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PubMed2002

Error analysis in cranial neuronavigation.

Neuronavigation systems are now an important component of many modern neurosurgical treatment strategies. Their support facilities intraoperative orientation and makes neurosurgical operations more precise and less traumatic. Computer-aided neurosurgery is definitively not a temporary fashionable phenomenon, the concept of neuronavigation is here to stay. This report summarizes a ten-years-long experience and presents an error analysis of 108 failures (12.4 %) in a total of 874 image-guided cranial neurosurgical procedures with an arm-linked (mechanical) system and two different infrared-light emitting (optical) systems. The application of neuronavigation incurs multiple reasons for pitfalls because of the complex man-machine interface. Principally, we have to differentiate two types of errors: "machine made errors" due to soft- or hardware failure and "man made errors" generally, due to inadequate handling of the navigation system. The error analysis demonstrated that the so-called human interface plays the main role causing a high error rate.

Bias↗

PubMed1995

Frameless neuronavigation in modern neurosurgery.

A fundamental effort in neurosurgery is to reduce surgical trauma. Microneurosurgical technique combined with precise localization of lesions, can minimize the invasiveness of neurosurgical procedures. This report summarizes the utility of frameless neuronavigator systems and examines their value in reducing operative invasiveness. The basic principle of neuronavigation is the virtual linkage between digitized neuroradiological data and real anatomical structures, allowing an excellent three-dimensional orientation by real-time graphic-anatomic interaction. As frameless graphic interactive neuronavigation is developed further, these devices should become an important component of the modern microneurosurgical armamentarium and reduce surgical morbidity.

Humans↗

PubMed1996

Endoscopic facial skeletal surgery using a neuronavigator.

In the reconstruction of asymmetrical deformities of the facial skeleton, both an endoscope and a neuronavigator have been used. The endoscope allows the surgeon a wide view of the object on a television monitor, reduces the scarring, minimizes the undermined field, and reduces the need to work blind. The neuronavigator is a frameless computed tomographic stereotactic device that has been mainly used in neurosurgery. The device is easy to use and can offer the surgeon three-dimensional coordinates of the status during the operation. We have used this new technique in three clinical cases, two involving augmentation of the zygomatic bone on one side and one involving reduction of the frontal bone on one side. The surgical techniques we used and the versatility of both the endoscope and the neuronavigator are discussed herein based on our own experience.

Adolescent↗

PubMed1991

Open surgery assisted by the neuronavigator, a stereotactic, articulated, sensitive arm.

A new computed tomographic-stereotactic device that translates the operating point onto preoperative computed tomographic (CT) images, the Neuronavigator, has been developed. We have applied this system to various neurosurgical procedures to examine its usefulness. The system consists of a 6-joint sensing arm and a 16-bit personal computer. It projects the location of the arm tip onto a corresponding CT slice with a cursor that guides the surgeon toward the intracranial target during open surgery. The system also projects the location of the tip onto angiograms, and when used in conjunction with echography or a transcranial Doppler (TCD) flow meter, the surgeon's ability to navigate is enhanced. Sixty-eight patients underwent operation with the Neuronavigator. The navigation system worked as the core of a multimodal three-dimensional data base that proved to be useful during surgery. The maximum detection error was 2.5 mm, which was considered sufficient for open microsurgery. It also proved useful in designing the position of a craniotomy, in targeting deep-seated mass lesions, and in tracing the tumor edge, which had been identified on a CT scan. When the angiogram was combined with the navigator, it became easy to identify key vessels within a small operating field. The system was also combined with a TCD flow meter. This combination makes it possible to translate the measuring point of the TCD directly into CT coordinates, improving the precision of location of the TCD probe. The Neuronavigator combines various diagnostic images into one database and effectively guides the surgeon during surgery.

