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The impact of an armless frameless neuronavigation system on routine brain tumour surgery: a prospective analysis of 51 cases.

A passive infrared armless and frameless neuronavigation system was introduced in routine intracranial and skull base surgery, and its impact on 51 cases in a one year period was assessed. No cases were rejected by the operating surgeon for lack of accuracy (> 3 mm). Operating time was not significantly lengthened, except in transphenoidal cases (255 +/- SD 168 min versus 185 +/- SD 119 min, p = 0.02). Length of stay was shorter in navigation cases in supratentorial glioma (12 +/- SD 7.3 days versus 15 +/- SD 7.9 days) and meningioma (11 +/- SD 5.3 days versus 16 +/- SD 6.7 days, p = 0.01). Outcome at 3 months was comparable in both the supratentorial glioma and meningioma group. Problems such as setup time and brain shift are addressed and discussed.

Adolescent↗

Visualization of the pyramidal tract in glioma surgery by integrating diffusion tensor imaging in functional neuronavigation.

OBJECT: The aim of this study was to investigate whether diffusion tensor imaging (DTI) can be integrated into functional navigation for the intraoperative visualization of the pyramidal tract. METHODS: A single-shot spin-echo diffusion-weighted echo planar imaging sequence on a 1.5 T magnetic resonance (MR) scanner was used for DTI. One null image and six diffusion-weighted images (high B value 1 000 mm/s (2)) were obtained. Color-encoded fractional anisotropy maps of the principal eigenvector rendered as a boxoid within each voxel were used for segmentation of the pyramidal tract. The segmented images were rigidly registered with a T(1)-weighted gradient echo 3D dataset for navigation in 16 patients with gliomas. In tumors adjacent to the motor cortex (n = 6) data from functional MR imaging were co-registered. RESULTS: The whole DTI processing lasted about 25-30 minutes in each case. In all cases DTI could be integrated into the navigational dataset resulting in an intraoperative visualization of the pyramidal tract by microscope-based navigation. Navigational accuracy measured as the target registration error was 1.2 +/- 0.46 mm. Registration of fractional anisotropy maps with the 3D navigational dataset was possible with an error of less than 2 mm. Co-registration with fMRI was consistent with DTI data. A neurological deterioration was observed only in one patient. CONCLUSIONS: DTI can be reliably integrated into navigational datasets. Thus, microscope-based neuronavigation can be used for an intraoperative visualization of the course of the pyramidal tract. However, a possible shifting of the pyramidal tract has to be taken into account after major tumor parts are removed.

Adolescent↗

Neuroendoscopy combined with frameless neuronavigation.

Minimal invasive neurosurgery is becoming more and more standard in neurosurgical procedures. Several types of lesions are now approached endoscopically. The surgical planning and intraoperative orientation during endoscopic surgical procedures are sometimes difficult. To solve this problem, a combination of the endoscopic procedure with a frameless, armless neuronavigation system is used in our service. The combination of the endoscope and the frameless navigation system was used in tumour surgery, ventriculostomies and arachnoid cyst operations. All procedures were performed successfully. The combination of both systems has proved to be advantageous because of safe surgical planning using the frameless stereotactic technique and the possibility of real time orientation of the endoscope. This technique is very useful in removing intraventricular and large brain mass lesions.

Arachnoid Cysts↗

Ultrasound-guided neuronavigation of deep-seated cavernous haemangiomas: clinical results and navigation techniques.

The aim of this study was to evaluate guidance techniques and patient outcomes of ultrasound-guided neuronavigation of deep-seated intracerebral cavernous hemangiomas (CAs). Thirty-five patients with deep-seated intracerebral CAs with sizes ranging between 7 and 45 mm were operated upon only with ultrasound-guidance. Twenty-seven were located in or near eloquent regions. In 30 patients dissection to the lesion was performed through sulci and fissures. The best approach to a lesion based on surface anatomy and depth was determined using sonographic information. Navigation was done sonographically. In five patients the shortest approach via a corticotomy was determined sonographically. Twenty-six patients had no neurological deficit postoperatively. Preoperative deficits improved in seven of nine patients. Fifteen of 19 patients suffering epileptic seizures had no seizures postoperatively. Intraoperative sonography revealed residual CA tissue after microsurgical extirpation in two cases. This report shows that intraoperative sonographic navigation provides safe guidance to deep-seated CAs with good clinical outcome independent of size.

