Dual Stewart platform mobility simulator.

A robotic mobility simulator is being developed to allow training on various hapticly simulated surfaces while still being in the safe clinical environment. The simulator is integrated with a rich virtual environment displayed in front of the patient. The system uses two Stewart platform robots to render the walking surface geometry and condition. The hardware components of the platforms and the considerations behind their design are presented here. In addition, the nine state algorithm used for simulating the treadmill functioning is described along with the procedure used to transform the motion of the robots into walking in the virtual environment.

Virtual rehabilitation--benefits and challenges.

OBJECTIVES: To discuss the advantages and disadvantages of rehabilitation applications of virtual reality. METHODS: VR can be used as an enhancement to conventional therapy for patients with conditions ranging from musculoskeletal problems, to stroke-induced paralysis, to cognitive deficits. This approach is called "VR-augmented rehabilitation." Alternately, VR can replace conventional interventions altogether, in which case the rehabilitation is "VR-based." If the intervention is done at a distance, then it is called "telerehabilitation." Simulation exercises for post-stroke patients have been developed using a "teacher object" approach or a video game approach. Simulations for musculo-skeletal patients use virtual replicas of rehabilitation devices (such as rubber ball, power putty, peg board). Phobia-inducing virtual environments are prescribed for patients with cognitive deficits. RESULTS: VR-augmented rehabilitation has been shown effective for stroke patients in the chronic phase of the disease. VR-based rehabilitation has been improving patients with fear of flying, Vietnam syndrome, fear of heights, and chronic stroke patients. Telerehabilitation interventions using VR have improved musculo-skeletal and post-stroke patients, however less data is available at this time. CONCLUSIONS: Virtual reality presents significant advantages when applied to rehabilitation of patients with varied conditions. These advantages include patient motivation, adaptability and variability based on patient baseline, transparent data storage, online remote data access, economy of scale, reduced medical costs. Challenges in VR use for rehabilitation relate to lack of computer skills on the part of therapists, lack of support infrastructure, expensive equipment (initially), inadequate communication infrastructure (for telerehabilitation in rural areas), and patient safety concerns.

Virtual reality-enhanced stroke rehabilitation.

A personal computer (PC)-based desktop virtual reality (VR) system was developed for rehabilitating hand function in stroke patients. The system uses two input devices, a CyberGlove and a Rutgers Master II-ND (RMII) force feedback glove, allowing user interaction with a virtual environment. This consists of four rehabilitation routines, each designed to exercise one specific parameter of hand movement: range, speed, fractionation or strength. The use of performance-based target levels is designed to increase patient motivation and individualize exercise difficulty to a patient's current state. Pilot clinical trials have been performed using the above system combined with noncomputer tasks, such as pegboard insertion or tracing of two-dimensional (2-D) patterns. Three chronic stroke patients used this rehabilitation protocol daily for two weeks. Objective measurements showed that each patient showed improvement on most of the hand parameters over the course of the training. Subjective evaluation by the patients was also positive. This technical report focuses on this newly developed technology for VR rehabilitation.

A virtual-reality-based telerehabilitation system with force feedback.

A PC-based orthopedic rehabilitation system was developed for use at home, while allowing remote monitoring from the clinic. The home rehabilitation station has a Pentium II PC with graphics accelerator, a Polhemus tracker, and a multipurpose haptic control interface. This novel interface is used to sample a patient's hand positions and to provide resistive forces using the Rutgers Master II (RMII) glove. A library of virtual rehabilitation routines was developed using WorldToolKit software. At the present time, it consists of three physical therapy exercises (DigiKey, ball, and power putty) and two functional rehabilitation exercises (peg board and ball game). These virtual reality exercises allow automatic and transparent patient data collection into an Oracle database. A remote Pentium II PC is connected with the home-based PC over the Internet and an additional video conferencing connection. The remote computer is running an Oracle server to maintain the patient database, monitor progress, and change the exercise level of difficulty. This allows for patient progress monitoring and repeat evaluations over time. The telerehabilitation system is in clinical trails at Stanford Medical School (CA), with progress being monitored from Rutgers University (NJ). Other haptic interfaces currently under development include devices for elbow and knee rehabilitation connected to the same system.

Evaluation of robot-based registration for subtraction radiography.

Digital subtraction of (plane film) radiographs of an area of interest taken over time is a powerful diagnostic tool. In dentistry for example, this is used to detect and treat periodontal disease (i.e. the sequence of diseases that leads to the loss of bone supporting the teeth). A precondition of subtraction radiography is correct three-dimensional registration of the film and X-ray source, without which the subtraction images are meaningless. A small misalignment can be compensated for by post-processing of the digitized films (by correspondence and rectification) to remove artifacts due to positioning errors. This paper presents a novel approach to subtraction radiography which replaces customary mechanical alignment methods (such as a stent or cephalostat) with a robot. A mechanical stent is a short rod attached at one end to the X-ray source and at the other to a mechanical appliance protruding from the patient's mouth. An experimental system was constructed which creates a 'sensorized stent' by integrating a plastic mouth appliance (with the impression of the patient's teeth), a robot carrying an X-ray source and a host computer. Results showed that the robotic system was superior to the mechanical alignment approach, due to its excellent accuracy and repeatability. This resulted in much less variation in the non-registered X-ray images, and in a smaller standard deviation in the intensities of subtracted images overall. The results suggest that in the future, diagnostic studies including subtraction radiography will not need either mechanical alignment (which is imprecise) or post-processing registration (which is time consuming).

Real-time sensing of tooth position for dental digital subtraction radiography.

Dental digital subtraction radiography requires accurate repositioning of the patient and X-ray source in order to facilitate correct diagnostic of bone loss. Present mechanical repositioning systems do not allow radiography of posterior teeth, and are uncomfortable for the patient. A new repositioning system that utilizes a six degrees of freedom position sensor and a robot arm with X-ray source is proposed. A mathematical model for the system is given, and the robot arm solution is obtained based on patient position. An error analysis is performed in order to determine the influence of sensor and robot errors on system accuracy. A series of experiments to determine sensor noise and accuracy are described. These tests showed relatively small errors over the work envelope of the sensor. Further tests showed that there is no adverse effect due to the presence of metal work in the patient's mouth. The high bandwidth of the sensor may allow real time tracking of small movements of the patient's head.