virtual skull model with a detailed dental surface.Int J Oral Maxillofac Surg. 2009; 38: 48-57Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar In medicine, tessellated surfaces are most often composed of triangular faces. With this method, complex 3-dimensional (3D) scenes are fluently visualized by 3D computer graphics. The possibilities are nearly unlimited, and therefore the challenge of increasing digitalization is to keep things simple and friendly to use. Wouldn't it be nice to see the patient records of an orthodontic case report in an article in an interactive 3D visualization? Or to send the 3D digital models with their corresponding analysis to a colleague by e-mail without the need for new software or online access? In this article, we describe a simple way to present 3D surface data with their analyses in articles or diagnostic reports. Electronic articles are generally published in the portable document format (PDF) and mostly consist of text and 2-dimensional pictures. However, an interactive multimedia object with 3D content can be displayed in a PDF document instead of a 2-dimensional picture. Three-dimensional software does not yet allow direct export of tessellated surfaces with analyses and annotations to a PDF document, but often to other open file formats such as STL, PLY, VRML, DAE, and OBJ.2Danz J.C. Katsaros C. Kieferorthopädische digitale modelle: anwendung, grundlagen, limiten.Inf Orthod Kieferorthop. 2010; 42: 223-233Crossref Google Scholar Up to now, the image-processing steps for embedding 3D surface data of a biologic specimen in a 3D interactive PDF document,3Ruthensteiner B. Heß M. Embedding 3D models of biological specimens in PDF publications.Microsc Res Tech. 2008; 71: 778-786Crossref PubMed Scopus (126) Google Scholar as well as the incorporation of 3D surface data in astronomy research articles with a free open-source software such as basic MiKTeX (version 2.8.3761; MiKTeX, Berlin, Germany; www.miktex.org), have been already described.4Barnes D.G. Fluke C.J. Incorporating interactive three-dimensional graphics in astronomy research papers.New Astronomy. 2008; 13: 599-605Crossref Scopus (54) Google Scholar In this method, knowledge of LaTeX document markup language is necessary (LaTeX2e, 10/15/2009, LaTeX project team, www.latex-project.org). In chemistry, 3D molecular structures have been documented by importing VRML files to a 3D interactive document.5Kumar P. Ziegler A. Ziegler J. Uchanska-Ziegler B. Ziegler A. Grasping molecular structures through publication-integrated 3D models.Trends Biochem Sci. 2008; 33: 408-412Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar, 6Vasilyev V. Towards interactive 3D graphics in chemistry publications.Theor Chem Acc. 2010; 125: 173-176Crossref Scopus (9) Google Scholar In contrast to surface data, embedding volume data is not yet as simple. Image stacks from histologic sections, confocal laser scanning microscopy, and microcomputed tomography have been volume rendered and then processed to each 3 stacks of PNG images. These images are displayed in a 3D interactive PDF document and represent closely the original volume rendering. However, this method seems to be complicated and additionally needs a Java script code (ECMA 262 5th Edition, December 2009, Ecma International, Geneva, Switzerland, www.ecma-international.org) to visualize the data in the PDF document.7Ruthensteiner B. Baeumler N. Barnes D.G. Interactive 3D volume rendering in biomedical publications.Micron. 2010; 41 (886.e1-17)Crossref PubMed Scopus (26) Google Scholar On the other hand, if the surface data are not present a priori, transformation of volume data to surface data by segmentation based mostly on thresholding algorithms,1Swennen G.R. Mommaerts M.Y. Abeloos J. De Clercq C. Lamoral P. Neyt N. et al.A cone-beam CT based technique to augment the 3D virtual skull model with a detailed dental surface.Int J Oral Maxillofac Surg. 2009; 38: 48-57Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar computer-assisted hand work,7Ruthensteiner B. Baeumler N. Barnes D.G. Interactive 3D volume rendering in biomedical publications.Micron. 2010; 41 (886.e1-17)Crossref PubMed Scopus (26) Google Scholar or other methods is possible, but quality and artefacts must be considered.2Danz J.C. Katsaros C. Kieferorthopädische digitale modelle: anwendung, grundlagen, limiten.Inf Orthod Kieferorthop. 