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At least 127 records · Page 7Linked to original sources
PubMed2002

Iterative neuronavigation using 3D ultrasound. A feasibility study.

Intra-operative ultrasound (iUS) can generate 2D images in real-time as well as near real-time 3D datasets of the current situation during an intervention. Tracked ultrasound can locate the images in 3D space and relate them to patient, devices, andpre-operative planning data. Therefore, tracked US is an efficient means for controlling the validity of pre-operative planning, recognition of changes (brain shift) during the intervention, replanning of the operational path due to situational changes (iterative navigation), and finally, controlling the results (residual tumor). This paper describes a neuronavigation system exploiting this potential of interventional tracked US for permanent control of intervention progress and iterative adaptation of the planned procedure to the current situation.

Brain Mapping↗
PubMed2000

[Sulcal identification and neuronavigation in supratentorial cavernoma surgery].

We present the use of cortical sulci, segmented from magnetic resonance imaging, in image guided neurosurgery. Sulcal information was transferred to a surgical microscope with enhanced reality features. This assistance was used for the resection of supratentorial cavernomas (7 patients). Sulci were semi-automatically segmented from 3D MRI data sets. Sulci close to the cavernoma were selected and transferred to the neuronavigation system which allows the superimposition of graphics into the right ocular of the microscope. Selected sulci were displayed on the workstation and superimposed into the ocular of the microscope. Cortical sulci proved to be useful for the recognition of the anatomical environment. The superimposed sulci helped to optimize location and size of the skin incision as well as to guide the access to the cavernoma by using the course of a sulcus as indirect trajectory.

Adult↗
PubMed2001

[Endoscopic closure of cranionasal cerebrospinal fluid fistulas with the use of neuronavigation--"Computer Aided Surgery"].

INTRODUCTION: Conventionally, cranionasal cerebrospinal fluid (CSF) fistulas have been closed by repair of the dural defect via an open craniotomy. These techniques may be cumbersome, not without complications, and far from successful. In recent years, endoscopic techniques have been developed in the field of nasal surgery and neurosurgery. Furthermore, by means of computer-aided surgery or neuronavigation, it is possible to identify the surgical track with a high degree of accuracy and, by the same token, identify the defect in the cranium. METHOD: By combining the endoscopic technique with computer-aided surgery, we have operated on six patients with cranionasal CSF fistulas endonasally. The fistula was confirmed before surgery by subaracnoidal injection of fluorescein. RESULTS: The surgery was successful and without any complications in all six cases. DISCUSSION: The method is recommended as the operation of first choice for cranionasal CFS fistulas, as compared to transcranial surgery. It is probably more efficient and with fewer complications than conventional surgery. A collaboration between neurosurgeons and ENT surgeons, like ours, can be recommended.

Adult↗
PubMed1995

[Neuronavigation. Computer-assisted surgery in neurosurgery].

Computers in Neurosurgery were limited to diagnostics, planning stereotactic procedures, Radiosurgery and Radiation therapy. The possibility of intra-operative localisation only evolved since the mid 80's with the advent of more powerful computers. The computer adds more precision to microneurosurgical procedures, allowing neuronavigation in interaction with the computer. Diverse neuronavigationsystems are described in the literature [7-9, 11, 13]. We are working with the "ISG Viewing Wand" since april 1994. 113 operations were planed and executed aided by this system. We report on our experiences, the advantages and limitations of this system.

Adult↗
PubMed1997

Image guided microsurgery with a semifreehand neuronavigational device.

