Cornelia Kober

HAW Hamburg | HAW · Faculty of Life Sciences

Capturing three-dimensional (3D) imaging is essential in the broad field of cranio-maxillofacial surgery. Laser scanners and stereophotogrammetry are more and more relevant for capturing (facial) soft tissues. For this purpose, a 3D laser scanning imaging system, using a nonhazardous laser, with a precise texture reproduction and in some models wit...

Serious mandibular diseases such as tumor or osteonecrosis often require segmental or marginal mandibulectomy, the latter with improved outcome thanks to preserved mandibular continuity. Nevertheless, gradual osteolytic and/or osteosclerotic skeletal changes frequently indicate repetitive resections. Based on the fundamental adaptivity of bone to m...

Mandibular pathologies as oral cancer, septic or aseptic osteonecrosis due to radiation or medication therapy, or severe atrophy cause progressing skeletal compromise with the risk of pathological mandibular fracture (PMF). In a recent clinical study, PMF was reported for 4 out of 44 cases after marginal mandibulectomy related to oral cancer. Motiv...

Objective: During therapy of distoclusion entailing a rigid, fixed orthodontic appliance, the mandibular fossa and condyle are ideally remodeled, while dentoalveolar effects occur through adaptive mechanisms. Adaptive processes, especially in the fossa region, have not been adequately investigated. Our magnetic resonance imaging (MRI) investigatio...

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Multiple craniomaxillofacial pathologies are characterized by ongoing skeletal compromise decisively influencing the mandibular biomechanical behaviour due to daily loading. Based on poro-micromechanical considerations, it was recently shown by Scheiner et al., that also bone strains of physiological order of magnitude contribute to skeletal adapta...

Osteoradionecrosis (ORN) is a serious side effect of oncologic radiation therapy. Often, surgical removal of the affected skeletal tissue is indicated. In cranio-maxillofacial surgery, partial or total resection of the upper or lower jaw implies a severe impairment of the patient‘s quality of life. Up to now, clear display of ORN is still a challen...

Background A remarkable amount of the population is suffering from severe and painful craniomandibular dysfunctions (CMD). During the last decades, computer assisted procedures for diagnosis and therapy planning gained more and more acceptance in the clinical setting. Material and methods In this article, several recent computer assisted methods f...

Bei Patienten mit kraniomandibulärer Dysfunktion (CMD) sind eine umfangreiche Anamnese, eine klinische Untersuchung, aber auch die Bildgebung sehr wichtig. In den vergangenen Jahren konnten große Fortschritte in der CMD-Diagnostik erzielt werden. Dieser Beitrag erläutert den aktuellen Stand verschiedener bildgebender Verfahren und deren Stellenwert...

In dentistry, clinical radiographs (also called X-ray images) reflect the intensity loss of an X-ray when being transmitted through the mandibular objects, and this loss is quantified in terms of grey values. While such images are standardly used for pathology detection by the experienced dentist, we here present a new method for getting more quant...

The minimal invasive procedure of vertebroplasty is a surgical technique to treat compression fractures of vertebral bodies. During the treatment, liquid bone cement gets injected into the affected vertebral body and therein cures to a solid. In order to investigate the treatment and the impact of injected bone cement, an integrated modelling and s...

Introduction: The load-carrying behavior of the human mandible can be described using finite element simulation, enabling investigations about physiological and pathological skeletal adaption. "Anatomical simulation" implies a stepwise approximation towards the anatomical reality. Method: The project is structured in three steps. In Step 1, the...

This contribution deals with the simulation based investigation of processes related to the surgical treatment of vertebroplasty. In this regard, a simulation framework has been developed, which includes the generation of microstructural computer models of cancellous bone structures, the simulation of bone cement injection by computational fluid dy...

Objectives: When metallic prosthetic appliances and dental fillings exist in the oral cavity, the appearance of metal-induced streak artefacts is not avoidable in CT images. The aim of this study was to develop a method for artefact reduction using the statistical reconstruction on multidetector row CT images. Methods: Adjacent CT images often d...

A new method is presented for ``extending'' 2D radiographs into the third dimension. Pixel grey values, reflecting X-ray intensity losses, are converted into average attenuation coefficients, and the latter are related to vascular porosities in cortical and trabecular bone. These conversions contain information on cortical and overall mandibular th...

Percutaneous vertebroplasty is a common clinical procedure to treat vertebral compression fractures and osteoporotic vertebral bodies. However, this operation technique is accompanied by different complications due to lack of knowledge about the complicated behaviour of bone cement within the human body. To contribute to a better understanding of t...

