Bringing MRI to low- and middle-income countries: Directions, challenges and potential solutions

The global disparity of magnetic resonance imaging (MRI) is a major challenge, with many low- and middle-income countries (LMICs) experiencing limited access to MRI. The reasons for limited access are technological, economic and social. With the advancement of MRI technology, we explore why these challenges still prevail, highlighting the importance of MRI as the epidemiology of disease changes in LMICs. In this paper, we establish a framework to develop MRI with these challenges in mind and discuss the different aspects of MRI development, including maximising image quality using cost-effective components, integrating local technology and infrastructure and implementing sustainable practices. We also highlight the current solutions-including teleradiology, artificial intelligence and doctor and patient education strategies-and how these might be further improved to achieve greater access to MRI.

Consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence: Part 1, general recommendations

Tumours of the anterior part of the pituitary gland represent just 1% of all childhood (aged <15 years) intracranial neoplasms, yet they can confer high morbidity and little evidence and guidance is in place for their management. Between 2014 and 2022, a multidisciplinary expert group systematically developed the first comprehensive clinical practice consensus guideline for children and young people under the age 19 years (hereafter referred to as CYP) presenting with a suspected pituitary adenoma to inform specialist care and improve health outcomes. Through robust literature searches and a Delphi consensus exercise with an international Delphi consensus panel of experts, the available scientific evidence and expert opinions were consolidated into 74 recommendations. Part 1 of this consensus guideline includes 17 pragmatic management recommendations related to clinical care, neuroimaging, visual assessment, histopathology, genetics, pituitary surgery and radiotherapy. While in many aspects the care for CYP is similar to that of adults, key differences exist, particularly in aetiology and presentation. CYP with suspected pituitary adenomas require careful clinical examination, appropriate hormonal work-up, dedicated pituitary imaging and visual assessment. Consideration should be given to the potential for syndromic disease and genetic assessment. Multidisciplinary discussion at both the local and national levels can be key for management. Surgery should be performed in specialist centres. The collection of outcome data on novel modalities of medical treatment, surgical intervention and radiotherapy is essential for optimal future treatment.

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.

Low-field MRI: Clinical promise and challenges

Modern MRI scanners have trended toward higher field strengths to maximize signal and resolution while minimizing scan time. However, high-field devices remain expensive to install and operate, making them scarce outside of high-income countries and major population centers. Low-field strength scanners have drawn renewed academic, industry, and philanthropic interest due to advantages that could dramatically increase imaging access, including lower cost and portability. Nevertheless, low-field MRI still faces inherent limitations in image quality that come with decreased signal. In this article, we review advantages and disadvantages of low-field MRI scanners, describe hardware and software innovations that accentuate advantages and mitigate disadvantages, and consider clinical applications for a new generation of low-field devices. In our review, we explore how these devices are being or could be used for high acuity brain imaging, outpatient neuroimaging, MRI-guided procedures, pediatric imaging, and musculoskeletal imaging. Challenges for their successful clinical translation include selecting and validating appropriate use cases, integrating with standards of care in high resource settings, expanding options with actionable information in low resource settings, and facilitating health care providers and clinical practice in new ways. By embracing both the promise and challenges of low-field MRI, clinicians and researchers have an opportunity to transform medical care for patients around the world. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 6.

Impact of Intraoperative Magnetic Resonance Imaging on Short-Term and Long-Term Outcomes After Transsphenoidal Resection of Pituitary Adenoma: A Systematic Review and Meta-Analysis

BACKGROUND

Intraoperative magnetic resonance imaging (iMRI) allows for greater tumor visualization and extent of resection. It is increasingly used in transsphenoidal surgeries but its role is not yet established.

OBJECTIVE

We aimed to clarify the usefulness of iMRI in transsphenoidal surgery using direct statistical comparisons, with additional subgroup and regression analyses to investigate which patients benefit the most from iMRI use.

METHODS

Systematic searches of PubMed, Embase, and Cochrane Central were undertaken from database inception to May 2020 for published studies reporting the outcomes of iMRI use in transsphenoidal resection of pituitary adenoma.

RESULTS

Thirty-three studies reporting 2106 transsphenoidal surgeries in 2099 patients were included. Of these surgeries, 1487 (70.6%) were for nonfunctioning pituitary adenomas, whereas 619 (29.4%) were for functioning adenomas. Pooled gross total resection (GTR) was 47.6% without iMRI and 66.8% with iMRI (risk ratio [RR], 1.32; P < 0.001). Subgroup and meta-regression analyses demonstrated comparable increases in GTR between microscopic (RR, 1.35; P < 0.001) and endoscopic (RR, 1.31; P < 0.001) approaches as well as functioning and nonfunctioning adenomas (P = 0.584). The pooled rate of hypersecretion normalization was 73.0% within 3 months and 51.7% beyond 3 months postoperatively. The pooled rate of short-term and long-term improvement in visual symptoms was 96.5% and 84.9%, respectively. The incidence of postoperative surgical complications was low. The pooled reoperation rate was 3.8% across 1106 patients.

CONCLUSIONS

The use of iMRI as an adjunct significantly increases GTR for both microscopic and endoscopic resection of pituitary adenomas, with comparable benefits for both functioning and nonfunctioning adenomas. Satisfactory endocrinologic and visual outcomes were achieved.

