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A virtual reality rendition of a fetal meningomyelocele at 32 weeks of gestation

2005; Wiley; Volume: 26; Issue: 7 Linguagem: Inglês

10.1002/uog.2635

1469-0705

Irene A.L. Groenenberg, A. H. Koning, R. J. H. Galjaard, Eric A.P. Steegers, Christoph Brezinka, Peter J. van der Spek,

Cerebrospinal fluid and hydrocephalus

Ultrasound in Obstetrics & GynecologyVolume 26, Issue 7 p. 799-801 Picture of the MonthFree Access A virtual reality rendition of a fetal meningomyelocele at 32 weeks of gestation I. A. L. Groenenberg, I. A. L. Groenenberg Division of Obstetrics and Prenatal Medicine, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this authorA. H. J. Koning, A. H. J. Koning Department of Bioinformatics, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this authorR. J. Galjaard, R. J. Galjaard Department of Clinical Genetics, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this authorE. A. P. Steegers, E. A. P. Steegers Division of Obstetrics and Prenatal Medicine, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this authorC. Brezinka, Corresponding Author C. Brezinka c.brezinka@erasmusmc.nl Division of Obstetrics and Prenatal Medicine, Erasmus Medical Centre, Rotterdam, The NetherlandsDivision of Obstetrics and Prenatal Medicine, Erasmus MC, PO Box 2040, NL 3000 CA, Rotterdam, The NetherlandsSearch for more papers by this authorP. J. van der Spek, P. J. van der Spek Department of Bioinformatics, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this author I. A. L. Groenenberg, I. A. L. Groenenberg Division of Obstetrics and Prenatal Medicine, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this authorA. H. J. Koning, A. H. J. Koning Department of Bioinformatics, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this authorR. J. Galjaard, R. J. Galjaard Department of Clinical Genetics, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this authorE. A. P. Steegers, E. A. P. Steegers Division of Obstetrics and Prenatal Medicine, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this authorC. Brezinka, Corresponding Author C. Brezinka c.brezinka@erasmusmc.nl Division of Obstetrics and Prenatal Medicine, Erasmus Medical Centre, Rotterdam, The NetherlandsDivision of Obstetrics and Prenatal Medicine, Erasmus MC, PO Box 2040, NL 3000 CA, Rotterdam, The NetherlandsSearch for more papers by this authorP. J. van der Spek, P. J. van der Spek Department of Bioinformatics, Erasmus Medical Centre, Rotterdam, The NetherlandsSearch for more papers by this author First published: 25 November 2005 https://doi.org/10.1002/uog.2635Citations: 16AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Using a virtual reality system to render images obtained with three-dimensional (3D) ultrasound a fetal lumbosacral meningomyelocele (L3–S2) is shown here at 32 weeks' gestation (Figure 1). The defect was originally observed in a 24-year-old primigravida during a routine sonogram at 22 weeks (Figure 2). After extensive counseling the patient decided not to have an amniocentesis and to continue with the pregnancy. Figure 1Open in figure viewerPowerPoint A three-dimensional (3D) image of a lumbosacral meningomyelocele (L3–S2) at 32 weeks' gestation is seen seemingly floating in space. On the far right, the hand of the operator is visible holding a joystick, while manipulating and viewing the fully 3D-rendered image. Figure 2Open in figure viewerPowerPoint The original ultrasound image used to create the three-dimensional image used in the I-Space. In this image the meningomyelocele is seen from a coronal view with the sac partially ‘cut open’. The slit-like dark structure in the center is the actual midline defect of the osseous structure of the spine. The spinal nerve roots can be observed running from the vertebral column towards the inside wall of the meningomyelocele where they adhere to the neural placode (Figure 3). The neural placode is the flat plate of dysplastic neural tissue, which is elevated to the dome of the meningomyelocele by the pressure of cerebrospinal fluid. The image, originally obtained during a 3D ultrasound examination, is seen hovering in space in front of the investigator, giving the impression of a 3D structure with a diameter of approximately 80 × 80 × 60 cm. The image can be moved, resized and turned around in space with the help of a hand-held joystick. The joystick also allows a part of the volume to be ‘cut away’. Figure 3Open in figure viewerPowerPoint A detailed picture of the meningomyelocele in the I-Space. Description of the I-Space™ A set of images obtained from a GE Voluson 730 Expert system (GE Medical Systems, Zipf, Austria) was transferred to the Barco I-Space installed at Erasmus Medical Centre a four-walled CAVE™-like virtual reality system (Barco BV Kuurne, Belgium)1. The CAVE™ concept was originally developed by the Electronic Visualization Laboratory of the University of Chicago as a multiperson successor of the head mounted display, better known as the ‘virtual reality helmet’2. In the I-Space, investigators are surrounded by computer-generated stereo images, which are projected by high-quality video projectors on three walls and the floor of a small room specifically built for this purpose. Looking at these images while wearing a lightweight pair of glasses with polarizing lenses allows the viewer to perceive the images with depth, to walk around them and also to look at them from below at different angles (Figure 4). The automatic adaptation of the images to the viewer's perspective is made possible by a wireless tracking system that sends the leading viewer's position and orientation to the computer, generating the images. The tracking system works with four infrared cameras, placed at the corners of the I-Space, that track small markers placed on the leading viewer's pair of stereo glasses. To