Intraoperative Magnetic Resonance Imaging Research Articles

Optimizing Glioma Resection Outcomes: A Systematic Review of Intraoperative Magnetic Resonance Imaging Guidance in Neurosurgery.

This systematic review evaluates the efficacy of intraoperative magnetic resonance imaging (iMRI) in enhancing glioma resection outcomes within neurosurgical procedures. Given the complexity and variability of gliomas, achieving precise and safe resections is challenging, necessitating the use of advanced imaging techniques like iMRI. This technology provides real-time, high-resolution insights during surgery, allowing for adaptations based on surgical dynamics and brain shifts. Our comprehensive search across multiple databases selected five significant studies that collectively demonstrate the beneficial impact of iMRI. These studies highlight its role in significantly improving the extent of tumor resection and suggest potential enhancements in both immediate and long-term patient outcomes. The findings indicate that iMRI facilitates more aggressive yet safe resections, particularly in high-risk glioma cases. However, the implementation of iMRI in clinical practice requires careful consideration of training, resource allocation, and the potential variability in outcomes due to study design heterogeneity. Future research should focus on randomized controlled trials to better understand the cost-effectiveness and long-term benefits of iMRI, promoting its wider adoption in neurosurgical settings.

Feasibility of targeting the cingulate gyrus using high-intensity focused ultrasound on a cadaveric specimen: illustrative case.

Cancer is commonly associated with pain. For patients with advanced cancer and intractable pain, ablative neurosurgical procedures can significantly improve pain and transition patients out of inpatient settings. These procedures are normally invasive, and this poses an important risk in this population. Cingulotomy has been reported to improve pain perception and contribute substantially to the quality of life of cancer patients with refractory pain. One fresh human cadaver specimen was used for the setup. The cingulate gyrus was targeted using intraoperative magnetic resonance images, and osseous aberrations were corrected after coregistration with the preoperative head computed tomography. After accounting for sinuses, membrane folds, and calcifications, a total of 737 elements were available for thermal ultrasound ablation. On high-power sonications, the total energy delivered reached a peak temperature of 57°C (15,050 J, 350 W, 45 seconds) in the right cingulate and 52°C (13,000 J, 405 W, 46 seconds) in the left cingulate. Despite the limitations of using a cadaver model (temperature, vascularization), cingulotomy appears to be feasible using high-intensity focused ultrasound. https://thejns.org/doi/10.3171/CASE2459.

Navigated Intraoperative Ultrasound Offers Effective and Efficient Real-Time Analysis of Intracranial Tumor Resection and Brain Shift.

Neuronavigation is a fundamental tool in the resection of intracranial tumors. However, it is limited by its calibration to preoperative neuroimaging, which loses accuracy intraoperatively after brain shift. Therefore, surgeons rely on anatomic landmarks or tools like intraoperative MRI to assess the extent of tumor resection (EOR) and update neuronavigation. Recent studies demonstrate that intraoperative ultrasound (iUS) provides point-of-care imaging without the cost or resource utilization of an intraoperative MRI, and advances in neuronavigation-guided iUS provide an opportunity for real-time imaging overlaid with neuronavigation to account for brain shift. We assessed the feasibility, efficacy, and benefits of navigated iUS to assess the EOR and restore stereotactic accuracy in neuronavigation after brain shift. This prospective single-center study included patients presenting with intracranial tumors (gliomas, metastasis) to an academic medical center. Navigated iUS images were acquired preresection, midresection, and postresection. The EOR was determined by the surgeon intraoperatively and compared with the postoperative MRI report by an independent neuroradiologist. Outcome measures included time to perform the iUS sweep, time to process ultrasound images, and EOR predicted by the surgeon intraoperatively compared with the postoperative MRI. This study included 40 patients consisting of gliomas (n = 18 high-grade gliomas, n = 4 low-grade gliomas, n = 4 recurrent) and metastasis (n = 18). Navigated ultrasound sweeps were performed in all patients (n = 83) with a median time to perform of 5.5 seconds and a median image processing time of 29.9 seconds. There was 95% concordance between the surgeon's and neuroradiologist's determination of EOR using navigated iUS and postoperative MRI, respectively. The sensitivity was 100%, and the specificity was 94%. Navigated iUS was successfully used for EOR determination in glioma and metastasis resection. Incorporating navigated iUS into the surgical workflow is safe and efficient and provides a real-time assessment of EOR while accounting for brain shift in intracranial tumor surgeries.

