Frameless Stereotactic System Research Articles

ARISE-The Accuracy Evaluation of a Patient-Specific 3D-Printed Biopsy System Based on MRI Data: A Cadaveric Study.

Brain biopsy is required for the accurate specification and further diagnosis of intracranial findings. The conventional stereotactic frames are used clinically for biopsies and offer the highest possible precision. Unfortunately, they come with some insurmountable technical and logistical limitations. The aim of the present work is to determine the clinical precision in the needle biopsy of the human brain using a new patient-specific stereotactic navigation device based on 3D printing. MRI data sets of human cadaver heads were used to plan 32 intracranial virtual biopsy targets located in different brain regions. Based on these data, 16 individualized stereotactic frames were 3D-printed. After the intraoperative application of the stereotactic device to the cadaver's head, the actual needle position was verified by postoperative CT. Thirty-two brain areas were successfully biopsied. The target point accuracy was 1.05 ± 0.63 mm, which represents the difference between the planned and real target points. The largest target point deviation was in the coronal plane at 0.60 mm; the smallest was in the transverse plane (0.45 mm). Three-dimensional-printed, personalized stereotactic frames or platforms are an alternative to the commonly used frame-based and frameless stereotactic systems. They are particularly advantageous in terms of accuracy, reduced medical imaging, and significantly simplified intraoperative handling.

Pipeline for Planning and Execution of Transcranial Ultrasound Neuromodulation Experiments in Humans.

Transcranial ultrasound stimulation (TUS) is an emerging non-invasive neuromodulation technique capable of manipulating both cortical and subcortical structures with high precision. Conducting experiments involving humans necessitates careful planning of acoustic and thermal simulations. This planning is essential to adjust for bone interference with the ultrasound beam's shape and trajectory and to ensure TUS parameters meet safety requirements. T1- and T2-weighted, along with zero-time echo (ZTE) magnetic resonance imaging (MRI) scans with 1 mm isotropic resolution, are acquired (alternatively computed tomography x-ray (CT) scans) for skull reconstruction and simulations. Target and trajectory mapping are performed using a neuronavigational platform. SimNIBS is used for the initial segmentation of the skull, skin, and brain tissues. Simulation of TUS is carried over with the BabelBrain tool, which uses the ZTE scan to produce synthetic CT images of the skull to be converted into acoustic properties. We use a phased array ultrasound transducer with electrical steering capabilities. Z-steering is adjusted to ensure that the target depth is reached. Other transducer configurations are also supported in the planning tool. Thermal simulations are run to ensure temperature and mechanical index requirements are within the acoustic guidelines for TUS in human subjects as recommended by the FDA. During TUS delivery sessions, a mechanical arm assists in the movement of the transducer to the required location using a frameless stereotactic localization system.

SURG-06. FRAMELESS STEREOTACTIC INTRACRANIAL CATHETER PLACEMENT FOR DELIVERY OF INTRATUMORAL CELLULAR THERAPIES

Abstract BACKGROUND As the leading disease-related cause of death in children, pediatric brain tumors, and in particular diffuse midline glioma, require novel treatment approaches. Cellular-based therapies offer promise, but challenges still exist in defining their optimal delivery route. Emerging data from our group suggest there may be a role for intratumoral injection in treatment algorithms. We here describe a surgical workflow for intratumoral injection of cellular therapies that utilizes existing and widely used neurosurgical technologies that can be incorporated into future clinical trials. METHODS Infusion target and catheter trajectory was planned using standard pre-operative MRI. Components from an FDA-approved frameless stereotactic intracranial biopsy system were chosen such that they would accept and guide an FDA-approved rigid intracranial catheter system intended for MR-guided procedures. Following catheter insertion, an intraoperative CT was used to determine accuracy of catheter placement by merging the image with the pre-operative MRI. RESULTS The proposed system was tested in a simulated fashion using a phantom cranial model registered to an accompanying brain MRI. The stereotactic biopsy mount was affixed to the skull at the planned entry site for a posterior fossa approach to the pons. Catheter insertion depth was determined using the stereotactic system and the catheter was inserted to this depth through the biopsy mount. Intraoperative CT confirmed the catheter tip location which correlated with the planned infusion target with sub-millimetric accuracy. CONCLUSION Our proposed intratumoral delivery method using frameless stereotaxy shows promise for use in future clinical trials that require intratumoral delivery of cellular therapies. Utilizing FDA-approved devices allows for quick integration into protocols and their wide-spread use makes the approach generalizable. This approach also eliminates the need for MR-guided procedures which can increase cost and require significant hospital resources to perform. Future work will be aimed at streamlining the intraoperative workflow.