Impact of intraoperative magnetic resonance imaging on gross total resection, extent of resection, and residual tumor volume in pituitary surgery: systematic review and meta-analysis

BACKGROUND

Residual tumor tissue after pituitary adenoma surgery, is linked with additional morbidity and mortality. Intraoperative magnetic resonance imaging (ioMRI) could improve resection. We aim to assess the improvement in gross total resection (GTR), extent of resection (EOR), and residual tumor volume (RV) achieved using ioMRI.

METHODS

A systematic review was carried out on PubMed/MEDLINE to identify any studies reporting intra- and postoperative (1) GTR, (2) EOR, or (3) RV in patients who underwent resection of pituitary adenomas with ioMRI. Random effects meta-analysis of the rate of improvement after ioMRI for these three surgical outcomes was intended.

RESULTS

Among 34 included studies (2130 patients), the proportion of patients with conversion to GTR (∆GTR) after ioMRI was 0.19 (95% CI 0.15-0.23). Mean ∆EOR was + 9.07% after ioMRI. Mean ∆RV was 0.784 cm3. For endoscopically treated patients, ∆GTR was 0.17 (95% CI 0.09-0.25), while microscopic ∆GTR was 0.19 (95% CI 0.15-0.23). Low-field ioMRI studies demonstrated a ∆GTR of 0.19 (95% CI 0.11-0.28), while high-field and ultra-high-field ioMRI demonstrated a ∆GTR of 0.19 (95% CI 0.15-0.24) and 0.20 (95% CI 0.13-0.28), respectively.

CONCLUSIONS

Our meta-analysis demonstrates that around one fifth of patients undergoing pituitary adenoma resection convert from non-GTR to GTR after the use of ioMRI. EOR and RV can also be improved to a certain extent using ioMRI. Endoscopic versus microscopic technique or field strength does not appear to alter the impact of ioMRI. Statistical heterogeneity was high, indicating that the improvement in surgical results due to ioMRI varies considerably by center.

Defining the timing and role of acute postoperative imaging in pituitary adenoma surgery: clinical study

BACKGROUND

The ideal timing of postoperative imaging after pituitary adenoma surgery has yet to be determined. We reviewed our pituitary database to determine whether timing of routine postoperative imaging has significantly changed patients' clinical course or outcomes.

METHODS

Retrospective chart review of patients undergoing resection of pituitary adenoma at our university center between 2012 and 2017 was performed. Timing and indication for postoperative imaging, findings of immediate and delayed postoperative imaging, as well as re-operations and radiosurgery details were recorded. Visual functions such as acuity and visual fields were used as clinical outcome indicators. Statistical analysis was run using Microsoft Excel.

RESULTS

Five hundred and nineteen patients were identified; 443 had imaging data in our system and were included in the study. Early (< 90 days) MRIs were obtained in 71 patients and late (≥ 90 days) in 372 patients. We found statistical differences in our demographic groups including larger tumors in the early MRI group (early mean 12.33 cm³, late mean 4.64 cm³, p < 0.001) and higher Knosp grade (p = 0.0006). We found a significant difference in rates of return to the OR (16.9% in the early group and 4.84% in the late group; p < 0.001). There was a significant difference in the rate of residual identified on first postoperative MRI: 52.11% in the early group and 29.57% in the late group (p < 0.001). There was no difference in visual outcomes between the patient cohorts.

CONCLUSION

After surgical treatment of pituitary adenoma, MRI obtained before 3 months is associated with higher rates of return to OR but no difference in long-term clinical outcomes. Due to cost efficiency, we argue for a delayed first postoperative MRI. The timing of MRI should also be governed by other factors such as large pituitary macroadenomas or postoperative complications. We recommend a consistent institutional protocol for determining the most cost-effective follow-up of postoperative pituitary patients.

Image-Guided Surgery and Intraoperative Imaging in Rhinology: Clinical Update and Current State of the Art

INTRODUCTION

Image-guided surgery (IGS) has gained widespread acceptance in otorhinolaryngology for its applications in sinus and skull base surgery. Although the core concepts of IGS have not changed, advances in image guidance technology, including the incorporation of intraoperative imaging, have the potential to enhance surgical education, allow for more rigorous preoperative planning, and aid in more complete surgery with improved outcomes.

OBJECTIVES

Provide a clinical update regarding the use of image guidance and intraoperative imaging in the field of rhinology and endoscopic skull base surgery with a focus on current state of the art technologies.

METHODS

English-language studies published in PubMed, Cochrane, and Embase were searched for articles relating to image-guided sinus surgery, skull base surgery, and intraoperative imaging. Relevant studies were reviewed and critical appraisals were included in this clinical update, highlighting current state of the art advances.

CONCLUSIONS

As image guidance and intraoperative imaging systems have advanced, their applications in sinus and skull base surgery have expanded. Both technologies offer invaluable real-time feedback on the status and progress of surgery, and thus may help to improve the completeness of surgery and overall outcomes. Recent advances such as augmented and virtual reality offer a window into the future of IGS. Future advancements should aim to enhance the surgeon's operative experience by improving user satisfaction and ultimately lead to better surgical results.

ICAR: endoscopic skull-base surgery

BACKGROUND

Endoscopic skull-base surgery (ESBS) is employed in the management of diverse skull-base pathologies. Paralleling the increased utilization of ESBS, the literature in this field has expanded rapidly. However, the rarity of these diseases, the inherent challenges of surgical studies, and the continued learning curve in ESBS have resulted in significant variability in the quality of the literature. To consolidate and critically appraise the available literature, experts in skull-base surgery have produced the International Consensus Statement on Endoscopic Skull-Base Surgery (ICAR:ESBS).

