Low field intraoperative MRI-guided surgery of gliomas: A single center experience

Intraoperative computed tomography, navigated ultrasound, 5-amino-levulinic acid fluorescence and neuromonitoring in brain tumor surgery: overtreatment or useful tool combination?

BACKGROUND

Brain tumor surgery is routinely supported by several intraoperative techniques, such as fluorescence, brain mapping and neuronavigation, which are often used independently. Efficacy of navigation is limited by the brain-shift phenomenon, particularly in cases of large or deep-sited lesions. Intraoperative imaging was introduced also to update neuronavigation data, to try and solve the brain-shift phenomenon-related pitfalls and increase overall safety. Nevertheless, each intraoperative imaging modality has some intrinsic limitations and technical shortcomings, making its clinical use challenging. We used a multimodal intraoperative imaging protocol to update neuronavigation, based on the combination of intraoperative Ultrasound (i-US) and intraoperative Computed Tomography (i-CT) integrated with 5-ALA fluorescence and neuromonitoring-guided resection.

METHODS

This is a pilot study on 52 patients (29 men), including four children, with a mean age of 57.67 years, suffering from brain low- (N.=10) or high-grade (N.=34) glioma or metastasis (N.=8), prospectively and consecutively enrolled. They underwent 5-ALA fluorescence-guided microsurgical tumor resection and neuromonitoring was used in cases of lesions located in eloquent areas, according to preoperative clinical and neuroradiological features. Navigated B-mode ultrasound acquisition was carried out after dural opening to identify the lesion. After tumor resection, i-US was used to identify residual tumor. Following further tumor resection or in cases of unclear US images, post-contrast i-CT was performed to detect and localize small tumor remnants and to allow further correction for brain shift. A final i-US check was performed to verify the completeness of resection. Clinical evaluation was based on comparison of pre- and postoperative Karnofsky Performance Score (KPS) and assessment of overall survival (OS) and progression-free survival (PFS). Extent of tumor resection (EOTR) was evaluated by volumetric postoperative Magnetic Resonance performed within 48 h after surgery.

RESULTS

Forty-one of the 52 (78.8%) patients were alive and still under follow-up in December 2017. 5-ALA was strongly or vaguely positive in 45 cases (86.5%). Seven lesions (four low-grade glioma, one high-grade glioma, and two metastases) were not fluorescent. i-US visualized residual tumor after resection of all fluorescent or pathological tissue in 22 cases (42.3%). After i-US guided resection, i-CT documented the presence of further residual tumor in 11 cases (21.1%). Mean EOTR was 98.79% in the low-grade gliomas group, 99.84% in the high-grade gliomas group and 100% in the metastases group. KPS changed from 77.88, preoperatively, to 72.5, postoperatively. At the last follow-up, mean KPS was 84.23.

CONCLUSIONS

The combination of different intraoperative imaging modalities may increase brain tumor safety and extent of resection. In particular, i-US seems to be highly sensitive to detect residual tumors, but it may generate false positives due to artifacts. Conversely, i-CT is more specific to localize remnants, allowing a more reliable updating of navigation data.

Intraoperative use of low-field magnetic resonance imaging for brain tumors: A systematic review

Background

Low-field magnetic resonance imaging (LF-MRI) has become a valuable tool in the diagnosis of brain tumors due to its high spatial resolution and ability to acquire images in a short amount of time. However, the use of LF-MRI for intraoperative imaging during brain tumor surgeries has not been extensively studied. The aim of this systematic review is to investigate the impact of low-field intraoperative magnetic resonance imaging (LF-IMRI) on the duration of brain tumor surgery and the extent of tumor resection.

Methods

A comprehensive literature search was conducted using PubMed, Scopus, and Google Scholar from February 2000 to December 2022. The studies were selected based on the inclusion criteria and reviewed independently by two reviewers. The gathered information was organized and analyzed using Excel.

Results

Our review of 21 articles found that low-field intraoperative MRI (LF-IMRI) with a field below 0.3T was used in most of the studies, specifically 15 studies used 0.15T LF-IMRI. The T1-weighted sequence was the most frequently reported, and the average scanning time was 24.26 min. The majority of the studies reported a positive impact of LF-IMRI on the extent of tumor resection, with an increase ranging from 11% to 52.5%. Notably, there were no studies describing the use of ultra-low-field (ULF) intraoperative MRI.

Conclusion

The results of this systematic review will aid neurosurgeons and neuroradiologists in making informed decisions about the use of LF-MRI in brain tumor surgeries. Further, research is needed to fully understand the impact of LF-MRI in brain tumor surgeries and to optimize its use in the clinical setting. There is an opportunity to study the utility of ULF-MRI in brain tumor surgeries.

Ultra-High-Field MRI in the Diagnosis and Management of Gliomas: A Systematic Review

Importance:

Gliomas, tumors of the central nervous system, are classically diagnosed through invasive surgical biopsy and subsequent histopathological study. Innovations in ultra-high field (UHF) imaging, namely 7-Tesla magnetic resonance imaging (7T MRI) are advancing preoperative tumor grading, visualization of intratumoral structures, and appreciation of small brain structures and lesions.

Objective

Summarize current innovative uses of UHF imaging techniques in glioma diagnostics and treatment.

Methods

A systematic review in accordance with PRISMA guidelines was performed utilizing PubMed. Case reports and series, observational clinical trials, and randomized clinical trials written in English were included. After removing unrelated studies and those with non-human subjects, only those related to 7T MRI were independently reviewed and summarized for data extraction. Some preclinical animal models are briefly described to demonstrate future usages of ultra-high-field imaging.

Results

We reviewed 46 studies (43 human and 3 animal models) which reported clinical usages of UHF MRI in the diagnosis and management of gliomas. Current literature generally supports greater resolution imaging from 7T compared to 1.5T or 3T MRI, improving visualization of cerebral microbleeds and white and gray matter, and providing more precise localization for radiotherapy targeting. Additionally, studies found that diffusion or susceptibility-weighted imaging techniques applied to 7T MRI, may be used to predict tumor grade, reveal intratumoral structures such as neovasculature and microstructures like axons, and indicate isocitrate dehydrogenase 1 mutation status in preoperative imaging. Similarly, newer imaging techniques such as magnetic resonance spectroscopy and chemical exchange saturation transfer imaging can be performed on 7T MRI to predict tumor grading and treatment efficacy. Geometrical distortion, a known challenge of 7T MRI, was at a tolerable level in all included studies.

Conclusion

UHF imaging has the potential to preoperatively and non-invasively grade gliomas, provide precise therapy target areas, and visualize lesions not seen on conventional MRI.

Use of intraoperative MRI for resection of intracranial tumors: A nationwide analysis of short-term outcomes

OBJECTIVE

Recent evidence supports the use of intraoperative MRI (iMRI) during resection of intracranial tumors due to its demonstrated efficacy and clinical benefit. Though many single-center investigations have been conducted, larger nationwide outcomes have yet to be characterized.