There is only limited experience with neuronavigators among the neurosurgical community so far. We evaluated such a prototype system in order to define indications for its succinct future use and to adjust it to daily clinical practice. We have employed an infrared light-linked computerized system (SPOCS; Aesculap/ISG) for preoperative planning and intraoperative navigation according to digitized images. A wired, penlike sensor-located "pointer" is used for navigation. Forty-eight patients (22 females, 26 males; aged 7-74 years) with a total of 53 intracranial lesions are included in the study. Fourteen lesions were smaller than 2 cm (26.4%), 33 were 2-4 cm (62.3%), and 6 were greater than 4 cm (11.3%). The documented accuracy was in the range of 3 mm or better in 33 patients throughout the whole operation and in an additional 7 through the most important surgical steps, with satisfactory results in all types of patient positioning except for the sitting position. In one patient the accuracy level decreased too early to perform useful intraoperative navigation. Technical dropouts early in the series led to abortion of the navigation in 7 instances but would currently no longer lead to abortion. There was no additional surgical morbidity associated with the use of the system. With more convenience in instrument design and development of techniques for real-time intraoperative reregistration, this kind of navigational device will play an increasingly important role for assistance during intracranial surgery. It proved to be helpful for planning of the craniotomy, intraoperative guidance on occasions of limited exposure and narrow visual field, localization and resection of small lesions in critical areas, and border definition of large lesions and for pure image guided resection of previously marked regions.

Adolescent↗
PubMed2003

Image fusion of MR images and real-time ultrasonography: evaluation of fusion accuracy combining two commercial instruments, a neuronavigation system and a ultrasound system.

OBJECTIVE: The aim of our study was to evaluate MRI/Ultrasonography fusion accuracy depending on three ultrasonographic parameters. METHOD: An ultrasonography and MRI compatible model was created, consisting of a plastic box, which contained 3 objects. MRI scans were performed with 128 sagittal slices. The objects were segmented and 3D reconstructions were created. A special ultrasound adapter with 3 reflective markers was fixed to the ultrasound probe. Thus, the probe could be tracked by the navigation system (Vector Vision(2), BrainLab, Heimstetten, Germany) and the segmented shape of the 3D-objects obtained from the MR images were overlaid onto the ultrasound display (Elegra, Siemens, Erlangen, Germany). The dependency of fusion accuracy on different depth of ultrasound display, different distances between probe and objects and different angles between the axis of the ultrasound probe and the centre of the spheres was evaluated. 435 single measurements were performed. FINDINGS: Overall fusion accuracy was 1.08 mm+/-0.61 mm (mean +/- standard deviation) for spheres and 1.6 mm+/-1.1 mm for arrow heads. If the ultrasound probe was directed more tangentially to the surface of the spheres the fusion became increasingly inaccurate (P<0.05). Fusion accuracy decreased the more distant the US probe was held to the object (P<0.05). Different depth of ultrasound display had no significant effect on fusion accuracy. CONCLUSIONS: Highly accurate fusion of MR images and real-time ultrasonography could be achieved. However, careful interpretation of the fused data is necessary, when different angles and distances of the US probe to the object are concerned.

Brain↗
PubMed2002

Image fusion for skull base neuronavigation. Technical note.

An automatic image fusion module (BrainLab, Munich, Germany) is used for the fusion of the magnetic resonance (MR) imaging and computed tomography (CT) data sets. The procedure of image fusion takes 5 minutes prior to surgery. The image fusion of CT and MR imaging data visualizes the skull base and tumor margins clearly. Color display of the different data sets allows the tumor and the skull base to be distinguished easily. The fused CT data in bone window mode provides useful additional information on the osseous skull base.

Brain Mapping↗
PubMed1998

Basic principles and clinical applications of neuronavigation and intraoperative computed tomography.

