Biomedical subjects

Robert Riener

Publications and source records attributed to Robert Riener.

15 recordsLinked to original sources

PubMed2006

A novel mechatronic body weight support system.

A novel mechatronic body weight support (BWS) system has been developed to provide precise body weight unloading for patients with neurological or other impairments during treadmill training. The system is composed of a passive elastic spring element to take over the main unloading force and an active closed-loop controlled electric drive to generate the exact desired force. Both force generating units, the passive spring and the active electric drive, act on the patient via a polyester rope connected to a harness worn by the patient. The length of the rope can be adjusted with an electric winch to adapt the system to different patient sizes. The system is fully computer controlled. At unloading loads of up to 60 kg and walking speeds of up to 3.2 km/h, the mean unloading error and the maximum unloading error of the presented BWS system was less than 1 and 3 kg, respectively. The performance was compared with those of two purely passive BWS systems currently being used by most other rehabilitation groups. This comprised counterweight systems and static BWS systems with fixed rope lengths. Counterweight systems reached mean and maximum unloading errors of up to 5.34 and 16.22 kg, respectively. The values for the static BWS were 11.02 kg and 27.67 kg, respectively. The novel mechatronic BWS system presented in this study adjusts desired unloading changes of up to 20 kg within less than 100 ms. Thus, not only constant BWS, but also gait cycle dependent or time variant oscillations of the desired force can be realized with high accuracy. Precise and constant unloading force is believed to be an important prerequisite for BWS gait therapy, where it is important to generate physiologically correct segmental dynamics and ground reaction forces. Thus, the novel BWS system presented in this paper is an important contribution to maximize the therapeutic outcome of human gait rehabilitation.

Biomechanical Phenomena↗

PubMed2006

Haptic device for a ventricular shunt insertion simulator.

In this paper we propose a new one-degree-of-freedom haptic device that can be used to simulate ventricular shunt insertion procedures. The device is used together with the BRAINTRAIN training simulator developed for neuroscience education, neurological data visualization and surgical planning. The design of the haptic device is based on a push-pull cable concept. The rendered forces produced by a linear motor connected at one end of the cable are transferred to the user via a sliding mechanism at the end-effector located at the other end of the cable. The end-effector provides the range of movement up to 12 cm. The force is controlled by an open-loop impedance algorithm and can become up to 15 N.

Computer Simulation↗

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

Patient-cooperative strategies for robot-aided treadmill training: first experimental results.

Task-oriented repetitive movements can improve motor performance in patients with neurological or orthopaedic lesions. The application of robotics and automation technology can serve to assist, enhance, evaluate, and document neurological and orthopedic rehabilitation. This paper deals with the application of "patient-cooperative" techniques to robot-aided gait rehabilitation of neurological disorders. We define patient-cooperative to mean that, during movement, the technical system takes into account the patient's intention and voluntary efforts rather than imposing any predefined movements or inflexible strategies. It is hypothesized that such cooperative robotic approaches can improve the therapeutic outcome compared to classical rehabilitation strategies. New cooperative strategies are presented that detect the patient's voluntary efforts. First, this enables the patient increased freedom of movement by a certain amount of robot compliance. Second, the robot behavior adapts to the existing voluntary motor abilities. And third, the robotic system displays and improves the patient contribution by visual biofeedback. Initial experimental results are presented to evaluate the basic principle and technical function of proposed approaches. Further improvements of the technical design and additional clinical testing is required to prove whether the therapeutic outcome can be enhanced by such cooperative strategies.

Exercise Test↗

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

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

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↗

PubMed2003

The JoyntStick: a new force-input-device for a multi-modal desktop simulator.

This paper presents a new force-torque input device that can be used to navigate within any kind of anatomical atlas. As an example, we demonstrate how it can be used to drive a virtual knee joint. The device is comprised by a realistic phantom shank that is attached to a self-made high-sensitive force-torque sensor. It records forces and moments in six degrees-of-freedom and feeds them into a biomechanical model of the knee. Resulting joint movements and sounds are displayed by a visual and acoustic display, respectively. The entire multi-modal simulation environment can provide a better understanding of joint anatomy, e.g. for the education of medical students. Furthermore, it can be a practical tool for resident orthopaedic physicians in order to enhance the consultation, clarification, and treatment planning together with the patient.

Biomechanical Phenomena↗

PubMed2002

Stair ascent and descent at different inclinations.

The aim of this study was to investigate the biomechanics and motor co-ordination in humans during stair climbing at different inclinations. Ten normal subjects ascended and descended a five-step staircase at three different inclinations (24 degrees, 30 degrees, 42 degrees ). Three steps were instrumented with force sensors and provided 6 dof ground reactions. Kinematics was analysed by a camera-based optoelectronic system. An inverse dynamics approach was applied to compute joint moments and powers. The different kinematic and kinetic patterns of stair ascent and descent were analysed and compared to level walking patterns. Temporal gait cycle parameters and ground reactions were not significantly affected by staircase inclination. Joint angles and moments showed a relatively low but significant dependency on the inclination. A large influence was observed in joint powers. This can be related to the varying amount of potential energy that has to be produced (during ascent) or absorbed (during descent) by the muscles. The kinematics and kinetics of staircase walking differ considerably from level walking. Interestingly, no definite signs could be found indicating that there is an adaptation or shift in the motor patterns when moving from level to stair walking. This can be clearly seen in the foot placement: compared to level walking, the forefoot strikes the ground first--independent from climbing direction and inclination. This and further findings suggest that there is a certain inclination angle or angular range where subjects do switch between a level walking and a stair walking gait pattern.

Adult↗

PubMed2002

Improved haptic rendering of anatomical data.

We perform haptic rendering of a polygonal mesh at a high speed, independent of its face count, using a topologically structured data representation that avoids edge gap effects from small numerical errors. Constraints on the virtual proxy's position on the mesh give good results in rendering concave edges. The algorithm allows force shading and smoothing at convex corners and edges by an approach originally developed for graphic rendering.

Algorithms↗

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↗

PubMedDate not supplied

Human-centered robotics applied to gait training and assessment.

Robot-aided gait training can increase the duration and number of training sessions while reducing the number of therapists required for each patient. However, current automated gait trainers do not adapt their movement to the patient's muscular efforts and passive musculoskeletal properties. Furthermore, robot-aided training without therapists lacks the feedback required for patient assessment. In this article, we present results from the literature and our research to provide an overview of novel human-centered strategies for robot behaviors that are patient-cooperative and support motor-function assessment. Combining robot-aided training with robot-aided assessment will likely make future gait therapy easier, more comfortable, and more efficient. Broad clinical testing is still required for proving this assumption.

Exercise Therapy↗