Stereotactic System Research Articles

PO-1715 Accuracy of a dedicated single isocenter stereotactic radiosurgery system for multiple brain lesions

PO-1715 Accuracy of a dedicated single isocenter stereotactic radiosurgery system for multiple brain lesions

Treatment Approach for Knee Osteoarthritis with Ipsilateral Femoral Cartilage Tumor: A Case Series

Osteoarthritis (OA) is a common pathology affecting the knee joint. Twenty percent of the cartilaginous tumors of bone are in the distal femur. This presents a challenge for treating patients with knee OA who also have ipsilateral distal femur cartilage tumors. We propose a classification system for knee OA with ipsilateral cartilaginous tumor and a treatment approach to address this issue. Intramedullary guides are avoided when performing total knee arthroplasty (TKA) in these patients so as not to further contaminate the femur with tumor cells. A non-image-based stereotactic surgical system is favored at our institution to achieve this goal. Seven patients underwent classification and treatment with TKA utilizing this approach. Average final follow-up was 15.3 months. Component alignment averaged 89.2° and all patients had 0° of extension with an average flexion to 107.5°. There were no postoperative complications and no radiographic evidence of component complication, tumor recurrence, or tumor expansion. Few studies have reported on the treatment of knee OA with concurrent cartilaginous tumor of the distal femur. All patients treated with the proposed approach had their OA successfully treated without complication related to their cartilaginous tumor or TKA components. This case series presents a novel classification and treatment algorithm to potentially guide arthroplasty surgeons in approaching these often-concurrent occurring pathologies.

A detailed analysis of anatomical plausibility of crossed and uncrossed streamline rendition of the dentato-rubro-thalamic tract (DRT(T)) in a commercial stereotactic planning system

BackgroundAn increasing number of neurosurgeons use display of the dentato-rubro-thalamic tract (DRT) based on diffusion weighted imaging (dMRI) as basis for their routine planning of stimulation or lesioning approaches in stereotactic tremor surgery. An evaluation of the anatomical validity of the display of the DRT with respect to modern stereotactic planning systems and across different tracking environments has not been performed.MethodsDistinct dMRI and anatomical magnetic resonance imaging (MRI) data of high and low quality from 9 subjects were used. Six subjects had repeated MRI scans and therefore entered the analysis twice. Standardized DICOM structure templates for volume of interest definition were applied in native space for all investigations. For tracking BrainLab Elements (BrainLab, Munich, Germany), two tensor deterministic tracking (FT2), MRtrix IFOD2 (https://www.mrtrix.org), and a global tracking (GT) approach were used to compare the display of the uncrossed (DRTu) and crossed (DRTx) fiber structure after transformation into MNI space. The resulting streamlines were investigated for congruence, reproducibility, anatomical validity, and penetration of anatomical way point structures.ResultsIn general, the DRTu can be depicted with good quality (as judged by waypoints). FT2 (surgical) and GT (neuroscientific) show high congruence. While GT shows partly reproducible results for DRTx, the crossed pathway cannot be reliably reconstructed with the other (iFOD2 and FT2) algorithms.ConclusionSince a direct anatomical comparison is difficult in the individual subjects, we chose a comparison with two research tracking environments as the best possible “ground truth.” FT2 is useful especially because of its manual editing possibilities of cutting erroneous fibers on the single subject level. An uncertainty of 2 mm as mean displacement of DRTu is expectable and should be respected when using this approach for surgical planning. Tractographic renditions of the DRTx on the single subject level seem to be still illusive.

Design and characterization of a prototype tertiary device for proton beam stereotactic radiosurgery

Though potentially beneficial, proton beam stereotactic radiosurgery has not been adopted widely secondary to the technical challenge of safely delivering multiple focused beams of proton radiation. In this study, we describe the design and characterization of a proton beam stereotactic radiosurgery system that can be adopted by existing passive scattering systems. This system utilizes a helmet-like device in which patient-specific brass apertures required for final beam collimation are positioned on a scaffold that is separate from the treatment gantry. The proton snout is then fitted with a generic aperture to focus the primary proton beam onto the patient specific apertures that are in the helmet-like device. The patient-specific apertures can all be placed at the start of the treatment, thus treatment with multiple beams can be accomplished without the delay of switching the apertures. In this report we describe a prototype design of this collimation system and dosimetric testing to verify efficacy. Subsequently, we describe a custom 3D printing of a prototype device and report on overall localization accuracy using Winston-Lutz tests. Our results show that it is possible to develop an add-on device for proton beam radiosurgery that is safe and efficient and capable of wide adoption on existing proton delivery systems.

