The endoluminal brachytherapy of peripherally located bronchial carcinoma is difficult because of the complexity to position an irradiation catheter led by a bronchoscope to a desired spot inside a human lung. Furthermore the size of the bronchoscope permits only rarely the insertion of a catheter into the fine segment bronchi. We are developing an image-guided navigation system which indicates a path for guidance to the desired bronchus. Thereby a thin catheter with an enclosed navigation probe can be led up directly to the target bronchus, either by the use of the video of the bronchoscope or by the use of virtual bronchoscopy. Because of the thin bronchi and their moving soft tissue, the navigation system has to be very precise. This accuracy is reached by a gradually registering navigation component which improves the accuracy in the course of the intervention through mapping the already covered path to the preoperatively generated graph based bronchial tree description. The system includes components for navigation, segmentation, preoperative planning, and intraoperative guidance. Furthermore the visualization of the path can be adapted to the lung specialist's habits (video of bronchoscope, 2D, 3D, virtual bronchoscopy etc.).
The paper presents a new method for the semiautomatic segmentation of anatomical or pathological structures in MRI, CT or ultrasound images. The concept of bounding-object segmentation is based on an efficient combination of a new interactive approach with well known automatic segmentation algorithms. The efficiency of this new method is based on the transparent interaction between a 3D scene as well arbitrary 2D views of the scene. Bounding-object segmentation can also be described as a combination of interactive 3D segmentation with region-based, level-set-based, and/or texture based 3D-segmentation algorithms.
KEYWORDS: Visualization, Optical spheres, Medical imaging, 3D displays, Arteries, 3D visualizations, Image visualization, Spherical lenses, 3D image processing, Imaging systems
Modern systems for visualization, image guided procedures and display allow not only one type of visualization, but a variety of different visualization options. Only a combination of two-dimensional image display and three-dimensional rendering provides enough information for many tasks. Multiplanar orthogonal and oblique reformations of image data are standard features of medical imaging software packages today. Additionally, curved reformations are useful. For example, diagnosis of stenotic vessels can be supported by curved reformations along the centerline of the vessel, showing the complete vessel in one two-dimensional view. In this paper, we present how the open-source Medical Imaging Interaction Toolkit (MITK, www.mitk.org), which is based on the Insight Toolkit (ITK) and the Visualization Toolkit (VTK), can be used to rapidly build interactive systems that provide curved reformations. MITK supports curved reformations not only for images, but also for other data types (e.g., surfaces). Besides visualizations of curved reformations, which can be combined and are kept consistent with other two- and three-dimensional views of the data, interactions on such non-planar manifolds are supported. The developer only has to define the curved manifold, everything else is dealt with by the toolkit. We demonstrate these capabilities by means of a tool for mapping of coronary vessel trees.
Atrial fibrillation (AF) is the most common arrhythmia and results in
an increased risk of ischemic stroke. Recently, a european consortium
has developed a new minimally invasive device for surgical AF
treatment. It consists of a micro-robot holding an end-effector called
"umbrella" containing 22 radiofrequency powered electrodes. Surgery
using this new device can only be performed having an appropriate
navigation technique. Therefore, we have developed an image-based
navigation workflow and a prototypic navigation application. First, a navigation workflow including an appropriate intra-operative
image-modality was defined. Intraoperative ultrasound became the
imaging modality of choice. Once the umbrella is unfolded inside the
left atrium, data is acquired and segmented. Using a reliable
communication protocol, mobility values are transferred from the
control software to the navigation system. A deformation model
predicts the behavior of the umbrella during repositioning. Prior to surgery, desired ablation lines can be interactively planned and actually made ablation lines are visualized during surgery. Several in-vitro tests were performed. The navigation prototype has been integrated and tested within the overall system successfully. Image acquisitions of the umbrella showed the feasibility of the navigation procedure. More in-vitro and in-vivo tests are currently performed to make the new device and the described navigation procedure ready for clinical use.
