Intraoperative ultrasound and magnetic resonance comparative analysis in brain tumor surgery: a valuable tool to flatten ultrasound's learning curve.

BACKGROUND: Intraoperative ultrasound (IOUS) is a profitable tool for neurosurgical procedures' assistance, especially in neuro-oncology. It is a rapid, ergonomic and reproducible technique. However, its known handicap is a steep learning curve for neurosurgeons. Here, we describe an interesting postoperative analysis that provides extra feedback after surgery, accelerating the learning process. METHOD: We conducted a descriptive retrospective unicenter study including patients operated from intra-axial brain tumors using neuronavigation (Curve, Brainlab) and IOUS (BK-5000, BK medical) guidance. All patients had preoperative Magnetic Resonance Imaging (MRI) prior to tumor resection. During surgery, 3D neuronavigated IOUS studies (n3DUS) were obtained through craniotomy N13C5 transducer's integration to the neuronavigation system. At least two n3DUS studies were obtained: prior to tumor resection and at the resection conclusion. A postoperative MRI was performed within 48 h. MRI and n3DUS studies were posteriorly fused and analyzed with Elements (Brainlab) planning software, permitting two comparative analyses: preoperative MRI compared to pre-resection n3DUS and postoperative MRI to post-resection n3DUS. Cases with incomplete MRI or n3DUS studies were withdrawn from the study. RESULTS: From April 2022 to March 2024, 73 patients were operated assisted by IOUS. From them, 39 were included in the study. Analyses comparing preoperative MRI and pre-resection n3DUS showed great concordance of tumor volume (p < 0,001) between both modalities. Analysis comparing postoperative MRI and post-resection n3DUS also showed good concordance in residual tumor volume (RTV) in cases where gross total resection (GTR) was not achieved (p < 0,001). In two cases, RTV detected on MRI that was not detected intra-operatively with IOUS could be reviewed in detail to recheck its appearance. CONCLUSIONS: Post-operative comparative analyses between IOUS and MRI is a valuable tool for novel ultrasound users, as it enhances the amount of feedback provided by cases and could accelerate the learning process, flattening this technique's learning curve.

Clinical evaluation of resection of functional area gliomas guided by intraoperative 3.0 T MRI combined with functional MRI navigation.

BACKGROUND: In assessing the clinical utility and safety of 3.0 T intraoperative magnetic resonance imaging (iMRI) combined with multimodality functional MRI (fMRI) guidance in the resection of functional area gliomas, we conducted a study. METHOD: Among 120 patients with newly diagnosed functional area gliomas who underwent surgical treatment, 60 were included in each group: the integrated group with iMRI and fMRI and the conventional navigation group. Between-group comparisons were made for the extent of resection (EOR), preoperative and postoperative activities of daily living based on the Karnofsky performance status, surgery duration, and postoperative intracranial infection rate. RESULTS: Compared to the conventional navigation group, the integrated navigation group with iMRI and fMRI exhibited significant improvements in tumor resection (complete resection rate: 85.0% vs. 60.0%, P = 0.006) and postoperative life self-care ability scores (Karnofsky score) (median ± interquartile range: 90 ± 25 vs. 80 ± 30, P = 0.013). Additionally, although the integrated navigation group with iMRI and fMRI required significantly longer surgeries than the conventional navigation group (mean ± standard deviation: 411.42 ± 126.4 min vs. 295.97 ± 96.48 min, P<0.0001), there was no significant between-group difference in the overall incidence of postoperative intracranial infection (16.7% vs. 18.3%, P = 0.624). CONCLUSION: The combination of 3.0 T iMRI with multimodal fMRI guidance enables effective tumor resection with minimal neurological damage.

Functional frontal lobectomy in the surgical treatment of pharmacoresistant frontal lobe epilepsy: how I do it.

BACKGROUND: Frontal lobe epilepsy is pharmacoresistant in 30% of cases, constituting 10-20% of epilepsy surgeries. For cases of no lesional epilepsy (negative MRI), frontal lobectomy is a crucial treatment, historically involving Frontal Anatomical Lobectomy (AFL) with a 33.3% complication risk and 55.7% seizure control. METHODS: We describe Frontal Functional Lobectomy (FFL), in which the boundaries are defined on the patient's functional cortico-subcortical areas, recognized with advanced intraoperative technologies such as tractography and navigated transcranial magnetic stimulation (nTMS). CONCLUSIONS: The FFL allows for a broader resection with a lower rate of postoperative complications than the AFL.