Development and in vivo assessment of a novel MRI‐compatible headframe system for the ovine animal model

The brain of sheep has primarily been used in neuroscience as an animal model because of its similarity to the human brain, in particular if compared to other models such as the lissencephalic rodent brain. Their brain size also makes sheep an ideal model for the development of neurosurgical techniques using conventional clinical CT/MRI scanners and stereotactic systems for neurosurgery. In this study, we present the design and validation of a new CT/MRI compatible head frame for the ovine model and software, with its assessment under two real clinical scenarios. Ex-vivo and in vivo trial results report an average linear displacement of the ovine head frame during conventional surgical procedures of 0.81mm for ex-vivo trials and 0.68mm for in vivo tests, respectively. These trial results demonstrate the robustness of the head frame system and its suitability to be employed within a real clinical setting.

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.

Treatment planning system and beam data validation for the ZAP-X: A novel self-shielded stereotactic radiosurgery system.

To evaluate the treatment planning system (TPS) performance of the ZAP-X stereotactic radiosurgery (SRS) system through nondosimetric, dosimetric, and end-to-end (E2E) tests. A comprehensive set of TPS commissioning and validation tests was developed using published guidelines. Nondosimetric validation tests included information transfer, computed tomography-magnetic resonance (CT-MR) image registration, structure/contouring, geometry, dose tools, and CT density. Dosimetric validation included comparisons between TPS and water tank/Solid Water measurements for various geometries and beam arrangements and end-to-end (E2E) tests. Patient-specific quality assurance was performed with an ion chamber in the Lucy phantom and with Gafchromic EBT3 film in the CyberKnife head phantom. RadCalc was used for independent verification of monitor units. Additional E2E tests were performed using the RPC Gamma Knife thermoluminescent dosimeter (TLD) phantom, MD Anderson SRS head phantom, and PseudoPatient gel phantom for independent absolute dose verification. CT-MR image registrations with known translational and rotational offsets were within tolerance (<0.5×maximum voxel dimension). Slice thickness and distance accuracy were within 0.1mm, and volume accuracy was within 0 to 0.11cm3 . Treatment planning system volume measurement uncertainty was within 0.1 to 0.4cm3 . Ion chamber point-dose measurements for a single beam in a water phantom agreed to TPS-calculated values within ±4% for collimator diameters 10 to 25mm, and ±6% for 7.5mm, for all measured depths (7, 50, 100, 150, and 200mm). In homogeneous Solid Water, point-dose measurements agreed to within ±4% for cones sizes 7.5 to 25mm. With 1-cm high/low density inserts, measurements were within ±4.2% for cone sizes 10 to 25mm. Film-based E2E using 4/5-mm cones resulted in a gamma passing rate (%GP) of 99.8% (2%/1.5mm). Point-dose measurements in a Lucy phantom with an ion chamber using 36 beams distributed along three noncoplanar arcs agreed to within ±4% for cone sizes 10 to 25mm. The RPC Gamma Knife TLD phantom yielded passing results with a measured-to-expected TLD dose ratio of 1.02. The MD Anderson SRS head phantom yielded passing results, with 4% TLD agreement and %GP of 95%/93% (5%/3mm) for coronal/sagittal film planes. The RTsafe gel phantom gave %GP of >95% (5%/2mm) for all four targets. For our first 58 patients, film-based patient-specific quality assurance has resulted in an average %GP of 98.7% (range, 94-100%) at 2%/2mm. Core ZAP-X features were found to be functional. On the basis of our results, point-dose and planar measurements were in agreement with TPS calculations using multiple phantoms and setup geometries, validating the ZAP-X TPS beam model for clinical use.

Hidden Error in Optical Stereotactic Navigation Systems and Strategy to Maximize Accuracy

