[Artificial intelligence in neurosurgery]. / Künstliche Intelligenz in der Neurochirurgie.

BACKGROUND: Artificial intelligence (AI) in neurosurgery is becoming increasingly more important as the technology advances. This development can be measured by the increase of publications on AI in neurosurgery over the last years. OBJECTIVE: This article provides insights into the current possibilities of using AI in neurosurgery. MATERIAL AND METHODS: A review of the literature was carried out with a focus on exemplary work on the use of AI in neurosurgery. RESULTS: The current neurosurgical publications on the use of AI show the diversity of the topic in this field. The main areas of application are diagnostics, outcome and treatment models. CONCLUSION: The various areas of application of AI in the field of neurosurgery with a refined preoperative diagnostics and outcome predictions will significantly influence the future of neurosurgery. Neurosurgeons will continue to make the decisions on the indications for surgery but an optimized statement on diagnosis, treatment options and on the risk of surgery will be made by neurosurgeons with the help of AI in the future.

3D ultrasound navigation in syrinx surgery - a feasibility study.

BACKGROUND: The prototype of a 3D ultrasound navigation system, with a trackable 4- to 8-MHz phased-array ultrasound probe was used in syrinx-surgery. The aim of this study was to evaluate the advantages offered by 3D ultrasound and navigation in syringomyelial surgery. METHODS AND MATERIALS: After laminectomy, with a free-handed tilt of the ultrasound probe, the 3D volume of the target area is acquired within 15 seconds. The data are visualized after reconstruction in an axial, coronal, and sagittal view, offering the possibility of ultrasound-based guided surgery. RESULTS: Based on the intraoperative volume information, it was possible to navigate with the 3D ultrasound images in all cases. The orientation and image quality with respect to resolution, spatial information, and the identification of anatomical structures facilitated the surgery in all seven cases. The navigation tool, with a length of 12 cm and a tip diameter of 1 mm, was simple to place into the surgical site. The availability of an up-to-date 3D-image resulted in less interruption of the surgical procedure, with no need to repeatedly fill the cavity with sterile saline for new ultrasound acquisitions. New ultrasound images were only required if shift occurred. The coronal and "trajectory-plane" views, offer additional information about the syrinx cavity. The target borders are easier to determine and orientation in separated cavities was possible. Particularly in syringomyelial surgery it was helpful to determine the surface point of the syrinx to place the myelotomy or insert a catheter. CONCLUSION: 3D ultrasound offers the advantages of visualizing the third dimension of the target. For orientation and border determination navigation within the 3D ultrasound volume is very helpful and can take place with the ultrasound probe out of the way. Any disruption in the surgical procedure is minimized by not having to repeatedly fill the cavity with a sterile saline solution, there are fewer difficulties with image orientation because of new image adjustments.

Acute posttraumatic paraplegia associated with asymptomatic thoracic meningioma.

A case of a patient with acute paraparesis after compression fracture of the twelfth vertebra with progressive neurological deterioration is reported. The occurrence of clinical asymptomatic thoracic meningioma and coincidence with posttraumatic compression fracture of the vertebra at the same level resulting in acute paraparesis is extremely rare.

Characterization of necrotic meningioma using diffusion MRI, perfusion MRI, and MR spectroscopy: case report and review of the literature.

Necrotic meningiomas are relatively rare, accounting for 1.3-3.9% of primary intracranial tumours and for 10-15% of meningiomas, but are of special clinical importance as they may resemble metastases or malignant gliomas. We report the magnetic resonance findings of diffusion-weighted imaging, perfusion-weighted imaging, and spectroscopy in a patient with a necrotic meningioma, in whom clinical symptoms and signs suggested a central nervous system infection.

High frequency stimulation of the basal ganglia for the treatment of movement disorders: current status and clinical results.

