Biomedical subjects

Rainer Burgkart

Publications and source records attributed to Rainer Burgkart.

11 recordsLinked to original sources

PubMed2005

Elastic properties of an intact and ACL-ruptured knee joint: measurement, mathematical modelling, and haptic rendering.

An analytical, dynamic model of the human knee joint has been developed to simulate the unloaded knee joint behaviour in 6 degrees of freedom. It is based on extensive robot-based measurements of the elastic properties of a human cadaver knee joint. The measured data are compared with data from the literature to ensure that a proper database for modelling is used. The analytical modelling of the passive elastic joint properties is done with Local Linear Model Trees. The deduced knee joint model incorporates passive elastic properties of the internal knee joint structures, passive elastic muscle forces, damping forces, gravitational forces, and external forces. There are two sets of parameters, one simulating the movement of the intact knee joint, and a second simulating the knee joint with ruptured anterior cruciate ligament. The dynamic model can be easily processed in real-time. It is implemented in the haptic display of the Munich Knee Joint Simulator (MKS), which enables a person to move a plastic leg driven by a robot manipulator and feel the simulated knee joint force. Orthopaedic physicians judged the performance of the dynamic knee joint model by executing physical knee joint tests at the MKS.

Anterior Cruciate Ligament↗

PubMed2005

BrainTrain: brain simulator for medical VR application.

The brain is known as the most complex organ in the human body. Due to its complexity, learning and understanding the anatomy and functions of the cerebral cortex without effective learning assistance is rather difficult for medical novices and students in health and biological sciences. In this paper, we present a new virtual reality (VR) simulator for neurological education and neurosurgery. The system is based on a new three-dimensional (3D) user-computer interface design with a tangible object and a force-torque sensor. The system is combined with highly interactive computer-generated graphics and acoustics to provide multi-modal interactions through the user's sensory channels (vision, tactile, haptic and auditory). The system allows the user to feel the simulated object from its physical model that formed the interface device, while exploring or interacting with the mimicked computer-generated object in the virtual environment (VE). Unlike other passive interface devices, our system can detect the position and orientation of the interacting force in real-time, based on the system's set-up and a force-torque data acquisition technique. As long as the user is touching the model, the positions of the user's fingertip in the VE can be determined and is synchronized with the finger's motion in the physical world without requirement of an additional six-degree-of-freedom tracking device. The prior works have shown the use of the system set-up in medical applications. We demonstrate the system for neurological education and neurosurgery as a recent application. The main functions of the simulator contribute to education in neuroanatomy and visualization for diagnostic and pre-surgery planning. Once the user has touched the model, the system will mark the associated anatomy region and will provide the information of the region in terms of text note and/or sound. The user can switch from anatomy to the brain's function module, which will give details of motor, sensory or other cortical functions associated to the touch areas. In addition, the user can generate and visualize arbitrary cross-sectional images from corresponding to the magnetic resonance imaging (MRI) datasets either for training or for diagnostic purpose. The user can manipulate the cross-section image interactively and intuitively by moving the finger on the interface device.

Brain↗

PubMed2004

The influence of right anterolateral thoracotomy in prepubescent female patients on late breast development and on the incidence of scoliosis.

BACKGROUND: It is assumed that a right anterolateral thoracotomy for correction of simple congenital cardiac defects (ie, atrial septal defect) achieves more favorable cosmetic results than a standard median sternotomy. METHODS: Ninety-five patients, 72 with right anterolateral thoracotomy and 23 with median sternotomy, who had corrective transatrial operations when they were younger than 12 years of age were contacted by questionnaire. The mean follow-up time was 23.1 years. Of these, 61 patients (46 thoracotomy and 15 sternotomy) were investigated clinically. Volume differences of the breasts were measured by 3-dimensional surface scanning. By using photographs of the upper chest, breast symmetry was described by an index. The degree of scoliosis was measured by clinical examination. RESULTS: According to the questionnaire analysis, 76% (thoracotomy group) versus 39% (sternotomy group) thought that the cosmetic result was excellent (P =.008). Breast volume measurement showed a volume difference greater than 20% (left side larger than right) in 55% (thoracotomy) versus 0% (sternotomy). With our index, asymmetry in the lower part of the right breast occurred in 61% (thoracotomy) versus 0% (sternotomy; P <.001). A total of 6.6% of the patients had scoliosis, without any differences between groups. CONCLUSIONS: Because our long-term follow-up in prepubescent female patients after right anterolateral thoracotomy revealed significantly impaired unilateral breast development, we propose to abandon right anterolateral thoracotomy in this subgroup of patients, although the subjective satisfaction with the cosmetic result was high. To avoid potential damage of future breast tissue, other surgical approaches, such as right posterior thoracotomy, should be considered. According to the orthopedic investigation, the surgical approach does not cause a higher rate of scoliosis.