Background: Optical neuronavigation has been established as a reliable and effective adjunct to many neurosurgical procedures. Operations such as asleep deep brain stimulation (aDBS) benefit from the potential increase in accuracy that these systems offer. Built into these technologies is a degree of tolerated error that may exceed the presumed accuracy resulting in suboptimal outcomes. Objective: The objective of this study was to identify an underlying source of error in neuronavigation and determine strategies to maximize accuracy. Methods: A Medtronic Stealth system (Stealth Station 7 hardware, S8 software, version 3.1.1) was used to simulate an aDBS procedure with the Medtronic Nexframe system. Multiple configurations and orientations of the Nexframe-Nexprobe system components were examined to determine potential sources of, and to quantify navigational error, in the optical navigation system. Virtual entry point and target variations were recorded and analyzed. Finally, off-plan error was recorded with the AxiEM system and visual observation on a phantom head. Results: The most significant source of error was found to be the orientation of the reference marker plate configurations to the camera system, with the presentation of the markers perpendicular to the camera line of site being the most accurate position. Entry point errors ranged between 0.134 ± 0.048 and 1.271 ± 0.0986 mm in a complex, reproducible pattern dependent on the orientation of the Nexprobe reference plate. Target errors ranged between 0.311 ± 0.094 and 2.159 ± 0.190 mm with a similarly complex, repeatable pattern. Representative configurations were tested for physical error at target with errors ranging from 1.2 mm to 1.4 mm. Throughout data acquisition, no orientation was indicated as outside the acceptable tolerance by the Stealth software. Conclusions: Use of optical neuronavigation is expected to increase in frequency and variety of indications. Successful implementation of this technology depends on understanding the tolerances built into the system. In situations that depend on extremely high precision, surgeons should familiarize themselves with potential sources of error so that systems may be optimized beyond the manufacturer’s built-in tolerances. We recommend that surgeons align the navigation reference plate and any optical instrument’s reference plate spheres in the plane perpendicular to the line of site of the camera to maximize accuracy.

Characterization of the ZAP-X® Peripheral Dose Fall-Off.

Various small-field radiation dose detectors were systematically compared and their impact on measured beam performance of the ZAP-X® dedicated stereotactic radiosurgery system (ZAP Surgical Systems, Inc., San Carlos, CA, USA) was determined. Three Physikalische Technische Werkstaetten (PTW) diodes, i.e., the microSilicon, the microDiamond, and the Stereotactic Radiosurgery (SRS) diode detectors of (PTW-Freiburg, Freiburg, Germany), as well as Gafchromic™ External Beam Therapy 3 (EBT) film (Ashland, Inc., Wilmington, DE, USA), were used and compared to arrive at a recommended standard for this critical component of small-field beam measurements. Beam profiles, including the dose fall-off region near the edge of the beam, were measured with the PTW diodes and EBT3 film and subsequently contrasted. The impact of detector physical and dosimetric characteristics on the results of the measurements was investigated and compared with film measurements. The beam penumbra was used to quantify the dose fall-off. The measurement acquired with the diodes and film showed the most significant differences in the fall-off region near the field edge. The film-based measurements clearly showed the steepest dose gradient verified by the penumbra value of 1.21 mm, followed by the SRS diode with 1.60 mm, the microSilicon diode with 1.67 mm, and the microDiamond diode with 1.83 mm. A clear correlation of each detector’s sensitive area with the penumbra was found, with the microDiamond detector at 2.2 mm diameter sensitive area having the largest penumbra, followed by the microSilicon and SRS diodes. Beam measurements for the purposes of system characterization or treatment planning system beam data acquisition depend, to a large extent, on detector characteristics. This is especially true for small-field dosimetry performed during stereotactic radiosurgery beam measurements. Careful consideration should be practiced which allows for the measurements to represent true beam characteristics and minimize the impact of the detector on the measurements. We conclude that film should be considered the reference method for such measurements with the ZAP-X due to its smallest physical measurement resolution of 23.1 µm. Potential drawbacks to this methodology are the need to calibrate the film relative to the dose and possible problems with saturation and non-linear film response for very high and very low optical densities.

Frame-based versus frameless stereotactic brain biopsies: A systematic review and meta-analysis.

Background: Stereotactic brain biopsy techniques have been a focus of rapid technological innovation. The recent advent of frameless stereotaxy has invited the question of whether it can provide the same diagnostic yield as frame-based techniques, without increasing risk of harm to patients. The goal of this meta-analysis was to compare each of these techniques in terms of yield and safety.Methods: We independently searched four databases for English studies comparing frameless and frame-based stereotactic brain biopsies. Our primary outcome was biopsy diagnostic yield. Our secondary outcomes included mortality, morbidity (e.g., symptomatic postbiopsy intracranial hemorrhage, asymptomatic postbiopsy intracranial hemorrhage, new postbiopsy neurological deficit, and postbiopsy seizure), and frequency of repeat biopsy. We calculated pooled estimates and relative risks for dichotomous outcomes using Review Manager 5.3, with corresponding 95% confidence intervals.Results: A total of 3256 stereotactic brain biopsies (2050 frame based and 1206 frameless), from 20 studies, were included in our final analysis. The results did not demonstrate any significant difference between the two stereotactic systems in terms of diagnostic yield (risk ratio [RR] 1.00, 95% confidence interval [CI] 0.99–1.02, P = 0.64, I2 = 0%). The only significant difference was the increased frequency of asymptomatic hemorrhages in the frameless group (RR 1.37, 95% CI 1.06–1.75, P = 0.01, I2 = 0%). Application of Grading of Recommendations Assessment, Development, and Evaluation to the results yielded very low quality of all outcomes.Conclusion: Based on very low-quality evidence, both frame-based and frameless stereotaxy are safe and effective for biopsy of intracranial tumors. Further study of patient preference and cost comparing analysis is required to identify if either modality should be preferred.