High frequency stimulation of the basal ganglia has gained much interest during the last years. Based on the reevaluation of the results of functional neurosurgery for movement disorders from Leksell's group, pallidotomy as lesional procedure was the first functional operation that underwent a renaissance for the treatment of movement disorders. The work by Benabid and Siegfried who carried out thalamic high frequency stimulation to suppress tremor, the knowledge about deep brain stimulation (DBS) for the treatment of chronic pain as well as better understanding in basal ganglia physiology and the development of reliable stimulation hardware led to an increasing number of centers worldwide who currently apply high frequency DBS for different movement disorders. In the present review the current status of DBS for movement disorders is presented and the results with high frequency stimulation targeted at different brain areas are summarized.

Initial experience with an ultrasound-integrated single-RACK neuronavigation system.

A prototype ultrasound-integrated neuronavigation system was tested in 34 operations as regards image quality, stability, and handling during daily use in the operating theatre. The system consists of a high-end ultrasound scanner, a navigation computer, and an active optical positioning and digitiser system, all integrated in a single rack. An Ethernet interface between the two hardware devices enables digital data transfer between the ultrasound scanner and the navigation device without loss of image quality. The integration of an ultrasound scanner and a navigation device offers the opportunity of navigating directly to an intracranial or intraspinal lesion using intra-operative 3D ultrasound images. The brainshift problem is thus avoided. The ability to directly compare MR images and 3D ultrasound simplifies the interpretation of ultrasound images. The single-rack solution is an advantage in times of restricted space in the operating theatre caused by the increasing volume of technical equipment needed for a neurosurgical operation. In 30 cases the prototype system showed good reliability. In four cases the navigation system failed during the operation; however, the capacity of the ultrasound scanner was still available as a stand-alone function. With the single-rack concept, the flexibility of the system is high and the complete device can easily be moved from one operating theatre to another.

Comparison of intraoperative MR imaging and 3D-navigated ultrasonography in the detection and resection control of lesions.

OBJECT: The authors undertook a study to compare two intraoperative imaging modalities, low-field magnetic resonance (MR) imaging and a prototype of a three-dimensional (3D)-navigated ultrasonography in terms of imaging quality in lesion detection and intraoperative resection control. METHODS: Low-field MR imaging was used for intraoperative resection control and update of navigational data in 101 patients with supratentorial gliomas. Thirty-five patients with different lesions underwent surgery in which the prototype of a 3D-navigated ultrasonography system was used. A prospective comparative study of both intraoperative imaging modalities was initiated with the first seven cases presented here. In 35 patients (70%) in whom ultrasonography was performed, accurate tumor delineation was demonstrated prior to tumor resection. In the remaining 30% comparison of preoperative MR imaging data and ultrasonography data allowed sufficient anatomical localization to be achieved. Detection of metastases and high-grade gliomas and intraoperative delineation of tumor remnants were comparable between both imaging modalities. In one case of a low-grade glioma better visibility was achieved with ultrasonography. However, intraoperative findings after resection were still difficult to interpret with ultrasonography alone most likely due to the beginning of a learning curve. CONCLUSIONS: Based on these preliminary results, intraoperative MR imaging remains superior to intraoperative ultrasonography in terms of resection control in glioma surgery. Nevertheless, the different features (different planes of slices, any-plane slicing, and creation of a 3D volume and matching of images) of this new ultrasonography system make this tool a very attractive alternative. The intended study of both imaging modalities will hopefully allow a comparison regarding sensitivity and specificity of intraoperative tumor remnant detection, as well as cost effectiveness.

A complication conference for internal quality control at the Neurosurgical Department of the University of Heidelberg.