Intraoperative MRI without an intraoperative MRI suite: a workflow for glial tumor surgery

BackgroundIntraoperative MRI (iMRI) has emerged as a useful tool in glioma surgery to safely improve the extent of resection. However, iMRI requires a dedicated operating room (OR) with an integrated MRI scanner solely for this purpose. Due to physical or economical restraints, this may not be feasible in all centers. The aim of this study was to investigate the feasibility of using a non-dedicated MRI scanner at the radiology department for iMRI and to describe the workflow with special focus on time expenditure and surgical implications.MethodsIn total, 24 patients undergoing glioma surgery were included. When the resection was deemed completed, the wound was temporarily closed, and the patient, under general anesthesia, was transferred to the radiology department for iMRI, which was performed using a dedicated protocol on 1.5 or 3 T scanners. After performing iMRI the patient was returned to the OR for additional tumor resection or final wound closure. All procedural times, timestamps, and adverse events were recorded.ResultThe median time from the decision to initiate iMRI until reopening of the wound after scanning was 68 (52–104) minutes. Residual tumors were found on iMRI in 13 patients (54%). There were no adverse events during the surgeries, transfers, transportations, or iMRI-examinations. There were no wound-related complications or infections in the postoperative period or at follow-up. There were no readmissions within 30 or 90 days due to any complication.ConclusionPerforming intraoperative MRI using an MRI located outside the OR department was feasible and safe with no adverse events. It did not require more time than previously reported data for dedicated iMRI scanners. This could be a viable alternative in centers without access to a dedicated iMRI suite.

Preclinical evaluation of transaxial intraputaminal trajectory for enhanced distribution of grafted cells in Parkinson's disease.

The objective of this study was to develop and evaluate the feasibility and safety of a novel transaxial surgical approach for the delivery of human induced pluripotent stem cell-derived dopaminergic neuroprogenitor cells (DANPCs) into the putamen nucleus using nonhuman primates and surgical techniques and tools relevant to human clinical translation. Nine immunosuppressed, unlesioned adult cynomolgus macaques (4 females, 5 males) received intraputaminal injections of vehicle or DANPCs (0.9 × 105 to 1.1 × 105 cells/µL) under real-time intraoperative MRI guidance. The infusates were combined with 1-mM gadoteridol (for intraoperative MRI visualization) and delivered via two tracks per hemisphere (ventral and dorsal) using a transaxial approach. The total volumes of infusion were 25 µL and 50 µL for the right and left putamen, respectively (infusion rate 2.5 µL/min). Animals were evaluated with a battery of clinical and behavioral outcome measures and euthanized 7 or 30 days postsurgery; full necropsies were performed by a board-certified veterinary pathologist. Brain tissues were collected and processed for immunohistochemistry, including against the human-specific marker STEM121. The optimized surgical technique and tools produced successful targeting of the putamen via the transaxial approach. Intraoperative MR images confirmed on-target intraputaminal injections in all animals. All animals survived to scheduled termination without clinical evidence of neurological deficits. The first 4 animals to undergo surgery had mild brain swelling noted at the end of surgery, of which 3 had transient reduced vision; administration of mannitol therapy and reduced intravenous fluid during the surgical procedure addressed these complications. Immunostaining against STEM121 confirmed the presence of grafted cells along the injection track within the targeted putamen area of DANPC-treated animals. All adverse histological findings were limited in scope and consistent with surgical manipulation, injection procedure, and postsurgical inflammatory response to the mechanical disruption caused by the cannula insertion. The delivery system, injection procedure, and DANPCs were well tolerated in all animals. Prevention of mild brain swelling by mannitol dosing and reduction of intravenous fluids during surgery allowed visual effects to be avoided. The results of the study established that this novel transaxial approach can be used to correctly and safely target cell injections to the postcommissural putamen and support clinical investigation.