The Impact of Intraoperative Image-Guidance Modalities and Neurophysiologic Monitoring in the Safety of Sacroiliac Fusions.

Study Design:Retrospective observational cohort.Objective:A review of efficiency and safety of fluoroscopy and stereotactic navigation system for minimally invasive (MIS) Sacroiliac (SI) fusion through a lateral technique.Methods:Retrospective analysis of an observational cohort of 96 patients greater than 18 years old, that underwent MIS SI fusion guided by fluoroscopy or navigation between January 2013 and April 2020 with a minimum of 3 months follow-up. Intraoperative neuromonitoring (IONM) with a variable combination of electromyography (EMG), somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) was also utilized.Results:The overall complication rate in the study was 9.4%, and there was no difference between the fluoroscopy (10.1%), and navigation groups (8%). Neurological complication rate was 2.1%, without a significant difference between both intraoperative guidance modality groups (p = 0.227). There was a significant difference between the modalities of IONM used and the occurrence of neurological injury (p = 0.01).The 2 patients who had a neurological complication postoperatively were monitored only with EMG and SSEP, but none of the patients (n = 76) in which MEPs were utilized had neurologic complication. The mean pain improvement 3 months after surgery was greater in the navigation group (2.44 ± 2.72), but was not statistically different than the improvement in the fluoroscopy group (1.90 ± 2.07) (p = 0.301).Conclusions:No difference in the safety of the procedure was found between the fluoroscopy and the stereotactic navigation techniques. The contribution of the IONM to the safety of SI fusions could not be determined, but the data indicates that MEPs provide the highest level of sensitivity.

Predicting ablation zones with multislice volumetric 2-D magnetic resonance thermal imaging

Background High-intensity focused ultrasound (HIFU) serves as a noninvasive stereotactic system for the ablation of brain metastases; however, treatments are limited to simple geometries and energy delivery is limited by the high acoustic attenuation of the calvarium. Minimally-invasive magnetic resonance-guided robotically-assisted (MRgRA) needle-based therapeutic ultrasound (NBTU) using multislice volumetric 2-D magnetic resonance thermal imaging (MRTI) overcomes these limitations and has potential to produce less collateral tissue damage than current methods. Objective To correlate multislice volumetric 2-D MRTI volumes with histologically confirmed regions of tissue damage in MRgRA NBTU. Methods Seven swine underwent a total of 8 frontal MRgRA NBTU lesions. MRTI ablation volumes were compared to histologic tissue damage on brain sections stained with 2,3,5-triphenyltetrazolium chloride (TTC). Bland-Altman analyses and correlation trends were used to compare MRTI and TTC ablation volumes. Results Data from the initial and third swine’s ablations were excluded due to sub-optimal tissue staining. For the remaining ablations (n = 6), the limits of agreement between the MRTI and histologic volumes ranged from −0.149 cm3 to 0.252 cm3 with a mean difference of 0.052 ± 0.042 cm3 (11.1%). There was a high correlation between the MRTI and histology volumes (r 2 = 0.831) with a strong linear relationship (r = 0.868). Conclusion We used a volumetric MRTI technique to accurately track thermal changes during MRgRA NBTU in preparation for human trials. Improved volumetric coverage with MRTI enhanced our delivery of therapy and has far-reaching implications for focused ultrasound in the broader clinical setting.