Neuronavigation assisted percutaneous balloon compression of the gasserian ganglion for trigeminal neuralgia. How I do it.

BACKGROUND: Surgical treatment for trigeminal neuralgia includes percutaneous techniques, including balloon compression, first described in 1983 by Mullan and Lichtor (J Neurosurg 59(6):1007-1012, 6). METHOD: Here we present a safe and simple navigation-assisted percutaneous technique for balloon compression, which can also be used for glycerol injection. CONCLUSION: The navigation-assisted percutaneous technique for balloon compression for trigeminal neuralgia is a quick and safe treatment for patients not candidates for microvascular decompression.

Impact of BrainLab VectorVision Infrared-Based Neuronavigation on Surgical Outcomes in Intracranial Meningioma Patients: A Retrospective Study.

BACKGROUND The BrainLab VectorVision neuronavigation system is an image-guided, frameless localization system used intraoperatively, which includes a computer workstation for viewing and analyzing operative microscopic images. This retrospective study aimed to evaluate the use of the BrainLab VectorVision infrared-based neuronavigation imaging system in 80 patients with intracranial meningioma removed surgically between 2013 and 2023. MATERIAL AND METHODS Data were retrospectively collected from 36 patients with convexity meningioma and 44 patients with parasagittal meningioma between 2013 and 2023. The surgical operation of 40 of these patients was performed with the help of neuronavigation, while the other 40 were performed without neuronavigation. Demographic data, preoperative and postoperative radiologic images, craniotomy measurements, surgical complications, and operative times of patients with and without neuronavigation were analyzed. RESULTS Using neuronavigation significantly increased surgery duration (P=0.023). In 6 patients without the use of neuronavigation, the craniotomy had to be enlarged and this resulted in superior sagittal sinus (SSS) damage (P=0.77, P=0.107). Patients for whom neuronavigation was used did not experience any sinus damage and did not require craniotomy enlargement. Postoperative epidural hematoma (EH) developed in 9 patients without navigation, whereas it developed in only 1 patient with navigation (P=0.104). Residual tumors were less common in patients using navigation (P=0.237). CONCLUSIONS The use of neuronavigation allows the incision and craniotomy to be reduced in size. Intraoperatively, it allows the surgeon to master the boundaries of the tumor and surrounding vascular structures, reducing the risk of complications. These results suggest that neuronavigation systems are an effective ancillary in meningioma surgery.

Scalp surface estimation and head registration using sparse sampling and 3D statistical models.

Registering the head and estimating the scalp surface are important for various biomedical procedures, including those using neuronavigation to localize brain stimulation or recording. However, neuronavigation systems rely on manually-identified fiducial head targets and often require a patient-specific MRI for accurate registration, limiting adoption. We propose a practical technique capable of inferring the scalp shape and use it to accurately register the subject's head. Our method does not require anatomical landmark annotation or an individual MRI scan, yet achieves accurate registration of the subject's head and estimation of its surface. The scalp shape is estimated from surface samples easily acquired using existing pointer tools, and registration exploits statistical head model priors. Our method allows for the acquisition of non-trivial shapes from a limited number of data points while leveraging their object class priors, surpassing the accuracy of common reconstruction and registration methods using the same tools. The proposed approach is evaluated in a virtual study with head MRI data from 1152 subjects, achieving an average reconstruction root-mean-square error of 2.95 mm, which outperforms a common neuronavigation technique by 2.70 mm. We also characterize the error under different conditions and provide guidelines for efficient sampling. Furthermore, we demonstrate and validate the proposed method on data from 50 subjects collected with conventional neuronavigation tools and setup, obtaining an average root-mean-square error of 2.89 mm; adding landmark-based registration improves this error to 2.63 mm. The simulation and experimental results support the proposed method's effectiveness with or without landmark annotation, highlighting its broad applicability.