Objective: The objective of this study was to reduce metal-induced streak artifact on oral and maxillofacial x-ray computed tomography (CT) images by developing the fast statistical image reconstruction system using iterative reconstruction algorithms. Study design: Adjacent CT images often depict similar anatomical structures in thin slices. So...

It is known from micromechanics research and macroscopic biomechanics that the local distribution and also the 3D-profile over the whole organ based on Hounsfield units (HU) from CT-data gives significant insight about the changes of the skeletal organ during treatment. Therefore, we applied a refined computer assisted evaluation scheme to a series...

By CT-based medical visualization, it was possible to identify kind of inner skeleton reflecting the inner material distribution for a plenty of mammalian skeletal organs. Based on refined micro-mechanical investigation, it could be deduced that there is an interdependence between i) the skeletal organ's tissue anisotropy and ii) the organ's outer...

Due to muscular deformation and movement, standard radiology provides only a snapshot of a probably never recurring situation. The scope of this project is dynamic rendering of muscular structures, starting from 4D-radiology, namely 3D+time, to macroscopic visualization and simulation based thereon. As full real time 4D-MRI is still beyond the tech...

To demonstrate feasibility of near-real-time oculodynamic magnetic resonance imaging (od-MRI) in depicting extraocular muscles and correlate quantitatively the motion degree in comparison with clinical testing in patients with diplopia. In 30 od-MRIs eye movements were tracked in the horizontal and sagittal plane using a a TrueFISP sequence with hi...

The finite element method is a promising tool to investigate the material properties and the structural response of the periodontal ligament (PDL). To obtain realistic and reproducible results during finite element simulations of the PDL, suitable bio-fidelic finite element meshes of the geometry are essential. In this study, 4 independent coworker...

Active and passive experiments on skeletal muscles are in general arranged on isolated muscles or by consideration of the whole muscle packages, such as the arm or the leg. Both methods exhibit advantages and disadvantages. By applying experiments on isolated muscles it turns out that no information about the surrounding tissues are considered what...

4D-visualization of the human upper arm based on sequential or dynamic MRI may be useful in functional orthopedic disorders and surgical planning. A cascade of 4D-visualization approaches have been applied including deformation of the soft tissue surfaces and muscular contraction. Skeletal structures and the epifascial tissue comprising vascular st...

Magnetic resonance imaging (MRI) has been approved as an appropriate radiological modality for temporomandibular joint (TMJ) diagnosis, whereas the results of international multicenter studies impressively show the limitations of static three-dimensional MRI. The state of the art for dynamic imaging of the TMJ in real-time are TrueFISP sequences in...

Computer-assisted methods were used to evaluate different variants of surgically assisted rapid maxillary expansion (SARME) in terms of bone repositioning, new bone formation in the osteotomy gap, and bone quality before and after surgery. Twenty-nine patients (18 male, 11 female) with a mean age of 29 years (16 to 44 years) were included in the st...

In the present paper, a method to compare displacement results of a muscle contraction simulation with results of optical experiments is proposed. A human skeletal muscle has been reconstructed to a volume element out of real two-dimensional MRI data. The surrounding tissue has also been taken into account in order to describe the interaction with...

Different mechanisms have been hypothesized as contributing to abduction deficit in high myopia: the size of the eye within the orbit, tightness of the medial rectus muscles, decompensation of longstanding esotropia, and inferior displacement of the lateral rectus muscle. Using oculodynamic magnetic resonance imaging, enhanced by computer-aided vis...

This project is dedicated to computer aided support of functional diagnostics of the entire human orbit, inter alia with focus on the extra-ocular muscles and the optic nerve. Therefore, radiological imaging by MRI has to be referred to. Three approaches were followed, firstly highly resolved 3D-reconstruction of the ocular anatomy, further so call...

Aim: Tumor surgery at the skull base is a demanding field due to the complex and delicate anatomical hard and soft tissue structures in this region. The tumorous structure is mostly difficult to reach and the possibility of complete tumor resection is often only limited. The precise planning of the operative interventions and the following treatme...

Based on so called “quasi-continuous MRI” of a highly trained volunteer, 4D-visualization of a moving human foot due to ankle joint flexion is provided. In particular, visualization of the pedestrial superficial soft tissue as well as of the skeletal tissue is given. By our approach, we inter alia contribute to various kind of simulation of the low...

