Ilka Hertel

Interactive visualization for neck-dissection planning

In this paper, we present visualization techniques for neck dissection planning. These interventions are carried out to remove lymph node metastasis in the neck region. 3d visualization is intended to explore and to quantify anatomic and pathologic structures and thus support decisions concerning the surgical strategy. For this purpose we developed and combined visualization and interaction techniques such as cutaway views, silhouettes and colorcoded distances. In addition, a standardized procedure for processing and visualization of the patient data is presented.

Segmentation of neck lymph nodes in CT datasets with stable 3d mass-spring models

The quantitative assessment of neck lymph nodes in the context of malign tumors requires an efficient segmentation technique for lymph nodes in tomographic 3D datasets. We present a Stable 3D Mass-Spring Model for lymph node segmentation in CT datasets. Our model for the first time represents concurrently the characteristic gray value range, directed contour information as well as shape knowledge, which leads to a much more robust and efficient segmentation process. Our model design and segmentation accuracy are both evaluated with lymph nodes from clinical CT neck datasets.

Enhancing slice-based visualizations of medical volume data

Slice-based visualizations of CT and MRI data are frequently used for diagnosis, intervention planning and intraoperative navigation since they allow a precise analysis and localization. We present new techniques to enhance the visualization of cross sectional medical image data. Our work is focussed on intervention planning and intraoperative navigation. We address the following problems of slice-based visualization in these areas: the lack of a graphical overview on the positions of anatomic structures, the localization of a target structure and the display of safety zones around pathologic structures. To improve the overview, we introduce LIFTCHARTs, attached as vertical bars to a slice-based visualization. For localizing target structures, we introduce halos. These techniques restrict the occlusion of the original data to a minimum and avoid any modification of the original data. To demonstrate the usability of these visualization techniques, we show two application scenarios in which the techniques come into operation.

Bildanalyse für die präoperative Planung von Neck Dissections

Mit dem Ziel einer 3D-Visualisierung der patienten-individuellen Pathologie sollen therapeutisch relevante Strukturen des Halses praoperativ segmentiert werden. Die vorliegende Arbeit untersucht die Eignung und Automatisierbarkeit grauwertbasierter Segmentierungsverfahren (Regionenwachstum, Interaktive Wasserscheidentransformation, Live-Wire) fur diese Aufgabe. Auserdem wird die Integration der Segmentierungsverfahren in den Software-Assistenten NeckVision beschrieben.

Evaluation of perception performance in neck dissection planning using eye tracking and attention landscapes

Neck dissection is a surgical intervention at which cervical lymph node metastases are removed. Accurate surgical planning is of high importance because wrong judgment of the situation causes severe harm for the patient. Diagnostic perception of radiological images by a surgeon is an acquired skill that can be enhanced by training and experience. To improve accuracy in detecting pathological lymph nodes by newcomers and less experienced professionals, it is essential to understand how surgical experts solve relevant visual and recognition tasks. By using eye tracking and especially the newly-developed attention landscapes visualizations, it could be determined whether visualization options, for example 3D models instead of CT data, help in increasing accuracy and speed of neck dissection planning. Thirteen ORL surgeons with different levels of expertise participated in this study. They inspected different visualizations of 3D models and original CT datasets of patients. Among others, we used scanpath analysis and attention landscapes to interpret the inspection strategies. It was possible to distinguish different patterns of visual exploratory activity. The experienced surgeons exhibited a higher concentration of attention on the limited number of areas of interest and demonstrated less saccadic eye movements indicating a better orientation.

A Tissue Relevance and Meshing Method for Computing Patient-Specific Anatomical Models in Endoscopic Sinus Surgery Simulation

This paper presents on-going work on a method for determining which subvolumes of a patient-specific tissue map, extracted from CT data of the head, are relevant to simulating endoscopic sinus surgery of that individual, and for decomposing these relevant tissues into triangles and tetrahedra whose mesh size is well controlled. The overall goal is to limit the complexity of the real-time biomechanical interaction while ensuring the clinical relevance of the simulation. Relevant tissues are determined as the union of the pathology present in the patient, of critical tissues deemed to be near the intended surgical path or pathology, and of bone and soft tissue near the intended path, pathology or critical tissues. The processing of tissues, prior to meshing, is based on the Fast Marching method applied under various guises, in a conditional manner that is related to tissue classes. The meshing is based on an adaptation of a meshing method of ours, which combines the Marching Tetrahedra method and the discrete Simplex mesh surface model to produce a topologically faithful surface mesh with well controlled edge and face size as a first stage, and Almost-regular Tetrahedralization of the same prescribed mesh size as a last stage.

Haptische Interaktion zur Planung von Nasennebenhöhlen-Operationen

Moderne Operationstechniken im Bereich der Nasennebenhohlen bringen Vorteile fur den Patienten, jedoch auch neue Herausforderungen fur den Operateur mit sich. Durch die endoskopischen Verfahren ist die Navigation und Orientierung wahrend des Eingriffs erschwert und setzt eine besonders grundliche Planung voraus. Bei Problemfallen ist die Nutzung von 2d-Schichtbildern, die traditionell Verwendung finden, schwieriger. Vor allem bei Rezidivoperationen fehlen oft zur Orientierung wichtige anatomische Landmarken. In diesem Paper wird ein System vorgestellt, das mit Hilfe virtueller Endoskopie eine patientenindividuelle Planung von endoskopischen Nasennebenhohlen-Eingriffen unterstutzt. Dabei wird besonderer Wert auf die Interaktion mit der 3d-Darstellung und eine intuitive Nutzerfuhrung gelegt.