Navigated intraoperative ultrasound in pediatric brain tumors.

PURPOSE: The aim of this study was to evaluate the diagnostic value and accuracy of navigated intraoperative ultrasound (iUS) in pediatric oncological neurosurgery as compared to intraoperative magnetic resonance imaging (iMRI). METHODS: A total of 24 pediatric patients undergoing tumor debulking surgery with iUS, iMRI, and neuronavigation were included in this study. Prospective acquisition of iUS images was done at two time points during the surgical procedure: (1) before resection for tumor visualization and (2) after resection for residual tumor assessment. Dice similarity coefficients (DSC), Hausdorff distances 95th percentiles (HD95) and volume differences, sensitivity, and specificity were calculated for iUS segmentations as compared to iMRI. RESULTS: A high correlation (R = 0.99) was found for volume estimation as measured on iUS and iMRI before resection. A good spatial accuracy was demonstrated with a median DSC of 0.72 (IQR 0.14) and a median HD95 percentile of 4.98 mm (IQR 2.22 mm). The assessment after resection demonstrated a sensitivity of 100% and a specificity of 84.6% for residual tumor detection with navigated iUS. A moderate accuracy was observed with a median DSC of 0.58 (IQR 0.27) and a median HD95 of 5.84 mm (IQR 4.04 mm) for residual tumor volumes. CONCLUSION: We found that iUS measurements of tumor volume before resection correlate well with those obtained from preoperative MRI. The accuracy of residual tumor detection was reliable as compared to iMRI, indicating the suitability of iUS for directing the surgeon's attention to areas suspect for residual tumor. Therefore, iUS is considered as a valuable addition to the neurosurgical armamentarium. TRIAL REGISTRATION NUMBER AND DATE: PMCLAB2023.476, February 12th 2024.

Neuronavigated percutaneous gasserian radiofrequency thermorhizotomy for trigeminal neuralgia: how I do it.

BACKGROUND: Radiofrequency thermorhizotomy (TRZ) is an established treatment for trigeminal neuralgia (TN). TRZ can result risky and painful in a consistent subset of patients, due to the need to perform multiple trajectories, before a successful foramen ovale cannulation. Moreover, intraoperative x-rays are required. METHOD: TRZ has been performed by using a neuronavigated stylet, before trajectory planning on a dedicated workstation. CONCLUSION: Navigated-TRZ (N-TRZ) meets the expectations of a safer and more tolerable procedure due to the use of a single trajectory, avoiding critical structures. Moreover, N-TRZ is x-ray free. Efficacy outcomes are similar to those reported in literature.

Neuronavigation-Guided Transcranial Histotripsy (NaviTH) System.

OBJECTIVE: The goal of the work described here was to develop the first neuronavigation-guided transcranial histotripsy (NaviTH) system and associated workflow for transcranial ablation. METHODS: The NaviTH system consists of a 360-element, 700 kHz transmitter-receiver-capable transcranial histotripsy array, a clinical neuronavigation system and associated equipment for patient-to-array co-registration and therapy planning and targeting software systems. A workflow for NaviTH treatments, including pre-treatment aberration correction, was developed. Targeting errors stemming from target registration errors (TREs) during the patient-to-array co-registration process, as well as focal shifts caused by skull-induced aberrations, were investigated and characterized. The NaviTH system was used in treatments of two <96 h post-mortem human cadavers and in experiments in two excised human skullcaps. RESULTS: The NaviTH was successfully used to create ablations in the cadaver brains as confirmed in post-treatment magnetic resonance imaging A total of three ablations were created in the cadaver brains, and targeting errors of 9, 3.4 and 4.4 mm were observed in corpus callosum, septum and thalamus targets, respectively. Errors were found to be caused primarily by TREs resulting from transducer tracking instrument design flaws and imperfections in the treatment workflow. Transducer tracking instrument design and workflow improvements reduced TREs to <2 mm, and skull-induced focal shifts, following pre-treatment aberration correction, were 0.3 mm. Total targeting errors of the NaviTH system following the noted improvements were 2.5 mm. CONCLUSIONS: The feasibility of using the first NaviTH system in a human cadaver model has been determined. Although accuracy still needs to be improved, the proposed system has the potential to allow for transcranial histotripsy therapies without requiring active magnetic resonance treatment guidance.