Magnetic Resonance Imaging-Guided Frameless Stereotactic Injections of the Bilateral Cerebellar Dentate Nuclei in Nonhuman Primates: Technical Note.

Nonhuman primates (NHPs) are important preclinical models for evaluating therapeutics because of their anatomophysiological similarities to humans, and can be especially useful for testing new delivery targets. With the growing promise of cell and gene therapies for the treatment of neurological diseases, it is important to ensure the accurate and safe delivery of these agents to target structures in the brain. However, a standard guideline or method has not been developed for stereotactic targeting in NHPs. In this article, we describe the safe use of a magnetic resonance imaging-guided frameless stereotactic system to target bilateral cerebellar dentate nuclei for accurate, real-time delivery of viral vector in NHPs. Seventeen rhesus macaques (Macaca mulatta) underwent stereotactic surgery under real-time MRI guidance using the ClearPoint® system. Bilateral cerebellar dentate nuclei were targeted through a single parietal entry point with a transtentorial approach. Fifty microliters of contrast-impregnated infusate was delivered to each dentate nucleus, and adjustments were made as necessary according to real-time MRI monitoring of delivery. Perioperative clinical outcomes and postoperative volumes of distribution were recorded. All macaques underwent bilateral surgery successfully. Superficial pin site infection occurred in 4/17 (23.5%) subjects, which resolved with antibiotics. Two episodes of transient neurological deficit (anisocoria and unilateral weakness) were recorded, which did not require additional postoperative treatment and resolved over time. Volume of distribution of infusate achieved satisfactory coverage of target dentate nuclei, and only 1 incidence (2.9%) of cerebrospinal fluid penetration was recorded. Mean volume of distribution was 161.22 ± 39.61 mm3 (left, 173.65 ± 48.29; right, 148.80 ± 23.98). MRI-guided frameless stereotactic injection of bilateral cerebellar dentate nuclei in NHPs is safe and feasible. The use of this technique enables real-time modification of the surgical plan to achieve adequate target coverage and can be readily translated to clinical use.

Stereotactic biopsy for brain lesions: Doing more with less.

Stereotactic biopsy (STB) is a potential diagnostic tool considering its minimal invasiveness, high diagnostic yield, and minimal associated complications. Over the years, various frame-based instrument systems and frameless stereotactic biopsy systems have emerged to be employed in clinical use. With this study, we intend to get more by doing less in the form of STB for the patients of doubtful intracranial lesions treated over the past 5 years. We also want to highlight the technique of performing the procedure under scalp block, which can be used as a versatile tool in many clinical scenarios. Stereotactic biopsies may be planned even in rural district-level health facilities. One-time investment to procure instruments and avail existing imaging can lead to establishing definitive diagnoses in many doubtful cases. This will result in lesser cost and early establishment of treatment. Independent risk factors determining the outcome, such as deep-seated lesions, associated edema, and intraoperative hypertension, were studied. Establishing the diagnosis helped in prognosticating the disease, explaining the natural progression of symptoms, and starting adjuvant therapy. This tissue biopsy would also help secure samples for research and molecular analysis. Twenty patients underwent STBs at our institution between January 2018 and December 2022. We retrospectively analyzed patient characteristics, tumor pathology, surgical procedures, and outcomes, including the diagnostic value and surgery-related complications. These patients were followed up, and their progression-free and overall survival were analyzed. The need for adjuvant treatment was noted and analyzed. All procedures were performed using Cosman Roberts Wells® stereotactic frame. Pre-procedure magnetic resonance scans were performed at the time of admission. Contrast-enhanced computerized tomography (CT) scan after frame application was performed to identify targets and calculate the coordinates. A post-procedure CT scan was done to confirm the accessibility of the targeted lesion. The most common location of the tumor was a deep-seated thalamic lesion. A definitive diagnosis was established in 19 patients (95%) at the first STB. The diagnoses were glioma in 55% of cases, primary central nervous system lymphoma, tuberculosis, and demyelinating disorders in 10% of each, and a metastatic brain tumor in 1 (5%). The post-operative complications were all transient except in one patient with deterioration of motor weakness. The follow-up was noted, and modes of adjuvant treatment needed in these patients were recorded. Stereotactic biopsy is a useful and effective method for achieving a definitive diagnosis and aiding in treating multifocal or small deep-seated lesions in or around eloquent regions.

