Tag: Intraoperative MRI

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The Role of Intraoperative Imaging Modalities in Surgical Resection of Supratentorial Gliomas: A Review of 300 Cases

Operative Neurosurgery 30:278–288, 2026

This retrospective study of 300 supratentorial glioma surgeries compares outcomes using intraoperative MRI (iMRI), navigated intraoperative ultrasound (iUS) and no intraoperative imaging. It reports higher gross total resection rates and greater contrast-enhancement extent with iMRI and iUS, with iMRI achieving the highest contrast-enhanced extent of resection (CE-EOR) but longer operative times.

Clinical outcomes show fewer postoperative weaknesses and better overall survival when intraoperative imaging is used. Postoperative cognitive and sensory deficits varied by modality; progression-free survival differences were not significant. Study limitations include a retrospective design, the temporal rollout of modalities and differing surgeon experience.

Gross Total Resection (GTR) Rates: GTR was significantly more common with intraoperative MRI (iMRI, 56.9%) and intraoperative ultrasound (iUS, 57.1%) than without intraoperative imaging guidance (34%) in glioma surgery.

Extent of Resection (EOR): The mean EOR of contrast enhancement was highest with iMRI (96.6%), followed by iUS (93.2%), and lowest without intraoperative imaging (92%).

Postoperative Neurological Deficits: Patients without intraoperative imaging had significantly higher rates of postoperative weakness compared to those with iMRI or iUS (odds ratio = 0.520, CI = 0.272-0.994, P = .048).

Overall Survival (OS): Overall survival was significantly worse in patients without intraoperative imaging guidance (odds ratio = 1.534, CI = 1.058-2.225, P = .024) than in those with iMRI or iUS.

Progression-Free Survival (PFS): No significant differences in progression-free survival were found between the subgroups using iMRI, iUS, or no intraoperative imaging.

Surgery Duration: Mean surgery duration was longest with iMRI (260 minutes), intermediate with iUS (194 minutes), and shortest without intraoperative imaging (175 minutes).

Postoperative Functional Status: Karnofsky Performance Status (KPS) at 1 year was lowest in patients without intraoperative imaging guidance, indicating worse functional outcomes.

Study Limitations: The retrospective design, differing periods of iMRI and iUS use, learning curves, and unequal subgroup sizes limit the ability to fully compare all factors and may affect recurrence rate assessments.

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Efficacy and safety of intraoperative MRI in glioma surgery: a systematic review and meta-analysis of prospective randomized controlled trials

J Neurosurg 142:1319–1330, 2025

This meta-analysis of randomized controlled trials found that intraoperative MRI significantly increases gross-total resection rates and progression-free survival in glioma surgery, without increasing neurological deficits or most complications, though it prolongs surgery and may raise infection risk. iMRI is effective and generally safe for maximizing tumor removal.

• Intraoperative MRI (iMRI) significantly increases the rate of gross-total resection (GTR) in glioma surgery compared to conventional neuronavigation.

• Greater extent of resection (EOR) with iMRI leads to improved progression-free survival (PFS), especially in high-grade gliomas.

• No significant difference in overall survival (OS) was observed between iMRI and conventional surgery groups.

• Rates of postoperative neurological deterioration, motor, and language decline are similar between iMRI and control groups.

• iMRI does not increase the risk of postoperative intracranial hemorrhage, but may be associated with higher rates of wound infections in some studies.

• Use of iMRI prolongs surgery time by an average of 42 minutes.

• Only three randomized controlled trials with a total of 384 patients met inclusion criteria for this meta-analysis.

• Combined use of iMRI and 5-ALA may further enhance EOR, but more randomized studies are needed for definitive conclusions.

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Comparative analysis of intraoperative MRI and early postoperative MRI findings in glioma surgery patients

J Neurosurg 142:1289–1297, 2025

The study compares intraoperative MRI (iMRI) and early postoperative MRI (epMRI) in glioma surgery, highlighting iMRI’s accuracy in extent of resection (EOR) and reduced surgically induced contrast enhancement (SICE). iMRI better detects postoperative neurological deficits, with fewer diffusion-weighted imaging abnormalities than epMRI.