Current Applications of VR/AR (Virtual Reality/Augmented Reality) in Pediatric Neurosurgery.

Neurosurgical procedures are some of the most complex procedures in medicine and since the advent of the field, planning, performing, and learning them has challenged the neurosurgeon. Virtual reality (VR) and augmented reality (AR) are making these challenges more manageable. VR refers to a virtual digital environment that can be experienced usually through use of stereoscopic glasses and controllers. AR, on the other hand, fuses the natural environment with virtual images, such as superimposing a preoperative MRI image on to the surgical field [1]. They initially were used primarily as neuronavigational tools but soon their potential in other areas of surgery, such as planning, education, and assessment, was noted and explored. Through this chapter, we outline the history and evolution of these two technologies over the past few decades, describe the current state of the technology and its uses, and postulate future directions for research and implementation.

Using camera-guided electrode microdrive navigation for precise 3D targeting of macaque brain sites.

Spatial accuracy in electrophysiological investigations is paramount, as precise localization and reliable access to specific brain regions help the advancement of our understanding of the brain's complex neural activity. Here, we introduce a novel, multi camera-based, frameless neuronavigation technique for precise, 3-dimensional electrode positioning in awake monkeys. The investigation of neural functions in awake primates often requires stable access to the brain with thin and delicate recording electrodes. This is usually realized by implanting a chronic recording chamber onto the skull of the animal that allows direct access to the dura. Most recording and positioning techniques utilize this implanted recording chamber as a holder of the microdrive or to hold a grid. This in turn reduces the degrees of freedom in positioning. To solve this problem, we require innovative, flexible, but precise tools for neuronal recordings. We instead mount the electrode microdrive above the animal on an arch, equipped with a series of translational and rotational micromanipulators, allowing movements in all axes. Here, the positioning is controlled by infrared cameras tracking the location of the microdrive and the monkey, allowing precise and flexible trajectories. To verify the accuracy of this technique, we created iron deposits in the tissue that could be detected by MRI. Our results demonstrate a remarkable precision with the confirmed physical location of these deposits averaging less than 0.5 mm from their planned position. Pilot electrophysiological recordings additionally demonstrate the accuracy and flexibility of this method. Our innovative approach could significantly enhance the accuracy and flexibility of neural recordings, potentially catalyzing further advancements in neuroscientific research.

ReMIND: The Brain Resection Multimodal Imaging Database.

The standard of care for brain tumors is maximal safe surgical resection. Neuronavigation augments the surgeon's ability to achieve this but loses validity as surgery progresses due to brain shift. Moreover, gliomas are often indistinguishable from surrounding healthy brain tissue. Intraoperative magnetic resonance imaging (iMRI) and ultrasound (iUS) help visualize the tumor and brain shift. iUS is faster and easier to incorporate into surgical workflows but offers a lower contrast between tumorous and healthy tissues than iMRI. With the success of data-hungry Artificial Intelligence algorithms in medical image analysis, the benefits of sharing well-curated data cannot be overstated. To this end, we provide the largest publicly available MRI and iUS database of surgically treated brain tumors, including gliomas (n = 92), metastases (n = 11), and others (n = 11). This collection contains 369 preoperative MRI series, 320 3D iUS series, 301 iMRI series, and 356 segmentations collected from 114 consecutive patients at a single institution. This database is expected to help brain shift and image analysis research and neurosurgical training in interpreting iUS and iMRI.

A comparative study of the dorsolateral prefrontal cortex targeting approaches for transcranial magnetic stimulation treatment: Insights from the healthy control data.