Accuracy and Utility of Frameless Stereotactic Placement of Stereoelectroencephalography Electrodes

Successful surgery for epilepsy hinges on identification of the epileptogenic focus. Stereoelectroencephalography (sEEG) is the most effective way to identify most seizure foci. There are multiple methods of inserting depth electrodes, including frame-based, frameless, and robot-assisted techniques. Studies have shown the accuracy of frame-based and robotic-assisted techniques to be statistically similar, while only one study has detailed the frameless sEEG insertion technique. Patients underwent placement of sEEG depth electrodes using frameless stereotaxy from September 2019 to September 2021 at Geisinger Medical Center by a single surgeon. Seizure history, electrode placement accuracy relative to the planned trajectories, surgical times, success rate of identifying the epileptogenic focus, and subsequent seizure control rates after surgical treatment were documented. Data were available for 21 patients and 181 electrodes inserted using the VarioGuide frameless stereotactic system. Each insertion took an average of 14.5 minutes per lead. Average entry variance was 2.7 mm with an average target variance of 4.6 mm. The epileptogenic focus was identified in 19 of 21 patients, and further surgical treatment was performed in 18 of 21 patients (85.7%). VarioGuide frameless stereotaxy for sEEG placement is comparable to frame-based and robotic-assisted techniques with statistically similar rates of epileptic focus identification. Lead placement accuracy is slightly lower and time per lead is slightly higher relative to robot-assisted surgeries. When a robot system is unavailable, surgeons can consider using a frameless stereotactic technique for sEEG insertion, allowing patients to benefit from a similarly high rate of epileptic zone identification.

Deep brain stimulation in a pediatric dystonia patient with cochlear implants and mitochondrial disorder: novel application of a frameless stereotactic system and navigating the anesthesia choice and neurosurgical complexities. Illustrative case.

This report presents a case of medically refractory dystonia in a pediatric patient successfully treated with bilateral subthalamic nucleus (STN) deep brain stimulation (DBS) while under general anesthesia by using microelectrode recordings (MERs) with intraoperative computed tomography (CT). The patient was an 18-year-old female with primary dystonia secondary to mitochondrial Leigh syndrome. Her past medical history was significant for complex partial epilepsy and hearing loss treated with cochlear implants. Her cochlear implants precluded anatomical targeting via magnetic resonance imaging. Additionally, the patient could not tolerate awake surgery with MER. The decision was made to proceed with bilateral STN DBS with intraoperative CT with the patient under general anesthesia. The patient's cochlear implants made standard frame placement difficult, so navigation was performed with the Nexframe system. Recordings were obtained with the patient under general anesthesia with ketamine, dexmedetomidine, and remifentanil. At the 3- and 6-month follow-ups, the patient demonstrated marked improvement in dystonia without neurological complications. This is the first case of dystonia secondary to Leigh syndrome treated with DBS. Additionally, the authors describe the novel use of the Nexframe for DBS lead placement in a pediatric patient. This demonstrates that STN DBS with the use of MER and intraoperative CT can be a safe and effective method of treating dystonia in certain pediatric patients.