Computed tomography (CT) images in combination with a navigation device enable three-dimensional (3-D) localization of intracranial lesions. Furthermore, CT scanning can be adapted for intraoperative application to actualize the image data and to check the anatomical situation during the operation. Frameless navigation was used in 100 patients. The procedure was performed in 46 cases with an optical navigation system, in 38 cases with a sensory arm, and in 16 cases with a navigated microscope. Six skin markers were used for registration. Mean fiducial registration error was 2.18 mm with a standard deviation of 1.03 mm. The indication for navigation was tumor localization and planning of the craniotomy in 81 cases, stereotactic biopsy in eight cases, and endoscopic procedures in 11 cases. Technical problems with the navigation system were observed in nine cases. In two additional cases the tumor was not found by navigation. All eight biopsy cases were successful, and histologically relevant specimens were obtained without complications. Navigation was helpful in 11 endoscopic cases for choosing an optimal trajectory through the foramen of Monro or for connecting multiple intraventricular cysts. For intraoperative CT imaging, the mobile Philips Tomoscan M was adapted to the needs of the operating environment. The mobile CT was used in 78 cases in the operating room: 16 patients who underwent a stereotactic procedure had only preoperative CT scans, 36 patients had an intraoperative CT during tumor surgery, and 26 patients during the test period of the device had only a postoperative CT investigation. In 10 cases (28%) of the intraoperative group the remaining tumor tissue could be demonstrated on the CT scans. The tumor remnants that were not visible in the microscopical surgical field were subsequently removed. According to our results, intraoperative navigation seems superior for the localization of intracranial lesions and intraoperative CT is more useful when considering the radicality of tumor removal.

Brain Neoplasms↗
PubMed1999

Image-guided endoscopic ventriculostomy with a new frameless armless neuronavigation system.

OBJECTIVE: Complications resulting from imprecise placement of the ventriculoscope and reduced visibility through the endoscopic lens under certain conditions during third ventriculostomy have been reported in the literature. The following is a report of our first experience with image-guided endoscopic ventriculostomy. MATERIALS AND METHODS: Between September 1996 and October 1997, 11 patients diagnosed with aqueduct stenosis were found to be eligible for image-guided neuroendoscopy. The image-guided system (BrainLab, Heimstetten, Germany) links a freehand probe, tracked by a passive-marker sensor system, to a virtual computer image space. A 4-mm rigid ventriculoscope (Storz Instruments GMBH, Tuttlingen, Germany) was used. RESULTS: Eight patients improved clinically directly after surgery, two patients stabilized, and one patient improved only after insertion of an additional ventriculo-peritoneal shunt. The computer- calculated registration accuracy ranged from 1. 1 to 3.1 mm (median 1.4 mm) using 3-mm computed tomographic slices. The accuracy of the tool tip calibration for the endoscope was in the range of 0.35-0.9 mm (mean = 0.47 +/- 0.21). The described technique provided maximal flexibility for the surgeon and helped in performing a safe and accurate endoscopical procedure. CONCLUSIONS: Although not all cases of ventriculostomy require additional image guidance, we found the technique to be helpful in patients with atypical or large ventricles, in cases where orientation became difficult owing to bloody or blurry cerebrospinal fluid, and in patients with small foramina of Monroe, where the entrance angle of the endoscope needs precise definition for an atraumatic procedure to be performed.

Adolescent↗
PubMed1999

Neuronavigation.

The fact that the visualization process has been deferred since MRI and CT scanning have become the imaging standards for today's neurosurgeons has led to the importance of developing a tool for testing and teaching young pediatric neurosurgeons in the future. Navigation and teaching in a virtual reality model seems a sound solution.

Developed Countries↗
PubMed2000

A new cortical electrode for neuronavigation-guided intraoperative neurophysiological monitoring: technical note.

Intraoperative neurophysiological mapping and monitoring of eloquent brain areas can be combined with image-guided localisation to enhance the safety and efficacy of surgical procedures in the motor cortex. We designed a new type of cortical electrode which can be repeatedly placed on the cortical surface and allows accurate and reproducible stimulation by means of a navigation pointer. The newly designed device consists of a monopolar electrode contact for direct cortical stimulation, housed in a holder which allows placement, easy removal, and precise repeated placement of a surgical navigation pointer. It can be used for navigation-guided, high-frequency anodal monopolar cortical stimulation (MCS) for the mapping of eloquent cortex, and for monitoring of motor pathways. While the cortex is stimulated, compound muscle action potentials (CMAP) are recorded from muscles of the contralateral extremities and are assessed both qualitatively and quantitatively. When the device is used in combination with intraoperative navigation, the stimulation sites may optionally be registered or displayed on the system monitor. This allows repeated pinpointing and obviates the need for strip or grid electrodes in the operative field; although such electrodes may be useful for continuous monitoring, they often are in the surgeon's way. In addition, the primary and supplementary motor cortex can be mapped by determining the location of the sites of stimulation on surface-projected images of the cerebral cortex.