Adolescent↗

Development of a frameless and armless stereotactic neuronavigation system with ultrasonographic registration.

OBJECTIVE: We have developed a frameless stereotactic neuronavigation system that allows navigation during neurosurgical procedures through an image formed from integrating ultrasonography and preoperative magnetic resonance (MR) imaging and/or x-ray computed tomography. METHODS: The system consists of a ultrasound imaging scanner, a workstation with an image capture board, and an ultrasonic tracking sensor with a 5-MHz ultrasonographic transducer. The ultrasonic tracking sensor measures the position and orientation of the ultrasonographic transducer. The oblique plane of the MR/computed tomographic image corresponding to the ultrasound image is then displayed on the workstation monitor. A three-dimensional computer graphic representation of the integrated image is also reported as a preliminary test. For the patient-image registration, the coordinates of digitized and imaged markers on a specifically developed reference frame are used. The reference frame is noninvasive because it is not bolted but only fastened to the patient's head with silicon. RESULTS: Based on the findings from the clinical application of the system in three cases, the system was advantageous because of the surgical procedures could be controlled by intraoperative ultrasonography as well as by preoperative MR/computed tomographic images. Missing parts in the ultrasonogram were supplemented with preoperative MR/computed tomographic images. At other times, spatial positioning and visualization by ultrasonography were useful for identifying anatomical objects in the image. CONCLUSION: This preliminary study of the frameless integration of ultrasonography into stereotactic space demonstrated its clinical usefulness. We believe that the concept of pre- and intraoperative image-guided surgery presented here will find increasing use in the future.

Adolescent↗

Advanced surgical approach for selective amygdalohippocampectomy through neuronavigation.

OBJECTIVE: Selective removal of the mesiobasal temporal structures through the transsylvian approach was introduced by Yasargil and Wieser in 1982. This alternative to standard temporal lobectomy provides excellent outcomes for seizure control. Basic actions in the transsylvian fissure exposure mainly serve to orient the surgeon, and they carry the risk of vasospasm and vessel damage. The aim of our study was to reduce landmark-guided surgery steps through neuronavigation. METHODS: During a 14-month period, 16 selective amygdalohippocampectomies were performed with the aid of the SMN (Carl Zeiss, Inc., Thornwood, NY) or StealthStation (Sofamor Danek, Memphis, TN) optically guided systems. We added safety procedures to the operation (including intraoperative rereferencing, obtaining additional bony reference points before craniotomy, performing a small craniotomy and making an accurate dural incision, and using contrast medium for vessel visualization) to develop a method that relies on navigational systems without further orientation by anatomic landmarks. RESULTS: Originally, performing an amygdalohippocampectomy required exposing the sylvian fissure from the carotid bifurcation to 2 cm beyond the middle cerebral artery bifurcation, which exposed one-third of the insula. By determining the entry point at the limen insulae and the target at the tip of the temporal horn, the mandatory extent of the opening to the sylvian fissure can be projected. Therefore, the exposure of the fissure can be limited to exactly the extent required for the transventricular approach through the uncinate fasciculus. CONCLUSION: Computer-assisted surgery is an effective tool in eliminating the exposure of anatomic landmarks in selective amygdalohippocampectomy. This modification combines the precision of targeting with minimal cortical and vessel traumatization.

Adult↗

The relationship of magnetic source imaging to ictal electrocorticography in a neuronavigational workspace.