Evaluation of Overshunting between Low and Medium Pressure Ventriculoperitoneal Shunts in Dogs with Severe Hydrocephalus Using Frameless Stereotactic Ventricular Shunt Placement

Hydrocephalus is a neurological disorder characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within the ventricular system of the brain, leading to cerebral ventricular dilation, brain parenchyma compression, and neuronal cell loss. Surgery is an effective method of draining excessive amounts of CSF. Ventriculoperitoneal shunt (VPS) allows excess CSF to divert into the abdomen; this device is the most commonly used in the treatment of hydrocephalus both in veterinary and human patients. This study aims to describe the application of two types of VPS, low-pressure valve and medium-pressure valve, using a frameless stereotactic neuronavigational system in eight severe hydrocephalus in dogs and, in particular, analyze the prevalence of postoperative overshunting. Non-communicating hydrocephalus was found in seven dogs, whereas the rest of them had communicating hydrocephalus caused by traumatic brain injury with a skull fracture. The criteria for pressure valve selection depended on the intraoperative intraventricular pressure (IVP) that was determined by the adaptive manometer, according to the human protocol. Low-pressure valve placement was performed in five dogs, and the others received medium-pressure valve placement. The follow-up period was 2 weeks, 4–12 weeks, and 12 weeks to 12 months. Pre- and postoperative information including neurological signs, CT-Scan or MRI, medical treatment, complications, and ventricular volume were compared in all dogs. Seven dogs showed neurological improvement within 2 weeks after surgery. Overshunting was seen in four dogs who received low-pressure valve placement. Three of them had shunt infections within 4 to 6 weeks after surgery. One dog underwent shunt revision from a low-pressure valve to a medium-pressure valve caused by severe overshunting and progressive neurological signs. In addition, cognitive and learning improvements were evaluated based on the owners’ feedback, and neurological signs were examined during the follow-up period in two dogs that received low-pressure valve placement. We conclude that a medium-pressure valve is recommended for overshunting prevention. However, low-pressure valve placement seems to improve cognitive function and learning ability, which is related to an increase in the brain parenchyma observed during long-term monitoring. Moreover, we also report our experience and surgical procedure for frameless stereotactic ventricular shunt placement (FSVSP) in VPS surgery in dogs affected by hydrocephalus.

Comparison of the Outcome of Deep Brain Stimulator Surgeries in Parkinson’s Disease by Using Frame Based and Frameless Stereotactic Systems

Comparison of the Outcome of Deep Brain Stimulator Surgeries in Parkinson’s Disease by Using Frame Based and Frameless Stereotactic Systems

Comparison of Accuracy of Frameless Stereotactic System (Neuronavigation) Against Frame Based Stereotaxy in Deep Seated Lesion of Brain

Objective: The determination of accuracy of frameless stereotactic system against frame based stereotaxy in deep seated lesion of brain. Study Type: randomized controlled trial. Study Place and Duration: Department of Neurosurgery, Nishtar Hospital Multan from June 2019 to June 2020. Material and methods: A total of 124 patients were included in the study after informed consent and eligible in accord to the inclusion and exclusion criteria. Total participants were 124 (randomized) and were divided into two randomized groups; frame-based stereotaxy group (FB) and stereotaxy group (SG) including 62 patients in each group. The angular deviation and target distance between actual and planned trajectory were the primary outcomes in this study. Independent samples were tested through 2-tailed t-tests for statistical testing. Mann-Whitney U test was performed for non-normally distributed data while for comparison of categorical variables Chi-square or Fisher tests were performed. P-value was 0.05 as a level off statistical significance. SPSS version 23 was used for statistical computations. Results: Trajectory length and distance were 42.32±10.38 mm and 2.43±1.02 mm in FB group, while 43.45±11.65 mm and 2.59±1.06 mm in VG group, and there was no statistically significant difference in these two parameters (p value 0.570 and 0.390, respectively). Trajectory deviation was 1.85±1.28 degree in FB group and 2.63±158 degree in VG group, and the difference was statistically significant (p=0.003). Table-II. Conclusion: Patients in which brain biopsy was done, the Varioguide system can be compared to the gold standard frame-based stereotaxy on the basis of means of trajectory accuracy, complications rate and diagnostic yield.