Brain Mapping↗
PubMed1998

An experimental approach to image guided skull base surgery employing a microscope-based neuronavigation system.

INTRODUCTION: A cadaveric study was undertaken to investigate the usefulness and reliability of a microscope based navigation system (NS) for skull base surgery. MATERIAL AND METHODS: CT-scans (1 mm slices) were performed in 10 fixed cadaver heads after implantation of fiducials. There upon, various skull base dissections were undertaken: transethmoidal-transsphenoidal approach to sella and clivus, retrosigmoidal approach to the internal auditory canal (IAC) and to the posterior semicircular canal (PSCC). The navigated dissections were performed with the MKM, a microscope based navigation system of Carl Zeiss (Oberkochen, Germany). RESULTS: The registration assessment by the NS yielded a mean deviation of 0.23 mm +/- 0.03 mm (mean +/- SD, n = 7, range 0.19 to 0.27 mm). The real anatomical deviation during dissection was 0.67 mm +/- 0.2 mm for navigation to the IAC and 0.71 mm +/- 0.37 mm to the PSCC. This accuracy was achieved with three fiducials (4 x 1 mm titanium screws) arranged as a triangle (side length 4-6 cm) nearby the surgical field. Navigation data on current position, direction and distance to a target structure were helpful in the transethmoidal-transsphenoidal approach to the clivus, as well as for accessing deep seated structures (C1-C2 junction, petrous bone tip). The contouring feature was beneficial for identifying structures embedded in the bone. However, due to inaccurate 3-D modelling this feature has a restricted reliability. DISCUSSION: Our cadaveric skull base study has shown that the MKM is a reliable tool with high anatomical accuracy and usefulness of most navigation features. However, in order to effectively and reliably use any NS the surgeon must be familiar with its potential features and limitations as is demonstrated in this study.

Equipment Design↗
PubMed2002

Anatomical landmarks for image registration in frameless stereotactic neuronavigation.

OBJECTIVE: Frameless stereotactic navigation devices require preoperative application of skin markers (SM) and planning radiography, which limits their even wider use. Therefore, we prospectively studied the applicability and accuracy of anatomic "natural" markers (NM) for image registration. METHODS: The accuracy of NM was evaluated in 26 patients operated on in the supine (n=24) or sitting (n=2) position, either by comparison to our standard navigation protocol using SM and planning radiography or by the deviation of anatomic landmarks using a routine diagnostic radiograph. In 21 cases, NM were compared to SM with planning radiography (computed tomography, or CT, in nine cases and magnetic resonance imaging, or MRI, in 12). The root mean square error (RMSE) of the registered volume was calculated by the Philips EasyGuide Neuro frameless stereotactic navigation system and compared between the two registration modalities. RESULTS: The mean RMSE was 3.2 mm+/-1.0 mm standard deviation using NM vs 2.9+/-1.0 mm using self-adhesive SM (P=0.13, Student's t-test). Computed tomography was slightly more accurate than MRI planning (mean RMSE 3.2 mm vs 3.3 mm). In three cases, diagnostic radiography (MRI) was used with a mean RMSE of 5.3 mm but acceptable intraoperative landmark correlation. CONCLUSION: Our pilot study demonstrates insignificant loss of registration accuracy using NM compared to SM. Additionally, the radiologic planning investigation and accuracy loss due to SM movement may be avoided.

Adolescent↗