• Objective: The study compares intraoperative MRI (iMRI) and early postoperative MRI (epMRI) findings in glioma surgery to assess the extent of resection (EOR) and postoperative neurological deficits.

• Methods: A retrospective analysis of 43 glioma patients who underwent surgery with iMRI, with no additional resection after iMRI, was conducted.

• Results: Discrepancies in EOR were found in 11.1% of nonenhanced and 4.0% of enhanced lesions. iMRI showed more accurate EOR and less surgically induced contrast enhancement (SICE) compared to epMRI.

• Findings: The positive rate of SICE was higher on epMRI (67.9%) than iMRI (25.0%). The positive rate of diffusion-weighted imaging (DWI) abnormality was also higher on epMRI (89.2%) compared to iMRI (73%).

• Clinical Outcomes: Two patients developed new neurological deficits postoperatively, both showing DWI abnormality on both iMRI and epMRI. No deficits were observed in the late-developing group.

• Conclusion: iMRI is more reliable for assessing accurate EOR and detecting postoperative neurological deficits than epMRI, despite higher late-developing DWI abnormalities on epMRI.

• Significance: The study underscores the importance of iMRI in optimizing glioma surgery outcomes and minimizing misinterpretation of residual tumors.

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Intraoperative MRI–based elastic fusion for anatomically accurate tractography of the corticospinal tract

Neurosurg Focus 50 (1):E9, 2021

Tractography is a useful technique that is standardly applied to visualize subcortical pathways. However, brain shift hampers tractography use during the course of surgery. While intraoperative MRI (ioMRI) has been shown to be beneficial for use in oncology, intraoperative tractography can rarely be performed due to scanner, protocol, or head clamp limitations. Elastic fusion (EF), however, enables adjustment for brain shift of preoperative imaging and even tractography based on intraoperative images. The authors tested the hypothesis that adjustment of tractography by ioMRI-based EF (IBEF) correlates with the results of intraoperative neuromonitoring (IONM) and clinical outcome and is therefore a reliable method.

METHODS In 304 consecutive patients treated between June 2018 and March 2020, 8 patients, who made up the basic study cohort, showed an intraoperative loss of motor evoked potentials (MEPs) during motor-eloquent glioma resection for a subcortical lesion within the corticospinal tract (CST) as shown by ioMRI. The authors preoperatively visualized the CST using tractography. Also, IBEFs of pre- and intraoperative images were obtained and the location of the CST was compared in relation to a subcortical lesion. In 11 patients (8 patients with intraoperative loss of MEPs, one of whom also showed loss of MEPs on IBEF evaluation, plus 3 additional patients with loss of MEPs on IBEF evaluation), the authors examined the location of the CST by direct subcortical stimulation (DSCS). The authors defined the IONM results and the functional outcome data as ground truth for analysis.

RESULTS The maximum mean ± SD correction was 8.8 ± 2.9 (range 3.8–12.0) mm for the whole brain and 5.3 ± 2.4 (range 1.2–8.7) mm for the CST. The CST was located within the lesion before IBEF in 3 cases and after IBEF in all cases (p = 0.0256). All patients with intraoperative loss of MEPs suffered from surgery-related permanent motor deficits. By approximation, the location of the CST after IBEF could be verified by DSCS in 4 cases.

CONCLUSIONS The present study shows that tractography after IBEF accurately correlates with IONM and patient outcomes and thus demonstrates reliability in this initial study.

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Maximizing safe resection of low- and high-grade glioma

dti-gliomas

J Neurooncol (2016) 130:269–282

Surgical resection plays a central role in the management of gliomas. In this study, we review the evidence in support of extent of resection to improve survival, symptom management, and time to malignant transformation in low- and high-grade gliomas, and summarize the findings from our literature search regarding the role of extent of resection and intraoperative practices to maximize safety.