Repetitive transcranial magnetic stimulation (rTMS) to the left dorsolateral prefrontal cortex (DLPFC) is an established treatment for medication-resistant depression. Several targeting methods for the left DLPFC have been proposed including identification with resting-state functional magnetic resonance imaging (rs-fMRI) neuronavigation, stimulus coordinates based on structural MRI, or electroencephalography (EEG) F3 site by Beam F3 method. To date, neuroanatomical and neurofunctional differences among those approaches have not been investigated on healthy subjects, which are structurally and functionally unaffected by psychiatric disorders. This study aimed to compare the mean location, its dispersion, and its functional connectivity with the subgenual cingulate cortex (SGC), which is known to be associated with the therapeutic outcome in depression, of various approaches to target the DLPFC in healthy subjects. Fifty-seven healthy subjects underwent MRI scans to identify the stimulation site based on their resting-state functional connectivity and were measured their head size for targeting with Beam F3 method. In addition, we included two fixed stimulus coordinates over the DLPFC in the analysis, as recommended in previous studies. From the results, the rs-fMRI method had, as expected, more dispersed target sites across subjects and the greatest anticorrelation with the SGC, reflecting the known fact that personalized neuronavigation yields the greatest antidepressant effect. In contrast, the targets located by the other methods were relatively close together with less dispersion, and did not differ in anticorrelation with the SGC, implying their limitation of the therapeutic efficacy and possible interchangeability of them.

Effects of the Use of Neuronavigation in Patients with Supratentorial Brain Gliomas: A Cohort Study.

OBJECTIVE: Despite the growing acceptance of neuronavigation in the field of neurosurgery, there is limited comparative research with contradictory results. This study aimed to compare the effectiveness (tumor resection rate and survival) and safety (frequency of neurological complications) of surgery for brain gliomas with or without neuronavigation. METHODS: This retrospective cohort study evaluated data obtained from electronic records of patients who underwent surgery for gliomas at Dr. Alejandro Dávila Bolaños Military Hospital and the Clinic Hospital of Barcelona between July 2016 and September 2022. The preoperative and postoperative clinical and radiologic characteristics were analyzed and compared according to the use of neuronavigation. RESULTS: This study included 110 patients, of whom 79 underwent surgery with neuronavigation. Neuronavigation increased gross total resection by 57% in patients in whom it was used; gross total resection was performed in 56% of patients who underwent surgery with neuronavigation as compared with 35.5% in those who underwent surgery without neuronavigation (risk ratio [RR], 1.57; P=0.056). The incidence of postoperative neurologic deficits (transient and permanent) decreased by 79% with the use of neuronavigation, (12% vs. 33.3%; RR, 0.21; P=0.0003). Neuronavigation improved survival in patients with grade IV gliomas (15 months vs. 13.8 months), but it was not statistically significant (odds ratio (OR), 0.19; P=0.13). CONCLUSIONS: Neuronavigation improved the effectiveness (greater gross total resection of tumors) and safety (fewer neurological deficits) of brain glioma surgery. However, neuronavigation does not significantly influence the survival of patients with grade IV gliomas.

Bony Surface-Matching Registration of Neuronavigation with Sectioned 3-Dimensional Skull in Prone Position.

BACKGROUND: Neuronavigation has become an essential system for brain tumor resections. It is sometimes difficult to obtain accurate registration of the neuronavigation with the patient in the prone position. Bony surface-matching registration should be more precise than skin surface-matching registration; however, it is difficult to establish bony registration with limited exposed bone. We created a new bony surface-matching method to a sectioned 3-dimensional (3D) virtual skull in a neuronavigation system and registered with a sectioned 3D skull. In this study, the bony surface-matching with sectioned 3D registration is applied to provide precise registration for brain tumor resection in the prone position. METHODS: From May 2023 to April 2024, 17 patients who underwent brain tumor resection in the prone position were enrolled. The navigation system StealthStation S8 (Medtronic, Dublin, Ireland) was used. Bony surface-matching registration with a whole 3D skull in a neuronavigation system was performed. Next, a sectioned 3D skull was made according to the surgical location to compare with the whole 3D skull registration. A phantom model was also used to validate the whole and sectioned 3D skull registration. RESULTS: Whole 3D skull registration was successful for only 2 patients (11.8%). However, sectioned 3D skull registration was successful for 16 patients (94.1%). The examinations with a phantom skull model also showed superiority of sectioned 3D skull registration to whole 3D skull registration. CONCLUSIONS: Sectioned 3D skull registration was superior to whole 3D skull registration. The sectioned 3D skull method could provide accurate registration with limited exposed bone.