METHODS

We used the American College of Surgeons National Surgical Quality Improvement Program database to examine baseline characteristics and 30-day postoperative outcomes among patients undergoing craniotomy for tumor resection with and without iMRI. Comparisons between outcomes were accomplished after propensity matching using chi-square tests for categorical variables and Welch two-sample t-tests for continuous variables.

RESULTS

A total of 38,003 patients met inclusion criteria. Of this population, 54 (0.1%) received iMRI, while 37,949 (99.9%) did not receive iMRI. After propensity score matching, the resulting groups consisted of an iMRI group (n = 54) and a matched non-iMRI group (n = 54). Procedures involving iMRI were associated with significantly increased operation length compared to those without (p < 0.01). Length of hospital stay was higher in patients without iMRI, with this difference trending towards significance (p = 0.05) in the unmatched comparison. Patients undergoing craniotomy without iMRI had a higher rate of readmission (p = 0.04). There was no significant difference in occurrence of other adverse events between the two patient groups.

CONCLUSION

Despite increasing operative length, iMRI is not associated with higher infection rate and may have a clinical benefit associated with reducing readmissions and a trend towards reducing inpatient length of stay. Additional nationwide analyses including more iMRI patients would provide further insight into the strength of these findings.

Intraoperative MRI for Brain Tumors

INTRODUCTION

The use of intraoperative imaging has been a critical tool in the neurosurgeon's armamentarium and is of particular benefit during tumor surgery. This article summarizes the history of its development, implementation, clinical experience and future directions.

METHODS

We reviewed the literature focusing on the development and clinical experience with intraoperative MRI. Utilizing the authors' personal experience as well as evidence from the literature, we present an overview of the utility of MRI during neurosurgery.

RESULTS

In the 1990s, the first description of using a low field MRI in the operating room was published describing the additional benefit provided by improved resolution of MRI as compared to ultrasound. Since then, implementation has varied in magnetic field strength and in configuration from floor mounted to ceiling mounted units as well as those that are accessible to the operating room for use during surgery and via an outpatient entrance to use for diagnostic imaging. The experience shows utility of this technique for increasing extent of resection for low and high grade tumors as well as preventing injury to important structures while incorporating techniques such as intraoperative monitoring.

CONCLUSION

This article reviews the history of intraoperative MRI and presents a review of the literature revealing the successful implementation of this technology and benefits noted for the patient and the surgeon.

Using Histopathology to Assess the Reliability of Intraoperative Magnetic Resonance Imaging in Guiding Additional Brain Tumor Resection: A Multicenter Study

BACKGROUND

Intraoperative magnetic resonance imaging (iMRI) is a powerful tool for guiding brain tumor resections, provided that it accurately discerns residual tumor.

OBJECTIVE

To use histopathology to assess how reliably iMRI may discern additional tumor for a variety of tumor types, independent of the indications for iMRI.

METHODS

A multicenter database was used to calculate the odds of additional resection during the same surgical session for grade I to IV gliomas and pituitary adenomas. The reliability of iMRI for identifying residual tumor was assessed using histopathology of tissue resected after iMRI.

RESULTS

Gliomas (904/1517 cases, 59.6%) were more likely than pituitary adenomas (176/515, 34.2%) to receive additional resection after iMRI (P < .001), but these tumors were equally likely to have additional tissue sent for histopathology (398/904, 44.4% vs 66/176, 37.5%; P = .11). Tissue samples were available for resections after iMRI for 464 cases, with 415 (89.4%) positive for tumor. Additional resections after iMRI for gliomas (361/398, 90.7%) were more likely to yield additional tumor compared to pituitary adenomas (54/66, 81.8%) (P = .03). There were no significant differences in resection after iMRI yielding histopathologically positive tumor between grade I (58/65 cases, 89.2%; referent), grade II (82/92, 89.1%) (P = .98), grade III (72/81, 88.9%) (P = .95), or grade IV gliomas (149/160, 93.1%) (P = .33). Additional resection for previously resected tumors (122/135 cases, 90.4%) was equally likely to yield histopathologically confirmed tumor compared to newly-diagnosed tumors (293/329, 89.0%) (P = .83).

CONCLUSION

Histopathological analysis of tissue resected after use of iMRI for grade I to IV gliomas and pituitary adenomas demonstrates that iMRI is highly reliable for identifying residual tumor.

Role of Resection in Glioblastoma Management

Whenever possible, maximal safe resection is the first intervention for management of glioblastoma. Resection offers tissue for diagnosis, decompression of the brain, cytoreduction, and has been associated with prolonged survival in numerous retrospective studies. In this review, we provide a critical overview of the literature associating glioblastoma resection with survival. We discuss techniques that enhance extent of resection, and the role of clinical and surgeon-variables. At last, we analyze the covariates and confounders that might influence the relationship between extent of resection and survival for glioblastoma, as these might ultimately also influence outcomes and other therapeutic interventions tested in trials.

Image-Guided Brain Surgery

In neurosurgery, the extent of resection plays a critical role, especially in the management of malignant gliomas. These tumors are characterized through a diffuse infiltration into the surrounding brain parenchyma. Delineation between tumor and normal brain parenchyma can therefore often be challenging. During the recent years, several techniques, aiming at better intraoperative tumor visualization, have been developed and implemented in the field of brain tumor surgery. In this chapter, we discuss current strategies for intraoperative imaging in brain tumor surgery, comprising conventional techniques such as neuronavigation, techniques using fluorescence-guided surgery, and further highly precise developments such as targeted fluorescence spectroscopy or Raman spectroscopy.

Surface-Registration Frameless Stereotactic Navigation Is Less Accurate During Prone Surgeries: Intraoperative Near-Infrared Visualization Using Second Window Indocyanine Green Offers an Adjunct

BACKGROUND

Frameless neuronavigation allows neurosurgeons to visualize and relate the position of surgical instruments to intracranial pathologies based on preoperative tomographic imaging. However, neuronavigation can often be inaccurate. Multiple factors have been proposed as potential causes, and new technologies are needed to overcome these challenges.

OBJECTIVE

To evaluate the accuracy of neuronavigation systems compared to near-infrared (NIR) fluorescence imaging using Second Window Indocyanine Green, a novel technique, and to determine factors that lead to neuronavigation errors.

METHODS

A retrospective analysis was conducted on 56 patients who underwent primary resections of intracranial tumors. Patients received 5 mg/kg ICG approximately 24 h preoperatively. Intraoperatively, neuronavigation was used to plan craniotomies to place the tumors in the center. After craniotomy, NIR imaging visualized tumor-specific NIR signals. The accuracy of neuronavigation and NIR fluorescence imaging for delineating the tumor boundary prior to durotomy was compared.