Adolescent↗

PubMed1999

Integration of functional magnetic resonance imaging supported by magnetoencephalography in functional neuronavigation

OBJECTIVE: In this study, the intraoperative visualization of functional data provided by functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) leading to functional neuronavigation is demonstrated in surgery around the motor strip. METHODS: In seven patients with lesions adjacent to the central region, fMRI was performed with a 1.5-Tesla magnetic resonance system, using axial echo-planar imaging with a motor and a sensory task. Somatosensory and motor evoked fields were recorded with a biomagnetometer. fMRI and MEG were matched to an anatomic three-dimensional magnetic resonance image set by a contour fit. Then this three-dimensional image data set was transferred to the navigation microscope and displayed in the eyepieces of the microscope during surgery. Additionally, intraoperative recording of somatosensory evoked potentials was performed for verification of the central sulcus. RESULTS: In all cases, the projection of fMRI and MEG data into the operating viewing field allowed easy identification of the central region, which was confirmed by phase reversal of somatosensory evoked potentials in each case. fMRI and MEG measurements yielded corresponding results in each patient. CONCLUSION: Functional neuronavigation with integration of fMRI and MEG allows the fast identification of eloquent brain areas. The widespread availability of fMRI will result in a broad availability of functional neuronavigation, which will, in turn, contribute to the successful surgery of lesions in eloquent brain areas with lower morbidity.

Journal Article↗

PubMed2001

Multimodal cranial neuronavigation: direct integration of functional magnetic resonance imaging and positron emission tomography data: technical note.

OBJECTIVE: This is the first report of the direct integration of functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) data into cranial neuronavigation. METHODS: In a patient with a left precentral oligodendroglioma (World Health Organization Grade III), the Zeiss MKM system (Carl Zeiss Co., Oberkochen, Germany) was used for navigation based on thin-slice, T1-weighted, contrast-enhanced magnetic resonance imaging (MRI) scans. fMRI and methionine PET data were integrated by landmark matching, with reference to skin fiducials. RESULTS: The inaccuracy of the image fusion between fMRI and T1-weighted MRI data was 1.7 mm, that between PET and T1-weighted MRI data was 4.3 mm, and that for the subsequent registration of the navigation was 1.2 mm. The correct fMRI localization of the precentral gyrus was intraoperatively verified by cortical somatosensory evoked potential (phase-reversal) monitoring. Although the tumor was not clearly defined in the MRI scans, [11C]methionine PET demonstrated a clear tumor border, enabling us to achieve gross total tumor removal without postoperative functional deficits. CONCLUSION: Functional neuronavigation permits observation and preservation of relevant brain areas. Other functional areas (such as short-term memory areas) that can be detected only by fMRI might also warrant future monitoring. The simultaneous integration of fMRI and PET data adds a new dimension to cranial neuronavigation, enabling the observation of tumors in relation to functional cortical areas (in our case, the motor strip).

Brain↗

PubMed2001

Methodological and technical issues for integrating functional magnetic resonance imaging data in a neuronavigational system.

OBJECTIVE: The aim of this article was to analyze the technical and methodological issues resulting from the use of functional magnetic resonance image (fMRI) data in a frameless stereotactic device for brain tumor or pain surgery (chronic motor cortex stimulation). METHODS: A total of 32 candidates, 26 for brain tumor surgery and six chronic motor cortex stimulation, were studied by fMRI scanning (61 procedures) and intraoperative cortical brain mapping under general anesthesia. The fMRI data obtained were analyzed with the Statistical Parametric Mapping 99 software, with an initial analysis threshold corresponding to P < 0.001. Subsequently, the fMRI data were registered in a frameless stereotactic neuronavigational device and correlated to brain mapping. RESULTS: Correspondence between fMRI-activated areas and cortical mapping in primary motor areas was good in 28 patients (87%), although fMRI-activated areas were highly dependent on the choice of paradigms and analysis thresholds. Primary sensory- and secondary motor-activated areas were not correlated to cortical brain mapping. Functional mislocalization as a result of insufficient correction of the echo-planar distortion was identified in four patients (13%). Analysis thresholds (from P < 0.0001 to P < 10(-12)) more restrictive than the initial threshold (P < 0.001) had to be used in 25 of the 28 patients studied, so that fMRI motor data could be matched to cortical mapping spatial data. These analysis thresholds were not predictable preoperatively. Maximal tumor resection was accomplished in all patients with brain tumors. Chronic motor cortex electrode placement was successful in each patient (significant pain relief >50% on the visual analog pain scale). CONCLUSION: In brain tumor surgery, fMRI data are helpful in surgical planning and guiding intraoperative brain mapping. The registration of fMRI data in anatomic slices or in the frameless stereotactic neuronavigational device, however, remained a potential source of functional mislocalization. Electrode placement for chronic motor cortex stimulation is a good indication to use fMRI data registered in a neuronavigational system and could replace somatosensory evoked potentials in detection of the central sulcus.

