Research Projects of the Division of Medical and Biological Informatics
Navigated Bronchoscopy
Model: We have developed a lung model that allows the movement of the bronchial tree during breathing to be simulated. CT data was acquired from the model, allowing the entire navigation system to be tested.
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Bronchoscopy is a procedure which enables medical experts to examine the inside of the lung. This procedure is used to diagnose and locally treat lung diseases. During a therapeutical application like the brachytherapy, a radioactive source is placed inside or directly near the tumor for a set period of time. The steep dose drop-off of the radiation source (Ir192) allows highly conformal dose distributions, so that the surrounding normal tissue can be avoided while high doses are applied to tumors. Due to the many ramifications of the airways (bronchial tree) determining one’s exact position during diagnostical as well as during therapeutical use turns out to be highly challenging. With increasing penetration of the bronchial tree and accompanying rising amount of ramifications, the difficulty of finding the correct path to peripherally located lung tumors increases as well. Also a change in smoking habits in recent years has led to a rise in the occurrence of more peripherally located bronchial carcinomas [Stanly80].
A solution in this case is to use an electromagnetic navigation system that shows, during the bronchoscopy, the location of the instrument in relation to the bronchial tree and the path leading to the peripherally located region. For this purpose an electromagnetic tracking system with a tiny in the tip of the instrument assimilated receiver coil can be used to capture the position of the tip in real time and display its further track. Such tracking systems are already commercially available (e.g. AURORA, Northern Digital Inc. (NDI); Waterloo, Ontario, Canada) and display a very high degree of precision. However they need to be enhanced when applied on soft tissue that is constantly in motion, in this case the lung.
Application Examples: Images of the different views in the operative navigation software using our navigation system in an intervention on a pig: 2D slice image at the position of the instrument (top left); 3D view of the entire bronchi tree topology with transparent bronchi surface, red line represents the target path and a red cone represents the instruments tip (top right); the target path superimposed on the video image of the bronchoscope (bottom left); virtual bronchoscopy at the position of the instrument with the path to the target bronchus (bottom right).
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Our “navigated bronchoscopy” project’s objective is to develop a non rigid navigation system, which takes in to account respiratory movement and hence shall display as precise as possible the current position of the tracked instrument during the entire intervention. Preinterventional CT-Scans are taken as basis to perform the segmentation of the bronchial tree. This is done in the -also developed in this department- Medical Imaging Interaction Toolkit (MITK) software. The developed navigation application covers the entire workflow from navigation planning, over simulation up to the realization. Subsequently the user can preoperatively calculate the path to the target region, fly in a 3D simulation mode to the specified target and finally observe the tracking of the instrument in real time, all in one and the same application. Under the assumption, that the movement is exclusively inside the bronchi, which is satisfied for most bronchoscopies, the appliance of appropriate compensation algorithms can compensate for the motion of the lung. At this juncture a color bar continuously displays the intensity of the motion compensation and thus the degree of accuracy of the current instrument position. A patent (PCT/EP05/02244; US2008/0033452A1) describes the incremental real time recording of tracked instruments in tubular organ structures inside the human body. The visualization of the navigation is kept flexible, 2D and 3D views of the lung can alternatively be displayed to the user. Furthermore, the video image of the bronchoscope can also be shown as a superimposed image including virtual objects like a carcinoma or the virtual path. It is also possible to display a virtual image corresponding to the video without needing the optic of the bronchoscope.
Real time ability and precision of the navigation system prototype were tested in an ex-vivo experiment. The results show that an accuracy below 5mm between matched and real position can be achieved [Wegner2008].
Selected Publications
- [Stanley80] Stanley KE. Prognostic factors for survival in patients with inoperable lung cancer. J Natl Cancer Inst, 65:25–32, 1980.
- [Wegner 2008] Wegner I, Tetzlaff R, Biederer J, Wolf I, Meinzer HP. An Evaluation Environment for Respiratory Motion Compensation in Navigated Bronchoscopy. In Cleary KR, Galloway RL JR (Eds). Proc. SPIE Medical Imaging 2008: Visualization, Image-Guided Procedures, Vol. 6918, ArtNr. 691811, 2008.
- Wegner I, Biederer J, Tetzlaff R, Wolf I, Meinzer HP. Evaluation and Extension of a Navigation System for Bronchoscopy inside Human Lungs. In Cleary KR, Michael I. Miga (Eds). Proc. SPIE Medical Imaging 2007: Visualization and Image-Guided Procedures, Vol. 6509, ArtNr.: 65091H, 2007.
- Wegner I, Vetter M, Schoebinger M, Wolf I, Meinzer HP. Development of a navigation system for endoluminal brachytherapy in human lungs. In Cleary KR, Galloway RL JR (Eds). Proc. SPIE Medical Imaging 2006: Visualization, Image-Guided Procedures, and Display, Vol. 6141, 23-30, 2006.
- „Incremental Real-Time Recording of Tracked Instruments in Tubular Organ Structures Inside The Human Body”; Intevtors: M.Vetter, I.Wolf, I.Wegner, H.-P.Meinzer, H.Becker; Assignee: DKFZ, Germany
Updated publications/patents can be seen at the menu item publication and patents.