RESULTS

The neuronavigation centers and NIR centers were 23.0 ± 7.7 % and 2.6 ± 1.1 % deviated from the tumor centers, respectively, relative to the craniotomy sizes. In 12 cases, significant changes were made to the planned durotomy based on NIR imaging. Patient position was a significant predictor of neuronavigation inaccuracy on both univariate and multivariate analysis, with the prone position having significantly higher inaccuracy (29.2 ± 8.1 %) compared to the supine (16.2 ± 8.1 %, p value < 0.001) or the lateral (17.9 ± 5.1 %, p value = 0.003) positions.

CONCLUSION

Patient position significantly affects neuronavigation accuracy. Intraoperative NIR fluorescence imaging before durotomy offers an opportunity to readjust the neuronavigation image space to better align with the patient space.

Impact of intraoperative MRI-guided resection on resection and survival in patient with gliomas: a meta-analysis

OBJECTIVE

This study addressed the benefit of intraoperative magnetic resonance imaging (iMRI) compared with conventional neuronavigation-guided resection in patients with gliomas.

RESEARCH DESIGN AND METHODS

The Medline, PubMed, Cochrane, and Google Scholar databases were searched up to 26 September 2015. Randomized controlled trials (RCTs), two-arm prospective studies, and retrospective studies in patients with glioblastoma/glioma who had received surgical treatment were included.

MAIN OUTCOME MEASURES

The primary outcome measures were the extent of tumor resection and tumor size reduction for using iMRI-guided or conventional neuronavigation-guided neurosurgery. Secondary outcomes included impact of surgery on 6 month progression-free survival (PFS), 12 month overall survival (OS) rates and surgical duration.

RESULTS

We found that iMRI was associated with greater rate of gross total resection (rGTR) compared with conventional neuronavigation procedures (3.16, 95% confidence interval [CI] 2.07-4.83, P < .001). We found no difference between the two neuronavigation approaches in extent of resection (EOR), tumor size reduction, or time required for surgery (P values ≥.065). Intraoperative MRI was associated with a higher rate of progression-free survival (PFS) compared with conventional neuronavigation (odds ratio, 1.84; 95% CI 1.15-2.95; P = .012), but the rate of overall survival (OS) between groups was similar (P = .799). Limitations of the study included the fact that data from non-RCTs was used, the small study population, and heterogeneity of outcomes across studies.

CONCLUSIONS

Our findings indicate that iMRI more frequently resulted in more complete resections leading to improved PFS in patients with malignant gliomas.

"Low-field" intraoperative MRI: a new scenario, a new adaptation

AIM

To describe the adaptation of Cruces University Hospital to the use of intraoperative magnetic resonance imaging (ioMRI), and how the acquisition and use of this technology would impact the day-to-day running of the neurosurgical suite.

MATERIALS AND METHODS

With the approval of the ethics committee, an observational, prospective study was performed from June 2012 to April 2014, which included 109 neurosurgical procedures with the assistance of ioMRI. These were performed using the Polestar N-30 system (PSN30; Medtronic Navigation, Louisville, CO), which was integrated into the operating room.

RESULTS

A total of 159 procedures were included: 109 cranial surgeries assisted with ioMRI and 50 control cases (no ioMRI use). There were no statistical significant differences when anaesthetic time (p=0.587) and surgical time (p=0.792) were compared; however, an important difference was shown in duration of patient positioning (p<0.0009) and total duration of the procedure (p<0.0009) between both groups.

CONCLUSIONS

The introduction of ioMRI is necessary for most neurosurgical suites; however, a few things need to be taken into consideration when adapting to it. Increase procedure time, the use of specific MRI-safe devices, as well as a checklist for each patient to minimise risks, should be taken into consideration.

Analysis of Treatment Tolerance and Factors Associated with Overall Survival in Elderly Patients with Glioblastoma

BACKGROUND

As the population ages, the proportion of elderly patients with glioblastomas has increased. Recently, many researchers have focused on the treatments available to and prognoses in elderly patients with glioblastomas.

METHODS

We conducted a retrospective study of glioblastoma patients aged 60 years old or older who were treated at the Neurosurgery Center at Beijing Tiantan Hospital from 2012 to 2014. Their clinical features, immunohistochemical characteristics, treatments, and outcomes were evaluated to determine treatment tolerance and identify prognostic factors.

RESULTS

Among the 70 included patients, the median survival time was 15 months. In the univariate analysis, patients who underwent a gross total resection had longer overall survival times than patients who had a subtotal resection (P < 0.05), and patients who received postoperative adjuvant therapy had longer overall survival times than those with no postoperative adjuvant therapy (P < 0.05). The expression of the p53 protein significantly affected overall survival. Patients with low p53 protein expression had a median survival of 17 months, whereas those who had high p53 protein expression had a median survival of 11.50 months (P < 0.05). Undergoing a gross total resection, receiving postoperative adjuvant therapy and having low p53 protein expression were factors that independently contributed to longer overall survival times in multivariate analysis.

CONCLUSIONS

Maximal safe surgical resection followed by radiotherapy with concurrent and adjuvant temozolomide significantly prolonged overall survival times and was well tolerated in elderly patients with glioblastomas. In addition, low p53 protein expression was a significant favorable prognostic indicator in this population.

Combination of 5-ALA and iMRI in re-resection of recurrent glioblastoma

Background Tumour resection plays a role in the initial treatment but also in the setting of recurrent glioblastoma (rGBM). To achieve maximum resection, 5-aminolevulinic acid (5-ALA) and intraoperative MRI (iMRI) are used as surgical tools. Aiming at complete tumour re-resection, we started combining iMRI with 5-ALA to find out if this leads to better surgical results. Methods We performed tumour resections in seven patients with rGBM, combining 5-ALA (20 mg/kg bodyweight) with iMRI (0.15 T). Radiologically complete resections were intended in all seven patients. We assessed intraoperative fluorescence findings and compared these with intraoperative imaging. All patients had early postoperative MRI (3 T) to verify final iMRI scans and received adjuvant treatment according to interdisciplinary tumour board decision. Results Median patient age was 63 years. Median KPS score was 90, and median tumour volume was 8.2 cm(3). In six of seven patients (85%), 5-ALA induced fluorescence of tumour-tissue was detected intraoperatively. All tumours were good to visualise with iMRI and contrast media. One patient received additional resection of residual contrast enhancing tissue on intraoperative imaging, which did not show fluorescence. Radiologically complete resections according to early postoperative MRI were achieved in all patients. Median survival since second surgery was 7.6 months and overall survival since diagnosis was 27.8 months. Conclusions 5-ALA and iMRI are important surgical tools to maximise tumour resection also in rGBM. However, not all rGBMs exhibit fluorescence after 5-ALA administration. We propose the combined use of 5-ALA and iMRI in the surgery of rGBM.