Poster 336: Reliability of Preoperative MRI in the Prediction of ACL Tear Type

Objectives: Anterior cruciate ligament (ACL) tears are among the most frequent ligament injuries in the United States. Most of these injuries are treated surgically, depending on patient-specific factors. Management of these injuries includes nonoperative management with stepwise rehabilitation or surgical treatment with ACL repair or reconstruction. Patient goals, a clinical evaluation, and preoperative MRI imaging are generally assessed to inform the choice of treatment. Classification of ACL tear-type based on stump morphology is critical to preoperative planning, as it can determine a patient’s eligibility for ACL preservation techniques. We aim to determine the efficacy of preoperative magnetic resonance imaging (MRI) in predicting ruptured ACL stump morphology and thus assist in preoperative planning and decision-making. Methods: This retrospective observational study utilized chart review from the case log of a single surgeon at an urban tertiary institution. The review identified patients who underwent the Bridge Enhanced ACL Repair (BEAR) procedure between January 1, 2022 and August 31, 2023. The inclusion criteria included patients who underwent a primary ACL repair with the BEAR technique and had adequate intraoperative and MRI images available for review. Patients excluded were those with inadequate intraoperative imaging or MRI imaging that was unavailable for review. For each patient included, the two senior authors assessed the morphology of the ACL stump on MRI (sagittal T2, coronal T2) and intraoperative arthroscopy images in a blinded manner and assigned a classification grade to each. The MRI-based morphology and the intraoperative image morphology of the tears were classified based on a system validated by DeFelice et al, which includes types 1 to 5 based on the location of the tear from most proximal to most distal. The correlation between the preoperative MRI assessment and the intraoperative arthroscopic assessment was interrogated using simple linear regression quantified with the Pearson correlation coefficient. Results: A total of 35 patients that underwent the BEAR procedure were identified. One patient was excluded due to inadequate intraoperative images. Of the remaining patients, 13 (38.2%) were male and 21 (61.8%) were female. The average patient age was 31, with a median age of 28. Most patients were injured while skiing (32.4%), while the second and third most prevalent mechanisms of injury were nonsports-related (23.4%) and soccer injuries (17.6%), respectively. Of the MRI tears that were analyzed, 9 (26.5%) were classified as type 1, 19 (55.9%) were type 2, and 5 (14.7%) were type 3. There were no tears identified as types 4 or 5 tears. Of the arthroscopic images that were analyzed, 21 (61.8%) were classified as type 1, 10 (29.4%) were type 2, 3 (8.8%) were type 3. Similarly, there were no tears identified as types 4 or 5. MRI accurately predicted the ACL tear type seen arthroscopically 55.9% (19/34) of the time. Of the (15) cases in which MRI did not correlate with the arthroscopic tear type, the MRI classification grade was within 1 grade of the arthroscopic grade 93.3% of the time (14/15). In the cases in which MRI was not correct in its grading, 93.3% of them (14/15) were classified as too high of a grade (MRI perceiving the tear to be more distal than it was in actuality). The Pearson correlation coefficient assessing the correlation between MRI identified tear type and arthroscopy identified tear type was 0.56. Conclusions: MRI accurately predicted the ACL tear type seen arthroscopically in only 55.9% of patients. In >90% of incorrect predictions, arthroscopy determined the ACL tear to be one classification more proximal than predicted by MRI. Our results demonstrate that while preoperative MRI can be useful in identifying approximate ACL tear location, it is essential to examine the ACL at time of arthroscopy for final determination of ACL stump size and viability for ACL restoration procedures. Moreover, a greater percentage of patients may be eligible for an ACL restoration procedure than predicted by preoperative MRI, highlighting the importance of discussing both ACL repair and ACL reconstruction with patients preoperatively. [Figure: see text]

Navigated intraoperative ultrasound in pediatric brain tumors

PurposeThe 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).MethodsA 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.ResultsA 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.ConclusionWe 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 datePMCLAB2023.476, February 12th 2024.