Adult↗

PubMed2004

Phantom-based multimodal interactions for medical education and training: the Munich Knee Joint Simulator.

Simulation environments based on virtual reality technologies can support medical education and training. In this paper, the novel approach of an "interactive phantom" is presented that allows a realistic display of haptic contact information typically generated when touching and moving human organs or segments. The key idea of the haptic interface is to attach passive phantom objects to a mechanical actuator. The phantoms look and feel as real anatomical objects. Additional visualization of internal anatomical and physiological information and sound generated during the interaction with the phantom yield a multimodal approach that can increase performance, didactic value, and immersion into the virtual environment. Compared to classical approaches, this multimodal display is convenient to use, provides realistic tactile properties, and can be partly adjusted to different, e.g., pathological properties. The interactive phantom is exemplified by a virtual human knee joint that can support orthopedic education, especially for the training of clinical knee joint evaluation. It is suggested that the technical principle can be transferred to many other fields of medical education and training such as obstetrics and dentistry.

Computer Graphics↗

PubMed2004

The delivery simulator: a new application of medical VR.

This paper presents an elementary overview of the potential of Multimodal Virtual Reality (MVR) techniques in medical education, e.g. obstetrics. The study shows how to transfer the concept of MVR from a time-independent environment, e.g. the Munich Knee Joint Simulator, to a time-critical simulation environment as it can be found in flight simulators. The simulator consists of a haptic, a graphical and an acoustic user interface, which are connected to a biomechanical model for the birth process itself and a physiological model of both mother and child, in order to simulate, e.g. a cardiotocograph (CTG). The user can just watch an uncomplicated birth or is acting as the responsible obstetrician who has a variety of treatment options during the delivery with the most relevant medication or forceps/vacuum-extraction. During this practical training a MVR feedback system assists the trainee and exposes his errors and, thus, allows him to learn faster without endangering a real mother and her child. This concept allows for the first time to transfer stored haptic expert-knowledge to the trainee without a tool-based feedback approach.

Computer Simulation↗

PubMed2004

A sensorized human torso phantom.

Force-torque measuring input devices can significantly enhance the performance of classical simulation environments that are, for example, based on pure passive phantoms. Such devices allow not only the determination of force/torque amplitude and direction but also the contact point on the phantom. The force/torque information can be displayed visually or acoustically, drive a realistic graphical animation environment or it can be saved and compared with a haptic library comprising the force/torque history of any medical specialist. In this paper the technical principle is exemplified by an interactive human torso. A plastic phantom model of a human torso is instrumented with a 6-degree-of-freedom force/torque sensor, thus, allowing an intuitive and interactive use for education of human anatomy.

Humans↗

PubMed2004

Phantom-based interactive simulation system for dental treatment training.

In this paper, we propose a new interactive simulation system for dental treatment training. The system comprises a virtual reality environment and a force-torque measuring device to enhance the capabilities of a passive phantom of tooth anatomy in dental treatment training processes. The measuring device is connected to the phantom, and provides essential input data for generating the graphic animations of physical behaviors such as drilling and bleeding. The animation methods of those physical behaviors are also presented. This system is not only able to enhance interactivity and accessibility of the training system compared to conventional methods but it also provides possibilities of recording, evaluating, and verifying the training results.