A special visualization approach for tumors in the cranio-maxillofacial region, e.g. skull base infiltrating tumors of large dimensions, was developed for diagnosis support as well as surgery and therapy planning. Methods: For complicated craniofacial tumors, mostly, high resolution CT and specially adapted MRI protocols are available. For later re...

Within a clinical study, 30 pre- and post-operative CT-data sets were acquired directly before and 6 – 11 weeks after surgical maxillary expansion. The pre- operative data were rigidly registered on the post-operative ones. Subsequent 3D-reconstruction showed the skeletal changes due to the surgery. By an approach developed in the group, new bone f...

The main objectives of this study were to generate individual finite element models of extracted human upper first premolars, and to simulate the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models for evaluation of the risk of root resorption. The individual extracted teeth were from a previous in vivo study...

Individual bone quality depends on genetic, biological, and mechanical influencing factors, where the latter is accessible via Finite Element Simulation. This work is part of an interdisciplinary research project with the purpose of stepwise refinement towards anatomical reality. This approach opened the door for many interrelated applications such...

Despite remarkable progress within the last decade, the treatment of mandibular fractures is still a highly discussed topic in oral and cranio-maxillofacial surgery. The possible traumatologic scenarios are characterized by high variability. A current project is focused on "resimulation" of traumatologic cases given by clinical radiographs by means...

Computer Tomographic (CT) image data have become a standard basis for structural analyses of bony organs. In this context, regression functions between stiffness components and Hounsfields units (HU) from CT, related to X-ray attenuation coefficients, are widely used for the definition of the (actually inhomogeneous and anisotropic) material behavi...

Computer Tomographic (CT) image data have become a standard basis for structural analyses of bony organs. In this context, regression functions between stiffness components and Hounsfields units (HU) from Computer Tomography, related to X-ray attenuation coefficients, are widely used for the definition of the (actually inhomogeneous and anisotropic...

Objective An approach of 3D-visualization of the temporomandibular joint (TMJ) with special focus on the articular disc based on magnetic resonance imaging (MRI) was developed for the purpose of diagnosis support. Materials and methods Mandibular condyle and fossa were reconstructed as 3D-surfaces. Articular disc, retrocondylar tissue, and the late...

Within the biomechanics of bony organs, individual tissue anisotropy and inhomogeneity are intensively discussed subjects. This paper is dedicated to the impact of a fully anisotropic and inhomogoneous material description on the structural behaviour of an elderly partially edentulous human mandible. Radial, axial, and circumferential trajectories...

To visualize the temporomandibular joint (TMJ) and the surrounding tissues in detail utilizing high-resolution MR images for the diagnosis of soft- and hard-tissue abnormalities. Clinically routine MR slices are processed by tissue segmentation and three-dimensional (3D) reconstruction and viewed with visualization software. A 1.5 T MRI system was...

By recording time dependent patients' behaviour, dynamic radiology is dedicated to capturing functional anatomy. Dynamic "quasi-continuous" MRI data of lateral eye movements of a healthy volunteer were acquired using SE imaging sequence (Siemens, 1.5 T). By means of combined application of several image processing and visualization techniques, name...

This article is dedicated to the evaluation of traumatologic standard situations of a human mandible by means of finite element simulation for the sake of improved therapy and surgery planning, as well as forensic examination. In a first step, an already existing parametric platform for flexible calculation of the stress/strain profiles due to huma...

Fixed functional orthopedic appliances used in 6 to 9 month-long treatments to correct distoclusion keep the mandible permanently in the therapeutically-desired protruded position. The principal aim of this approach is to achieve an increase in length of the lower jaw by stimulating mandibular growth. Ideally, adaptive mechanisms in adolescents and...

This case report was aimed at primary clinical experience concerning surgical extraction of a displaced tooth with the help of the Er:YAG laser based on refined computer-assisted presurgical planning. The case refers to the extraction of a displaced maxillary canine in a female patient. For the osteotomy, a pulsed Er:YAG laser was applied with puls...

For soft tissue organs, standard 3D-reconstructions can only provide a snapshot of a dynamically deforming structure. A reasonable possibility to overcome this drawback is the transition forward from 3D-reconstruction to 4D-visualization, i. e. rendering time dependent behavior based on dynamical radiological data sets. This article is dedicated to...

We here present a strategy for reliable prediction of elastic properties from X-ray attenuation coefficients visualized in Computer Tomographic images, as basis for Finite Element models. By example, we show the distribution of the axial normal stress throughout a human mandible, due to a bite on the leftmost premolar. Remarkably, this distribution...