KEYWORDS: Visualization, Medical imaging, Image segmentation, Surgery, 3D vision, Data acquisition, 3D image processing, Image processing, Image processing algorithms and systems, Data processing
The aim of the Medical Imaging Interaction Toolkit (MITK) is to facilitate the creation of clinically usable
image-based software. Clinically usable software for image-guided procedures and image analysis require a high
degree of interaction to verify and, if necessary, correct results from (semi-)automatic algorithms. MITK is
a class library basing on and extending the Insight Toolkit (ITK) and the Visualization Toolkit (VTK). ITK
provides leading-edge registration and segmentation algorithms and forms the algorithmic basis. VTK has
powerful visualization capabilities, but only low-level support for interaction (like picking methods, rotation,
movement and scaling of objects). MITK adds support for high level interactions with data like, for example, the
interactive construction and modification of data objects. This includes concepts for interactions with multiple
states as well as undo-capabilities. Furthermore, VTK is designed to create one kind of view on the data
(either one 2D visualization or a 3D visualization). MITK facilitates the realization of multiple, different views
on the same data (like multiple, multiplanar reconstructions and a 3D rendering). Hierarchically structured
combinations of any number and type of data objects (image, surface, vessels, etc.) are possible. MITK can
handle 3D+t data, which are required for several important medical applications, whereas VTK alone supports
only 2D and 3D data. The benefit of MITK is that it supplements those features to ITK and VTK that are
required for convenient to use, interactive and by that clinically usable image-based software, and that are
outside the scope of both. MITK will be made open-source (http://www.mitk.org).
This contribution presents a novel method for image-guided navigation in oncological liver surgery. It enables the perpetuation of the registration for deeply located intrahepatic structures during the resection. For this purpose, navigation aids localizable by an electro-magnetic tracking system are anchored within the liver. Position and orientation data gained from the navigation aids are used to parameterize a real-time deformation model. This approach enables for the first time the real-time monitoring of target structures also in the depth of the intraoperatively deformed liver. The dynamic behavior of the deformation model has been evaluated with a silicon phantom. First experiments have been carried out with pig livers ex vivo.
We propose a procedure for the intraoperative generation of attributed relational vessel graphs. It builds the prerequisite for a vessel-based registration of a virtual, patient-individual, preoperative, three-dimensional liver model with the intraopeatively deformed liver by graph matching. An image processing pipeline is proposed to extract an abstract representation of the vascular anatomy from intraoperatively acquired three-dimensional ultrasound. The procedure is transferable to other vascularized soft tissues like the brain or the kidneys. We believe that our approach is suitable for intraoperative application as basis for efficient vessel-based registration of the surgical volume of interest. By reducing the problem of intraoperative registration in visceral surgery to the mapping of corresponding attributed relational vessel graphs a fast and reliable registration seems feasible even in the depth of deformed vascularized soft tissues like in human livers.
KEYWORDS: Image segmentation, 3D modeling, Liver, Visualization, 3D visualizations, 3D image processing, Medical imaging, 3D acquisition, Image processing, Kidney
In medical imaging, segmentation is an important step for many visualization tasks and image-guided procedures. Except for very rare cases, automatic segmentation methods cannot guarantee to provide the correct segmentation. Therefore, for clinical usage, physicians insist on full control over the segmentation result, i.e., to verify and interactively correct the segmentation (if necessary). Display and interaction in 2D slices (original or multi-planar reformatted) are more precise than in 3D visualizations and therefore indispensable for segmentation, verification and correction. The usage of slices in more than one orientation (multi-planar reformatted slices) helps to avoid inconsistencies between 2D segmentation results in neighboring slices. For the verification and correction of three-dimensional segmentations as well as for generating a new 3D segmentation, it is therefore desirable to have a method that constructs a new or improved 3D segmentation from 2D segmentation results. The proposed method enables to quickly extend segmentations performed on intersecting slices of arbitrary orientation to a three-dimensional surface model by means of interpolation with specialized Coons patches. It can be used as a segmentation tool of its own as well as for making more sophisticated segmentation methods (that need an initialization close to the boundary to detect) feasible for clinical routine.
In this contribution a postprocessing method is introduced that enables dynamic accuracy examinations of position and angle measurements of two not interfering localizing systems describing the same subspace of Euclidian R3. Furthermore, the method can be used for realization of a hybrid localizing system given a common temporal synchronization of the measurements. Therewith, this article provides a flexible method for examining the influence of the operating room on magnetic tracking by dynamic comparison with reference measurements of an optical localizing system.
A substantial component of an image-guided surgery system (IGSS) is the kind of three-dimensional (3D) presentation to the surgeon because the visual depth perception of the complex anatomy is of significant relevance for orientation. Therefore, we examined for this contribution four different visualization techniques, which were evaluated by eight surgeons. The IGSS developed by our group supports the intraoperative orientation of the surgeon by presenting a visualization of the spatially tracked surgical instruments with respect to vitally important intrahepatic vessels, the tumor, and preoperatively calculated resection planes. In the preliminary trial presented here, we examined the human ability to perceive an intraoperative virtual scene and to solve given navigation tasks. The focus of the experiments was to measure the ability of eight surgeons to orientate themselves intrahepatically and to transfer the perceived virtual spatial relations to movements in real space. With auto-stereoscopic visualization making use of a prism-based display the navigation can be performed faster and more accurate than with the other visualization techniques.
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