How can the accuracy of SEEG be increased?-an analysis of the accuracy of multilobe-spanning SEEG electrodes based on a frameless stereotactic robot-assisted system.

A frameless stereotactic robot-assisted system allows stereoelectroencephalography (SEEG) electrodes to span multiple lobes. As the angularity and length are increased, maintaining accuracy of the electrodes becomes more challenging. The goal of this study was to analyze the factors that influence the accuracy of multilobe-spanning SEEG electrodes inserted using a frameless stereotactic robot-assisted system. A total of 322 SEEG electrodes were implanted in 39 patients with refractory epilepsy, and sixty-one multilobe-spanning SEEG electrodes were selected to analyze the factors that influenced the accuracy of implantation. The target error, entrance error, depth error, and angular error were calculated by a specialized computer program. Factors including electrode depth, angular deviation, referencing method, head holder choice, and use of a predrill procedure were analyzed to determine their effects on accuracy. Thirty-nine patients (aged 2-35 years, median: 19 years; 21 females) underwent frameless robot-assisted SEEG electrode implantation. The mean distance between the intended target and actual tip location was 2.57±1.70 mm (range, 0.42-9.02 mm). The mean distance between the intended entrance point and the actual location was 2.2±1.29 mm (range, 0.70-6.13 mm). The mean length of the electrodes was 84.63±7.61 mm (range, 70.60-103.99 mm). The depth error was 1.36±1.22 mm (range, 0.03-6.69 mm), and the angular deviation was 1.64±1.12 degrees (range, 0.15-4.93 degrees). Multifactor regression analysis showed that entrance error, electrode depth, depth error, angular deviation, referencing method, and head holder choice could explain 59.5% of the electrode target error. Angular deviation, choice of registration approach and head holder and the use of a predrill procedure could explain 48.1% of the electrode entrance error. Use of a predrill procedure significantly reduced the electrode angular deviation (P<0.05). Head holder choice, use of a predrill procedure and angular deviation are the primary influencing factors of the accuracy of multilobe-spanning SEEG electrode placement. The Leksell frame and a predrill procedure can be used to increase the accuracy of SEEG electrode placement.

A retrospective analysis of setup and intrafraction positional variation in stereotactic radiotherapy treatments.

PurposeThe aim of this study was to provide a comprehensive assessment of patient intrafraction motion in linac‐based frameless stereotactic radiosurgery (SRS) and radiotherapy (SRT).MethodsA retrospective review was performed on 101 intracranial SRS/SRT patients immobilized with the Klarity stereotactic thermoplastic mask (compatible with the Brainlab frameless stereotactic system) and aligned on a 6 Degree of Freedom (DoF) couch with the Brainlab ExacTrac image guidance system. Both pretreatment and intrafraction correction data are provided as observed by the ExacTrac system. The effects of couch angle and treatment duration on positioning outcomes are also explored.ResultsInitial setup data for patients is shown to vary by up to ±4.18 mm, ±2.97°, but when corrected with a single x‐ray image set with ExacTrac, patient positions are corrected to within ±2.11 mm, ±2.27°. Intrafraction patient motion is shown to be uniformly random and independent of both time and couch angle. Patient motion was also limited to within approximately 3 mm, 3° by the thermoplastic mask.ConclusionsOur results indicate that since patient intrafraction motion is unrelated to couch rotation and treatment duration, intrafraction patient monitoring in 6 DoF is required to minimize intracranial SRS/SRT margins.