METHODS

Using previously described methodology, topics spanning the breadth of ESBS were identified and assigned a literature review, evidence-based review or evidence-based review with recommendations format. Subsequently, each topic was written and then reviewed by skull-base surgeons in both neurosurgery and otolaryngology. Following this iterative review process, the ICAR:ESBS document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:ESBS document addresses the role of ESBS in primary cerebrospinal fluid (CSF) rhinorrhea, intradural tumors, benign skull-base and orbital pathology, sinonasal malignancies, and clival lesions. Additionally, specific challenges in ESBS including endoscopic reconstruction and complication management were evaluated.

CONCLUSION

A critical review of the literature in ESBS demonstrates at least the equivalency of ESBS with alternative approaches in pathologies such as CSF rhinorrhea and pituitary adenoma as well as improved reconstructive techniques in reducing CSF leaks. Evidence-based recommendations are limited in other pathologies and these significant knowledge gaps call upon the skull-base community to embrace these opportunities and collaboratively address these shortcomings.

10 Years' Experience of Using Low-Field Intraoperative MRI in Transsphenoidal Surgery for Pituitary Adenoma: Results of the Swiss Pituitary Registry (SwissPit)

BACKGROUND

For 20 years, several studies have reported intraoperative magnetic resonance imaging (iMRI) utility to achieve gross total resections in transsphenoidal pituitary adenoma surgery. Although few studies on low-field iMRI included >100 patients, data on hormonally active tumors remain scarce and follow-up times are <3 years. This is not sufficient to judge the long-term efficiency of the use of low-field iMRI. The aim of this retrospective study is to report the detailed outcome of iMRI-controlled transsphenoidal surgery in >200 patients during a follow-up exceeding 5 years.

METHODS

Patients undergoing surgery for pituitary adenoma by iMRI-controlled, endoscopically assisted transsphenoidal surgery at the authors' institution between 2006 and 2016 were eligible for inclusion. Data were collected in the Swiss Pituitary Registry. A Polestar 0.15T-scanner was used.

RESULTS

A total of 231 patients had surgery for 160 nonfunctioning adenomas; 28 hGH-, 27 PRL-, 10 ACTH-secreting and 6 mixed adenomas and were followed for 62 months (9-178). Additional iMRI-guided resections were possible in 54% and increased the gross total resection rate by 4% (P = 0.004). Remission rates were as follows: nonfunctioning adenoma, 53%; acromegaly, 61%; prolactinoma, 50%; Cushing disease, 90%. Tumor regrowth and recurrence was detected at a mean time of 24 and 63 months, respectively. Recovery of deficient hormone axes was detected in 22% to 27%. The risk for new postoperative hormonal deficiencies was 15%. Postoperative relieve of visual field and visual acuity deficiencies was seen in 94 (86%) and 73 (81%) patients, respectively.

CONCLUSION

Judged by long-term follow-ups of >200 nonfunctioning/functioning pituitary adenomas, the use of low-field iMRI in transsphenoidal surgery increases resection rates and sustainably influences outcomes.

High-Field Intraoperative Magnetic Resonance Imaging Increases Extent of Resection and Progression-Free Survival for Nonfunctioning Pituitary Adenomas

BACKGROUND

The effect of intraoperative magnetic resonance imaging (iMRI) on tumor control during endoscopic transsphenoidal surgery (TSS) for nonfunctioning pituitary adenomas (NFPAs) has not yet been completely characterized. The present study assessed the effect of the iMRI findings on gross total resection (GTR) and progression-free survival at a mean follow-up of 62 ± 9.4 months.

METHODS

Retrospective analyses were performed on the data from 133 consecutive patients with NFPA who had undergone endoscopic TSS with iMRI using a 1.5T scanner.

RESULTS

Compared with the first and final iMRI scans, the GTR rate increased from 42.9% to 63.9%. Multivariate logistic regression analysis revealed that a lower GTR rate was associated with a higher Knosp score (odds ratio [OR], 3.612; 95% confidence interval [CI], 1.568-8.321; P = 0.003), an increased tumor volume (OR, 0.926; 95% CI, 0.866-0.991; P = 0.025), and a history of surgery (OR, 0.376; 95% CI, 0.155-0.917; P = 0.031). During follow-up, 8 tumors (9.4%) recurred, and 29 remnants (60.4%) regenerated. The recurrence and regeneration rates were 0.019 and 0.121 patient/year, respectively. Kaplan-Meier analysis revealed that the tumor recurrence rates were lower for patients who had undergone GTR (P < 0.01) compared with those who had not. Univariate Cox regression analysis suggested that the presence of tumor remnants (hazard ratio, 1.546; 95% CI, 1.071-2.232; P = 0.02) was the influencing factor associated with tumor progression.

CONCLUSIONS

High-field iMRI can increase the GTR rate in endoscopic TSS for NPFAs. The increased GTR rate was associated with longer progression-free survival. Cavernous sinus invasion, tumor size, and surgical history were important predictors of GTR in patients with NFPA.

Intraoperative low field MRI in transsphenoidal pituitary surgery

BACKGROUND

Intraoperative low field MRI (iMRI, 0.15 T) during transsphenoidal surgery on pituitary adenomas (PAs) may significantly improve tumor removal. However, extensive surgery can lead to pituitary hormone deficiency. Furthermore, introduction of iMRI will prolong duration of surgery, which may elevate risk of postoperative infections.