Adolescent↗

PubMed2000

Factors influencing the application accuracy of neuronavigation systems.

OBJECTIVE: The overall accuracy of neuronavigation systems may be influenced by (1) the technical accuracy, (2) the registration process, (3) voxel size and/or distortion of image data and (4) intraoperative events. The aim of this study was to test the influence of the registration and imaging modality on the accuracy. METHODS: A plexiglas phantom with 32 rods was taken for navigation targeting. Sixteen fiducials were attached to the surface of the phantom forming two different attachment patterns (clustered vs. diffusely scattered). This model was scanned by MRI and CT (1-mm slices). Registration was performed using different numbers and attachment patterns of the fiducials. Using CT or MRI, the localization error was measured in image space as the Euclidean distance between targets defined in image space and those detected in the physical space. Accuracy was measured with two commercial systems, the Zeiss MKM and the StealthStation. RESULTS: The mean localization error varied between 1.59 +/- 0.29 mm (MKM, 8 scattered fiducials, CT scanning) and 3.86 +/- 2.19 mm (MKM, 4 clustered fiducials, MRI). The worst localization error was 9.5 mm (MKM). In case of an optimal registration, the 95th percentile for the localization error was 2.2 (MKM) and 2.75 mm (StealthStation). The imaging modality has only minor influence on the localization error, with CT increasing accuracy minimally. Both the fiducial number and the attachment pattern critically influence the localization error: 8 fiducials and a generalized attachment pattern increase the accuracy significantly. No correlation between the calculated registration accuracy and the measured localization accuracy was found. CONCLUSION: The application accuracy of different neuronavigation systems critically depends on the registration. The calculated registration accuracy provided by the system does not correspond to the localization error found in reality. The accuracy of frameless neuronavigation systems is comparable to that of classical frame-based stereotactic devices.

Magnetic Resonance Imaging↗

PubMed1997

Infrared-based neuronavigation and cortical motor stimulation in the management of central-region tumors.

An infrared-based neuronavigation device (Surgical Microscope Navigator) integrating a pointer system with microscope guidance, is presented. We report our experience with this system in 17 patients undergoing surgery for space-occupying lesions of the central region. Cortical motor stimulation was additionally used in selected cases. The system was helpful in all operations by guiding craniotomy, corticotomy, or extent of tissue resection. Gross total tumor removal was possible in all patients but 1. Technical problems occurred in 1 case. Postoperative neurological worsening was found in 3 patients; this was reversible within a few weeks in 2 of them. In 9 cases, neuronavigation (combined with cortical stimulation, if necessary) probably prevented permanent neurological injury by exactly localizing tumors in the central area. It is concluded that neuronavigation (combined with motor cortex stimulation) may decrease neurological injury or neurosurgical invasiveness in lesions of the central region.

Astrocytoma↗

PubMed1999

[Quality securing procedures in neurosurgical operations. Experiences with intraoperative computed tomography and neuronavigation].

In the department of Neurosurgery of the Unfallkrankenhaus Berlin, experiences with neuronavigation and intraoperative computed tomography were acquired and reviewed on a descriptive basis. The main parameter for the evaluation was target point accuracy for the neuronavigation and image quality for the intraoperative ct. Additionally, both systems were evaluated about the requirement of time, staff and technical equipment. The analysis shows that both techniques are apted for quality control with the operation of intracranial lesions. Most problems with the handling of the new methods decreased with growing experience. On the technical aspect there are still problems with target accuracy for the neuronavigation and image quality for the ct-scans. However, solutions due to future technical improvement are perceived. The increase of time requirement is compensated with the rise of operation security. An even higher quality control is achieved with combination of both systems.

Brain↗

PubMed2000

[Neuronavigation in third ventricle tumors].

The authors present the results of neuronavigation as a help to open neurosurgery for the tumors of the third ventricle. From January, 1995 to August, 1999, six image-guided surgical procedures were performed to remove third ventricle lesions : 4 colloïd cysts, 1 ependymoma, and 1 craniopharyngioma. The operative approach was transcortical in 5 cases, and transcallosal in 1 case. The use of neuronavigation allows a decrease of the surgical trauma during the surgical approach. The procedure secures the neurosurgeon in the choice and execution of his pathway to the target. It becomes however less accurate after opening the ventricle, because of the brainshift induced by the loss of cerebrospinal fluid becomes important. Nevertheless, neuronavigation is useful in the surgery of the third ventricle, especially if it is used with neuroendoscopy.

