Frameless Stereotactic System Research Articles

Frameless Stereotactic Navigation in Transsphenoidal Surgery: Comparison with Fluoroscopy

Surgical navigation systems (frameless stereotaxy) have been used in addition to or instead of fluoroscopy during transsphenoidal surgery. This study compares the intraoperative localization by an optical tracking system (Elekta Viewscope) with fluoroscopy. Viewscope and fluoroscope sagittal images were compared by the establishment of a Cartesian coordinate system based on anatomical landmarks and by the spatial localization of surgically relevant points for 20 patients. The Viewscope was found to have a total deviation of 3.0 ± 0.6 mm (mean ± SD) compared to fluoroscopy (p < 0.01). Much of the error resulted from the registration process, which according to the Viewscope software had an expected error of 3.1 ± 0.8 mm for this series of patients, and from the probe-to-system correlation (error of 1.0 ± 0.3 mm). Although frameless stereotactic systems give the surgeon useful trajectory data with three-dimensional visualizations, they remain somewhat inaccurate. The multiplanar abilities of the Viewscope provide an additional but not mandatory advantage to the simplicity and accuracy of fluoroscopy during this type of surgery.

Cyberknife frameless real-time image-guided stereotactic radiosurgery for the treatment of spinal lesions

Purpose/Objective: The role of stereotactic radiosurgery for the treatment of intracranial lesions is well established. Its use for the treatment of spinal lesions has been limited by the availability of effective target immobilization devices. Conventional external beam radiotherapy lacks the precision to allow delivery of large doses of radiation near radiosensitive structures such as the spinal cord. This study evaluated a new image-guided frameless stereotactic radiosurgery delivery system known as the CyberKnife (Accuray, Inc., Sunnyvale, CA) for the treatment of spinal lesions with a single fraction radiosurgical technique.

Stereotactic radiosurgery for lung tumors: preliminary report of a phase I trial

Background Stereotactic radiosurgery is well established for the treatment of intracranial neoplasms but its use for lung tumors is novel. Methods Twenty-three patients with biopsy-proven lung tumors were recruited into a two-institution, dose-escalation, phase I clinical trial using a frameless stereotactic radiosurgery system (CyberKnife). Fifteen patients had primary lung tumors and 8 had metastatic tumors. The age range was 23 to 87 years (mean, 63 years). After undergoing computed tomography–guided percutaneous placement of two to four small metal fiducials directly into the tumor, patients received 1,500 cGY of radiation in a single fraction using a linear accelerator mounted on a computer-controlled robotic arm. Safety, feasibility, and efficacy were studied. Results Nine patients were treated with a breath-holding technique, and 14 with a respiratory-gating, automated, robotic technique. Tumor size ranged from 1 to 5 cm in maximal diameter. There were four complications related to fiducial placement: three pneumothoraces requiring chest tube insertion and one emphysema exacerbation. There were no grade 3 to 5 radiation-related complications. Follow-up ranged from 1 to 26 months (mean, 7.0 months). Radiographic response was scored as complete in 2 patients, partial in 15, stable in 4, and progressive in 2. Four patients died of non–treatment-related causes at 1, 5, 9, and 11 months after radiation. Conclusions Single-fraction stereotactic radiosurgery is safe and feasible for the treatment of selected lung tumors. Additional studies are planned to investigate the optimal radiation dose, best motion-suppression technique, and overall treatment efficacy.

Chronometry of parietal and prefrontal activations in verbal working memory revealed by transcranial magnetic stimulation

We explored the temporal dynamics of parietal and prefrontal cortex involvement in verbal working memory employing single-pulse transcranial magnetic stimulation (TMS). In six healthy volunteers the left or right inferior parietal and prefrontal cortex was stimulated with the aid of a frameless stereotactic system. TMS was applied at 10 different time points 140–500 ms into the delay period of a two-back verbal working memory task. A choice reaction task was used as a control task. Interference with task accuracy was induced by TMS earlier in the parietal cortex than in the prefrontal cortex and earlier over the right than the left hemisphere. This suggests a propagation of information flow from posterior to anterior cortical sites converging in the left prefrontal cortex. Significant interference with reaction time was observed after 180 ms with left prefrontal cortex stimulation. These effects were not observed in the control task, underlining the task specificity of our results. We propose that the interference with right-sided prefrontal cortex stimulation leads to impaired performance due to disturbed input into the left prefrontal cortex, whereas left-sided TMS interferes directly with the final information processing. Left- and right-sided brain areas might be involved in parallel processing of semantic and object features of the stimuli, respectively.

Frameless stereotactic brain biopsy procedures using the Stealth Station: indications, accuracy and results.

