Achim Mayer

Virtual planning of liver resections: image processing, visualization and volumetric evaluation

Operability of a liver tumor depends on its three dimensional relation to the intrahepatic vascular trees as well as the volume ratio of healthy to tumorous tissue. Precise operation planning is complicated by anatomic variability and distortion of the vascular trees by the tumor or preceding liver resections. We have developed a computer based 3D virtual operation planning system which is ready to go in routine use. The main task of a system in this domain is a quantifiable patient selection by exact prediction of post-operative liver function. It provides the means to measure absolute and relative volumes of the organ structures and resected parenchyma. Another important step in the pre-operative phase is to visualize the relation between the tumor, the liver and the vessel trees for each patient. The new 3D operation planning system offers quantifiable liver resection proposals based on individualized liver anatomy. The results are presented as 3D movies or as interactive visualizations as well as in quantitative reports.

High performance medical image processing in client/server-environments

As 3D scanning devices like computer tomography (CT) or magnetic resonance imaging (MRI) become more widespread, there is also an increasing need for powerful computers that can handle the enormous amounts of data with acceptable response times. We describe an approach to parallelize some of the more frequently used image processing operators on distributed memory architectures. It is desirable to make such specialized machines accessible on a network, in order to save costs by sharing resources. We present a client/server approach that is specifically tailored to the interactive work with volume data. Our image processing server implements a volume visualization method that allows the user to assess the segmentation of anatomical structures. We can enhance the presentation by combining the volume visualizations on a viewing station with additional graphical elements, which can be manipulated in real-time. The methods presented were verified on two applications for different domains.

Extending a teleradiology system by tools for visualization and volumetric analysis through a plug-in mechanism

This paper describes ongoing research concerning interactive volume visualization coupled with tools for volumetric analysis. To establish an easy to use application, the three-dimensional-visualization has been embedded in a state of the art teleradiology system, where additional functionality is often desired beyond basic image transfer and management. Major clinical requirements for deriving spatial measures are covered by the tools, in order to realize extended diagnosis support and therapy planning. Introducing a general plug-in mechanism, this work exemplarily describes the useful extension of an approved application. Interactive visualization was achieved by a hybrid approach taking advantage of both the precise volume visualization based on the Heidelberg ray-tracing model and the graphics acceleration capabilities of modern workstations. Several tools for volumetric analysis extend the three-dimensional-viewing. They are controlled by adequate input devices to select locations in the data volume, measure anatomical structures or initiate a segmentation process. Moreover, a haptic interface can be connected to provide a more realistic feedback while navigating within the three-dimensional-reconstruction. The work is closely related to research in the field of heart, liver and head surgery. In cooperation with our medical partners the development of tools as presented facilitates the integration of image analysis into the clinical routine.

Medical image processing and visualization on heterogenous clusters of symmetric multiprocessors using MPI and POSIX threads

In this paper we present the design and implementation of a parallel system for interactive segmentation and visualization of three-dimensional medical images which is distributed on a heterogenous cluster of workstations or personal computers. All image processing functions are multithreaded to use the advantages of symmetric multiprocessors. Its platform-independence is achieved using standardized libraries like MPI and POSIX Threads.

Technical aspects of virtual liver resection planning.

Operability of a liver tumor is depending on its three dimensional relation to the intrahepatic vascular trees which define autonomously functioning liver (sub-)segments. Precise operation planning is complicated by anatomic variability, distortion of the vascular trees by the tumor or preceding liver resections. Because of the missing possibility to track the deformation of the liver during the operation an integration of the resection planning system into an intra-operative navigation system is not feasible. So the main task of an operation planning system in this domain is a quantifiable patient selection by exact prediction of post-operative liver function and a quantifiable resection proposal. The system quantifies the organ structures and resection volumes by means of absolute and relative values. It defines resection planes depending on security margins and the vascular trees and presents the data in visualized form as a 3D movie. The new 3D operation planning system offers quantifiable liver resection proposals based on individualized liver anatomy. The results are visualized in digital movies as well as in quantitative reports.

Extending a teleradiology system by tools for 3D-visualization and volumetric analysis through a plug-in mechanism.

This paper describes ongoing research concerning interactive volume visualization coupled with tools for volumetric analysis. To establish an easy to use application, the 3D-visualization has been embedded in a state of the art teleradiology system, where additional functionality is often desired beyond basic image transfer and management. Major clinical requirements for deriving spatial measures are covered by the tools, in order to realize extended diagnosis support and therapy planning. Introducing the general plug-in mechanism this work exemplarily describes the useful extension of an approved application. Interactive visualization was achieved by a hybrid approach taking advantage of both the precise volume visualization based on the Heidelberg Raytracing Model and the graphics acceleration of modern workstations. Several tools for volumetric analysis extend the 3D-viewing. They offer 3D-pointing devices to select locations in the data volume, measure anatomical structures or control segmentation processes. A haptic interface provides a realistic perception while navigating within the 3D-reconstruction. The work is closely related to research work in the field of heart, liver and head surgery. In cooperation with our medical partners the development of tools as presented proceed the integration of image analysis into clinical routine.

Volume visualization and interactive tools plugged into a teleradiology system

This paper presents ongoing research in the field of volume visualization, interactive volumetric analysis and teleradiology. To cover the complete scenario from image acquisition to computer-based diagnosis and therapy support, interactive tools for volume visualization and volumetric analysis have been integrated into a state of the art teleradiology system through a general plug-in mechanism. Visualization is demonstrated as a hybrid approach integrating precise volume visualization based on the Heidelberg Raytracing Model with fast surface rendering. With respect to volumetric analysis, tools extend the 3D-viewing. They allow to measure distances, angles, areas and volumes through 3D- pointing and user controlled segmentation processes. Various input devices can be connected to control the navigation of the viewer or objects in the scene. Moreover, a haptic interface has been investigated. The realistic perception through force feedback while navigating within the 3D- reconstruction was positively judged by the medical users as well as software developers. The work is closely related to research in the field of heart, liver and cranio-facial surgery planning. In cooperation with our medical partners the development of tools as presented proceed the integration of image analysis into the clinical routine.

Echtzeit 3D I/O für netzwerkorientierte Anwendungen der Volumenvisualisierung

Diese Arbeit beschreibt Ansatze, die es erlauben, Anwendungen basierend auf rechenaufwendigen, jedoch qualitativ hochwertigen, Volumenvisualisierungen interaktiv bedienbar zu machen. Die Volumenvisualisierung und die volumenorientierte Bildverarbeitung kann in einem Netzwerk auf einen zentralen, leistungsfahigen Rechner ausgelagert werden. Der Benutzer kann auf einer Viewing-Station mit den Visualisierungen im dreidimensionalen Raum interagieren, wobei sich mehrere solcher Clients die Resourcen des Servers teilen konnen. Ein hybrider Volumenvisualisierungsansatz erlaubt die Integration von Oberflachen-und volumenorientierten Objektmodellen.

Befundungsunterstützung in der kontrastmittelverstärkten MR-Mammographie mit Methoden der Bildverarbeitung

Mit der vorgestellte Methode zur automatischen Segmentierung und dreidimensionalen Rekonstruktion verdachtiger Lasionen in der kontrastmittelverstarkten MR-Mammographie wurde ein ganzheitliches Losungskonzept umgesetzt, das alle fur die diagnostische Entscheidung relevanten Merkmale berucksichtigt. Besonders im Bereich der diffusen Kontrastmittelanreicherungen hat die automatische Aufbereitung der Daten das Potential, die Forschung weiter anzuregen.