Neuronavigated Repetitive Transcranial Ultrasound Stimulation Induces Long-Lasting and Reversible Effects on Oculomotor Performance in Non-human Primates.

Since the late 2010s, Transcranial Ultrasound Stimulation (TUS) has been used experimentally to carryout safe, non-invasive stimulation of the brain with better spatial resolution than Transcranial Magnetic Stimulation (TMS). This innovative stimulation method has emerged as a novel and valuable device for studying brain function in humans and animals. In particular, single pulses of TUS directed to oculomotor regions have been shown to modulate visuomotor behavior of non-human primates during 100 ms ultrasound pulses. In the present study, a sustained effect was induced by applying 20-s trains of neuronavigated repetitive Transcranial Ultrasound Stimulation (rTUS) to oculomotor regions of the frontal cortex in three non-human primates performing an antisaccade task. With the help of MRI imaging and a frame-less stereotactic neuronavigation system (SNS), we were able to demonstrate that neuronavigated TUS (outside of the MRI scanner) is an efficient tool to carry out neuromodulation procedures in non-human primates. We found that, following neuronavigated rTUS, saccades were significantly modified, resulting in shorter latencies compared to no-rTUS trials. This behavioral modulation was maintained for up to 20 min. Oculomotor behavior returned to baseline after 18–31 min and could not be significantly distinguished from the no-rTUS condition. This study is the first to show that neuronavigated rTUS can have a persistent effect on monkey behavior with a quantified return-time to baseline. The specificity of the effects could not be explained by auditory confounds.

Feasibility and performance of a frameless stereotactic system for targeting subcortical nuclei in nonhuman primates.

Deep brain stimulation (DBS) is an effective therapy for different neurological diseases, despite the lack of comprehension of its mechanism of action. The use of nonhuman primates (NHPs) has been historically important in advancing this field and presents a unique opportunity to uncover the therapeutic mechanisms of DBS, opening the way for optimization of current applications and the development of new ones. To be informative, research using NHPs should make use of appropriate electrode implantation tools. In the present work, the authors report on the feasibility and accuracy of targeting different deep brain regions in NHPs using a commercially available frameless stereotactic system (microTargeting platform). Seven NHPs were implanted with DBS electrodes, either in the subthalamic nucleus or in the cerebellar dentate nucleus. A microTargeting platform was designed for each animal and used to guide implantation of the electrode. Imaging studies were acquired preoperatively for each animal, and were subsequently analyzed by two independent evaluators to estimate the electrode placement error (EPE). The interobserver variability was assessed as well. The radial and vector components of the EPE were estimated separately. The magnitude of the vector of EPE was 1.29 ± 0.41 mm and the mean radial EPE was 0.96 ± 0.63 mm. The interobserver variability was considered negligible. These results reveal the suitability of this commercial system to enhance the surgical insertion of DBS leads in the primate brain, in comparison to rigid traditional frames. Furthermore, our results open up the possibility of performing frameless stereotaxy in primates without the necessity of relying on expensive methods based on intraoperative imaging.

Modified Frameless Stereotactic System for Intracerebral Delivery of Viral Vector in Young Children.

Stereotaxic surgery for viral vector delivery in young children is highly challenging because of their small cranial size, thin and fragile skull, and deformity of the skull or brain after prolonged bed ridden condition. To develop a modified frameless stereotactic system especially suitable for intracerebral delivery of viral vector in young children for accurate localization of intracerebral targets during stereotactic surgery. A modified frameless stereotactic system was developed for intracerebral delivery of viral vector in pediatric patients with congenital enzyme deficiency. Localization markers and a stereotactic stabilizer were designed specifically for surgery in pediatric patients, and this equipment is used along with a pre-existing frameless stereotactic and computer-assisted planning and navigation system. We applied this modified frameless stereotactic system to treat 10 children with aromatic L-amino acid decarboxylase deficiency. It is potentially suitable for stereotactic functional neurosurgery in pediatric patients as young as 1 yr and 8 mo of age.