There is a growing body of evidence supporting improved overall survival, improved progression-free survival, and superior quality of life with greater extent of resection.

Additionally, a better understanding of central nervous system plasticity allows for a staged approach to the surgical management of low- and intermediate-grade gliomas.

A number of intraoperative techniques have been utilized to offer safer glioma surgery with greater extent of resection. Approaches such as awake brain tumor surgery can be safely performed with low failure rates and excellent long-term functional outcomes.

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Resting-state functional MRI in an intraoperative MRI setting

Resting-state functional MRI in an intraoperative MRI setting-1

J Neurosurg 125:401–409, 2016

The authors’ aim in this paper is to prove the feasibility of resting-state (RS) functional MRI (fMRI) in an intraoperative setting (iRS-fMRI) and to correlate findings with the clinical condition of patients pre- and postoperatively.

Methods: Twelve patients underwent intraoperative MRI-guided resection of lesions in or directly adjacent to the central region and/or pyramidal tract. Intraoperative RS (iRS)–fMRI was performed pre- and intraoperatively and was correlated with patients’ postoperative clinical condition, as well as with intraoperative monitoring results. Independent component analysis (ICA) was used to postprocess the RS-fMRI data concerning the sensorimotor networks, and the mean z-scores were statistically analyzed.

Results: iRS-fMRI in anesthetized patients proved to be feasible and analysis revealed no significant differences in preoperative z-scores between the sensorimotor areas ipsi- and contralateral to the tumor. A significant decrease in z-score (p < 0.01) was seen in patients with new neurological deficits postoperatively. The intraoperative z-score in the hemisphere ipsilateral to the tumor had a significant negative correlation with the degree of paresis immediately after the operation (r = -0.67, p < 0.001) and on the day of discharge from the hospital (r = -0.65, p < 0.001). Receiver operating characteristic curve analysis demonstrated moderate prognostic value of the intraoperative z-score (area under the curve 0.84) for the paresis score at patient discharge.

Conclusions: The use of iRS-fMRI with ICA-based postprocessing and functional activity mapping is feasible and the results may correlate with clinical parameters, demonstrating a significant negative correlation between the intensity of the iRS-fMRI signal and the postoperative neurological changes.

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Low-grade Glioma Surgery in Intraoperative Magnetic Resonance Imaging

Hypnosis for Awake Surgery of Low-grade Gliomas

Neurosurgery 78:775–786, 2016

The ideal treatment strategy for low-grade gliomas (LGGs) is a controversial topic. Additionally, only smaller single-center series dealing with the concept of intraoperative magnetic resonance imaging (iMRI) have been published.

OBJECTIVE: To investigate determinants for patient outcome and progression-freesurvival (PFS) after iMRI-guided surgery for LGGs in a multicenter retrospective study initiated by the German Study Group for Intraoperative Magnetic Resonance Imaging.

METHODS: A retrospective consecutive assessment of patients treated for LGGs (World Health Organization grade II) with iMRI-guided resection at 6 neurosurgical centers was performed. Eloquent location, extent of resection, first-line adjuvant treatment, neurophysiological monitoring, awake brain surgery, intraoperative ultrasound, and fieldstrength of iMRI were analyzed, as well as progression-free survival (PFS), new permanent neurological deficits, and complications. Multivariate binary logistic and Cox regression models were calculated to evaluate determinants of PFS, gross total resection (GTR), and adjuvant treatment.

RESULTS: A total of 288 patients met the inclusion criteria. On multivariate analysis, GTR significantly increased PFS (hazard ratio, 0.44; P < .01), whereas “failed” GTR did not differ significantly from intended subtotal-resection. Combined radiochemotherapy as adjuvant therapy was a negative prognostic factor (hazard ratio: 2.84, P < .01). Field strength of iMRI was not associated with PFS. In the binary logistic regression model, use of high-field iMRI (odds ratio: 0.51, P < .01) was positively and eloquent location (odds ratio: 1.99, P < .01) was negatively associated with GTR. GTR was not associated with increased rates of new permanent neurological deficits.