The registration of adverse events is an important issue in the field of medicine. Even today adverse event screening and registration is not part of the routine in most medical areas. In 1994, the Department of Neurosurgery at the University of Heidelberg implemented a conference for screening and registering adverse events. The aim was to record all complications occurring for an internal quality control. High priority was given to improving the process of data screening and registering. The conference is held every 2 weeks and all medical staff and residents of the department are obligated to be present. Screening of the adverse events encompasses all operations performed during a bi-weekly period. Every single operation is revised for an adverse event during or following the hospital stay. Adverse events are registered on a standardized data sheet and later transferred to a database for use in further investigations. After 6 years, the conference has been fully accepted and become an integral part of the workflow of the department. During this period, 8160 operations were screened and 1335 adverse events registered. The next step will be to integrate the data-collection process into the daily ward rounds using a personal digital assistant (PDA). This process is less time consuming and may perhaps augment the number of registered cases.

[Virtual reality in neurosurgery]. / Virtuelle Realität in der Neurochirurgie.

DEFINITION: Virtual reality enables users to immerse themselves in a virtual three-dimensional world and to interact in this world. The simulation is different from the kind in computer games, in which the viewer is active but acts in a nonrealistic world, or on the TV screen, where we are passively driven in an active world. In virtual reality elements look realistic, they change their characteristics and have almost real-world unpredictability. USE OF VIRTUAL REALITY: Virtual reality is not only implemented in gambling dens and the entertainment industry but also in manufacturing processes (cars, furniture etc.), military applications and medicine. Especially the last two areas are strongly correlated, because telemedicine or telesurgery was originated for military reasons to operate on war victims from a secure distance or to perform surgery on astronauts in an orbiting space station. In medicine and especially neurosurgery virtual-reality methods are used for education, surgical planning and simulation on a virtual patient.

An integrated head-holder/coil for intraoperative MRI in open neurosurgery.

With the invention of "open" magnetic resonance imaging (MRI) systems, access to the patient is possible during the imaging procedure. An important application of these systems is intraoperative MRI to control the extent of resection during tumor surgery. Up to now flexible surface coils wrapped around, or placed at each side of the head, were used for imaging. These flexible coils have several disadvantages such as unreliability, interindividual problems, difficult handling, poor hygienic properties, and often unsatisfactory or inhomogeneous image quality. To solve most of these problems, an MR-compatible head-holder in combination with an integrated surface coil for use in a 0.2 T C-shaped magnet was developed. Forty-eight patients with known cranial tumors underwent MRI intraoperatively. In 32 patients (67%), residual tumor was found, and additional surgical resection was performed. The integrated head-holder/coil is a safe and practical tool for intraoperative MRI, providing efficient and reliable resection control during neurosurgical procedures.

Clinical evaluation and follow-up results for intraoperative magnetic resonance imaging in neurosurgery.

OBJECTIVE: The use of intraoperative magnetic resonance imaging (MRI) in neurosurgery has increased rapidly, and a variety of concepts have recently been presented. Although the feasibility of the procedure has been demonstrated repeatedly, no conclusive analysis of its effects on the surgical procedures, the extent of tumor removal, and outcomes, or its possible problems, has been performed. METHODS: Of 242 operations performed with intraoperative MRI, 97 procedures for supratentorial glioma treatment were analyzed with respect to intraoperative imaging results and postoperative outcomes. Analysis of the images included assessment of imaging artifacts, image quality, and extent of tumor removal. Patients were monitored to determine radiological progression, survival times, postoperative complications, and morbidity rates. RESULTS: No intraoperative complications related to the imaging procedure were observed. Image quality was good or fair in 85.5% of the cases. Different types of surgically induced imaging changes could be identified. In 56 cases, resection was continued using navigation with intraoperative MRI data sets (rereferencing accuracy, 0.9 mm). For high-grade gliomas, the percentage of cases in which residual tumor was identified by MRI could be significantly reduced from 62% intraoperatively to 33% postoperatively, which was paralleled by a significant increase in survival times for patients without residual tumor. Complication and morbidity rates were within the ranges reported for other studies. CONCLUSION: Intraoperative MRI is safe and allows reliable updating of neuronavigational data, with compensation for brain shifting. Surgically induced imaging changes, which have been identified as a possible problem with intraoperative MRI in general, necessitated comparisons with preoperative scans and require future attention. The extent of tumor removal and survival times were increased significantly. Overall, patients seemed to benefit from the method.