Frameless Deep Brain Stimulation Surgery: A Single-Center Experience and Retrospective Analysis of Placement Accuracy of 220 Electrodes in a Series of 110 Patients

Background: Proper lead placement is considered one of the key factors in achieving a good clinical outcome in deep brain stimulation (DBS), but there is still considerable controversy surrounding the accuracy of the frameless in comparison to the frame-based technique. Objective: We report our single-center experience with DBS electrode placement to evaluate the accuracy of the frameless stereotactic system. Methods: We prospectively analyzed the data of 110 patients who underwent DBS surgery for Parkinson disease, dystonia, essential tremor, or refractory epilepsy. The final targets (FTs) of the 220 leads were: subthalamic nucleus, globus pallidus pars interna, ventralis intermedius nucleus, and anterior nuclei of thalamus in thalamus. A bilateral stereotactic approach using a combined identification of target based on preoperative images (MRI and CT scan fusion) and intra-operative micro-electrode recording (MER) were done. We collected and compared the coordinates of planned target (PT), the definitive expected target (ET) during MER, and the effective final location (FT) of the lead using the postoperative CT. Accuracy was assessed by both vector error (VE) and deviation from the PT. Results: The mean and SD from PTs was 0.78 ± 0.43 mm in the x direction, 0.68 ± 0.41 mm in the y direction, and 0.76 ± 0.41 mm in the z direction. Global VE was 1.43 ± 0.37. Conclusion: Frameless systems appear to be a reliable and accurate technique.

Prospective evaluation of fiducial migration and complications after placement for hepatocellular carcinoma treated with stereotactic body radiotherapy using cyberkinife and influence on treatment delivery: A tertiary cancer centre experience

Background: Hepatocellular carcinoma (HCC) is the most common primary tumor of the hepatobiliary system. The Cyberknife represents a new, frameless stereotactic radiosurgery system with image-guided radiation delivery using fiducials as markers to overcome the movement of intra-abdominal organs due to respiration. However fiducial placement and treatment have its issues such as migration and other complications. Objectives: We evaluated the accuracy and feasibility of fiducial placement under image guidance and complications during and after placement such as migration including pain score. Materials and methods: A prospective observational study was carried out on 36 subjects with clinically and radiologically diagnosed hepatocellular carcinoma receiving Cyberknife based stereotactic based radiotherapy (SBRT). Fiducial markers for SBRT were introduced under percutaneous Ultrasound (US) or CT guidance. After placement, fiducial migration rate, pain score, fiducial placement related complications were noted during and after therapy. IBM SPSS statistical software version 21 was used for statistical analysis. Results: 8.4% had gross fiducial displacement on the day of the procedure. 90.9% had minimal migration during treatment.There was no gross migration seen during treatment or post-treatment. Post fiducial placement, 2.8 % had a major complication in the form of liver decompensation resulting in death while minor complications were observed in 13.9%. The average pain score was minimal (0.86) post fiducial placement. There was no pain in any of the patients during or after the treatment. Conclusion: Image-guided implantation of fiducial markers in the liver for stereotactic body radiation therapy had a high technical success rate and is a safe procedure with rare complications.There is minimal fiducial migration seen during the treatment. But being a descriptive study with a small sample size limits the generalizability of our study findings..

Use of Frameless Stereotactic Navigation System Combined with Intraoperative Magnetic Resonance Imaging and 5-Aminolevulinic Acid