investigate the time series of 3D ultrasound images, we use our own volume-rendering application called Cave Volume Renderer (CAVORE). This application uses 3D texture-mapping techniques to render 3D visualizations of volumetric datasets (e.g. computed tomography, magnetic resonance or 3D ultrasound data). CAVORE utilizes the SGI OpenGL Volumizer (Silicon Graphics Inc., Mountain View, CA, USA) library to implement the volume-rendering algorithms. Figure 4Open in figure viewerPowerPoint A picture of the entire I-Space installation with one operator (in the foreground) feeding the ultrasound image into the cave and the other operator (in the background) manipulating the image using a joystick. In the I-Space this results in a ‘hologram’ of the dataset being visualized, hovering in space in front of the viewers. Interaction with this ‘hologram’ is by means of a virtual pointer extending from the user's wireless joystick, also being tracked by the infrared cameras along with the stereo glasses. By applying one or more clipping planes to the volume, it becomes possible to have an unobstructed view of any part of fetal anatomy. The application allows both axis-aligned clipping planes as well as an arbitrary clipping plane that can be manipulated in real time by the user. This last clipping plane is attached to the virtual pointer and is presented as a thin blue ‘sword’ with which to cut into the hovering image. Simply by moving his hand, the user can position it at any arbitrary angle and position in the dataset. The user also has a simple yet powerful way to change the gray-value mapping of the original dataset in order to obtain a better rendering. Color (or gray value) and transparency can both be modified using a so-called transfer function. A widget (graphical user interface object) showing this transfer function is part of the graphical user interface (GUI) of the CAVORE application. The user can manipulate the control points of this transfer function with the joystick and the images in the I-Space are updated immediately, making it easy to obtain a good rendering. The potential of the I-Space in obstetric ultrasound The process of cutting and rendering fetal 3D ultrasound images long after the actual ultrasound examination and on computers separate from the ultrasound machine has been in clinical practice for more than half a decade. Image-rendering techniques enable investigators to delete structures that obstruct the view of the area of interest, such as fetal hands, the umbilical cord, etc. The result is a clear-cut image of a specific structure as often adorns the title pages of this journal. I-Space takes this post-ultrasound image rendering a step further, creating a hologram-like virtual 3D image that appears to be hovering in the room with the investigator able, quite literally, to walk around it. Binocular depth perception provides a realistic 3D illusion that allows better assessment of fetal structures. Direct manipulation of the virtual 3D image by cutting it with the virtual pointer further augments the understanding of the spatial arrangement of fetal structures. In this highly interactive environment one can intuitively explore the virtual 3D image as if it were a physical object suspended in space. The quality of the virtual image depends, of course, on the quality of the original ultrasound image obtained. Requirements for optimal visualization in the I-Space are comparable to those for conventional 3D/four-dimensional (4D) imaging: structures containing fluid, such as cysts and, as in this example, a meningomyelocele, are more likely to result in good images than solid structures without fluid interfaces. We believe that the I-Space has great potential in enhancing the possibilities of 3D and 4D ultrasound by creating enlarged, hologram-like images in space. It is also a very good aid in teaching 3D ultrasound. After they have learned to move the image around (and move around it themselves) in the I-Space, operators who are relatively inexperienced at 3D ultrasound find it much easier to render the images they have obtained on their ultrasound machines. We also find that the set-up and the experience of working in the I-Space (a rather unusual mix of Star Wars and Ghostbusters) greatly motivates people who are being trained in ultrasound, as does the possibility to discuss the changes brought to the image with more experienced users. One of the great advantages of this method is that several observers, one of them usually an instructor, can stand around the hovering object and watch simultaneously while it is being worked upon with the joystick pointer. At present we are concentrating on easy-to-visualize structures such as cysts, and surfaces such as the fetal face, the umbilical cord and the fetal genitalia, where the original ultrasound image ideally contains an unobstructed view of the structure/area of interest. We are also working on a way to make datasets of the fetal heart, obtained with spatio-temporal image correlation technology, visible in the I-Space. This will make it possible to teach fetal echocardiography in the I-Space and to evaluate complex cardiac malformations. We consider the I-Space a valuable tool for the refined rendering of images obtained on fetal 3D and 4D ultrasound. There is great potential for this method, both in helping to solve tricky diagnostic questions and in teaching and training ultrasound operators. The potential of this technique is far from being fully explored. References 1Barco. Virtual & Augmented Reality—I-Space. http://www.barco.com/VirtualReality/en/products/product.asp?element=911 [Accessed 20 October 2005]. Google Scholar 2The CAVE Virtual Reality System. http://www.evl.uic.edu/pape/CAVE/ [Accessed 20 October 2005]. Google Scholar Citing Literature Volume26, Issue7December 2005Pages 799-801 FiguresReferencesRelatedInformation