P.142 The use of intraoperative magnetic resonance imaging for endoscopic transnasal transsphenoid surgery in children

Background: Sellar and suprasellar pediatric lesions are uncommon. Endoscopic transnasal transphenoidal surgery (ETTS) is the preferred treatment, but early post-op MRI is hindered by sphenoidal packing. This study aims to assess iMRI safety and efficacy in pediatric ETTS cases. Methods: We performed a retrospective review from Jan 01, 2015 to Dec 31, 2022, evaluating use of iMRI. We determined if the goals of the surgery (biopsy, cyst decompression, subtotal resection, gross total resection) were met, and iMRI’s influence on surgery outcomes. We examined patient age, surgery duration, length of stay, histopathology results, surgical complications, post-op MRIs within 1 month, and tumor progression/recurrence. Results: Over eight years, 20 pediatric ETTS procedures, 14 with iMRI, were conducted. Achieving goals in 13 cases, iMRI prompted extra surgery once. Two adenomas progressed, requiring a second surgery, and craniopharyngioma cases had complications, needing further interventions. Hospital stays varied (1-9 days), with a mean surgery duration of 6 hours and 47 minutes. The study underscores iMRI’s potential impact, stressing the necessity for more research in pediatric transsphenoidal surgeries. Conclusions: While intraoperative MRI in pediatric transsphenoidal surgeries may aid goal verification, this small study doesn’t conclusively demonstrate improved outcomes. Complication rates align with non-IMRI procedures, highlighting the need for further 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.

Microsurgical Resection of a Pediatric Tegmentum Tumor Through the Paramedian Supracerebellar Transtentorial Approach With the Tentorial Cut Technique: 2-Dimensional Operative Video.

The brainstem contains a highly complex group of nuclei and major white matter tracts within a small volume.1 The complex nature of its anatomy creates challenges for surgery in this area, impeding the standardization of approaches. Therefore, the concept of the "safe entry zone" should be considered with caution, and the strategy for each patient should be tailored based on the relevant subunit of the brainstem and individual patient characteristics. The critical parameter to target in patients is achieving the highest possible extent of resection while preserving function.1 The paramedian supracerebellar transtentorial approach is usually suitable for midbrain lesions. This approach allows for targeting tegmental tumors through the posterolateral midbrain surface.1 It is typically performed through a paramedian suboccipital craniotomy, ideally with the patient in the semisitting position, and is now considered a standard and safe approach.2 In patients with a spontaneous atrial right-to-left shunt, lateral or semilateral positions are viable alternatives, with the semilateral preferred for intraoperative magnetic resonance imaging.1 The cerebellar hemispheric tentorial bridging veins are usually located in the surgical route, narrowing the surgical corridor.3 Sacrifice or unintended rupture of these veins can sometimes lead to unexpected serious complications. Therefore, it is essential to preserve these veins during supracerebellar approaches.3 In this study, we demonstrate the resection of a pediatric tegmentum tumor through the left-sided paramedian supracerebellar transtentorial approach. In addition, we show the tentorial cut technique used to preserve the cerebellar hemispheric tentorial bridging veins. The patient's parents consented to the procedure and to the publication of his image.

Appearance of intracranial cottonoids on intraoperative magnetic resonance imaging.