Magnetic source imaging (MSI) registers magnetoencephalographic (MEG) activity to a three-dimensional MRI volume. State-of-the-art MSI allows concurrent whole head coverage, but is practically restricted to interictal recording. However, the purpose of the presurgical evaluation of epileptic patients, in which MSI is playing an increasing role, is the elucidation of the ictal epileptogenic focus. The manner in which interictal MSI activity relates to the ictal focus has not yet been adequately examined. To facilitate this analysis, we are developing techniques to precisely coregister MSI to the ictal onset zone as defined by extraoperative intracranial grid/strip monitoring. The neuronavigational workspace is a convenient area in which to precisely coregister these (and other) imaging and physiological data sets.

Cerebral Cortex↗

Intraoperative computer-assisted neuronavigation in functional neurosurgery.

The clinical experience with a frameless computer-assisted neuronavigational system (ISG. Canada) used in functional neurosurgery is described. The advantage of image-guided surgery is stressed for functional procedures of the cortex with delineation of the gyral pattern, e.g. motor cortex stimulation and procedures at the base of the skull with triplanar and three-dimensional reconstruction of the bony landmarks. A general use of the device for aiming at subcortical targets cannot be recommended. Limitations are the accuracy (< or = 2.2 mm) and software deficiencies and the lack of a reliable fixation of the position sensing arm (wand).

Cerebral Cortex↗

Neuronavigation--impact on operating time.

It is uncertain whether the use of image-guided surgery has an influence on operating time. We prospectively studied the time requirements which have to be invested for using image-guided surgery and performed a comparison of operating room times from 125 matched pairs of image-guided and conventional operations. Our study revealed that neuronavigation has to be regarded as time neutral in general neurosurgery, whereas in stereotactic surgery, namely biopsy retrival, a significant reduction of anaesthetic time can be achieved through the complete separation of imaging and operation in the frameless approach.

Anesthesia↗

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↗

[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↗

[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↗

[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↗

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↗

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↗

Automated three-dimensional volume rendering of helical computed tomographic angiography for aneurysms: an advanced application of neuronavigation technology.

OBJECTIVE: To introduce the possibility of volume-rendered helical computed tomographic (CT) angiographic data sets by use of Medtronic StealthStation Treon surgical navigation technology (Medtronic Surgical Navigation Technologies, Louisville, CO) and to evaluate the clinical usefulness of the method in planning and performing surgical treatment of intracranial aneurysms. METHODS: Between November 2002 and July 2003, we studied 15 patients with suspected intracranial aneurysms. All patients but two received conventional digital subtraction angiography, which failed to provide the requested information. Helical CT angiography was performed in all patients, and data sets were transferred to the StealthStation system across an electronic network to be automatically postprocessed by use of three-dimensional (3-D) volume rendering. The 3-D volume-rendered images were accurately analyzed to obtain more complete information about the aneurysm and to provide accurate treatment planning. In all patients, the 3-D volume-rendered model was displayed on the screen of the StealthStation system for the duration of the surgical procedure and compared with the intraoperative image. RESULTS: Data sets from CT angiography were automatically postprocessed by the StealthStation in seconds with excellent results, providing us, before and during surgery, with additional information not always available on traditional digital subtraction angiographic investigation. Because of the very short time necessary to complete this process (<5 min to obtain 3-D volume-rendered images), it was possible to perform emergency clipping of the aneurysms in two patients who had been admitted in very compromised neurological conditions. In 12 patients, integrated digital subtraction angiography and automated 3-D volume-rendered images allowed an accurate presurgical evaluation. Furthermore, in all patients on whom surgery was performed, aneurysms were found in the exact location and with the same anatomic features as depicted by the 3-D volume-rendered models. CONCLUSION: Reports in the literature indicate that information gathered by CT angiography with volume rendering shows a significant impact on aneurysm management. The StealthStation system upgraded with the adequate algorithm seems to provide a time- and cost-effective method of performing automated 3-D volume rendering of CT angiography and provides an interesting alternative to the available investigation modalities in case of emergency.

Aged↗

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↗