Adult↗

PubMed2000

SonoWand, an ultrasound-based neuronavigation system.

OBJECTIVE: We have integrated a neuronavigation system into an ultrasound scanner and developed a single-rack system that enables the surgeon to perform frameless and armless stereotactic neuronavigation using intraoperative three-dimensional ultrasound data as well as preoperative magnetic resonance or computed tomographic images. The purpose of this article is to describe our two-rack prototype and present the results of our work on image quality enhancement. DESCRIPTION OF INSTRUMENTATION: The system consists of a high-end ultrasound scanner, a modest-cost computer, and an optical positioning/digitizer system. Special technical and clinical efforts have been made to achieve high image quality. A special interface between the ultrasound instrument and the navigation computer ensures rapid transfer of digital three-dimensional data with no loss of image quality. OPERATIVE TECHNIQUE: The positioning system tracks the position and orientation of the patient, the ultrasound probe, the pointer, and various surgical instruments. This makes it possible to update the three-dimensional map during surgery and navigate by ultrasound data in a similar manner as with magnetic resonance data. METHODS: The two-rack prototype has been used for clinical testing since November 1997 at the University Hospital in Trondheim. EXPERIENCE AND RESULTS: The image quality improvements have enabled us, in most cases, to extract information from ultrasound with clinical value similar to that of preoperative magnetic resonance imaging. The overall clinical accuracy of the ultrasound-based navigation system is expected to be comparable to or better than that of a magnetic resonance imaging-based system. CONCLUSION: The SonoWand system enables neuronavigation through direct use of intraoperative three-dimensional ultrasound. Further research will be necessary to explore the potential clinical value and the limitations of this technology.

Equipment Design↗

PubMed1998

[Usefulness of neuroendoscopy and a neuronavigator for removal of clival chordoma].

We report a case of large clival chordoma. The patient was a 56-year-old male who was admitted to our hospital with left eye ptosis and diplopia of 2 months duration. On admission, neurological examinations revealed oculomotor nerve palsy of the left eye. Skull radiographs with polytomographs demonstrated marked destruction of the clivus. A plain computed tomography (CT) scan revealed a large iso-attenuated mass in the clivus, extending anteriorly into the sphenoidal sinus, superiorly into the suprasellar cistern, bilaterally into the petrous apex, posteriorly into the prepontine cistern and caudally into the foramen magnum. An enhanced CT scan demonstrated a slightly enhanced tumor. A high-resolution bone-window CT scan revealed marked destruction of the clivus and bilateral petrous apex. Magnetic resonance imaging (MRI) scans disclosed a large enhanced mass extending superiorly into the suprasellar cistern, bilaterally into the petrous apex and inferiorly into the foramen magnum. The tumor extended so widely that we decided on a one-stage operation via a transsphenoidal sublabial transseptal approach and transoral transpalatal approach. At surgery, we employed a neuronavigator and Codman 4-mm rigid neuroendoscope with 0 degree, 30 degrees and 70 degrees angled lenses. The tumor was very soft and suckable, and could be easily removed by applying CUSA, a pituitary curette and suction. The neuronavigator was particularly useful because the surgeon had a real-time two-dimensional representation of the position of the tip of this device in the corresponding imaging space intraoperatively. The neuroendoscope also proved useful, since remnant tumor tissues that could not be seen under an operating microscope were frequently recognized near or around the entrance of the tumor cavity, cavernous sinus region and petroclival junction area. The surgeon was able to remove these remnants safely by checking on the neuroendoscope monitor. The tumor was excised completely. The dead space of the tumor cavity was reconstructed using a free rectus abdominis muscle flap. Postoperatively, cerebrospinal fluid leakage and meningitis were recognized, but improved following spinal drainage for one week and intrathecal injection of antibiotic. The oculomotor nerve palsy of the left eye also showed good recovery at one month after the operation. Recently, skull base surgery has undergone considerable developments. Neuroendoscopes and neuronavigators are very helpful for the neurosurgeon in performing skull base tumor surgery safely and with precision, although further instrument modifications are needed.

Chordoma↗

PubMed1998

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.

Adolescent↗

PubMed2003

Combining MEG and MRI with neuronavigation for treatment of an epileptiform spike focus in the precentral region: a technical case report.