CONCLUSION: GTR was an independent positive prognostic factor for PFS in LGG surgery. Patients with accidentally left tumor remnants showed a similar prognosis compared with patients harboring only partially resectable tumors. Use of high-field iMRI was significantly associated with GTR. However, the field strength of iMRI did not affect PFS.

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Combination of Intraoperative Magnetic Resonance Imaging and Intraoperative Fluorescence to Enhance the Resection of Contrast Enhancing Gliomas

Combination of Intraoperative Magnetic Resonance Imaging and Intraoperative Fluorescence to Enhance the Resection of Contrast Enhancing Gliomaspdf

Neurosurgery 77:16–22, 2015

Evidence suggests that extent of resection (EOR) is a prognostic factor for patients harboring gliomas. Recent studies have displayed the importance of intraoperative magnetic resonance imaging (iMRI) with 5-aminolevulinic acid (5-ALA) fluorescence-guidance in order to maximize EOR.

OBJECTIVE: To compare iMRI and 5-ALA fluorescence-guidance and the impact on patient survival.

METHODS: Thirty-two patients with contrast-enhancing gliomas undergoing intended gross total resection (GTR) were included in a prospective study. Surgeries were started under white-light conditions. When GTR was thought to be achieved, an iMRI scan was performed and a blue light turned on to search for unintentionally remaining tumor tissue. iMRI findings were compared with intraoperative fluorescence findings. Histological examination of tumor bulk and any additionally resected tissue was performed. All patients underwent early postoperative high-field MRI to determine EOR.

RESULTS: In 13 patients (40.6%), iMRI and fluorescence unequivocally did not show residual tumor intraoperatively. In 19 patients (59.4%), resection was continued due to iMRI or fluorescence findings. In 9 of these (47.4%), iMRI and fluorescence findings were inconsistent regarding residual tumor. GTR according to postoperative MRI was achieved in all but 1 patient. Histological examination ruled out false positive findings in all additionally resected specimens. Sensitivity and specificity to detect residual tumor tissue were 75% and 100%, respectively, for iMRI and 70% and 100% for 5-ALA fluorescence.

CONCLUSION: Use of iMRI as well as fluorescence-guidance are appropriate methods to improve the extent of resection in surgery of contrast-enhancing gliomas. Best results can be achieved by complementary use of both modalities.

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Intraoperative high-field MRI for transsphenoidal reoperations of nonfunctioning pituitary adenoma

Intraoperative high-field MRI for transsphenoidal reoperations of nonfunctioning pituitary adenoma

J Neurosurg 121:1166–1175, 2014

The loss of anatomical landmarks, frequently invasive tumor growth, and tissue changes make transsphenoidal reoperation of nonfunctioning pituitary adenomas (NFAs) challenging. The use of intraoperative MRI (iMRI) may lead to improved results. The goal of this retrospective study was to evaluate the impact of iMRI on transsphenoidal reoperations for NFA.

Methods. Between September 2002 and July 2012, 109 patients underwent reoperations in which 111 transsphenoidal procedures were performed and are represented in this study. A 1.5-T Magnetom Sonata Maestro Class scanner (Siemens) was used for iMRI. Follow-up iMRI scans were acquired if gross-total resection (GTR) was suspected or if no further removal seemed possible.

Results. Surgery was performed for tumor persistence and regrowth in 26 (23%) and 85 (77%) patients, respectively. On the initial iMRI scans, GTR was confirmed in 19 (17%) patients. Remnants were located as follows: 65 in the cavernous sinus (71%), 35 in the suprasellar space (38%), 9 in the retrosellar space (10%). Additional resection was possible in 62 (67%) patients, resulting in a significant volume reduction and increased GTR rate (49%). The GTR rates of invasive tumors on initial iMRI and postoperative MRI (poMRI) were 7% and 25%, respectively. Additional remnant resection was possible in 64% of the patients. Noninvasive tumors were shown to be totally resected on the initial iMRI in 31% of cases. After additional resection for 69% of the procedures, the GTR rate on poMRI was 75%. Transcranial surgery to resect tumor remnants was indicated in 5 (5%), and radiotherapy was performed in 29 (27%) patients. After GTR, no recurrence was detected during a mean follow-up of 2.2 ± 2.1 years.