METHODS

Overall, 180 transsphenoidal surgeries for PAs from 2007 to 2015 were included. IMRI was available from 2011 to 2015, during this period 67/78 (86%) surgeries were with iMRI (iMRI, n = 67). A total of 113 surgeries were performed without iMRI (controls). All surgical procedures were performed by microscopic technique. Tumor size, hormonal status and vision were assessed before surgery and 3-5 months postoperatively.

RESULTS

Gross total resection (GTR), mean tumor remnant volume and ∆-volumes were comparable between iMRI and controls: 15% (10/66) vs 23% (26/109) (P = 0.17), 2.97 cm³ (0.9-5) vs 2.1 cm³ (1.6-2.6) (P = 0.3) and 4.5 cm³ (3.6-5.5) vs 5.1 cm³ (4.2-6) (P = 0.4), respectively. Duration of surgery was significantly longer during iMRI vs controls: 126 min (117-135) vs 98 min (92-103) (P < 0.001). New pituitary-adrenal deficiency in iMRI vs controls was seen in 35% (17/48) and 35% (23/66) of surgeries, respectively (P = 0.95). New thyroid deficiency was found in 33% (13/29) and 41% (28/69) and visual field deficiencies improved in 44% (19/43) and 38% (23/60) in iMRI vs controls, respectively (P > 0.1).

CONCLUSION

Tumor remnant after pituitary surgery was not significantly reduced using intraoperative low field MRI. Duration of surgery was increased in iMRI, but was not associated with increased infection rate. Pituitary hormonal function and vision were comparable between iMRI and controls.

iMRI During Transsphenoidal Surgery

A variety of intraoperative MRI (iMRI) systems are in use during transsphenoidal surgery (TSS). The variations in iMRI systems include field strengths, magnet configurations, and room configurations. Most studies report that the primary utility of iMRI during TSS lies in detecting resectable tumor residuals following maximal resection with conventional technique. Stereotaxis, neuronavigation, and complication avoidance/detection are enhanced by iMRI use during TSS. The use of iMRI during TSS can lead to increased extent of resection for large tumors. Improved remission rates from hormone-secreting tumors have also been reported with iMRI use. This article discusses the history, indications, and future directions for iMRI during TSS.

Intraoperative magnetic resonance imaging assessment of non-functioning pituitary adenomas during transsphenoidal surgery

PURPOSE

To review the utility of intraoperative imaging in facilitating maximal resection of non-functioning pituitary adenomas (NFAs).

METHODS

We performed an exhaustive MEDLINE search, which yielded 5598 articles. Upon careful review of these studies, 31 were pertinent to the issue of interest.

RESULTS

Nine studies examined whether intraoperative MRI (iMRI) findings correlated with the presence of residual tumor on MRI taken 3 months after surgical resection. All studies using iMRI of >0.15T showed a ≥90% concordance between iMRI and 3-month post-operative MRI findings. 24 studies (22 iMRI and 2 intraoperative CT) examined whether intraoperative imaging improved the surgeon's ability to achieve a more complete resection. The resections were carried out under microscopic magnification in 17 studies and under endoscopic visualization in 7 studies. All studies support the value of intraoperative imaging in this regard, with improved resection in 15-83% of patients. Two studies examined whether iMRI (≥0.3T) improved visualization of residual NFA when compared to endoscopic visualization. Both studies demonstrated the value of iMRI in this regard, particularly when the tumor is located lateral of the sella, in the cavernous sinus, and in the suprasellar space.

CONCLUSION

The currently available literature supports the utility of intraoperative imaging in facilitating increased NFA resection, without compromising safety.

Pituitary surgery and volumetric assessment of extent of resection: a paradigm shift in the use of intraoperative magnetic resonance imaging

OBJECTIVE

The aim of this study was to quantitatively assess the role of intraoperative high-field 3-T MRI (3T-iMRI) in improving the gross-total resection (GTR) rate and the extent of resection (EOR) in endoscopic transsphenoidal surgery (TSS) for pituitary adenomas.

METHODS

Radiological and clinical data from a prospective database were retrospectively analyzed. Volumetric measurements of adenoma volumes pre-, intraoperatively, and 3 months postoperatively were performed in a consecutive series of patients who had undergone endoscopic TSS. The quantitative contribution of 3T-iMRI was measured as a percentage of the additional rate of GTR and of the EOR achieved after 3T-iMRI.

RESULTS

The cohort consisted of 50 patients (51 operations) harboring 33 nonfunctioning and 18 functioning pituitary adenomas. Mean adenoma diameter and volume were 21.1 mm (range 5–47 mm) and 5.23 cm3 (range 0.09–22.14 cm3), respectively. According to Knosp's classification, 10 cases were Grade 0; 8, Grade 1; 17, Grade 2; 12, Grade 3; and 4, Grade 4. Gross-total resection was the surgical goal (targeted [t]GTR) in 34 of 51 operations and was initially achieved in 16 (47%) of 34 at 3T-iMRI and in 30 (88%) of 34 cases after further resection. In this subgroup, the EOR increased from 91% at 3T-iMRI to 99% at the 3-month MRI (p < 0.05). In the 17 cases in which subtotal resection (STR) had been planned (tSTR), the EOR increased from 79% to 86% (p < 0.05) and GTR could be achieved in 1 case. Intrasellar remnants were present in 20 of 51 procedures at 3T-iMRI and in only 5 (10%) of 51 procedures after further resection (median volume 0.15 cm3). Overall, the use of 3T-iMRI led to further resection in 27 (53%) of 51 procedures and permitted GTR in 15 (56%) of these 27 procedures; thus, the GTR rate in the entire cohort increased from 31% (16 of 51) to 61% (31 of 51) and the EOR increased from 87% to 95% (p < 0.05).