To our knowledge, this is a unique report of intraoperative magnetic resonance imaging (iMRI) of an intracranial cottonoid. The current literature describes images of cottonoids as a post-operative finding in the setting of an unintentionally retained foreign body; however, the iMRI images we present are important as the use of iMRI in the resection of complex tumors and epilepsy foci increases. This series of images was obtained during a craniotomy for tumor resection of a patient with dysembryoplastic neuroepithelial tumor. To determine both the degree of tumor resection and the amount of residual tumor, cottonoids were left in our patient's resection cavity and underwent iMRI. The ability to distinguish cottonoids in these images is important for intraoperative localization of resection margins and to prevent the retention of cottonoids.

Intraoperative magnetic resonance imaging in glioma surgery: a single-center experience.

To investigate the effect of intraoperative magnetic resonance imaging (Io MRI) on overall and progression-free survival (OS and PFS), on the extent of resection (EOR) in patients with glioma, and impact of the radiological diagnosis on the decision to continue the surgery when a residual mass was detected on Io MRI. The study comprised 153 glioma patients who received surgical treatment between 2013 and 2023. One-hundred twenty-five of them had Io MRI guidance during surgery. The remainder 28 patients constituted the control group who did not undergo Io MRI. All patients' age at surgery, gender, initial radiological diagnosis, primary tumor localization, EOR, last histopathological diagnosis, and the follow-up periods were recorded. The rate of tumor recurrence in Io MRI cases was significantly lower compared to the cases in the control group (p < .0001). It was decided to continue the operation in 45 Io MRI applied cases. This raised the gross total resection (GTR) rate from 33.6% to 49.6% in the Io MRI group. The frequency of GTR was significantly higher in patients with an initial radiological diagnosis of low grade glioma than those with high grade glioma. The shortest OS was seen in occipital gliomas. In this study, the convenience provided by the high-field MRI device was explored and proven both in reducing the tumor burden, increasing the PFS, and providing the surgeon with a maximal resection in the first operation.

Evaluation of the extent of resection of intracranial tumors with virtual intraoperative MRI: a case series.

Intraoperative MRI (iMRI) is the gold-standard technique for intraoperative evaluation of the extent of resection in brain tumor surgery. Unfortunately, it is currently available at only a few neurosurgical centers. A commercially available software, Virtual iMRI Cranial, provides an elastic fusion between preoperative MRI and intraoperative CT (iCT). The aim of this study was to evaluate the accuracy of this software in determining the presence of residual tumor. Virtual iMRI was performed in patients who underwent iCT after intracranial tumor resection. The results of the software in terms of presence or absence of tumor residual were then compared with postoperative MRI performed within 48 hours after surgery to evaluate the diagnostic accuracy of virtual iMRI. Sixty-six patients were included in the present study. The virtual iMRI findings were concordant with the postoperative MRI data in 35 cases (53%) in the detection of tumor residual (p = 0.006). No false-negative findings (i.e., presence of residual on postoperative MRI and absence of residual on virtual iMRI) were encountered. Virtual iMRI had a sensitivity of 1 (95% CI 0.86-1), specificity of 0.26 (95% CI 0.14-0.42), positive predictive value of 0.44 (95% CI 0.3-0.58), and negative predictive value of 1 (95% CI 0.72-1). Subgroup analysis revealed that the virtual iMRI findings were concordant with postoperative MRI findings in all cases (n = 9) of lower-grade glioma (LGG) with a sensitivity of 1 (95% CI 0.59-1) and a specificity of 1 (95% CI 0.16-1) (p = 0.003); a statistically significant association was also found for grade 4 gliomas with a sensitivity of 1 (95% CI 0.69-1) and a specificity of 0.33 (95% CI 0.08-0.7) (p = 0.046) (19 patients). No significant association was found when considering meningiomas or metastases. The commercially available virtual iMRI can predict the presence or absence of tumor residual with high sensitivity. The diagnostic accuracy of this method was higher in LGGs and much lower for meningiomas or metastases; these findings must be evaluated in prospective studies in a larger population.

