“IOMaster 7D”—a new device for virtual neuroendoscopy
Purpose: Within a scope of a cooperative project called “HapticIO” (funded by the German Ministry of Education and Research (BMBF)), a completely new force feedback device “IOMaster 7D” was intended to be developed for simulation of endoscopic ventriculo-cisternostomy (VCS). Methods: A VR model for endoscopic ventriculostomy was generated based on a MRI data set of a real hydrocephalic brain. Different software modules were used for segmentation (VESUV), modelling (KisMo) and visualization (KISMET). The software modules were implemented on a WIN32 platform and are running on Windows-NT, Win2000 or WinXP. A force feedback system for capturing of the position of both the trocar and the acting instrument was developed. Large arms are counterbalanced to reduce gravitational forces and torques. The position and orientation of the input handle is determined by taking the joint angles of the linkages and using the forward kinematics calculation. Force data returned by the simulation is mapped to a set of torques to be produced by the motors by using a so-called Jacobian transformation. Real microsurgical instruments (MINOP, Aesculap, Germany) were used and adapted to the simulator to provide for a design and haptic properties close to real situation in the OR. The system was evaluated in a pilot series. Results: The force feedback system IOMaster 7D offers 7 degrees of freedom and consists of two coupled force feedback elements. Both the trocar and the acting instruments (scissor, bipolar coagulation, forceps, inflatable balloon catheter) are captured separately. In this way, the trocar's position determines the view of the endoscopic 30° lens camera, the access to the target and the possible operating range of the instruments. A complex elastodynamic hydrocephalic configured ventricular system with realistic proportions and anatomical structures could be modelled. An interactive virtual preparation with force feedback was implemented coupling real surgical instruments (MINOP) with the force feedback system. The VR system provides different interactions like axial movement or rotation of the instruments, cutting, grasping as well as realistic elastodynamic deformations of the ventricle wall. First evaluations proved a reduction of the median failure rate and a reduction of the median required time to reach the target. Analysis of the total distance of instruments movement also showed a reduction. Conclusion: VR systems can simulate realistic and real-time surgical procedures and may open new perspectives for the neurosurgical training. The training of potentially hazardous procedures can be uncoupled from the patient resulting in a reduction of surgical morbidity. The integration of haptic information increases the quality of these training systems. The definition of no-touch areas and targets and the possibility of automatic registration of both kinetic parameters, failure rate and the time course of the procedure provide objective criteria for the appreciation of a learning effect.
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