Brain surgery involves the adjustment of a stereotactic frame attached to a fixation device which is rigidly screwed to the skull. Scanning always precedes the actual intervention in order to precisely locate the patient's target lesions. Up till now, no software has assisted in the initial placement of the fixation device which holds fiducial localiser markers during scan as well as the stereotactic frame during surgery afterwards. At the National University of Singapore (NUS), Dr. Luis Serra is currently leading a project to develop a Virtual Brain Bench in which the user can manipulate a computer model of the stereotactic frame to plan against registered brain structures from both the Electronic Brain Atlas and the patient's individual data. Last december, Tomorrow's World, a scientific BBC TV broadcast, reported on the latest results of brain surgery rehearsal at the NUS-based Institute of System Science (ISS).
At the beginning of this century, brain surgeons used X-rays to determine the exact target location while nowadays, far more accurate volume scans such as CAT and MR have reduced morbidity and cost. Yet, experts still rely on 2D display paradigms and 2D brain atlases for their surgical planning. Dr. Luis Serra and his ISS team now have introduced 3D brain models and virtual reality techniques in their new and revolutionary system, referred to as the Virtual Brain Bench (VBB). The VBB is based around two key technologies, namely the Virtual Workbench, a 3D user interface and an Electronic Brain Atlas.
The first constitutes a tool for control of 3D data, aimed at productive work environments, also outside the medical field. The latter integrates electronic versions of several print paper brain atlases used in everyday clinical practice. The atlas data from the print atlases are digitised, enhanced, colour coded, labelled, organised into volumes and turned into 3D extensions. Within the Virtual Workbench, the user reaches behind a mirror in which a 3D display shows both the patient's data and a visual echo of the physical tool handle, controlled by the user's hand and interacting with the data as a grasper, cutter or marker, as arranged by the software. The atlas acts as a guide to the target structure in the patient's data.
The first step in the stereotactic procedure involves the placement of a virtual version of the frame fixation device over a 3D model of the patient's head to check whether the surgeon can find a path to the target location, avoiding any screws or other frame constraints. The real fixation device then can be similarly attached to take the fiducial-equipped scan. Next follows the linking of the patient's data with the frame fixation device and with the brain atlas. The Singapore team has designed a Multimodal Registration tool for accurate relative placement of data from different modalities for a single patient. A 3D proportional grid system conforms the atlas to the individual patient's brain scan.
Finally, the surgeon selects the correct probe path. The stereotactic frame consists of a probe guide moving in straight line along an arc while an entry path is chosen to minimise damage to the structures along the penetrated path. To offer the surgeon more detailed help, the VBB also provides a Vessel Editor allowing to sketch points, edges and polylines directly on volume data to display blood vessels, cranial nerves or any other data. Afterwards, the system prints out the mechanical adjustment values to which the frame has to be set. So far, the surgeon's task has been an isolated one but Serra's team currently investigates possible collaborative approaches in adding networking capabilities to the VBB. This would enable several distant users to simultaneously look from different viewpoints at various data sets.
As an initial test, the VBB system's results will be compared with those of the traditional stereotactic method in educational and training environments. Each planning process can be saved into a referential database. This will equally help Dr. Serra and his team to extend and refine the system in order to move it eventually to the operating theatre and have it used in Augmented Reality so that computer generated 3D images are superimposed and registered on the real patient. You still want to know more about it? Please, find a clear, detailed and illustrated, scientific paper on the Virtual Brain Bench by Dr. Luis Serra and his colleagues on the Institute of System Science's web site.