297 Impact of Navigated Intraoperative Ultrasound on Brain Shift and Gross Tumor Resection

INTRODUCTION: Intraoperative imaging and neuronavigation aid in achieving maximum tumor resection. However, tissue removal during surgery can cause brain shift, which alters the relative anatomy and “de-calibrates” the standard approaches. While intraoperative MRI (iMRI) is the gold-standard to correct for brain shift, it is expensive, time-consuming, and logistically difficult. As an alternative, we investigated an approach which combines intraoperative ultrasound (ioUS) technology with preoperative imaging to allow for real-time compensation of brain shift and assessment of extent of resection (EOR). METHODS: We prospectively enrolled patients undergoing neurosurgical tumor resection at Massachusetts General Hospital beginning April 2023. Patients were registered with Brainlab Ultrasound Navigation prior to surgery. ioUS sweeps were acquired before cortex incision, mid-resection, and post-resection with bkActiv and fused to preoperative MRIs. Four points around the tumor were longitudinally tracked to assess brain shift. Data included sweep duration, image processing speed, extent of brain shift as determined by intraoperative markers, and EOR assessed from the ioUS compared with postoperative MRIs. RESULTS: Seven patients were enrolled (average age 62 ± 15, 75% male) with frontal (n = 5), temporal (n = 1), and occipital (n = 1) gliomas (n = 4) and metastases (n = 3). All patients exhibiting total resection as determined by ioUS also demonstrated total resection on post-operative MRI, evaluated independently by a neuroradiologist. The average time of scan and image processing (n = 19) was 5.7 ± 1.9 and 27.8 ± 6.5 seconds respectively. CONCLUSIONS: Navigated ioUS offers accurate and efficient assessment of EOR during surgery for tumor resections. Furthermore, when brain shift is detected, navigated ioUS can allow for compensation and continued utilization of navigation via the acquisition of a brand new, navigable, intraoperatively acquired dataset.

1248 Optimal Connectivity Map Predicts Seizure Freedom Rates After Laser Interstitial Thermal Therapy in Mesial Temporal Lobe Epilepsy

INTRODUCTION: Laser Interstitial Thermal Therapy (LiTT) is increasingly becoming a first-line surgical therapy for mesial temporal lobe epilepsy (mTLE). While promising, its seizure outcomes have also been highly variable, presumably due to an incomplete understanding of mechanisms behind LiTT. Epilepsy is a network disorder, and therefore it is crucial to account for both the effect on local destruction of epileptogenic foci, as well as global intervention of limbic circuitry, to elucidate the circuit-level mechanisms of LiTT and devise improved ablation strategies. In this study, we explore LiTT's network-level effect by investigating functional connectivity patterns and identifying optimal connectivity patterns predictive of seizure freedom. METHODS: 27 mTLE patients who underwent unilateral LiTT were classified as seizure-free (ILAE Class I) or seizure-present (ILAE Class II–VI) cohort based on one-year postoperative outcomes. Individual ablation volumes were segmented from intraoperative MRI sequences. Ablation volumes were seeded into a normative functional connectome (Brain Genomics Superstruct Project) to extract patient-specific connectivity profiles associated with ablation volumes. FC patterns were compared between the two cohorts to produce voxel-wise “t-maps” to identify local and global differences in connectivity strengths predictive of seizure freedom. RESULTS: Ten mTLE patients achieved complete seizure freedom. In seizure-free patients, right ablated volumes shared higher FC with regions such as calcarine, cuneus, and thalamic anterior pulvinar nucleus than patients with seizure presence. CONCLUSIONS: For the right-sided ablations, seizure freedom was associated with a distinctive whole-brain connectivity pattern beyond the local surgical target. Further investigation is required to explore if this pattern is specific between the two surgical sides in mTLE population.

Intraoperative MRI: A Review of Applications Across Neurosurgical Specialties.