We have described the integrated use of a neuronavigation-guided system for frameless stereotaxy (VarioGuide [Brainlab AG, Munich, Germany]) with intraoperative magnetic resonance imaging (iMRI) and 5-aminolevulinic acid (5-ALA) and report the advantages and disadvantages that the use of these tools together can have in the treatment of various types of intracerebral lesions. After the skin incision, creation of a burr hole at the entry point, and dura opening, the VarioGuide procedure was started. Initially, the wizard software will require positioning of the stereotactic arm over the burr hole and provides feedback regarding the correct position. The procedure is performed in an iMRI theater furnished with a surgical microscope (Kinevo [Carl Zeiss AG, Oberkochen, Germany]) supplied with a violet-blue excitation light for 5-ALA fluorescence. At the end of the surgery, iMRI was performed. We present 2 exemplary cases to describe the application and workflow of these tools. When used for traditional biopsy, the possibility of performing a new iMRI scan could be of paramount importance because the brain shift can be compensated for and an alternative trajectory can be calculated from the new images and fiber tracking reconstruction. The fluorescence of the tissue sample examined under the microscope filter can provide immediate information about the nature of the lesion, allowing for the possibility of converting the procedure to open craniotomy and tumor removal. The use of combination frameless stereotaxy with iMRI and 5-ALA has shown benefits in terms of safety and precision. Moreover, the use of these tools can simplify tumor removal after simple biopsy, widening the spectrum of indications.

Development of a novel frameless skull-mounted ball-joint guide array for use in image-guided neurosurgery.

Successful convection-enhanced delivery of therapeutic agents to subcortical brain structures requires accurate cannula placement. Stereotactic guiding devices have been developed to accurately target brain nuclei. However, technologies remain limited by a lack of MRI compatibility, or by devices' size, making them suboptimal for direct gene delivery to brain parenchyma. The goal of this study was to validate the accuracy of a novel frameless skull-mounted ball-joint guide array (BJGA) in targeting the nonhuman primate (NHP) brain. Fifteen MRI-guided cannula insertions were performed on 9 NHPs, each targeting the putamen. Optimal trajectories were planned on a standard MRI console using 3D multiplanar baseline images. After cannula insertion, the intended trajectory was compared to the final trajectory to assess deviation (euclidean error) of the cannula tip. The average cannula tip deviation was 1.18 ± 0.60 mm (mean ± SD) as measured by 2 independent reviewers. Topological analysis showed a superior, posterior, and rightward directional bias, and the intra- and interclass correlation coefficients were > 0.85, indicating valid and reliable intra- and interobserver evaluation. The data demonstrate that the BJGA can be used to reliably target subcortical brain structures by using MRI guidance, with accuracy comparable to current frameless stereotactic systems. The size and versatility of the BJGA, combined with a streamlined workflow, allows for its potential applicability to a variety of intracranial neurosurgical procedures, and for greater flexibility in executing MRI-guided experiments within the NHP brain.

Robot-Assisted Responsive Neurostimulator System Placement in Medically Intractable Epilepsy: Instrumentation and Technique.

The management of medically refractory epilepsy patients who are not surgical candidates has remained challenging. Closed loop-or responsive-neurostimulation (RNS) is now an established therapy for the treatment of epilepsy with specific indications. The RNS® system (NeuroPace Inc, Mountainview, California) has recently been shown to be effective in reducing the seizure frequency of partial onset seizures. The electrode design consists of either intracerebral depth electrodes or subdural strip electrodes, and stereotaxis is typically used to guide placement into the EZ. Details on the operative techniques used to place these electrodes have been lacking. To address the advantage of using a robotic-assisted technique to place depth electrodes for RNS® system placement compared to the typical frame-based or frameless stereotactic systems. We retrospectively reviewed our single center, technical operative experience with RNS® system placement using robotic assistance from 2014 to 2016 via chart review. Twelve patients underwent RNS® system placement using robotic assistance. Mean operative time was 121 min for a median of 2 depth electrodes with mean deviation from intended target of ∼3 mm in x, y, and z planes. Two patients developed wound infections, 1 of whom was reimplanted. Seizures were reduced by ∼40% at 2 yr, similar to the results seen in the open label portion of the pivotal RNS trial. Robotic-assisted stereotaxis can be used to provide a stable and accurate stereotactic platform for insertion of intracerebral RNS electrodes, representing a safe, efficient and accurate procedure.