Computer Simulation↗

PubMed2003

Femoro-tibial cartilage metrics from coronal MR image data: Technique, test-retest reproducibility, and findings in osteoarthritis.

MRI-based measures of cartilage morphology are being increasingly used as surrogate markers in osteoarthritis. In contrast to other knee joint surfaces, quantitative analysis of the femoral condyles from sagittal MRI suffers from limited precision. The objective, therefore, was to develop a technique for reproducible assessment of femoral cartilage morphology from coronal image data. Coronal MR images (3D T(1)-w FLASHwe) of the knee were obtained in 16 healthy volunteers and in 7 patients with severe osteoarthritis (OA, prior to knee arthroplasty), with repositioning between repeated scans. After segmentation the cartilage volume, thickness, and joint surface areas were quantified in the tibia and in an anatomically defined region of the femoral condyle. Immediate test-retest interscan precision errors (CV%) for femoral cartilage volume were 3.0% (SD = 26 microl) and 3.2% (29 microl) medially and laterally in volunteers, and 3.0% (34 microl) and 7.0% (37 microl) in OA patients. The estimated loss, from cross sectional data, in the patients in the medial femoral condyle (-61%/-4.4 SD) was higher than that in the medial tibia (-45%/-3.1 SD) and compared favorably with precision errors (ratio > 16:1). The technique proposed overcomes some of the problems associated with sagittal scans and thus shows high promise for reliable assessment of femoro-tibial cartilage loss in OA.

Adult↗

PubMed2003

Numerical determination of the susceptibility caused geometric distortions in magnetic resonance imaging.

The goal of this work is the design of highly accurate surgical navigation methods purely based on magnetic resonance imaging. In this context we numerically examine the geometrical distortions which occur in magnetic resonance imaging. We extend an existing method for computing magnitude and direction of distortions for any internal point. In particular, a multi-grid approach for a fast and efficient calculation of the static magnetic field throughout the imaging volume is presented and compared to the analytical solution for simple geometries. We found that shifts in the range of up to 2.5 mm occur in MRI of femur bones with 1.5 Tesla. Our new method was implemented and has been found capable of accurately correcting for geometrical distortions within reasonable computing times. In particular, we show that the registration accuracy for mutual information (MI) based MR-CT fusion can be much improved. Thus the value of the optimization functional in MI registration for MR-CT substantially increases after our distortion correction.

Abdomen↗

PubMed2003

Force-torque input enhances medical VR applications.

Force-torque measuring input devices can significantly enhance the performance of classical simulation environments that are, for example, based on pure passive phantoms. Such devices allow not only the determination of force/torque amplitude and direction but also the contact point, where a torque-free force is applied to the phantom. The force/torque information can be displayed visually or acoustically, drive a realistic graphical animation environment or it can be saved and compared with a haptic library comprising the force/torque history of any medical specialist.

Computer Simulation↗

PubMed2002

A new haptic interface for VR medical training.

Successful applications of haptic displays are limited to tool-based interfaces that simulate haptic effects on surgical and other medical instruments. However, no satisfactory haptic display exist so far, that enable the simulation of high fidelity palpation of human tissue or body segments. Existing approaches developed for medical training fail due to unrealistic haptic effects, time-consuming donning and doffing, and inconvenient use (e.g., mechatronic tactile and kinesthetic displays) or due to restricted function and adjustability (e.g., passive mannequins). The key idea of the new haptic interface is to attach artificial organs or segments (e.g. a plastic leg) to a force actuating mechatronic unit (e.g. robot). A set of different materials combined in certain layers yield components that look and feel like real objects. When the user touches the artificial object the contact forces and position changes are measured and fed into a model-based controller. Thus, the actuator moves the object so that the user gets the impression that he had induced the movement. The new haptic display has been verified with a setup developed for the training of functional joint evaluation after knee injuries. Compared to classical approaches, this display is convenient to use, provides realistic tactile properties and can be partly adjusted to different system properties (e.g. pathological joint properties). This kind of new interface can be applied to many different medical applications, where the clinician directly touches human limbs or tissue, such as in obstetrics, reanimation, organ palpation, etc.

Artificial Organs↗