BACKGROUND: Epileptic foci are often located in the vicinity but not necessarily within the boundaries of intra-axial brain tumors. Resection of these tumors is based on two major goals: first, maximizing tumor removal without provoking new neurologic deficits, and second, minimizing epileptic seizure activity. Magnetic source imaging (MSI) depicts the generators of magnetic fields overlaid on individual magnetic resonance (MR) images. Established application areas are lesions located adjacent to or partly within the sensory and motor cortex, or in the depth of the brain, necessitating a surgical approach through functionally highly relevant cortical regions. Magnetoencephalography (MEG) is also applicable for epileptiform spike foci recording during interictal activity. CASE DESCRIPTION: A patient with a recurrent glioma close to the Rolandic cortex scheduled for epilepsy and tumor surgery was investigated with MSI. The MSI data showed an epileptiform spike focus outside the tumor boundaries. The resulting MSI images were integrated into our neuronavigation system. This procedure allowed for the preoperative identification of the sensory and motor cortex, the precise localization of the epileptiform spike focus, and careful planning of the surgical procedure. In this case, we were able to safely resect the recurrent tumor and the epileptiform spike focus under general anesthesia using MSI-based neuronavigational guidance but no conventional intraoperative mapping techniques. CONCLUSION: Magnetic source imaging can be a valuable, noninvasive method for planning and performing tumor resections in high-risk brain regions, especially if an epileptiform spike focus has to be localized and included into the resection strategy.

Brain Neoplasms↗

PubMed2003

Neuronavigation accuracy dependence on CT and MR imaging parameters: a phantom-based study.

Clinical benefits from neuronavigation are well established. However, the complexity of its technical environment requires a careful evaluation of different types of errors. In this work, a detailed phantom study which investigates the accuracy in a neuronavigation procedure is presented. The dependence on many different imaging parameters, such as field of view, slice thickness and different kind of sequences (sequential and spiral for CT, T1-weighted and T2-weighted for MRI), is quantified. Moreover, data based on CT images are compared to those based on MR images, taking into account MRI distortion. Finally, the contributions to global accuracy coming from image acquisition, registration and navigation itself are discussed. Results demonstrate the importance of imaging accuracy. Procedures based on CT proved to be more accurate than procedures based on MRI. In the former, values from 2 to 2.5 mm are obtained for 95% fractiles of cumulative distribution of Euclidean distances between the intended target and the reached one while, in the latter, the measured values range from 3 to 4 mm. The absence of imaging distortion proved to be crucial for registration accuracy in MR-based procedures.

Algorithms↗

PubMed2003

Neuronavigated rTMS in a patient with chronic tinnitus. Effects of 4 weeks treatment.

Clinical, neurophysiological and neuroimaging data suggest that chronic tinnitus resembles neuropsychiatric syndromes characterised by focal brain activation. Low frequency repetitive transcranial magnetic stimulation (rTMS) has been proposed as an efficient method in treating brain hyperexcitability disorders. In one patient suffering from chronic tinnitus, [18F]deoxyglucose PET revealed increased metabolic activity in a circumscript area of the left primary auditory cortex (PAC). The effect of MRI and PET guided neuronavigated 1 Hz rTMS of this area was evaluated in a single-blind, sham-controlled, cross-over manner, followed by a 4-week open treatment. Following active stimulation there was a remarkable effect, enduring several weeks, on tinnitus sensation, which was paralleled by altered cortical excitability. These findings suggest that neuronavigated rTMS of increased PAC activity might offer a new option for treating auditory phantom perceptions like chronic tinnitus.

Chronic Disease↗

PubMed2001

Clinical experiences in neuronavigation.

We have successfully used a navigation system in more than 120 neurosurgical operations for past two years. The neuronavigation system provides high levels of mechanical accuracy in surgical localization, especially for small deep-seated masses or epileptic foci, surgical planning for intrinsic and extrinsic brain tumors, and arteriovenous malformation and guidance of instrumentation of spinal surgery. The ages of the patients were from 12 months to 75 years. The sex distribution was equal. Computed tomography or magnetic resonance imaging with 2-3 mm thick slices were employed for image guidance. The clinical experiences included 50 cases of deep-seated mass, 50 cases of surgical planning for tumor or vascular mass excision and 20 cases of spinal instrumentation treatment. There were no mechanical failures. Neuronavigation definitely provides a good technology in frameless brain and spinal surgeries.

Brain Neoplasms↗