HeaDax: A simple pre-surgical procedure for localizing superficial brain lesions in resource-limited environments

Background: Intracranial convexity lesions are poorly defined by recognizable anatomical landmarks. Even in expert hands, exact localization of small subcortical lesion and its projection to the skull is sometimes unreliable and can cause potential surgical complications. In this report, a simple and handy technique for localizing superficial intracranial lesions on the scalp under computed tomography (CT)-scan guidance is described.Methods: This technique, HeaDax, is based on using extracranial landmarks. We constructed an isosceles square triangle with three pieces of copper electrical wire and placed it on the skin scalp. Then, we took a CT-scan but without the need of the classic head reference planes (e.g., orbitomeatal or along the orbital roof).Results: For the measurements, we need to have the intracranial lesion located on the CT slice with respect to the two landmarks which are the height and hypotenuse of the triangle. The promising preliminary results of HeaDax applied to a phantom skull model encourage us to use it successfully for our first patient presenting a right subcortial supramarginal retrorolandic cavernoma.Conclusion: HeaDax procedure is a good alternative for localizing superficial intracranial lesions on the skin scalp under CT-scan or magnetic resonance imaging guidance. It can be used as a substitute when stereotactic and neuronavigation systems are not easily available, especially in developing countries and in resource-limited environments. HeaDax has a true potential for further developments and applications in cranial surgery.

An Illustrative Review of Common Modern Craniotomies.

Craniotomy, or a surgical opening into the skull, has been observed as early as Paleolithic and Neolithic periods. Early craniotomies carried great morbidity and mortality and standardized during the 20th century, improving surgical outcomes. The simultaneous evolution of medical imaging and stereotactic navigation systems has allowed imaging to correlate findings with surgical approaches, further optimizing patient safety. We review the history of craniotomy and provide an imaging review of the most common craniotomy approaches.

Navigated laparoscopic microwave ablation of tumour mimics in pig livers: a randomized ex-vivo experimental trial

BackgroundIn order to efficiently perform laparoscopic microwave ablation of liver tumours precise positioning of the ablation probe is mandatory. This study evaluates the precision and ablation accuracy using the innovative laparoscopic stereotactic navigation system CAS-One-SPOT in comparison to 2d ultrasound guided laparoscopic ablation procedures.MethodsIn a pig liver ablation model four surgeons, experienced (n = 2) and inexperienced (n = 2) in laparoscopic ablation procedures, were randomized for 2d ultrasound guided laparoscopic or stereotactic navigated laparoscopic ablation procedures. Each surgeon performed a total of 20 ablations. Total attempts of needle placements, time from tumor localization till beginning of ablation and ablation accuracy were analyzed.ResultsThe use of the laparoscopic stereotactic navigation system led to a significant reduction in total attempts of needle placement. The experienced group of surgeons reduced the mean number of attempts from 2.75 ± 2.291 in the 2d ultrasound guided ablation group to 1.45 ± 1.191 (p = 0.0302) attempts in the stereotactic navigation group. Comparable results could be observed in the inexperienced group with a reduction of 2.5 ± 1.50 to 1.15 ± 0.489 (p = 0.0005). This was accompanied by a significant time saving from 101.3 ± 112.1 s to 48.75 ± 27.76 s (p = 0.0491) in the experienced and 165.5 ± 98.9 s to 66.75 ± 21.96 s (p < 0.0001) in the inexperienced surgeon group. The accuracy of the ablation process was hereby not impaired as postinterventional sectioning of the ablation zone revealed.ConclusionThe use of a stereotactic navigation system for laparoscopic microwave ablation procedures of liver tumors significantly reduces the attempts and time of predicted correct needle placement for novices and experienced surgeons without impairing the accuracy of the ablation procedure.

Test cases for commissioning an add-on micro multi-leaf collimator Apex for stereotactic radiosurgery treatments

Two comprehensive test cases are presented for dosimetric commissioning of a radiosurgery system, in a hospital where dedicated phantoms are not available. The system consisted of an Elekta Precise linear accelerator, an Apex micro multi-leaf collimator, and a Monaco treatment planning system (TPS). The purpose of Test I was to assess the dose accuracy with coplanar arc beams. Test II was an end-to-end type test, a rigid Leksell stereotactic frame was fixed to a watermelon phantom and Ergo++ TPS was used for stereotactic coordinates definition. The purpose of Test II was to assess the dose accuracy with non-coplanar arc beams and the influence of geometrical accuracy in the whole process. Ionization chambers were used for dose measurements. Results of Test I showed that discrepancies below 1% are achievable, while results of Test II allowed detection of geometric shifts &lt; 1 mm with dose discrepancies lower than 1%. To the best of our knowledge, there are not published works reporting test cases for commissioning a stereotactic radiosurgery system like the one tested in this work. The designed test cases showed adequacy for assessment of TPS accuracy in complex treatment configurations, like those used in stereotactic radiosurgery.