For diagnosis of soft-tissue abnormality of the TMJ, high resolution MR imaging using parasagittal images oriented according to the angle of the mandibular condyle has evolved as actual standard in clinical routine The standard slice thickness is 3 mm which renders 3D-reconstruction a challenge. The purpose of this article is visualization of TMJ i...

This article is focused on the role of anisotropic elasticity in the simulation of the load distribution in a human mandible, due to a lateral bite on the leftmost premolar. Based on experimental evidence, orthotropy of the elastic properties of the bone tissue has been adopted. The trajectories of anisotropic elasticity are reconstructed from (i)...

Despite complex hierarchical organization of bone and wood, it was recently possible to identify a few elementary components at the micro and nanolevel of these material classes for the explanation of the diversity of macroscopic (poro-)elastic properties of different bones and woods [2, 3]. The mechanical properties (i.e. elasticity) of these elem...

Advanced composite components with integrated sensors and actuators become increasingly important due to the demand for very large, low-mass devices. Using shape memory alloys (SMA) as fiber reinforcement gives structures numerous adaptive capabilities. The shape memory effect can be described very basically as follows: An alloy in the low-temperat...

In the field of biomechanics, FEM-Simulation (FEM: finite element method) has become a well estimated research tool for the prediction of regional stress and stress-compatibility. Prerequisite of an analysis of the interaction of modern osteosynthesis material applied on the human jawbone is a deep understanding of the mechanical behaviour of the u...

Because of their adaptive mechanical properties, their corrosion resistance and their bio-compatibility, the field of applications of shape memory alloys (SMA) is increasing, namely in medicine, microsystem or aerospace technology. One main objective is structural vibration control, esp. the adaptability and the responsiveness to external disturban...

Structural mechanics simulation of bony organs is of general medical and biomechanical interest, because of the interdependence of the inner architecture of bone and its functional loading already stated by Wolff in 1892. This work is part of a detailed research project concerning the human mandible. By adaptive finite element techniques, stress/st...

In the biomedical context, image segmentation is the process of dividing an image into different subregions, usually different organs or tissue types. But mostly, the gray values of the inner voxels and, by this, the major part of the information remain unused. The purpose of this work is a new way of segmentation and visualization of these voxels....

We use a concrete simulation scenario to study the effect of hexahedral mesh size and mesh quality on the accuracy of the solution of a finite element analysis (FEA). Our test cases stem from biomedical research. We investigate a composite two-material model of a piece of bone from the human mandible on which we simulate a bite. In particular, we a...

We provide a case study for the generation of pure hexahedral meshes for the numerical simulation of physiological stress scenarios of the human mandible. Du to its complex and very detailed free-form geometry, the mandible model is very demanding. This test case is used as a running example to demonstrate the applicability of a combinatorial appro...

For the stress analysis of the human mandible a flexible simulation concept basing on finite element-method has been developed. One of the main issues is the prediction of fractures as a consequence of known forces as well as the forensic reconstruction of the traumatologic situation. At first, the individual geometry was reconstructed by 3D-CT-Sca...

Für die Spannungsanalyse des menschlichen Unterkiefers wurde ein flexibles numerisches Simulationskonzept auf der Basis einer Finite Element-Modellierung entwickelt. Eines der Ziele ist es, nicht nur Frakturen bei bekannter Gewalteinwirkung voherzusagen sondern umgekehrt auch forensisch die Rekonstruktion eines traumatologischen Geschehens zu ermög...

We use a concrete simulation scenario to study the effect of hexahedral mesh size and mesh quality on the accuracy of the solution of a finite element analysis (FEA). Our test cases stem from biomedical research. We investigate a composite two-material model of a piece of bone from the human mandible on which we simulate a bite. In partic- ular, we...

A combinatorial approach for the generation of hexahedral meshes by means of successive dual cycle elimination has been proposed by the second author in previous work. We provide a case study for the applicability of our hexahedral mesh generation approach to the simulation of physiological stress scenarios of the human mandible. Due to its complex...

The article describes part of a research project aiming to develop a new modular software tool for the individual dynamic numerical simulation of the human mandible using the finite element method (FEM). Its planned use in the clinical setting makes it very important to validate the results of the simulations. Here, the function of the masticatory...

A new modular software concept for individual numerical simulation of the human mandible using the finite element method (FEM) is presented. The main task is an individual analysis of regional stress and stress-compatibility on the basis of computed tomographic data in individual patients. Simulation should, however, also be possible in parallel wi...