Intraoperative MRI (iMRI) made its debut to great fanfare in the mid-1990s. However, the enthusiasm for this technology with seemingly obvious benefits for neurosurgeons has waned. We review the benefits and utility of iMRI across the field of neurosurgery and present an overview of the evidence for iMRI for multiple neurosurgical disciplines: tumor, skull base, vascular, pediatric, functional, and spine. Publications on iMRI have steadily increased since 1996, plateauing with approximately 52 publications per year since 2011. Tumor surgery, especially glioma surgery, has the most evidence for the use of iMRI contributing more than 50% of all iMRI publications, with increased rates of gross total resection in both adults and children, providing a potential survival benefit. Across multiple neurosurgical disciplines, the ability to use a multitude of unique sequences (diffusion tract imaging, diffusion-weighted imaging, magnetic resonance angiography, blood oxygenation level-dependent) allows for specialization of imaging for various types of surgery. Generally, iMRI allows for consideration of anatomic changes and real-time feedback on surgical outcomes such as extent of resection and instrument (screw, lead, electrode) placement. However, implementation of iMRI is limited by cost and feasibility, including the need for installation, shielding, and compatible tools. Evidence for iMRI use varies greatly by specialty, with the most evidence for tumor, vascular, and pediatric neurosurgery. The benefits of real-time anatomic imaging, a lack of radiation, and evaluation of surgical outcomes are limited by the cost and difficulty of iMRI integration. Nonetheless, the ability to ensure patients are provided by a maximal yet safe treatment that specifically accounts for their own anatomy and highlights why iMRI is a valuable and underutilized tool across multiple neurosurgical subspecialties.

Maximal Resection of Gliomas Adjacent to the Corticospinal Tract Using 3-T Intraoperative Magnetic Resonance Imaging

BackgroundGliomas adjacent to the corticospinal tract (CST) should be carefully resected to preserve motor function while achieving maximal surgical resection. Modern high-field intraoperative magnetic resonance imaging (iMRI) enables precise visualization of the residual tumor and intraoperative tractography. We prospectively evaluated the extent of resection and distance between the tumor resection cavity and CST using 3-T iMRI combined with motor evoked potentials (MEP) in glioma surgery. MethodParticipants comprised patients who underwent surgery for solitary supratentorial glioma located within 10 mm of the CST. All cases underwent surgery using neuronavigation with overlaid CST under MEP monitoring. The correlation between distance from CST and transcortical MEP amplitude was calculated using Spearman rank correlation. ResultsAmong the 63 patients who underwent surgery, 27 patients were enrolled in the study. Gross total resections were achieved in 26 of the 27 cases. Volumetric analysis showed the extent of resection was 98.6%. Motor function was stable or improved in 24 patients (Stable/Improved group) and deteriorated in 3 patients (Deteriorated group). All patients in the Deteriorated group showed motor deficit before surgery. Mean intraoperative minimal distance was significantly longer in the Stable/Improved group (7.3 mm) than in the Deteriorated group (1.1 mm; p < 0.05). MEP amplitude correlated with minimal distance between the resection cavity and CST (R=0.64). ConclusionsResection of gliomas adjacent to CST with a navigation system using 3-T iMRI could result in an ultimate EOR >98%. The combination of intraoperative tractography and MEP contributes to maximal removal of motor-eloquent gliomas.

