Image guidance in neurosurgical procedures, the "Visages" point of view.

This paper gives an overview of the evolution of clinical neuroinformatics in the domain of neurosurgery. It shows how image guided neurosurgery (IGNS) is evolving according to the integration of new imaging modalities before, during and after the surgical procedure and how this acts as the premise of the Operative Room of the future. These different issues, as addressed by the VisAGeS INRIA/INSERM U746 research team (http://www.irisa.fr/visages), are presented and discussed in order to exhibit the benefits of an integrated work between physicians (radiologists, neurologists and neurosurgeons) and computer scientists to give adequate answers toward a more effective use of images in IGNS

Framework for a low-cost intra-operative image-guided neuronavigator including brain shift compensation

In this paper we present a methodology to address the problem of brain tissue deformation referred to as 'brain-shift'. This deformation occurs throughout a neurosurgery intervention and strongly alters the accuracy of the neuronavigation systems used to date in clinical routine which rely solely on pre-operative patient imaging to locate the surgical target, such as a tumour or a functional area. After a general description of the framework of our intra-operative image-guided system, we describe a procedure to generate patient specific finite element meshes of the brain and propose a biomechanical model which can take into account tissue deformations and surgical procedures that modify the brain structure, like tumour or tissue resection

Development and evaluation of image-guided neuroendoscopy, with investigation of post-imaging brain distortion and accuracy of frameless stereotaxy

Neuroendoscopy enables a surgeon to operate deep within the brain whilst limiting morbidity through a minimally invasive approach. Technical advances in illumination, instrumentation and camera design, along with evidence for improved clinical outcome, have increased the indications for this technique and have ensured widespread popularity. However, broader application of neuroendoscopy is restricted by the necessity for direct vision of targets and by spatial disorientation. The aim of this investigation was to overcome these limitations by combining neuronavigation with neuroendoscopy to develop Image-Guided Neuroendoscopy (IGN). The strategy adopted for this was firstly to select, assess and validate a neuronavigation system, secondly to develop methods of endoscope tracking and frameless stereotactic implantation. Thirdly, to assess the impact of post-imaging brain distortion upon neuronavigation, fourthly to correct distortion of the endoscope image and finally to assess the use of graphics overlay in IGN. Laboratory phantom accuracy assessments revealed a mean point localisation error for the navigation system pointers of0.8mm (SD 0.4mm) with CT imaging, for the tracked endoscope of 1.5mm (SD 0.8mm) and for frameless stereotaxy of 1.3mm (SD 0.6mm). An in vivo study revealed a mean Euclidean error of 4.8mm (SD 2.0mm) for frame less stereotactic biopsy. The navigation system was evaluated through a clinical series of 100 cases, the frameless stereotactic technique was employed in 21 brain biopsy procedures and IGN evaluated in 5 procedures. The magnitude of post-imaging brain distortion was determined and correlations discovered with pre-operative image characteristics. The conclusions of this thesis are that IGN can be accomplished with acceptable accuracy, including frameless stereotactic implantation, and that the impact of postimaging brain distortion will not negate the value of IGN in most cases. Thus, the method developed for IGN has overcome both major constraints of neuroendoscopy, enabling endoscopic surgery to pass through and beyond the ventricular wall, to be undertaken safely in cases with distorted anatomy and opening the potential for wider application of these minimally invasive techniques

Navigated Brain Stimulation (NBS) for Pre-Surgical Planning of Brain Lesion in Critical Areas: Basic Principles and Early Experience

none3noModern neurosurgery attempts to get the difficult goal of combining an "aggressive" resection of brain tumors with the fundamental purpose of preserving brain functions and best possible quality of life. One of the most important evolutions of neurosurgical therapies is the opportunity to provide a customized surgical intervention by using modern methods to "map" the eloquent areas of the brain. This allows the identification of brain functional areas to be preserved from possible inadvertent intraoperative damage. Direct cortical stimulation (DCS) is an intraoperative technique that uses electrodes placed directly on the exposed cortical surface of the brain to stimulate activity of functional areas by simultaneously recording the evoked responses peripherally. DCS is very precise and reliable and can be considered the gold standard in brain mapping and intraoperative functional monitoring. Nevertheless, the neurosurgeon discovers the spatial relationship between the disease and eloquent cortical surfaces only after having completed a craniotomy and dural opening. A pre-surgical mapping method would give the opportunity to plan the treatment of brain diseases optimizing many aspects of the surgical treatment, including patient positioning, type of anesthesia, size of craniotomy, and extent of resection. Moreover, pre-surgical mapping would allow more precise prediction of the efficacy and risks of treatments that can be discussed with the patient and influence the therapeutic strategy. New techniques have been proposed in an attempt to provide a reliable method for the functional study that can be, however, exploited pre-operatively. The most recent of these methods of mapping cortical activities is navigated brain stimulation (NBS), which is based on the neurophysiological technique of transcranial magnetic stimulation (TMS) of the cerebral cortex combined with the conventional neuronavigation. Basic principles of NBS will be here discussed together with our preliminary experience using this technique in different neurosurgical diseases.mixedDr. Terry Lichtor; Alafaci C; Conti A; Tomasello F.Dr. Terry Lichtor; Alafaci C; Conti A; Tomasello F