CONCLUSIONS

The use of high-definition 3T-iMRI allowed precise visualization and quantification of adenoma remnant volume. It helped to increase GTR and EOR rates in both tGTR and tSTR patient groups. Moreover, it helped to achieve low rates of intrasellar remnants. These data support the use of 3T-iMRI to achieve maximal, safe adenoma resection.

Current imaging techniques for the diagnosis of pituitary adenoma

Stepwise improvements in the imaging of pituitary adenomas in the last 100 years have had a tremendous impact on patient care. Pituitary tumors are now diagnosed earlier in the time course of the disease, improving chances of endocrine and visual recovery. There is improved pre-surgical planning due to a better understanding of the investment of the tumor around important surrounding parasellar structures. Approaches to tumors are now safer due to stereotactic navigation and residual disease can be radiographically followed for a lifetime and treated prior to irreversible neurological damage. Furthermore, adjuvant radiotherapy can be more precisely delivered to the tumor bed with the aid of higher resolution images. Thanks to these incremental improvements previously formidable macroadenomas, which carried a high risk for morbidity and residual disease, can now be treated safely and effectively. Here, we review modern imaging modalities used to diagnose pituitary adenomas, and identify areas for further improvement.

"Intrasellar Balloon Technique" in intraoperative MRI guided transsphenoidal endoscopic surgery for sellar region tumors. Usefulness on image interpretation and extent of resection evaluation. Technical note

BACKGROUND

Intraoperative magnetic resonance imaging (iMRI) is an effective and proven tool in transsphenoidal endoscopic surgery. However, image interpretation is not always easy and can be hindered by the presence of blood, tumor remains or the displacement of surrounding structures. In this article we present a novel technique based on using intrasellar ballons to reduce these difficulties and facilitate the surgeon's intraoperative assessment by iMRI.

METHODS

Eighteen patients with pituitary macroadenomas underwent transsphenoidal surgery during 2013-2014 under low-field iMRI control (PoleStar N20, 0.15 T). Intrasellar balloons were used in all of them to assess the presence of tumoral remnants. We compared the findings in iMRI and postoperative high-field MRI control scans and also analyzed the number of intermediate imaging controls needed during surgery using this technique.

RESULTS

In total, of the 18 patients, 14 underwent a complete resection. In the remaining four patients, a safe maximal resection was performed, leaving a remnant because of cavernous sinus invasion. In all cases, the balloons were a major help in distinguishing the anatomical structures from the tumoral remnants. Fewer imaging controls were required, and there were no false-positives or negative intraoperative findings. No complications related to the technique were registered.

CONCLUSION

The "intrasellar balloon technique" is a useful tool that facilitates surgeons' intraoperative decision making. It is an important contribution to overcome the limitations of low-field iMRI as it provides a precise delineation of the resection margins, reduces false-positives and -negatives, and decreases the number of intermediate imaging controls required.

Transsellar Ultrasound in Pituitary Surgery With a Designated Probe: Early Experiences

BACKGROUND

Anatomic orientation in transsphenoidal surgery can be difficult, and residual tumors are common. A major limitation of both direct microscopy and endoscopic visualization is the inability to see below the surface of the surgical field to confirm the location of vessels, nerves, tumor remnants, and normal pituitary tissue.

OBJECTIVE

To present our initial experience with a new forward-looking, custom-designed ultrasound probe for transsellar imaging.

METHODS

The center frequency of the prototype tightly curved linear array, bayonet-shaped probe is 12 MHz. Twenty-four patients with pituitary adenomas were included after informed consent.

RESULTS

With the use of transsellar ultrasound, we could confirm the location of important neurovascular structures and improve the extent of resection in 4 of 24 cases, as rated subjectively by the operating surgeons. Image quality was good. In 17 patients (71%), biochemical cures and/or complete resections were confirmed at 3 months.

CONCLUSION

We found the images from our custom-designed ultrasound probe to be clinically helpful for anatomic orientation during surgery, and the technology is potentially helpful for improving the extent of resection during transsphenoidal surgery. This quick and flexible form of intraoperative imaging in transsphenoidal surgery could be of great support for surgeons in both routine use and difficult cases. The concept of transsellar intraoperative ultrasound imaging can be further refined and developed.

Combined high-field intraoperative magnetic resonance imaging and endoscopy increase extent of resection and progression-free survival for pituitary adenomas

PURPOSE

The clinical benefit of combined intraoperative magnetic resonance imaging (iMRI) and endoscopy for transsphenoidal pituitary adenoma resection has not been completely characterized. This study assessed the impact of microscopy, endoscopy, and/or iMRI on progression-free survival, extent of resection status (gross-, near-, and sub-total resection), and operative complications.

METHODS

Retrospective analyses were performed on 446 transsphenoidal pituitary adenoma surgeries at a single institution between 1998 and 2012. Multivariate analyses were used to control for baseline characteristics, differences during extent of resection status, and progression-free survival analysis.