2010; 42: 223-233Crossref Google Scholar, 8Adobe Acrobat X Pro. Available at: http://www.adobe.com/support/acrobat/. Accessed March 10, 2011.Google Scholar An alternative way that is suitable for embedding 3D surface data of dental and medical records in 3D interactive PDF files is demonstrated in this article with the example of orthodontic digital models. The 3D surfaces (Fig 1, Fig 2) were exported from the software Digimodel (version 2.37; OrthoProof BV, Nieuwegein, The Netherlands, www.orthoproof.com), converted to the open source universal 3D file format (U3D),9General Assembly ECMA International. Universal 3D file format. ECMA-363 4th edition, June 2007. Available at: www.ecma-international.org. Accessed March 10, 2011.Google Scholar by using the free open-source software meshlab (version 1.2.3; Visual Computing Lab, ISTI-CNR, Pisa, Italy; meshlab.sourceforge.net) and the free software DAZ Studio (version 3.1.2.19; DAZ Productions, Draper, Utah) and then assembled to a PDF multimedia model by using the commercial software Adobe Acrobat X Pro (version 10.0; Adobe, San Jose, Calif; www.adobe.com). Direct Import of 3D data to Adobe Acrobat X Pro requires data of the formats U3D or PRC.8Adobe Acrobat X Pro. Available at: http://www.adobe.com/support/acrobat/. Accessed March 10, 2011.Google Scholar The plug-in 3D PDF converter (Tetra 4D, Cheyenne, Wyo; www.tetra4d.com) enhances the import functions of Adobe Acrobat X Pro. More supported file formats for import as well as import and compression settings have become available.10Tetra4D. 3D PDF converter supported file formats. Available at: http://www.tetra4d.com/. Accessed March 10, 2011.Google Scholar Compression by remeshing or simplification of surface data should only be applied with caution. The boundaries of the mesh should be preserved within clearly specified limits.11Oeztireli A.C. Guennebaud G. Gross M. Feature preserving point set surfaces based on non-linear kernel regression.Comput Graph Forum. 2009; 28: 493-501Crossref Scopus (300) Google Scholar For example, geometric constructions from computer-aided design software can be imported by conversion to a triangulated mesh with a boundary representation at a tolerance of 0.01 mm.8Adobe Acrobat X Pro. Available at: http://www.adobe.com/support/acrobat/. Accessed March 10, 2011.Google ScholarFig 2This 3D digital model presents the views "standard" and "overjet" as an example of a sagittally clipped view with the measurement overjet and "clip molars," so that transverse discrepancies can be assessed. The functions explained in Figure 1 are also available here (these functions are available only in the digital version).View Large Image Figure ViewerDownload Hi-res image Download (PPT) The PDF document is simple in its use by the reader. The 3D model is activated by simply clicking on its picture. Moreover, a navigation bar that appears on the top of the picture presents special tools for selecting projection type, shading, light, and background color and shows special preselected views. These preselected views can be used to report specific information (measurements, regions of interest, and so on), and they can be especially useful in easy communication of diagnostic reports. The reader can also change the settings (visibility, transparency, and shading) of the structural parts of the 3D model (maxilla, mandible, wax bite), which is presented in the model tree on the left part of the PDF document. Increased electronic data interchange raises the question of security and privacy of health data. The creator can limit the access of PDF files by passwords, restrict certain features such as printing and editing, and secure the file by 128-bit RCA or AES encryption.8Adobe Acrobat X Pro. Available at: http://www.adobe.com/support/acrobat/. Accessed March 10, 2011.Google Scholar Encryption of the file efficiently prevents unauthorized access. It is well known that all contents of a PDF file can be extracted, at least indirectly, as soon as the contents are accessible. Extraction of 3D data, however, seems to be more complicated because special software or programming is necessary. 1.Display of 3D surface models and their analyses in electronic publications or diagnostic reports is simple and user friendly, and there are several security and privacy options.2.The original surface data should be maintained during import. If the data size is too large, compression by remeshing or simplification of surface data could be an option, if applied with caution to preserve the boundaries of the mesh within clearly specified limits.3.A direct export function of 3D content with analyses and annotations to a 3D interactive PDF document from dental and medical software is necessary for simplification of the procedure.