Portable Intraoperative Computed Tomography Scan in Image-Guided Surgery for Brain High-grade Gliomas: Analysis of Technical Feasibility and Impact on Extent of Tumor Resection

BACKGROUND

Intraoperative magnetic resonance imaging is the gold standard among image-guided techniques for glioma surgery. Scant data are available on the role of intraoperative computed tomography (i-CT) in high-grade glioma (HGG) surgery.

OBJECTIVE

To verify the technical feasibility and usefulness of portable i-CT in image-guided surgical resection of HGGs.

METHODS

This is a retrospective series control analysis of prospectively collected data. Twenty-five patients (Group A) with HGGs underwent surgery using i-CT and 5-aminolevulinic acid (5-ALA) fluorescence. A second cohort of 25 patients (Group B) underwent 5-ALA fluorescence-guided surgery but without i-CT. We used a portable 8-slice CT scanner and, in both groups, neuronavigation. Extent of tumor resection (ETOR) and pre- and postoperative Karnofsky performance status (KPS) scores were measured; the impact of i-CT on overall survival (OS) and progression-free survival (PFS) was also analyzed.

RESULTS

In 8 patients (32%) in Group A, i-CT revealed residual tumor, and in 4 of them it helped to also resect pathological tissue detached from the main tumor. EOTR in these 8 patients was 97.3% (96%-98.6%). In Group B, residual tumor was found in 6 patients, whose tumor's mean resection was 98% (93.5-99.7). The Student t test did not show statistically significant differences in EOTR in the 2 groups. The KPS score decreased from 67 to 69 after surgery in Group A and from 74 to 77 in Group B (P = .07 according to the Student t test). Groups A and B did not show statistically significant differences in OS and PFS (P = .61 and .46, respectively, by the log-rank test).

CONCLUSION

No statistically significant differences in EOTR, KPS, PFS, and OS were observed in the 2 groups. However, i-CT helped to verify EOTR and to update the neuronavigator with real-time images, as well as to identify and resect pathological tissue in multifocal tumors. i-CT is a feasible and effective alternative to intraoperative magnetic resonance imaging. Portable i-CT can provide useful real-time information during brain surgery and can be easily introduced in neurosurgical theaters in daily practice.

Real-time ultrasound-guided endoscopic surgery for putaminal hemorrhage

OBJECT

Endoscopic surgery plays a significant role in the treatment of intracerebral hemorrhage. However, the residual hematoma cannot be measured intraoperatively from the endoscopic view, and it is difficult to determine the precise location of the endoscope within the hematoma cavity. The authors attempted to develop real-time ultrasound-guided endoscopic surgery using a bur-hole-type probe.

METHODS

From November 2012 to March 2014, patients with hypertensive putaminal hemorrhage who underwent endoscopic hematoma removal were enrolled in this study. Real-time ultrasound guidance was performed with a bur-hole-type probe that was advanced via a second bur hole, which was placed in the temporal region. Ultrasound was used to guide insertion of the endoscope sheath as well as to provide information regarding the location of the hematoma during surgical evacuation. Finally, the cavity was irrigated with artificial cerebrospinal fluid and was observed as a low-echoic space, which facilitated detection of residual hematoma.

RESULTS

Ten patients with putaminal hemorrhage>30 cm3 were included in this study. Their mean age (±SD) was 60.9±8.6 years, and the mean preoperative hematoma volume was 65.2±37.1 cm3. The mean percentage of hematoma that was evacuated was 96%±3%. None of the patients exhibited rebleeding after surgery.

CONCLUSIONS

This navigation method was effective in demonstrating both the real-time location of the endoscope and real-time viewing of the residual hematoma. Use of ultrasound guidance minimized the occurrence of brain injury due to hematoma evacuation.

Intraoperative Magnetic Resonance Imaging in Intracranial Glioma Resection: A Single-Center, Retrospective Blinded Volumetric Study

BACKGROUND

Intraoperative magnetic resonance imaging (IoMRI) was devised to overcome brain shifts during craniotomies. Yet, the acceptance of IoMRI is limited.

OBJECTIVE

To evaluate impact of IoMRI on intracranial glioma resection outcome including overall patient survival.

METHODS

A retrospective review of records was performed on a cohort of 164 consecutive patients who underwent resection surgery for newly diagnosed intracranial gliomas either with or without IoMRI technology performed by 2 neurosurgeons in our center. Patient follow-up was at least 5 years. Extent of resection (EOR) was calculated using pre- and postoperative contrast-enhanced and T2-weighted MR-images. Adjusted analysis was performed to compare gross total resection (GTR), EOR, permanent surgery-associated neurologic deficit, and overall survival between the 2 groups.

RESULTS

Overall median EOR was 92.1%, and 97.45% with IoMRI use and 89.9% without IoMRI, with crude (unadjusted) P < 0.005. GTR was achieved in 49.3% of IoMRI cases, versus in only 21.4% of no-IoMRI cases, P < 0.001. GTR achieved was more with the use of IoMRI among gliomas located in both eloquent and noneloquent brain areas, P = 0.017 and <0.001, respectively. Permanent surgery-associated neurologic deficit was not (statistically) more significant with no-IoMRI, P = 0.284 (13.8% vs. 6.7%). In addition, the IoMRI group had better 5-year overall survival, P < 0.001.

CONCLUSION

This study shows that the use of IoMRI was associated with greater rates of EOR and GTR, and better overall 5-year survival in both eloquent brain areas located and non-eloquent brain areas located gliomas, with no increased risk of neurologic complication.

Outcomes after combined use of intraoperative MRI and 5-aminolevulinic acid in high-grade glioma surgery

Background

Previous studies have shown the individual benefits of 5-aminolevulinic acid (5-ALA) and intraoperative (i)MRI in enhancing survival for patients with high-grade glioma. In this retrospective study, we compare rates of progression-free and overall survival between patients who underwent surgical resection with the combination of 5-ALA and iMRI and a control group without iMRI.

Methods

In 200 consecutive patients with high-grade gliomas, we recorded age, sex, World Health Organization tumor grade, and pre- and postoperative Karnofsky performance status (good ≥80 and poor <80). A 0.15-Tesla magnet was used for iMRI; all patients operated on with iMRI received 5-ALA. Overall and progression-free survival rates were compared using multivariable regression analysis.

Results

Median overall survival was 13.8 months in the non-iMRI group and 17.9 months in the iMRI group (P = .043). However, on identifying confounding variables (ie, KPS and resection status) in this univariate analysis, we then adjusted for these confounders in multivariate analysis and eliminated this distinction in overall survival (hazard ratio: 1.23, P = .34, 95% CI: 0.81, 1.86). Although 5-ALA enhanced the achievement of gross total resection (odds ratio: 3.19, P = .01, 95% CI: 1.28, 7.93), it offered no effect on overall or progression-free survival when adjusted for resection status.

Conclusions

Gross total resection is the key surgical variable that influences progression and survival in patients with high-grade glioma and more likely when surgical adjuncts, such as iMRI in combination with 5-ALA, are used to enhance resection.

