ResearchResearch Projects
Einsatz der OCT-Bildgebung zur medizinischen Navigation

Integration of an OCT in a Medical Navigation System

Email:  jesus.diazdiaz@imes.uni-hannover.de
Team:  Dipl.-Math. Jesús Díaz Díaz
Year:  2010
Date:  19-07-10
Sponsors:  German Research Foundation (DFG)

There is an increasing need of high accuracy of mechatronic assistance systems in the field of minimal invasive surgery. Since standard systems do not satisfy the accuracy requirements, we are developping in cooperation with the Institute of Measurement and Automatic Control and the department of otolaryngology of the Medical School Hanover a mechatronic assistance system which includes an optical coherence tomograph (OCT). High accurate positioning of a robot is possible with the information of this sensor on the basis of multimodal image registration of preoperative CT- and intraoperative OCT-data.

Beschreibung

The topic of this project is the development of methods for minimally invasive surgical interventions at the lateral skull base. The goal is to increase the accuracy and safety of such interventions incorporating mechatronic assistance. The project is executed in a close cooperation with surgeons from the department of otolaryngology of the Hannover Medical School.

As a target application, a minimally invasive opening of the inner ear during cochlear implantation is considered. Cochlear implantation is the only efficient treatment of patients with severe to profound sensorineural hearing loss or deafness. During the intervention, an electrode array is implanted to the windings of the inner ear (cochlea) and electrically stimulates the auditory nerve. This results in a hearing impression for the patient and allows them to understand spoken language or listen to music. In order to achieve the desired accuracy and improve the surgeon’s physical precision, intraoperative navigation and robotic assistance are combined in this project. High accuracy in minimally invasive surgery is achieved by combining the key technologies of electrooptical navigation, high resolution imaging, especially optical coherence tomography, and robotic assistance.

First CT-image data is acquired using flat panel computerised tomography and used to create three dimensional models of the patient’s lateral skull base. This model includes the position and orientation of the cochlea, as well as position and orientation of functionally important structures such as the facial nerve, the chorda tympani or the auditory canal. Afterwards, the coordinates of a minimally invasive approach to the inner ear are optimised, which includes drilling a channel to the cochlea while preserving functional important structures.
In order to align the surgical drill to the preplanned coordinates, a robot is used. It is equipped with reference markers, which are tracked by a stereo-optical localizer. As the patient is equipped with markers in the same way, a pose estimation of the robot relative to the patient can take place and the drill can be driven to the desired position. Optical coherence tomography as a high-resolution imaging technique plays a key role in order to achieve the high accuracy. It is used to specify the exact pose of the end effector before and while drilling.It is also used to detect patient movement in order to compensate the erroneous pose or to stop the drilling. With additional inertial sensors, further information about the robot’s kinematic state is derived, which improves the robustness of the pose estimation. The different types of sensor information are processed, using appropriate control algorithms, so that the drilling can take place with high accuracy