This study presents the results of 57 stereotactic brain biopsies using a frameless neuronavigation system, the Stealth Station. The supratentorial lesions had a mean diameter of 33 mm and a mean distance of 32 mm from the entry point at brain surface. In all cases the stereotactic procedure was planned in the preoperative 3-D magnetic resonance data set. In seven cases additional data for identification of eloquent brain areas was integrated from magnetoencephalography or functional magnetic resonance imaging. During surgery the samples were sent to neuropathological examination and the operation completed after the confirmation of pathological tissue. Using this method, in 56 cases a pathological tissue was obtained and a diagnostic yield of 98% was achieved. In two cases (3.5%) a new neurological deficit remained (hemiparesis and visual field deficit). The mean operation time was 92 minutes including examination of frozen sections. The results of our series demonstrate, that frameless stereotactic systems can also be reliably applied for biopsy of supratentorial lesions larger than 15 mm. Frameless stereotaxy in combination with intraoperative pathological confirmation is a safe and reliable method for stereotactic brain biopsy with a diagnostic yield comparable to frame-based stereotaxy.

An Analysis of the Accuracy of the CyberKnife: A Robotic Frameless Stereotactic Radiosurgical System

An Analysis of the Accuracy of the CyberKnife: A Robotic Frameless Stereotactic Radiosurgical System

An analysis of the accuracy of the CyberKnife: a robotic frameless stereotactic radiosurgical system.

The use of stereotactic radiosurgical systems to treat intracranial and extracranial tumors and other lesions requires a high degree of accuracy in target identification and localization. The purpose of this study was to evaluate the total system accuracy of the CyberKnife (Accuray, Inc., Sunnyvale, CA), a frameless, image-guided, stereotactic radiosurgery system. Clinically relevant accuracy or application accuracy of the CyberKnife radiosurgery system is based on 1) the beam delivery accuracy, which combines the robot and the camera image tracking system, and 2) target localization accuracy, which combines computed tomographic (CT) imaging and treatment planning. Clinically relevant accuracy can be measured by delivering a radiation dose to phantoms, in which the target is defined on a set of CT images using all components of the CyberKnife system, including the treatment planning software, the robot, the camera tracking system, and the linear accelerator. Clinically relevant accuracy was measured in head phantoms loaded with packs of radiochromic film. The accuracy measured is the displacement of the dose contours from the treatment plan to that measured in the radiosurgically exposed phantom. Measurements of mean errors of the second-generation CyberKnife system at Stanford University Medical Center, installed in 2001, ranged from 0.7 mm for a CT slice thickness of 0.625 mm to 1.97 mm for a CT slice thickness of 3.75 mm. The frameless, image-guided, second-generation CyberKnife radiosurgery system has a clinically relevant accuracy of 1.1 +/- 0.3 mm when CT slice thicknesses of 1.25 mm are used. CyberKnife precision is comparable to published localization errors in current frame-based radiosurgical systems.

An Analysis of the Accuracy of the CyberKnife: A Robotic Frameless Stereotactic Radiosurgical System

An Analysis of the Accuracy of the CyberKnife: A Robotic Frameless Stereotactic Radiosurgical System

Surgical treatment of brain stem cavernous malformations

The indications for treatment of cavernous malformations of the brain stem have evolved greatly in the past decade. As more experience has been gained with these lesions, it has become evident that surgical excision is possible with acceptable rates of surgical morbidity and mortality. Criteria for surgical indications include a symptomatic lesion that reaches a pial or ependymal surface and that can be reached without the need to traverse eloquent brain stem parenchyma. Advances in frameless stereotactic systems have improved localization and made resection safer, even for “intrinsic” symptomatic lesions that are reached through a small incision in “safe entry-zones” on the surface of the brain stem. Although with caution, surgical excision should also be considered for selected young asymptomatic patients with relatively large lesions that reach a pial or ependymal surface. This article summarizes the clinical characteristics, indications for surgery, technical surgical pitfalls, and outcomes of surgical resection of brain stem cavernous malformations.