A compact stereotactic system for image-guided surgical intervention

Objective. Stereotactic technology enables fine navigation to small structures in the human body. While current stereotactic systems facilitate accurate targeting, they are mechanically cumbersome and limited in scope. Here, we hypothesized that a stereotactic system could be developed with a reduced footprint while maintaining broad targeting capabilities in order to improve versatility in frame placement location and surgical workflow. Approach. We designed a stereotactic system around the center-of-arc principle, with mechanical properties that would enable a compact design and ample targeting and trajectory maneuverability. To examine the opportunity for a low-cost rapidly-deployable system we developed two fabrication variants, one using three dimensional (3D)-printing and the other using conventional machining. Mechanical and image-guided accuracies were tested in phantom studies using magnetic resonance imaging (MRI) and computed tomography. Using human cadaver head specimens, we assessed the system’s surgical workflow and its ability to reliably and accurately implant electrodes in deep brain stimulation (DBS) surgery. Main results. We developed a small 7.7 × 5.4 cm2 device platform that rigidly mounts to curvilinear bone and supports the attachment of surgical instrumentation. Attachment of two surgical instruments, an imaging localizer and a compact targeting device, demonstrated successful MRI-guided intervention in phantom studies with a vector error of 1.79 ± 0.41 mm. Evaluation of the 3D-printed system for DBS surgery confirmed ease of device platform attachment and instrument functionality, as well as demonstrated a surgical targeting accuracy of 1.83 ± 0.15 mm. In addition, we found the surgical time to be 78.3 ± 5.4 min for bilateral electrode implantation. Significance. We developed a light and compact stereotactic system whose accuracy is on par with those used clinically. This technology is suitable for clinical translation and its flexibility in positioning will seamlessly expand the capabilities for stereotaxy to treat a wide range of conditions, both within neurosurgery and beyond.

Impact of needle positioning on ablation success of irreversible electroporation: a unicentric retrospective analysis

Irreversible electroporation (IRE) is an ablation procedure in which cell death is induced by ultrashort electrical pulses. In this unicentric retrospective study we investigated the influence of needle positioning on ablation success. 15 IREs with residual tumor after ablation, detected in the first follow-up MRI, were included, and compared with 30 successful ablations. Evaluation of needle geometry revealed significantly higher values for needle divergence (NDiv, 7.0° vs. 3.7°, p = 0.02), tumor-center-to-ablation-center distance (TACD, 11.6 vs. 3.2 mm, p < 0.001), tumor-to-needle distance (4.7 vs. 1.9 mm, p = 0.04), and tumor diameter per needle (7.5 vs. 5.9 mm/needle, p = 0.01) in patients with residual tumor. The average number of needles used was higher in the group without residual tumor after ablation (3.1 vs. 2.4, p = 0.04). In many cases with residual tumor, needle depth was too short (2.1 vs. 6.8 mm tumor overlap beyond the most proximal needle tip, p < 0.01). The use of a stereotactic navigation system in 10 cases resulted in a lower NDiv value (2.1° vs. 5.6°, p < 0.01). Thus, correct needle placement seems to be a crucial factor for success and the assistance of a stereotactic navigation system might be helpful. As most important geometrical parameter TACD could be identified. Main reasons for high TACD were insufficient needle depth and a lesion location out of the needle plane.

Stereotactic Biopsy in The Diagnosis of Small Brain Lesion

Background: Stereotactic neurosurgery involves mapping the brain in a three-dimensional coordinate system. With the help of MRI and CT scans and 3D computer workstations, neurosurgeons are able to accurately target any area of the brain especially deep seated and brain stem.&#x0D; Objectives: Stereotactic brain biopsy is a minimally invasive procedure that uses this technology to obtain samples of brain tissue for diagnostic purpose of multiple brain disorder where start to any medication was impossible or no response to any medical management for long term.&#x0D; Materials and Methods: Twenty-five patients underwent stereotactic biopsy of brain lesions using“KOMAI” Stereotactic frame system and were enrolled.&#x0D; Results: Of the 25 cases, positive tissue biopsy was found in 20 cases. In 5 patients, biopsy showed gliotic brain tissue or normal brain tissue. There was no post-operative new deficits or mortality seen.&#x0D; Conclusion: Stereotaxy is minimally invasive procedure having no complication. So, before starting any medication blindly stereotactic tissue diagnosis can help a lot in many medical and surgical diseases.&#x0D; J Bangladesh Coll Phys Surg 2021; 39(1): 24-35

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.