RESULTS

Additional surgery was performed after iMRI in 56/156 cases (35.9%), which led to increased extent of resection status in 15/156 cases (9.6%). Multivariate ordinal logistic regression revealed no increase in extent of resection status following iMRI or endoscopy alone; however, combining these modalities increased extent of resection status (odds ratio 2.05, 95% CI 1.21-3.46) compared to conventional transsphenoidal microsurgery. Multivariate Cox regression revealed that reduced extent of resection status shortened progression-free survival for near- versus gross-total resection [hazard ratio (HR) 2.87, 95% CI 1.24-6.65] and sub- versus near-total resection (HR 2.10; 95% CI 1.00-4.40). Complication comparisons between microscopy, endoscopy, and iMRI revealed increased perioperative deaths for endoscopy versus microscopy (4/209 and 0/237, respectively), but this difference was non-significant considering multiple post hoc comparisons (Fisher exact, p = 0.24).

CONCLUSIONS

Combined use of endoscopy and iMRI increased pituitary adenoma extent of resection status compared to conventional transsphenoidal microsurgery, and increased extent of resection status was associated with longer progression-free survival. Treatment modality combination did not significantly impact complication rate.

Follow-up and long-term outcome of nonfunctioning pituitary adenoma operated by transsphenoidal surgery with intraoperative high-field magnetic resonance imaging

BACKGROUND

Intraoperative MRI (iMRI) increases gross total resection (GTR) rates in transsphenoidal surgery; however, long-term follow-up data is lacking. The objective is to assess the outcome of patients with nonfunctioning pituitary adenomas (NFA) at a mean follow-up of > 5 years.

METHODS

Patients with NFA operated in a single institution with resection control by a 1.5 T intraoperative magnetic resonance imaging (iMRI) scanner and no previous pituitary surgery were included. Microscopical transsphenoidal approaches with optional endoscopy were used. The iMRI was chosen for spacious suprasellar or retrosellar and/or invasive tumours. IMRI-scans were made if GTR or if nonresectable remnants were presumed. The patients had a full neuroradiological, endocrinological and ophthalmological follow-up at the institution.

RESULTS

Eighty-five patients (67 % male;55 ± 14 years) with a follow-up of 5.6 ± 1.9 years were included. The initial GTR rate on iMRI was 44 %. In 83 %, further resections were possible, resulting in a final GTR rate of 66 %. In invasive tumours, the GTR rate was increased by 29 %. The detection of remnants by iMRI had high sensitivity and specificity (100 %), as opposed to endoscopy (21 %;78 %). During follow-up, four (7 %) tumours recurred and 14 (64 %) remnants grew. The recurrence and regrowth rate were 0.013 and 0.114 patients/years, respectively. Seventy-nine percent of the growing remnants were seen < 5 years postoperatively.

CONCLUSIONS

The use of iMRI for transsphenoidal resection leads to low recurrence rates. Even in case of invasive tumours, distinctly more patients show long tumour-free follow-ups. Tumour remnants detected by iMRI are at high risk to grow within 5 years after surgery.

Outcome of endoscopic transsphenoidal surgery in combination with somatostatin analogues in patients with growth hormone producing pituitary adenoma

Objective

To determine the efficacy of endoscopic surgery in combination with long-acting somatostatin analogues (SSAs) in treating patients with growth hormone (GH)-secreting pituitary tumor.

Methods

We performed retrospective analysis of 133 patients with GH producing pituitary adenoma who underwent pure endoscopic transsphenoidal surgery in our center from January 2007 to July 2012. Patients were followed up for a range of 3-48 months. The radiological remission, biochemical remission and complication were evaluated.

Results

A total of 110 (82.7%) patients achieved radiological complete resection, 11 (8.2%) subtotal resection, and 12 (9.0%) partial resection. Eighty-eight (66.2%) patients showed nadir GH level less than 1 ng/mL after oral glucose administration. No mortality or severe disability was observed during follow up. Preoperative long-acting SSA successfully improved left ventricle ejection fraction (LVEF) and blood glucose in three patients who subsequently underwent success operation. Long-acting SSA (20 mg every 30 days) achieved biochemical remission in 19 out 23 (82.6%) patients who showed persistent high GH level after surgery.

Conclusion

Endoscopic transsphenoidal surgery can biochemically cure the majority of GH producing pituitary adenoma. Post-operative use of SSA can improve biochemical remission.

Intraoperative 3T MRI for pituitary macroadenoma resection: Initial experience in 73 consecutive patients

OBJECTIVE

To report a single-center experience with a 3T intraoperative magnetic resonance imaging (iMRI) to assess transsphenoidal microsurgery on pituitary macroadenomas.

METHODS

In a dual, independent operating room (OR) magnetic resonance imaging (MRI) suite, the operating table with the anesthetized patient was moved on rail tracks once a supposed maximized resection was reached to the MRI room for intraoperative image acquisition and interpretation. After the assessment of the iMRI images, the neurosurgeon evaluated whether additional resection was still possible. The resection rates were assessed on iMRI and postoperative MRI at 3 months.

RESULTS

A total of 73 macroadenomas benefited from an iMRI from March 2006 to October 2011. The gross total resection (GTR) rate at the time of the first iMRI was 58.9% (n=43). Based on the iMRI, eight patients (10.9%) underwent a second surgical resection. In 3 cases, the intraoperative imaging results were suspicious for a minor residue but not convincing enough for further surgery. Fortunately, the 3 months postoperative MRI control did not disclose any residual tumor in these cases. Finally, the GTR rate at the 3-month postoperative MRI increased to 72.6% (n=53).

CONCLUSIONS

3T intraoperative MRI offered excellent quality images. Its use during transsphenoidal microsurgery on pituitary macroadenomas led to an increase not only in the extent of tumor resection (in 8 patients) but also in the rate of radical resections (69% instead of 60%). No complications due to the iMRI procedure were observed.