Interventional radiology

The capabilities of interventional radiology are developing faster than perhaps any other branch of medicine. Coupled with and fuelled by parallel advances in computer technology, medical physics and developments in endovascular catheter technology, interventional radiologists are innovating not only replacements for open surgeries, but entirely new therapies as well. This has, however, provided a range of new potential complications for the patient and, in contrast to other areas, presents risks for the anesthesiologist as well. The techniques involved in interventional radiology have found applications throughout not only medicine but surgery in particular. Here there has been a medicalization of surgical procedures. CT scanning has evolved to the extent that it is now possible to utilize multislice CT scanners, ones with multiple, flat panel digital detectors, to provide real time CT fluoroscopy. Similarly this technology has facilitated the construction of hybrid iMR/X-ray systems, thus enabling dual modality imaging without moving the patient. Another facet of the new breed of iMR systems is their integration in real time with computerized, frameless stereotactic navigation systems. This has enabled the radiological image to keep pace with the changes in anatomy consequent to anesthetic and surgical manipulations. In the light of these new developments in interventional radiology there is much research to be done. Further developments in imaging and computer processing technology will doubtless make possible the real time integration of anatomical image with metabolic state and functional anatomy. The impact of the hazards of these new techniques on the safety of anesthesia has, however, been the subject of virtually no research. A particularly needy area will be the ergonomics of the delivery of anesthesia care in these new environments.

Frameless stereotaxy as an alternative to fluoroscopy for transsphenoidal surgery: use of the InstaTrak®-3000 and a novel headset

Our aim was to evaluate the applicability of an electromagnetic-based frameless stereotactic system for use in transsphenoidal surgery. The system utilizes a novel headset that acts as a replaceable fiducial frame as well as a fixation point for the system's transmitter. It can replace the fluoroscope as a guide to navigation in the sphenoid sinus and sella. The system was used in a consecutive series of 11 patients undergoing transsphenoidal surgery. It was used in conjunction with intraoperative fluoroscopy. We found the Instatrak®-3000 to correlate well with lateral fluoroscopic images, and provide additional information in the axial and coronal planes.The InstaTrak®-3000 frameless stereotactic system is accurate and obviates the need for intraoperative fluoroscopy during transsphenoidal surgery. Compared to other frameless systems, it avoids the use of fiducial skin markers and head fixation. In common with other frameless stereotactic systems, it provides additional information important for safely approaching the sella and avoids intraoperative radiation exposure for the patient and operating room staff.

Anatomical landmarks for image registration in frameless stereotactic neuronavigation.

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. 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. 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. 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.

Insertion of depth electrodes with or without subdural grids using frameless stereotactic guidance systems -- technique and outcome

Over recent years frameless stereotactic systems have begun replacing framed systems for many neurosurgical procedures. However, little has been published regarding the use of these systems to guide intracranial electrode implantation for epilepsy surgery patients. Here we report our experience utilising such a system to insert depth electrodes and subdural grid electrodes. The SteathStation Image-Guided System TM (SSIGS) (Sofamor Danek, Memphis TN.) was used to insert bilateral depth electrodes in 13 patients, of whom 5 also underwent the insertion of subdural grids or strip electrodes. Initially, a surgical plan based on an entry and target point on axial and sagittal images was performed for the insertion of electrodes. Navigational views, using three-planar images, were then performed to determine which structures the electrodes would pass through to be correctly placed in the amygdala and hippocampus. The correct site of electrode implantation was confirmed post-operatively by spiral CT scans in 4 patients (which were then co-registered to the preimplantation MRI using a surface matching technique) and the other 9 patients by post-implantation MRI. The SSIGS was found to have a mean registration error of 2.0 mm (range 1.8-2.5) in 10 cases; in the 3 cases where the error was greater than 2.5 mm a surfacemerge technique was used with a mean error 0.9 (0.8-1.00). The post-implantation MRI or CT-MRI co-registration confirmed an accurate electrode placement in the mesial temporal region in all cases. Seizure onset lateralisation was achieved in 11 patients, all of whom went onto formal resections based on these results. The only long-term complication was a case of osteomyelitis which required removal of the bone flap. 73% of patients had an excellent seizure outcome. Frameless stereotactic systems can be safely used to intracranial electrodes, avoid the disadvantages of the framed system and have the added advantage of the surgeon being able to visualise the trajectory and to adjust this to avoid vital structures. As well they eliminate surgical obstruction to the insertion of subdural grids at the same operation, which may be caused by a framed system.

Comparison of Registration Accuracy of Skin- and Bone-Implanted Fiducials for Frameless Stereotaxis of the Brain: A Prospective Study

The registration accuracy of skin- and bone-implanted fiducials using a frameless stereotactic system were analyzed prospectively.Twenty-eight patients underwent resection of intra-axial neoplasmas after both skin- and bone-implantable fiducial markers were placed. Both sets of fiducials were independently co-registered to a magnetic resonance imaging data set acquired preoperatively using the ISG Viewing Wandtrade mark. Root mean square errors were recorded as an objective measure of registration accuracy of the two types of fiducials.Root mean square errors of bone-implanted fiducials registration were lower than those of skin fiducials; however, this difference was not statistically significant (p = 0.206).The registration accuracy of skin- and bone-implanted fiducials appears to be similar. Still, bone-implanted fiducials may be advantageous compared to skin fiducials when re-registration of the patient-image space is desired intraoperatively such as during major drift in the patient's position or after surgical repositioning.