Conclusions. The use of iMRI in transsphenoidal reoperations for NFA leads to significantly higher GTR rates. It thus prevents additional operations and reduces the number of tumor remnants. The complication rates do not exceed the incidences reported in the literature for primary transsphenoidal surgery. If complete tumor resection is not possible, iMRI guidance can facilitate tumor volume reduction.

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Increased Frameless Stereotactic Accuracy With High-Field Intraoperative Magnetic Resonance Imaging

Captura de pantalla 2012-12-23 a la(s) 11.07.11 

Neurosurgery 71[ONS Suppl 2]:ons321–ons328, 2012

Frameless stereotaxy commonly registers preoperative magnetic resonance imaging (MRI) to patients by using surface scalp anatomy or adhesive fiducial scalp markers. Patients’ scalps may shift slightly between preoperative imaging and final surgical positioning with pinion placement, introducing error. This might be reduced when frameless stereotaxy is performed in a high-field intraoperative MRI (iMRI), as patients are positioned before imaging. This could potentially improve accuracy.

OBJECTIVE: To compare frameless stereotactic accuracy using a high-field iMRI with that using standard preoperative MRI.

METHODS: Data were obtained in 32 adult patients undergoing frameless stereotacticguided brain tumor surgery. Stereotactic images were obtained with 1.5T MRI scanner either preoperatively (14 patients) or intraoperative (18 patients). System-generated accuracy measurements and distances from the actual center of each fiducial marker to that represented by neuronavigation were recorded. Finally, accuracy at multiple deep targets was assessed by using a life-sized human head stereotactic phantom in which fiducials were placed on deformable foam to mimic scalp.

RESULTS: System-generated accuracy measurements were significantly better for the iMRI group (mean 6 SEM = 1.04 6 0.05 mm) than for the standard group (1.82 6 0.09 mm; P , .001). Measured distances from the actual center of scalp fiducial markers to that represented by neuronavigation were also significantly smaller for iMRI (1.72 6 0.10 mm) in comparison with the standard group (3.17 6 0.22 mm; P , .001). Deep accuracy in the phantom model was significantly better with iMRI (1.67 6 0.12 mm) than standard imaging (2.28 6 0.14 mm; P = .003).

CONCLUSION: Frameless stereotactic accuracy is increased by using high-field iMRI compared with standard preoperative imaging.

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Typical 3-D localization of tumor remnants of WHO grade II hemispheric gliomas—lessons learned from the use of intraoperative high-field MRI control

Acta Neurochir (2011) 153:479–487. DOI 10.1007/s00701-010-0911-3

Complete resection of grade II gliomas might prolong survival but is not always possible. The goal of the study was to evaluate the location of unexpected grade II gliomas remnants after assumed complete removal with intraoperative (iop) MRI and to assess the reason for their non-detection.

Methods Intraoperative MR images of 35 patients with hemispheric grade II gliomas, acquired after assumed complete removal of preoperatively segmented tumor/ tumor part, were studied for existence of unexpected tumor remnants. Remnants location was classified in relation to tumor cavity in axial and vertical planes. The relation of remnants to retractor position and to surgeons’ visual axis, and the role of neuronavigational accuracy and brain shift, was assessed.

Results Unexpected remnants were found in 16 patients (46%). In 29.2%, the reason was loss of neuronavigational accuracy. In 21%, remnants were in that part of the resection cavity, where the retractor had been placed initially. In 17%, they were deeply located and hidden by the retractor. In 13%, remnants were hidden by the overlapping brain; and in 21%, the reason was not obvious. In 75% of all temporomesial tumors, remnants were posterolateral to the resection cavity. Remnants detection with iopMRI and update of neuronavigational data allowed further removal in 14 of 16 cases. In two cases, remnant location precluded their removal.