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

OBJECT

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.

Use of high-field intraoperative magnetic resonance imaging during endoscopic transsphenoidal surgery for functioning pituitary microadenomas and small adenomas located in the intrasellar region

The usefulness of 1.5-T high-field intraoperative magnetic resonance (iMR) imaging during transsphenoidal surgery for functioning pituitary adenomas was retrospectively evaluated based on long-term endocrine remission from the records of 14 patients who underwent transsphenoidal surgery with iMR imaging for functioning pituitary microadenomas and small adenomas located in the intrasellar region. The maximum tumor diameter was 9.3 ± 2.6 mm. Patients were diagnosed with acromegaly (n = 7), prolactinoma (n = 4), and Cushing's disease (n = 3). If iMR imaging detected tumor remnants after resection, the resection cavity was reexamined and further resection was performed. Postoperative endocrine follow-up period was mean 33.7 ± 13.3 months. Tumor remnants were detected after the first resection in seven patients. Further resection was performed in five of these patients, and three achieved long-term endocrine remission. As a result, the overall long-term endocrine remission rate was 78.5% (11/14), instead of the 57.1% (8/14) that would be expected if iMR imaging had not been performed. Long-term endocrine remission had a tendency to be associated with the absence of tumor remnants on the final iMR images, but this was not significant (p = 0.09). Long-term endocrine remission was associated with presence of tumor remnants in the cavernous sinus on the final iMR images (p = 0.03). High-field iMR imaging is useful for depicting tumor remnants after resection, and increased the long-term endocrine remission rate for patients with functioning pituitary microadenomas and small adenomas.

Determining the utility of intraoperative magnetic resonance imaging for transsphenoidal surgery: a retrospective study

OBJECT

Intraoperative MRI (iMRI) provides updated information for neuronavigational purposes and assessments on the status of resection during transsphenoidal surgery (TSS). The high-field technique additionally provides information about vascular structures at risk and precise information about extrasellar residual tumor, making it readily available during the procedure. The imaging, however, extends the duration of surgery. To evaluate the benefit of this technique, the authors conducted a retrospective study to compare postoperative outcome and residual tumor in patients who underwent conventional microsurgical TSS with and without iMRI.

METHODS

A total of 143 patients were assessed. A cohort of 67 patients who had undergone surgery before introduction of iMRI was compared with 76 patients who had undergone surgery since iMRI became routine in TSS at the authors' institution. Residual tumor, complications, hormone dependency, biochemical remission rates, and improvement of vision were assessed at 6-month follow-up. A volumetric evaluation of residual tumor was performed in cases of parasellar tumor extension.

RESULTS

The majority of patients in both groups suffered from nonfunctioning pituitary adenomas. At the 6-month follow-up assessment, vision improved in 31% of patients who underwent iMRI-assisted surgery versus 23% in the conventional group. One instance of postoperative intrasellar bleeding was found in the conventional group. No major complications were found in the iMRI group. Minor complications were seen in 9% of patients in the iMRI group and in 5% of those in the conventional group. No differences between groups were found for hormone dependency and biochemical remission rates. Time of surgery was significantly lower in the conventional treatment group. Overall a residual tumor was found after surgery in 35% of the iMRI group, and 41% of the conventional surgery group harbored a residual tumor. Total resection was achieved as intended significantly more often in the iMRI group (91%) than in the conventional group (73%) (p < 0.034). Patients with a planned subtotal resection showed higher mean volumes of residual tumor in the conventional group. There was a significantly lower incidence of intrasellar tumor remnants in the iMRI group than in the conventional group. Progression-free survival after 30 months was higher according to Kaplan-Meier analysis with the use of iMRI, but a statistically significant difference could not be shown.

CONCLUSIONS

The use of high-field iMRI leads to a significantly higher rate of complete resection. In parasellar tumors a lower residual volume and a significantly lower rate of intrasellar tumor remnants were shown with the technique. So far, long-term follow-up is limited for iMRI. However, after 2 years Kaplan-Meier analyses show a distinctly higher progression-free survival in the iMRI group. No significant benefit of iMRI was found for biochemical remission rates and improvement of vision. Even though the surgical time was longer with the adjunct use of iMRI, it did not increase the complication rate significantly. The authors therefore recommend routine use of high-field iMRI for pituitary surgery, if this technique is available at the particular center.

Pituitary macroadenoma presenting with pituitary apoplexy, acromegaly and secondary diabetes mellitus - a case report

Pituitary adenomas are associated with significant morbidity. The usual symptoms on presentation are of endocrine dysfunction and mass effects. A 31-year-old African female presented with headache, irregular menses, blurring of vision in the right eye and complete loss of vision in the left eye for 1 year. She had coarse facial features, enlarged hands and feet. Her right eye had temporal hemianopia with decreased visual acuity and her left eye had no perception of light. Investigations revealed an elevated fasting blood sugar and an elevated prolactin and growth hormone level. A CT scan and MRI done showed a hemorrhagic pituitary macroadenoma. She was put on bromocriptine, ocreotide, analgesics and insulin. Thereafter, she underwent transphenoidal surgery, where near total resection of the tumor was achieved. Patient is doing well post-operatively. This case highlights the importance of the use of a high clinical index of suspicion and radiological findings in diagnosis.