Head model dataset for mixed reality navigation in neurosurgical interventions for intracranial lesions.

Mixed reality navigation (MRN) technology is emerging as an increasingly significant and interesting topic in neurosurgery. MRN enables neurosurgeons to "see through" the head with an interactive, hybrid visualization environment that merges virtual- and physical-world elements. Offering immersive, intuitive, and reliable guidance for preoperative and intraoperative intervention of intracranial lesions, MRN showcases its potential as an economically efficient and user-friendly alternative to standard neuronavigation systems. However, the clinical research and development of MRN systems present challenges: recruiting a sufficient number of patients within a limited timeframe is difficult, and acquiring low-cost, commercially available, medically significant head phantoms is equally challenging. To accelerate the development of novel MRN systems and surmount these obstacles, the study presents a dataset designed for MRN system development and testing in neurosurgery. It includes CT and MRI data from 19 patients with intracranial lesions and derived 3D models of anatomical structures and validation references. The models are available in Wavefront object (OBJ) and Stereolithography (STL) formats, supporting the creation and assessment of neurosurgical MRN applications.

Three-Dimensional Structure Light Robot-Assisted Frameless Stereotactic Brain Biopsy.

BACKGROUND AND OBJECTIVES: To assess the feasibility, accuracy, and safety of 3-dimensional (3D) structure light robot-assisted frameless stereotactic brain biopsy. METHODS: Five consecutive patients (3 males, 2 females) were included in this study. The patients' clinical, imaging, and histological data were analyzed, and all patients received a 3D structure light robot-assisted frameless stereotactic brain biopsy. The raw and/or analyzed data of the study are available from the corresponding author. RESULTS: The statistical results showed a mean age of 59.6 years (range 40-70 years), a mean target depth of 60.9 mm (range 53.5-65.8 mm), a mean radial error of 1.2 ± 0.7 mm (mean ± SD), a mean depth error of 0.7 ± 0.3 mm, and a mean absolute tip error of 1.5 ± 0.6 mm. The calculated Pearson product-moment correlation coefficient ( r = 0.23) revealed no correlation between target depth and absolute tip error. All biopsy needles were placed in line with the planned trajectory successfully, and diagnostic specimens were harvested in all cases. Histopathological analysis revealed lymphoma (2 cases), lung adenocarcinoma (1 case), glioblastoma multiforme (1 case), and oligodendroglioma (1 case). CONCLUSION: Surface registration using the 3D structure light technique is fast and precise because of the achievable million-scale point cloud data of the head and face. 3D structure light robot-assisted frameless stereotactic brain biopsy is feasible, accurate, and safe.

Dynamic Workflow Proposal for Continuous Frameless Electromagnetic Neuronavigation in Rigid Neuroendoscopy.

BACKGROUND: Ventriculoscopic neuronavigation has been described in several articles. However, there are different ventriculoscopes and navigation systems. Due to these different combinations, it is difficult to find detailed neuronavigation protocols. We describe, step-by-step, a simple method to navigate both the trajectory until reaching the ventricular system, as well as the intraventricular work. METHODS: We use a rigid ventriculoscope (LOTTA, KarlStorz) with an electromagnetic stylet (S8-StealthSystem, Medtronic). The protocol is based on a modified or 3-dimensionally printed trocar for navigating the extraventricular step and on a modified pediatric nasogastric tube for the intraventricular navigation. RESULTS: This protocol can be set up in less than 10 minutes. The extraventricular part is navigated by introducing the electromagnetic stylet inside the modified or 3-dimensionally printed trocar. Intraventricular navigation is done by combining a modified pediatric nasogastric tube with the electromagnetic stylet inside the endoscope's working channel. The most critical point is to obtain a blunt-bloodless ventriculostomy while achieving perfect alignment of all targeted structures via pure straight trajectories. CONCLUSIONS: This protocol is easy-to-set-up, avoids head rigid-fixation and bulky optical-based attachments to the ventriculoscope, and allows continuous navigation of both parts of the surgery. Since we have implemented this protocol, we have noticed a significant enhancement in both simple and complex ventriculoscopic procedures because the surgery is dramatically simplified.