Practice Patterns for Managing Recurrent Glioblastoma Multiforme

Abstract Introduction Glioblastoma multiforme (GBM) is a devastating form of cancer with a poor prognosis despite available treatments. Managing recurrent GBM remains challenging and lacks guidelines. This study aims to provide practice patterns for managing recurrent GBMs in India. Methods A panel of experts was assembled to develop practice patterns using the Delphi technique. Their responses were analyzed anonymously to ensure impartiality and generate recommendations. The statements were intended to be nonbinding and focused on promoting best practices in the field, without legal or regulatory authority. Results A total of 23 experts participated in the study, providing their opinions on various aspects of managing recurrent GBM. Consensus was achieved on individualized and multidisciplinary management as the preferred approach. Surgery in combination with other treatments was found to impact survival in patients older than 65 years, with re-surgery and adjuvant radiation and chemotherapy being the preferred options. Gadolinium-enhanced magnetic resonance imaging (MRI) brain with spectroscopy and diffusion-weighted imaging was favored. Molecular profiling was considered significant, with O6-methylguanine DNA methyltransferase methylation being most relevant. Surgery was recommended for recurrent GBMs, primarily based on Karnofsky's performance score (KPS). Surgical adjuncts such as neuronavigation and intraoperative MRI were considered valuable. Radiation therapy, specifically stereotactic radiosurgery, was recommended for selected cases, while opinions on re-chemotherapy were divided. Palliative care was deemed important. Conclusion This study presents practice patterns for managing recurrent GBM in India, providing standardized recommendations for practice. By implementing these, clinicians can make informed decisions, leading to improved patient outcomes and reduced variability in the management of recurrent GBM.

Improving advanced intraoperative MRI methods during pediatric neurosurgery.

Advanced intraoperative MR images (ioMRI) acquired during the resection of pediatric brain tumors could offer additional physiological information to preserve healthy tissue. With this work, we aimed to develop a protocol for ioMRI with increased sensitivity for arterial spin labeling (ASL) and diffusion MRI (dMRI), optimized for patient positioning regularly used in the pediatric neurosurgery setting. For ethical reasons, ASL images were acquired in healthy adult subjects that were imaged in the prone and supine position. After this, the ASL cerebral blood flow (CBF) was quantified and compared between both positions. To evaluate the impact of the RF coils setups on image quality, we compared different setups (two vs. four RF coils) by looking at T1-weighted (T1w) signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), as well as undertaking a qualitative evaluation of T1w, T2w, ASL, and dMR images. Mean ASL CBF did not differ between the surgical prone and supine positions in any of the investigated regions of interest or the whole brain. T1w SNR (gray matter: p = 0.016, 34% increase; white matter: p = 0.016, 32% increase) and CNR were higher (p = 0.016) in the four versus two RF coils setups (18.0± 1.8 vs. 13.9± 1.8). Qualitative evaluation of T1w, T2w, ASL, and dMR images resulted in acceptable to good image quality and did not differ statistically significantly between setups. Only the nonweighted diffusion image maps and corticospinal tract reconstructions yielded higher image quality and reduced susceptibility artifacts with four RF coils. Advanced ioMRI metrics were more precise with four RF coils as the standard deviation decreased. Taken together, we have investigated the practical use of advanced ioMRI during pediatric neurosurgery. We conclude that ASL CBF quantification in the surgical prone position is valid and that ASL and dMRI acquisition with two RF coils can be performed adequately for clinical use. With four versus two RF coils, the SNR of the images increases, and the sensitivity to artifacts reduces.

Two years of neurosurgical intraoperative MRI in Sweden - evaluation of use and costs.

The current shortage of radiology staff in healthcare provides a challenge for departments all over the world. This leads to more evaluation of how the radiology resources are used and a demand to use them in the most efficient way. Intraoperative MRI is one of many recent advancements in radiological practice. If radiology staff is performing intraoperative MRI at the operation ward, they may be impeded from performing other examinations at the radiology department, creating costs in terms of exams not being performed. Since this is a kind of cost whose importance is likely to increase, we have studied the practice of intraoperative MRI in Sweden. The study includes data from the first four hospitals in Sweden that installed MRI scanners adjacent to the operating theaters. In addition, we included data from Karolinska University Hospital in Solna where intraoperative MRI is carried out at the radiology department. Scanners that were moved into the operation theater and doing no or few other scans were used 11-12% of the days. Stationary scanners adjacent to the operation room were used 35-41% of the days. For scanners situated at the radiology department doing intraoperative scans interspersed among all other scans, the proportion was 92%. Our study suggests that performing exams at the radiology department rather than at several locations throughout the hospital may be an efficient approach to tackle the simultaneous trends of increasing demands for imaging and increasing staff shortages at radiology departments.