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

BACKGROUND:

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.

Role of neurochemical navigation with 5-aminolevulinic acid during intraoperative MRI-guided resection of intracranial malignant gliomas

OBJECTIVE

To evaluate the role of the neurochemical navigation with 5-aminolevulinic acid (5-ALA) during intraoperative MRI (iMRI)-guided resection of the intracranial malignant gliomas.

METHODS

The analysis included 99 consecutive surgical cases. Resection of the bulk of the neoplasm was mainly guided by the updated neuronavigation based on the low-field-strength (0.3T) iMRI, whereas at the periphery of the lesion neurochemical navigation with 5-ALA was additionally used.

RESULTS

In total, 286 tissue specimens were obtained during surgeries for histopathological examination. According to iMRI 98 samples with strong (91 cases), weak (6 cases), or absent (1 case) fluorescence corresponded to the bulk of the lesion and all of those ones contained tumor. Out of 188 tissue specimens obtained from the "peritumoral brain," the neoplastic elements were identified in 89%, 81% and 29% of samples with, respectively, strong (107 cases), weak (47 cases) and absent (34 cases) fluorescence. Positive predictive values of the tissue fluorescence for presence of neoplasm within and outside of its boundaries on iMRI were 100% and 86%, respectively.

CONCLUSION

Neurochemical navigation with 5-ALA is useful adjunct during iMRI-guided resection of intracranial malignant gliomas, which allows identification of the tumor extension beyond its radiological borders.

The evolving role of neurological imaging in neuro-oncology

Neuroimaging has played a critical role in the management of patients with neurological disease, since the first ventriculogram was performed in 1918 by Walter Dandy (Mezger et al. Langenbecks Arch Surg 398(4):501-514, 2013). Over the last century, technology has evolved significantly, and within the last decade, the role of imaging in the management of patients with neuro-oncologic disease has shifted from a tool for gross identification of intracranial pathology, to an integral part of real-time neurological surgery. Current neurological imaging provides detailed information about anatomical structure, neurological function, and metabolic and metabolism-important characteristics that help clinicians and surgeons non-invasively manage patients with brain tumors. It is valuable to review the evolution of neurological imaging over the past several decades, focusing on its role in the management of patients with intracranial tumors. Novel neuro-imaging tools and developing technology with the potential to further transform clinical practice will be discussed, as will the key role neurological imaging plays in neurosurgical planning and intraoperative navigation. With increasingly complex imaging modalities creating growing amounts of raw data, validation of techniques, data analysis, and integrating various pieces of imaging data into individual patient management plans, remain significant challenges for clinicians. We thus suggest mechanisms that might ultimately allow for evidence based integration of imaging in the management of patients with neuro-oncologic disease.

Neurosurgical oncology: advances in operative technologies and adjuncts

Modern glioma surgery has evolved around the central tenet of safely maximizing resection. Recent surgical adjuncts have focused on increasing the maximum extent of resection while minimizing risk to functional brain. Technologies such as cortical and subcortical stimulation mapping, intraoperative magnetic resonance imaging, functional neuronavigation, navigable intraoperative ultrasound, neuroendoscopy, and fluorescence-guided resection have been developed to augment the identification of tumor while preserving brain anatomy and function. However, whether these technologies offer additional long-term benefits to glioma patients remains to be determined. Here we review advances over the past decade in operative technologies that have offered the most promising benefits for glioblastoma patients.

Surgical and clinical aspects of cerebellar pilomyxoid-spectrum astrocytomas in children

BACKGROUND

Cerebellar pilomyxoid astrocytomas (PMAs) and intermediate pilomyxoid astrocytomas (IPAs) are collectively called "pilomyxoid-spectrum astrocytomas (PMSAs)." Cerebellar PMSAs are thought to behave more aggressively than pilocytic astrocytomas (PAs). Our objective is to compare PMSAs to PAs in terms of surgical and clinical profiles.

METHODS

This retrospective study included 66 cases (35 males and 31 females) with cerebellar astrocytomas treated between July 2007 and December 2012 at Children's Cancer Hospital Egypt (CCHE 57357) with a mean age of 7 (±1.5) years. Cases were divided into three subgroups as follows: 44 PAs, 10 IPAs, and 12 PMAs. Comparison between all groups was focusing on brain stem invasion, intrinsic necrotic cavitation, extent of resection, recurrence, leptomeningeal dissemination (LD), metastases, need for CSF diversion, and cerebellar mutism (CM).

RESULTS

Cerebellar PMAs and IPAs separately and collectively had higher incidence of brain stem invasion, intrinsic necrotic cavitation, tumor recurrence, and LD when compared to PAs (P < 0.001). Gross total resection was 13.6 % in PMSAs versus 90.9 % in PAs (P < 0.001). PMAs had a higher incidence of tumor recurrence than IPAs (66.7 versus 20 %, P < 0.001). Incidence of recurrence in PAs was 9.1 % in partially resected cases. Mean interval to recurrence was 9 (±1.5) months in PMSAs and 42 (±2) months in PAs.

CONCLUSIONS

Cerebellar PMSAs express an aggressive clinical behavior and impose more operative challenges than PAs. These tumors may represent a clinical spectrum-at its benign end lies PA, while PMA lies at the aggressive end, with IPA lying just behind. Such concepts could be used to guide management in the future.

Role of surgical resection in low- and high-grade gliomas

OPINION STATEMENT

Central nervous system tumors are a major cause of morbidity and mortality in the United States. Outside of brain metastasis, low- and high-grade gliomas are the most common intrinsic brain tumors. Low-grade gliomas have a 5- and 10-year survival rate of 97 % and 91 %, respectively, when extent of resection is greater than 90 %. High-grade gliomas are extremely aggressive with the vast majority of patients experiencing recurrence and a median survival of 1 to 3 years. Survival of patients with both low- and high-grade gliomas is enhanced with maximal tumor resection. The pursuit of more aggressive extent of resection must be balanced with preservation of functional pathways. Several innovations in neurosurgical oncology have expanded our understanding of individualized patient neuroanatomy, physiology, and function. Emerging imaging technologies as well as intraoperative techniques have expanded our ability to resect maximal amounts of tumor while preserving essential function. Stimulation mapping of language and motor pathways is well-established for the safe resection of intrinsic brain lesions. Additional techniques including neuro-navigation, fluorescence-guided microsurgery using 5-aminolevulinic acid, intraoperative magnetic resonance imaging, and high-frequency ultrasonography can all be used to improve extent of resection in glioma patients.