Interventional MRI-guided brain biopsies using inductively coupled surface coils.

The technical realization of inductively coupled surface coils for interventional MR-guided procedures, and the application to brain biopsies in a 0.2 T magnet is described. The advantages compared to standard coils are discussed, and the results of 26 biopsies on eight different neuropathologic diagnoses from varying locations within the brain are presented. Initial experience shows that inductively coupled coils can offer an increased number of indications for interventional procedures in the brain, easier handling of sterility, and often a better access for the surgeon, compared to the use of standard MR head coils.

Integration of generic indicators for quality management in hospital information systems.

Hospital information systems may contribute in different ways to quality management activities such as monitoring of quality indicators. Most existing quality management activities in hospitals are adjusted to a special medical field or particular disease. These activities often run simultaneously with other procedures and the documentation of patient care. To determine an interdisciplinary integrated quality management procedure, a pilot study was carried out at the Neurosurgery Department and Neonatology Division of the Medical Center of the University of Heidelberg. Predefined generic indicators that may be integrated in an existing information system and used in hospital routine were the basis of this project. The aim of the study was to support the quality management with periodic reports of these indicators. The pilot study showed that there were barriers along the path to an integrated generic quality management. To meet the requirements of routine monitoring, using predefined generic indicators of hospital care, much integration effort, directed at organizational aspects of information processing and information systems architecture, is still needed.

Modified Headholder and operating table for intra-operative MRI in neurosurgery.

In order to facilitate intra-operative use of magnetic resonance imaging (MRI) in neurosurgery an MRI-compatible headholder was developed and adapted to a modified MR-couch simultaneously serving as tabletop for the operating table. To allow shock-free transport into the scanner the wheels of the operating table were replaced by an air cushion mechanism. In 75 procedures the system proved to be reliable and safe. Image quality was not impaired by the fixation device. With growing routine the transfer became straightforward, requiring approximately 10 min. Intra-operative MRI is thus made possible with minimal changes to the standard surgical environment. Its benefit however, still remains to be critically investigated.

Neuronavigation--first experiences with three different commercially available systems.

Growing interest in neuronavigation also referred to as frameless stereotaxy has led to the development of various navigational devices employing different localization methods. In 152 procedures the authors have used neuronavigation. Cases included 89 intracranial- and 26 skull base tumours, 9 biopsies, 21 vascular and 7 functional procedures on 144 patients since July 1993. In 75 cases the lesions were located in eloquent areas. In 82% (124) MRI, 13% (18) CT and 5% (8) both imaging methods were employed. Three neuronavigational devices with different localization methods were used for the procedures. The Viewing Wand (VW, ISG, Canada), a multijointed arm was used in 101 procedures. In 15 cases the SPOCS (Aesculap, Germany) consisting of cameras detecting infrared light from LED's mounted on instruments and in 51 cases the microscope-integrated MKM (ZEISS, Germany) was investigated, 15 times two systems were used simultaneously. Mean time necessary for preoperative registration was 23 +/- 13 min (VW), 21 +/- 16 min (SPOCS) and 27 +/- 22 min (MKM) respectively. The mean accuracy of registration measured as RMS was 2.9 +/- 1.2 mm (VW), 3.3 +/- 0.9 mm (SPOCS) and 3.1 +/- 1.0 (MKM) respectively. Regarding intraoperative handling the VW was found to be a robust but sometimes bulky and hindering device whereas the SPOCS was more flexible but with the need of unobstructed visibility between cameras and pointers. The MKM without these restrictions required training to get used to handling.

[Neuronavigation. Methods and prospects]. / Neuronavigation. Methoden und Ausblick.