Metabolic and electrophysiological validation of functional MRI

OBJECTIVESAlthough functional MRI is widely used for preoperative planning and intraoperative neuronavigation, its accuracy to depict the site of neuronal activity is not exactly known. Experience with methods that may...

Initial clinical experience with frameless stereotactic radiosurgery: analysis of accuracy and feasibility

Purpose: To report on preliminary clinical experience with a novel image-guided frameless stereotactic radiosurgery system.Methods and Materials: Fifteen patients ranging in age from 14 to 81 received radiosurgery using a commercially available frameless stereotactic radiosurgery system. Pathologic diagnoses included metastases (12), recurrent primary intracranial sarcoma (1), recurrent central nervous system (CNS) lymphoma (1), and medulloblastoma with supratentorial seeding (1). Treatment accuracy was assessed from image localization of the stereotactic reference array and reproducibility of biteplate reseating. We chose 0.3 mm vector translation error and 0.3 degree rotation about each axis as the maximum tolerated misalignment before treating each arc.Results: The biteplates were found on average to reseat with a reproducibility of 0.24 mm. The mean registration error from CT localization was found to be 0.5 mm, which predicts that the average error at isocenter was 0.82 mm. No patient treatment was delivered beyond the maximum tolerated misalignment. The radiosurgery treatment was delivered in approximately 25 min per patient.Conclusion: Our initial clinical experience with stereotactic radiotherapy using the infrared camera guidance system was promising, demonstrating clinical feasibility and accuracy comparable to many frame-based systems.

The interfractional three-dimensional reproducibility of a frameless stereotactic radiotherapy system

The interfractional three-dimensional reproducibility of a frameless stereotactic radiotherapy system

Navigation with the StealthStation™ in Skull Base Surgery: An Otolaryngological Perspective

The introduction of computer-assisted navigation systems has played a significant role in assuring the integration and consistent intraoperative use of radiological information. We used a frameless stereotactic navigation system to treat 62 patients with a variety of skull base pathologies. The optoelectric appliance uses digital imaging information to locate surgical instruments in the operative area. The aim of this study was to evaluate the clinical accuracy, practicality, and impact of this navigation system on otolaryngological procedures. In conjunction with rigid head fixation and bone-anchored registration markers, the precision of registration was 0.8 mm and the accuracy of clinical measurements was less than 2 mm. With conventional fiducials and flexible head positioning, deviations were as large as 4.5 mm. The additional use of surface registration increased the precision of registration. Preoperative preparations took 15 to 35 minutes, depending on the complexity of the planning. Intraoperative computer support is an important aid to a surgeon's orientation, especially when a patient's anatomy is atypical. Navigation systems will likely improve the quality of surgery and facilitate training.

Use of Internal Fiducial Markers in Frameless Stereotactic Navigational Systems during Spinal Surgery: Technical Note

The use of frameless stereotaxy has expanded the spine surgeon's ability to perform surgical procedures with instrumentation in areas of narrow anatomic tolerance. In many circumstances, however, it is difficult to register the frameless stereotactic probe using known anatomic landmarks. This occurs typically because landmarks are indistinct, and congenital or surgical defects limit the availability of anatomic fiducials. We propose an accurate and efficient method for registering the frameless stereotactic probe for spinal surgery when a staged procedure is planned. During the first stage of a planned two-stage procedure, a minimum of four cranial fiducial screws are implanted in the posterior element of each vertebra in which stereotactic registration is desired. Stage 1 is completed, and all suture closure is performed. A computed tomographic scan formatted for the frameless stereotactic unit is obtained postoperatively. In the second stage of surgery, registration is performed using cranial screws as internal fiducial markers. Registration is performed easily and quickly using cranial screws as internal fiducial markers. No more than four registration points are necessary to calibrate the system to accuracy within 1.5 mm. Implantation of fiducial markers during Stage 1 of a complex staged spinal surgery renders the frameless stereotactic navigational system registration extremely fast and accurate. We advocate the technique to enhance the use of frameless navigational systems for reliable and quick registration of the spine.

Use of Internal Fiducial Markers in Frameless Stereotactic Navigational Systems during Spinal Surgery: Technical Note

Use of Internal Fiducial Markers in Frameless Stereotactic Navigational Systems during Spinal Surgery: Technical Note