Benefit of tumor resection for recurrent glioblastoma

In the treatment of glioblastoma (GBM) the impact of radical tumor resection as first line therapy is beyond controversy. The significance of a second resection in case of tumor-recurrence remains unclear and is an issue of debate. Since GBMs always recur, it is important to determine whether or not patients will benefit from repeat surgery. We performed a retrospective analysis of our prospectively collected database and evaluated all re-resected patients with primary GBM who underwent second surgery during a 3 years period. All patients underwent early postoperative magnetic resonance imaging. We determined survival after re-resection with regard to possible prognostic factors using Kaplan-Meier estimates and Cox regression analyses. Forty patients were included in this study. Median age was 58 years and median KPS score was 80. Average tumor volume was 5.5 cm(3). A radiologically confirmed complete resection was achieved in 29 patients (72.5 %). Median follow-up was 18.8 months, and median survival after re-resection was 13.5 months. Only complete removal of contrast enhancing tumor was significantly correlated with survival after re-resection according to multivariate analysis. There was a statistical trend for KPS score influencing survival. In contrast, time between first diagnosis and tumor-recurrence, tumor volume at recurrence, MGMT status and MSM score were not significantly correlated with survival after second surgery. In the event of tumor recurrence, patients in good clinical condition with recurrent GBM amenable to complete resection should thus not be withheld second surgery as a treatment option.

Using intraoperative dynamic contrast-enhanced T1-weighted MRI to identify residual tumor in glioblastoma surgery

OBJECT

The goal of surgery in high-grade gliomas is to maximize the resection of contrast-enhancing tumor without causing additional neurological deficits. Intraoperative MRI improves surgical results. However, when using contrast material intraoperatively, it may be difficult to differentiate between surgically induced enhancement and residual tumor. The purpose of this study was to assess the usefulness of intraoperative dynamic contrast-enhanced T1-weighted MRI to guide this differential diagnosis and test it against tissue histopathology.

METHODS

Preoperative and intraoperative dynamic contrast-enhanced MRI was performed in 21 patients with histopathologically confirmed WHO Grade IV gliomas using intraoperative 3-T MRI. Standardized regions of interest (ROIs) were placed manually at 2 separate contrast-enhancing areas at the resection border for each patient. Time-intensity curves (TICs) were generated for each ROI. All ROIs were biopsied and the TIC types were compared with histopathological results. Pharmacokinetic modeling was performed in the last 10 patients to confirm nonparametric TIC analysis findings.

RESULTS

Of the 42 manually selected ROIs in 21 patients, 25 (59.5%) contained solid tumor tissue and 17 (40.5%) retained the brain parenchymal architecture but contained infiltrating tumor cells. Time-intensity curves generated from residual contrast-enhancing tumor and their preoperative counterparts were comparable and showed a quick and persistently increasing slope ("climbing type"). All 17 TICs obtained from regions that did not contain solid tumor tissue were undulating and low in amplitude, compared with those obtained from residual tumors ("low-amplitude type"). Pharmacokinetic findings using the transfer constant, extravascular extracellular volume fraction, rate constant, and initial area under the curve parameters were significantly different for the tumor mass, nontumoral regions, and surgically induced contrast-enhancing areas.

CONCLUSIONS

Intraoperative dynamic contrast-enhanced MRI provides quick, reproducible, high-quality, and simply interpreted dynamic MR images in the intraoperative setting and can aid in differentiating surgically induced enhancement from residual tumor.

The safety and effectiveness of low field intraoperative MRI guidance in frameless stereotactic biopsies of brain tumours-design and interim analysis of a prospective randomized trial

The aim of the study was to assess the safety and effectiveness of stereotactic brain tumour biopsy (STx biopsy) guided by low-field intraoperative magnetic resonance imaging (iMRI) in comparison with its frameless classic analogue based on a prospective randomized trial. A pilot group of 42 brain tumour patients was prospectively randomized into a low-field iMRI group and a control group that underwent a frameless STx biopsy. The primary endpoints of the analysis were postoperative complication rate and diagnostic yield, and the secondary endpoints were length of hospital stay and duration of operation. The iMRI group (21 patients) and the control group (21 patients) did not differ significantly according to demographic and epidemiological data. No major postoperative complications were noted in either group. In addition, no significant differences in the diagnostic yield (p = 1.00) and length of hospital stay (p = 0.16) were observed. The mean total OR time was 111 ± 24 min in iMRI and 78 ± 29 min in the control group (p = 0.0001). Usage of iMRI may prolong the time of the procedure but seems to be comparable in safety and effectiveness to the standard frameless STx biopsy.

The role of intraoperative magnetic resonance imaging in complex meningioma surgery

Intraoperative magnetic resonance imaging (iMRI) has gained importance in the treatment of gliomas and sellar tumors. In intracranial meningiomas, the extent of surgical tumor removal is one of the most important factors in the prevention of tumor recurrence and patient survival. Complex meningiomas located at the skull base or near eloquent brain regions show higher recurrence rates, morbidity and mortality. The aim of this study was to evaluate whether iMRI contributes to more extensive surgical resection in these tumors. Patients undergoing complex meningioma resection using iMRI from January 2007 to January 2011 were included in this study. The indication for iMRI-guided tumor resection included patients presenting with meningiomas located in the skull base or compressing eloquent brain areas in whom a radical resection was considered to be difficult. Intraoperative 0.15-T MRI scan (PoleStar; Medtronic Navigation, Louisville, CO, USA) was performed before and after maximal possible resection using standard microsurgical and neuronavigation techniques. All patients underwent fluorescence-guided resection. The following data were analyzed: tumor localization, histological grade, Simpson resection grade, duration of the procedure, iMRI scan time, iMRI findings, resection extent based on postresection iMRI, hospitalization time, surgical complications and outcome, and MRI follow-up 2-27months postoperation. Twenty-seven consecutive patients undergoing complex meningioma resection using iMRI were included. In this series, only one patient (3.4%) underwent resection of tumor remnant after iMRI, although without improvement of the Simpson resection grade. Temporary neurologic deficits were found in 8 patients (27.6%) postoperatively, whereas 11 patients (37.9%) had permanent postoperative neurologic deficits. In one case (3.4%), fatal postoperative bleeding occurred which was not detected by iMRI. Our results show that iMRI has no influence on intraoperative strategy in terms of resection grade or detection of early postoperative complications. The benefits of iMRI in complex meningioma surgery are therefore doubtful; however, it may still prove to be effective in certain subsets of complex meningiomas.

Intraoperative magnetic resonance spectroscopy for identification of residual tumor during low-grade glioma surgery: clinical article

OBJECT

The authors had previously shown that 3-T intraoperative MRI (ioMRI) detects residual tumor tissue during low-grade glioma and that it helps to increase the extent of resection. In a proportion of their cases, however, the ioMRI disclosed T2-hyperintense areas at the tumor resection border after the initial resection attempt and prompted a differential diagnosis between residual tumor and nontumoral changes. To guide this differential diagnosis the authors used intraoperative long-TE single-voxel proton MR spectroscopy (ioMRS) and tested the correlation of these findings with findings from pathological examination of resected tissue.