With the recent developments in computer technology and the improvements in modern neuroimaging, frame-based stereotactic guidance for open microsurgical procedures has been increasingly replaced by neuronavigation, also called frameless stereotaxy. It allows transfer of individual patientís images onto the operative field to assist the neurosurgeon intraoperatively in defining the tumor margins or identifying functionally important brain areas. The different localization techniques employed are articulated position-sensing arms, infrared or ultrasound systems working with the principle of satellite navigation and robotic systems integrated with the operating microscope. In 200 operations performed with different systems (arm-based, robotic and infrared) the method proved to be helpful, enabling fewer invasive procedures to be performed. With a mean deviation of 2.87 +/- 1.9 mm for intraoperative localization, the accuracy was only slightly worse than in frame-based stereotaxy with deviations below 2 mm. Neuronavigation was most helpful for operations on deeply seated lesions, skull-base tumors and lesions in brain areas with high functionality. The major disadvantage is the use of preoperative data for navigation, leading to inaccuracies when anatomical structures are altered during the operation by resection of tumors or shift of intracranial soft tissue. Intraoperative magnetic resonance imaging (MRI) might be a solution for this problem. With the method of intraoperative MRI developed in our department it has already been possible to update neuronavigation with images reflecting intraoperative changes in anatomy. Therefore, neuronavigation is definitely a method with growing importance in operative routine, and it will also spread into other surgical specialties.

Intraoperative diagnostic and interventional magnetic resonance imaging in neurosurgery.

OBJECTIVE: The benefits of intraoperative magnetic resonance (MR) imaging for diagnostic and therapeutic measures are as follows: 1) intraoperative update of data sets for navigational systems, 2) intraoperative resection control of brain tumors, and 3) frameless and frame-based on-line MR-guided interventions. The concept of an intraoperative MR scanner in the sterile environment of operating theater is presented, and its advantages, disadvantages, and limitations are discussed. METHODS: A 0.2-tesla magnet (Magnetom Open; Siemens AG, Erlangen, Germany) inside a radiofrequency cabin with a radiofrequency-shielded sliding door was installed adjacent to one of the operating theaters. A specially designed patient transport system carried the patient in a fixed position on an air cushion to the scanner and back to the surgeon. RESULTS: In a series of 27 patients, intraoperative resection control was performed in 13 cases, with intraoperative reregistration in 4 cases. Biopsies, cyst aspirations, and catheter placements (mainly frameless) were performed under direct MR visualization with fast image sequences. The MR-compatible equipment and the patient transport system are safe and reliable. CONCLUSION: Intraoperative MR imaging is a safe and successful tool for surgical resection control and is clearly superior to computed tomography. Intraoperative acquisition of data sets eliminates the problem of brain shift in conventional navigational systems. Finally, on-line MR-guided interventional procedures can be performed easily with this setting. As with all MR systems, individual testing with phantoms, application of correction programs, and determination of the optimal amount of contrast media are absolute prerequisites to guarantee patient safety and surgical success.

Intraoperative magnetic resonance imaging to update interactive navigation in neurosurgery: method and preliminary experience.

We report on the first successful intraoperative update of interactive image guidance based on an intraoperatively acquired magnetic resonance imaging (MRI) date set. To date, intraoperative imaging methods such as ultrasound, computerized tomography (CT), or MRI have not been successfully used to update interactive navigation. We developed a method of imaging patients intraoperatively with the surgical field exposed in an MRI scanner (Magnetom Open; Siemens Corp., Erlangen, Germany). In 12 patients, intraoperatively acquired 3D data sets were used for successful recalibration of neuronavigation, accounting for any anatomical changes caused by surgical manipulations. The MKM Microscope (Zeiss Corp., Oberkochen, Germany) was used as navigational system. With implantable fiducial markers, an accuracy of 0.84 +/- 0.4 mm for intraoperative reregistration was achieved. Residual tumor detected on MRI was consequently resected using navigation with the intraoperative data. No adverse effects were observed from intraoperative imaging or the use of navigation with intraoperative images, demonstrating the feasibility of recalibrating navigation with intraoperative MRI.