Frameless image-guided neurosurgery in motion

Abstract

The general objective of this thesis was the enhancement of image-guidance system use by optimizing “man-machine” interaction in frameless image-guided neurosurgery. Part I. The application of frameless stereotaxy in the neurosurgical practice We aimed to compare three patient-to-image registration methods in frameless stereotaxy in terms of their application accuracy (the accuracy with which the position of a target can be determined intraoperatively). The results of this study showed that skin adhesive fiducial marker registration is the most accurate non-invasive registration method (application accuracy of 2-3 mm). Another objective was to quantify intra- and interobserver variability of manual fiducial localization in image space. The maximal intraobserver fiducial localization variability and target shift was submillimetric in computed tomographic image space and in magnetic resonance image space. Therefore, we concluded that determining centroids of skin adhesive fiducial markers in image space by hand is justified. Part II. Novel applications in frameless trajectory-aligned neurosurgery We described a novel frameless stereotactic subcaudate tractotomy procedure with promising initial results in a patient suffering from intractable obsessive-compulsive disorder. We also introduced a simple modification to the free-hand frameless stereotactic placement of ventriculoperitoneal shunts in undersized ventricles. The use of an image-guided instrument holder prevented off-track deflection and was considered a valuable modification. Initial clinical results were good in shunt dependent idiopathic intracranial hypertension patients. Part III. Intraoperative feedback in open image-guided neurosurgery One of our aims was to analyze the movement of surgical instruments during frameless image-guided neurosurgical procedures. A custom-made log-mode has been implemented in the image-guidance software to file instrument coordinates intraoperatively. To mimic ordinary open neurosurgery, future neurosurgical (tele)robotic systems should at least support the instrument excursions and speeds found in our studies. Also, we described the clinical introduction of a novel type of man-machine interaction in neuronavigation using auditory feedback. We measured the effect of auditory feedback during image-guided surgery in a phantom setup and in a clinical setting. If not for enhancing extent of resection, auditory cues might be helpful to prevent damage of eloquent brain structures or to facilitate the aiming process in frameless point-stereotaxy. Furthermore, we developed a novel visualization interface for neuronavigation in brain tumor surgery enabling intraoperative feedback on the progress of surgery. With the novel interface the progress and extent of surgical resection, displacement of cortical anatomy and digitized functional data could be visualized intraoperatively. We concluded that the embedding of workflow and volumetric feedback contributes to the improvement of surgical awareness and tumor resection in frameless image-guided neurosurgery in a swift and simple manner. In our endeavor to enhance the use and efficacy of neuronavigation systems by improving hardware and augmenting the man-machine interface, we have shown that the field of frameless image-guided neurosurgery is still in motion. With the augmented man-machine interface, we have moved into an entirely new field of neuronavigation development, concerning the relay of the available information to the neurosurgeon. Converging multidisciplinary efforts may lead to integrating medical robotics and novel (intraoperative) direct visualization techniques with advanced neuronavigation systems.