METHODS

Patients who were undergoing surgery for hemispheric or insular WHO Grade II gliomas and were found to have T2 changes around the resection cavity at the initial ioMRI were prospectively examined with ioMRS and biopsies were taken from corresponding localizations. In 14 consecutive patients, the ioMRS diagnosis in 20 voxels of interest was tested against the histopathological diagnosis. Intraoperative diffusion-weighted imaging (ioDWI) was also performed, as a part of the routine imaging, to rule out surgically induced changes, which could also appear as T2 hyperintensity.

RESULTS

Presence of tumor was documented in 14 (70%) of the 20 T2-hyperintense areas by histopathological examination. The sensitivity of ioMRS for identifying residual tumor was 85.7%, the specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 75%. The specificity of ioDWI for surgically induced changes was high (100%), but the sensitivity was only 60%.

CONCLUSIONS

This is the first clinical series to indicate that ioMRS can be used to differentiate residual tumor from nontumoral changes around the resection cavity, with high sensitivity and specificity.

[First intraoperative magnetic resonance imaging in a Spanish hospital of the public healthcare system: initial experience, feasibility and difficulties in our environment]

OBJECTIVE

Intraoperative MRI is considered the gold standard among all intraoperative imaging technologies currently available. Its main indication is in the intraoperative detection of residual disease during tumour resections. We present our initial experience with the first intraoperative low-field MRI in a Spanish hospital of the public healthcare system. We evaluate its usefulness and accuracy to detect residual tumours and compare its intraoperative results with images obtained postoperatively using conventional high-field devices.

MATERIAL AND METHODS

We retrospectively reviewed the first 21 patients operated on the aid of this technology. Maximal safe resection was the surgical goal in all cases. Surgeries were performed using conventional instrumentation and the required assistance in each case.

RESULTS

The mean number of intraoperative studies was 2.3 per procedure (range: 2 to 4). Intraoperative studies proved that the surgical goal had been achieved in 15 patients (71.4%), and detected residual tumour in 6 cases (28.5%). After comparing the last intraoperative image and the postoperative study, 2 cases (9.5%) were considered as "false negatives".

CONCLUSIONS

Intraoperative MRI is a safe, reliable and useful tool for guided resection of brain tumours. Low-field devices provide images of sufficient quality at a lower cost; therefore their universalisation seems feasible.

Intraoperative magnetic resonance-guided frameless stereotactic biopsies - initial clinical experience

BACKGROUND AND PURPOSE

We present our early experience in intraoperative magnetic resonance (iMRI)-guided stereotactic frameless biopsies with special regard to its safety, efficacy and diagnostic value.

MATERIAL AND METHODS

The records of patients who underwent frameless stereotactic iMRI-guided biopsies between June 2009 and April 2011 were analysed prospectively. All the operations were performed under local anaesthesia, with the use of a passive side-cutting biopsy needle. The needle was introduced into the pathological lesion with the help of optic neuronavigation system guidance. The iMRI scans served as reference images. We analysed the patients' demographic and epidemiological data, the preparation and surgery times, diagnostic values of collected specimens, lengths of the hospital stay (LOS) and the complication rate.

RESULTS

Fifteen iMRI-guided stereotactic biopsies were performed in the analysed period. The mean patient age was 52 ± 18 yrs, the median WHO score was 2 (range: 1-3), there were 9 (60%) males in the study group. The average preparation time was 53 ± 24 minutes and the operation time 69 ± 25 minutes. No major complications were noted. The median total length of hospital stay was 5 days. The histopathological diagnoses were as follows: glioblastoma multiforme - 6 cases, low-grade gliomas - 4 cases, lymphomas - 3 cases, and other pathologies - 2 cases. In all the cases biopsy material allowed specified histopathological diagnoses to be obtained.

CONCLUSIONS

Frameless stereotactic iMRI-guided brain tumour biopsy is a safe and diagnostically effective procedure. The use of iMRI might increase the diagnostic value and safety of stereotactic biopsy and positively influence its economic balance.

Intraoperative image guidance in neurosurgery: development, current indications, and future trends

Introduction. As minimally invasive surgery becomes the standard of care in neurosurgery, it is imperative that surgeons become skilled in the use of image-guided techniques. The development of image-guided neurosurgery represents a substantial improvement in the microsurgical treatment of tumors, vascular malformations, and other intracranial lesions. Objective. There have been numerous advances in neurosurgery which have aided the neurosurgeon to achieve accurate removal of pathological tissue with minimal disruption of surrounding healthy neuronal matter including the development of microsurgical, endoscopic, and endovascular techniques. Neuronavigation systems and intraoperative imaging should improve success in cranial neurosurgery. Additional functional imaging modalities such as PET, SPECT, DTI (for fiber tracking), and fMRI can now be used in order to reduce neurological deficits resulting from surgery; however the positive long-term effect remains questionable for many indications. Method. PubMed database search using the search term "image guided neurosurgery." More than 1400 articles were published during the last 25 years. The abstracts were scanned for prospective comparative trials. Results and Conclusion. 14 comparative trials are published. To date significant data amount show advantages in intraoperative accuracy influencing the perioperative morbidity and long-term outcome only for cerebral glioma surgery.

Optimizing the extent of resection in eloquently located gliomas by combining intraoperative MRI guidance with intraoperative neurophysiological monitoring

Several methods have been introduced to improve the extent of resection in glioma surgery. Yet, radical tumor resections must not be attempted at the cost of neurological deterioration. We sought to assess whether the use of an intraoperative MRI (iMRI) in combination with multimodal neurophysiological monitoring is suitable to increase the extent of resection without endangering neurological function in patients with eloquently located gliomas. Fifty-four patients were included in this study. In 21 patients (38.9 %), iMRI led to additional tumor resection. A radiologically complete resection was achieved in 31 patients (57.4 %), while in 12 of these, iMRI had depicted residual tumor tissue before resection was continued. The mean extent of resection was 92.1 % according to volumetric analyses. Postoperatively, 13 patients (24.1 %) showed new or worsening of pre-existing sensory motor deficits. They were severe in 4 patients (7.4 %). There was no correlation between the occurrence of either any new (P = 0.77) or severe (P = 1.0) sensory motor deficit and continued resection after intraoperative image acquisition. Likewise, tumor location, histology, and tumor recurrence did not influence complication rate on uni- and multivariate analysis. We conclude that the combination of iMRI guidance with multimodal neurophysiological monitoring allows for extended resections in glioma surgery without inducing higher rates of neurological deficits, even in patients with eloquently located tumors.

Anaesthesia for magnetic resonance imaging and positron emission tomography

PURPOSE OF REVIEW

This article reviews the important aspects of managing patients undergoing anaesthesia and monitoring for MRI and PET.

RECENT FINDINGS

The use of MRI and PET is expanding and an increasing number of specialized procedures are being undertaken on patients who require anaesthesia or critical care management. Magnetic resonance systems are using more powerful magnetic fields, whereas PET involves imaging patients following administration of radioactive isotopes. Patients who undergo such procedures require careful anaesthesia and monitoring within an isolated and unfamiliar environment, which poses a risk to staff and patients.