Conclusions Distribution of tumor remnants of grade II gliomas tends to follow some patterns. Targeted attention to the areas of possible remnants could increase the radicality of surgery, even if intraoperative imaging is not performed.

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A Moveable 3-Tesla Intraoperative Magnetic Resonance Imaging System

Neurosurgery 68[ONS Suppl 1]:ons168–ons179, 2011 DOI: 10.1227/NEU.0b013e3182045803

Based on success with a prototype 1.5T intraoperative magnetic resonance imaging (iMRI) system and the desire for increased signal-to-noise ratio, along with its relationship to image quality and advanced applications, a 3.0T system that uses the same novel moveable magnet configuration was developed.

OBJECTIVE: To assess clinical applicability by prospectively applying the higher-field system to a neurosurgical cohort.

METHODS: Upgrading to 3.0T required substantial modification of an existing iMRIequipped operating room. The 1.5T magnet was replaced with a ceiling-mounted, moveable 3.0T magnet with a 70-cm working aperture. Local radiofrequency shielding was replaced with whole-room shielding. A new hydraulic operating table, highperformance gradients, and advanced image processing software were also installed. The new system was used as an adjunct to standard neurosurgical practice.

RESULTS: The iMRI system upgrade required 6 months. Since completion, the 3.0T iMRI system has successfully guided neurosurgery in 120 patients without system failure in a patient-focused environment. Intraoperative image quality was superior to that obtained at 1.5T and enabled intraoperative acquisition of advanced imaging sequences, including tractography. Intraoperative imaging was found to modify surgery in a substantial number of patients.

CONCLUSION: Implementation of an iMRI system based on a moveable 3.0T magnet is feasible. From clinical experience with 120 patients, iMRI at 3.0T is safe, reliable, and capable of directing image-guided surgery with exceptional image quality.

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Intraoperative X-Ray Detection and MRI-Based Quantification of Brain Shift Effects Subsequent to Implantation of the First Electrode in Bilateral Implantation of Deep Brain Stimulation Electrodes

Stereotact Funct Neurosurg 2009;87:322-329 (DOI:10.1159/000235804)

After implantation of the first electrode in bilateral deep brain stimulation (DBS) lead implantation, brain shift effects in the target region and along the implantation trajectory of the second electrode are quantified with intraoperative magnetic resonance imaging (MRI). We investigated intraoperative X-ray imaging for its feasibility in indirect detection of brain shift.

Methods: In 25 patients who underwent bilateral DBS lead implantation, X-ray and MRI were performed before and after implantation of the first electrode. Two parameters of brain shift were assessed with nonrigid free-form deformation field analysis of the MRI data: global brain shift along the anterior and posterior commissure (AC-PC) line and specific brain shift along the implantation trajectory of the second electrode. Pre- and intraoperative X-ray images were geometrically and intensity corrected for detection of significant signal changes through intracranial air accumulation during implantation of the first electrode.

Results: After implantation of the first electrode, brain shift greater than 1 mm (maximum 1.3 mm) was observed at the AC and brain shift greater than 2 mm (maximum 2.5 mm) was observed along the planned implantation trajectory of the second electrode. In 1 patient, the implantation trajectory of the second electrode went through a sulcus after cortical brain shift. In 9 patients, intracranial air volume between 0.1 and 38.5 ml was observed with MRI after implantation of the first electrode. Significant X-ray absorption changes were induced by an intracranial air volume of greater than 8 ml.

Conclusion: In bilateral DBS implantation, brain shift effects can cause misallocation of the second electrode with the risk of adverse or no stimulation effects as well as unnecessary cortical damage. A lack of X-ray signal changes caused by intracranial air invasion during DBS lead implantation indicates a lack of clinically relevant brain shift.

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