SUMMARY

The availability of high-field MRI and other complex imaging studies, like PET is increasing. This requires that anaesthesiologists and critical care physicians understand the principles, safety concerns and appropriate management of patients undergoing imaging within such environments.

Prospective study on the efficacy of low-field intraoperative magnetic resonance imaging in neurosurgical operations

BACKGROUND AND PURPOSE

The application of intraoperative magnetic resonance imaging (iMRI) is related to a series of challenges of both a technical and an organizational nature. We present our experience in the application of low-field iMRI in everyday neurosurgical practice.

MATERIAL AND METHODS

A group of 58 patients operated on using low-field iMRI was subject to prospective controlled observation. The significance of differences in the range of preparation time, duration and direct operation results between the iMRI group and controls was analysed. The influence of epidemiological and demographic factors and technical aspects related to iMRI application on direct outcome of the surgery was assessed.

RESULTS

Twenty-eight tumour resections using craniotomy, 17 transsphenoidal resections of pituitary adenomas and 13 stereotactic procedures were conducted in the group of 24 men and 34 women operated on using iMRI. The control group was not significantly different in terms of epidemiological and demographic factors. The preparation and operation times were significantly longer in the iMRI group (p < 0.001 and p = 0.002, respectively). Longer duration of the surgery was not related to an increased frequency of complications. A higher percentage of postoperative improvement in neurological status (31% vs. 14%, p = 0.045), lower complication percentage (10% vs. 28%, p = 0.03) and a similar time of hospitalization (13 ± 7 vs. 12 ± 4 days, p = 0.33) were noted in the iMRI group.

CONCLUSIONS

The application of low-field iMRI prolongs the duration of neurosurgical procedures but does not negatively influence their safety. It is associated with above-average functional results and a lower percentage of total complications.

Correlation of the extent of tumor volume resection and patient survival in surgery of glioblastoma multiforme with high-field intraoperative MRI guidance

Extent of resection (EOR) still remains controversial in therapy of glioblastoma multiforme (GBM). However, an increasing number of studies favor maximum EOR as being associated with longer patient survival. One hundred thirty-five GBM patients underwent tumor resection aided by 1.5T intraoperative MRI (iMRI) and integrated multimodal navigation. Tumor volume was quantified by manual segmentation. The influences of EOR, patient age, recurrent tumor, tumor localization, and gender on survival time were examined. Intraoperative MRI detected residual tumor volume in 88 patients. In 19 patients surgery was continued; further resection resulted in final gross total resection (GTR) for 9 patients (GTR increased from 47 [34.80%] to 56 [41.49%] patients). Tumor volumes were significantly reduced from 34.25 ± 23.68% (first iMRI) to 1.22 ± 16.24% (final iMRI). According to Kaplan-Meier estimates, median survival was 14 months (95% confidence interval [CI]: 11.7-16.2) for EOR ≥ 98% and 9 months (95% CI: 7.4-10.5) for EOR <98% (P< .0001); it was 9 months (95% CI: 7.3-10.7) for patients ≥ 65 years and 12 months (95% CI: 8.4-15.6) for patients <65 years (P < .05). Multivariate analysis showed a hazard ratio of 0.39 (95% CI: 0.24-0.63; P = .001) for EOR ≥ 98% and 0.61 (95% CI: 0.38-0.97; P < .05) for patient age <65 years. To our knowledge, this is the largest study including correlation of iMRI, tumor volumetry, and survival time. We demonstrate that navigation guidance and iMRI significantly contribute to optimal EOR with low postoperative morbidity, where EOR ≥ 98% and patient age <65 years are associated with significant survival advantages. Thus, maximum EOR should be the surgical goal in GBM surgery while preserving neurological function.

Intraoperative MRI guidance and extent of resection in glioma surgery: a randomised, controlled trial

BACKGROUND

Intraoperative MRI is increasingly used in neurosurgery, although there is little evidence for its use. We aimed to assess efficacy of intraoperative MRI guidance on extent of resection in patients with glioma.

METHODS

In our prospective, randomised, parallel-group trial, we enrolled adults (≥18 years) with contrast enhancing gliomas amenable to radiologically complete resection who presented to Goethe University (Frankfurt, Germany). We randomly assigned patients (1:1) with computer-generated blocks of four and a sealed-envelope design to undergo intraoperative MRI-guided surgery or conventional microsurgery (control group). Surgeons and patients were unmasked to treatment group allocation, but an independent neuroradiologist was masked during analysis of all preoperative and postoperative imaging data. The primary endpoint was rate of complete resections as established by early postoperative high-field MRI (1·5 T or 3·0 T). Analysis was done per protocol. This study is registered with ClinicalTrials.gov, number NCT01394692.

FINDINGS

We enrolled 58 patients between Oct 1, 2007, and July 1, 2010. 24 (83%) of 29 patients randomly allocated to the intraoperative MRI group and 25 (86%) of 29 controls were eligible for analysis (four patients in each group had metastasis and one patient in the intraoperative MRI group withdrew consent after randomisation). More patients in the intraoperative MRI group had complete tumour resection (23 [96%] of 24 patients) than did in the control group (17 [68%] of 25, p=0·023). Postoperative rates of new neurological deficits did not differ between patients in the intraoperative MRI group (three [13%] of 24) and controls (two [8%] of 25, p=1·0). No patient for whom use of intraoperative MRI led to continued resection of residual tumour had neurological deterioration. One patient in the control group died before 6 months.

INTERPRETATION

Our study provides evidence for the use of intraoperative MRI guidance in glioma surgery: such imaging helps surgeons provide the optimum extent of resection.

FUNDING

None.

Intraoperative MRI-guided resection of glioblastoma multiforme: a systematic review

We did a systematic review to address the added value of intraoperative MRI (iMRI)-guided resection of glioblastoma multiforme compared with conventional neuronavigation-guided resection, with respect to extent of tumour resection (EOTR), quality of life, and survival. 12 non-randomised cohort studies matched all selection criteria and were used for qualitative synthesis. Most of the studies included descriptive statistics of patient populations of mixed pathology, and iMRI systems of varying field strengths between 0·15 and 1·5 Tesla. Most studies provided information on EOTR, but did not always mention how iMRI affected the surgical strategy. Only a few studies included information on quality of life or survival for subpopulations with glioblastoma multiforme or high-grade glioma. Several limitations and sources of bias were apparent, which affected the conclusions drawn and might have led to overestimation of the added value of iMRI-guided surgery for resection of glioblastoma multiforme. Based on the available literature, there is, at best, level 2 evidence that iMRI-guided surgery is more effective than conventional neuronavigation-guided surgery in increasing EOTR, enhancing quality of life, or prolonging survival after resection of glioblastoma multiforme.