Application of low-field intraoperative magnetic resonance imaging in transsphenoidal surgery for pituitary adenomas: technical points to improve the visibility of the tumor resection margin

BACKGROUND

Intraoperative magnetic resonance imaging (iMRI) is proven to be advantageous in transsphenoidal surgery (TSS) for pituitary adenomas. We evaluated the efficacy of low-field iMRI. Also, we described several techniques to enhance the visibility of the tumor resection margin.

METHODS

Two hundred twenty-nine patients who underwent TSS using low-field iMRI were analyzed. iMRI was acquired in cases where the tumor removal was thought to meet the surgical goal after the tumor resection cavity had been packed with contrast-soaked cotton pledgets to improve the visibility of the tumor resection margin. Suspicious remnants were localized and explored using updated iMRI-based semi-real-time navigation. A merging technique was adopted for very small tumors. The final outcome was evaluated using postoperative 3-T diagnostic magnetic resonance imaging (MRI).

RESULTS

Among 198 patients in whom total resection was attempted, total resection seemed to have been achieved in 184 patients based on iMRI findings. However, immediate postoperative MRI revealed remnant tumors in 4 out of 184 patients (false-negative rate, 2.2 %). The other 31 patients underwent intended subtotal resection of the tumors. Overall, in 47 patients (20.5 %), the use of iMRI led to further resection. Those patients benefited from the use of iMRI to achieve the planned extent of tumor resection.

CONCLUSIONS

iMRI maximizes the extent of resection and minimizes the possibility of unexpected tumor remnants in TSS for pituitary adenomas. It is essential to reduce imaging artifacts and enhance the visibility of the tumor resection margin during the use of low-field iMRI.

Value of endoscopy for maximizing tumor removal in endonasal transsphenoidal pituitary adenoma surgery

OBJECT

Endoscopy as a visual aid (endoscope assisted) or as the sole visual method (fully endoscopic) is increasingly used in pituitary adenoma surgery. Authors of this study assessed the value of endoscopic visualization for finding and removing residual adenoma after initial microscopic removal.

METHODS

Consecutive patients who underwent endoscope-assisted microsurgical removal of pituitary adenoma were included in this study. The utility of the endoscope in finding and removing residual adenoma not visualized by the microscope was noted intraoperatively. After maximal tumor removal under microscopic visualization, surgeries were categorized as to whether additional tumor was removed via endoscopy. Tumor removal and remission rates were also noted. Patients undergoing fully endoscopic tumor removal during this same period were excluded from the study.

RESULTS

Over 3 years, 140 patients (41% women, mean age 50 years) underwent endoscope-assisted adenoma removal of 30 endocrine-active microadenomas and 110 macroadenomas (39 endocrine-active, 71 endocrine-inactive); 16% (23/140) of patients had prior surgery. After initial microscopic removal, endoscopy revealed residual tumor in 40% (56/140) of cases and the additional tumor was removed in 36% (50 cases) of these cases. Endoscopy facilitated additional tumor removal in 54% (36/67) of the adenomas measuring ≥ 2 cm in diameter and in 19% (14/73) of the adenomas smaller than 2 cm in diameter (p < 0.0001); additional tumor removal was achieved in 20% (6/30) of the microadenomas. Residual tumor was typically removed from the suprasellar extension and folds of the collapsed diaphragma sellae or along or within the medial cavernous sinus. Overall, 91% of endocrine-inactive tumors were gross-totally or near-totally removed, and 70% of endocrine-active adenomas had early remission.

CONCLUSIONS

After microscope-based tumor removal, endoscopic visualization led to additional adenoma removal in over one-third of patients. The panoramic visualization of the endoscope appears to facilitate more complete tumor removal than is possible with the microscope alone. These findings further emphasize the utility of endoscopic visualization in pituitary adenoma surgery. Longer follow-ups and additional case series are needed to determine if endoscopic adenomectomy translates into higher long-term remission rates.

"Awake" intraoperative functional MRI (ai-fMRI) for mapping the eloquent cortex: Is it possible in awake craniotomy?

As a promising noninvasive imaging technique, functional MRI (fMRI) has been extensively adopted as a functional localization procedure for surgical planning. However, the information provided by preoperative fMRI (pre-fMRI) is hampered by the brain deformation that is secondary to surgical procedures. Therefore, intraoperative fMRI (i-fMRI) becomes a potential alternative that can compensate for brain shifts by updating the functional localization information during craniotomy. However, previous i-fMRI studies required that patients be under general anesthesia, preventing the wider application of such a technique as the patients cannot perform tasks unless they are awake. In this study, we propose a new technique that combines awake surgery and i-fMRI, named “awake” i-fMRI (ai-fMRI). We introduced ai-fMRI to the real-time localization of sensorimotor areas during awake craniotomy in seven patients. The results showed that ai-fMRI could successfully detect activations in the bilateral primary sensorimotor areas and supplementary motor areas for all patients, indicating the feasibility of this technique in eloquent area localization. The reliability of ai-fMRI was further validated using intraoperative stimulation mapping (ISM) in two of the seven patients. Comparisons between the pre-fMRI-derived localization result and the ai-fMRI derived result showed that the former was subject to a heavy brain shift and led to incorrect localization, while the latter solved that problem. Additionally, the approaches for the acquisition and processing of the ai-fMRI data were fully illustrated and described. Some practical issues on employing ai-fMRI in awake craniotomy were systemically discussed, and guidelines were provided.

Intraoperative magnetic resonance imaging during surgery for pituitary adenomas: pros and cons

Surgery for pituitary adenomas still remains a mainstay in their treatment, despite all advances in sophisticated medical treatments and radiotherapy. Total tumor excision is often attempted, but there are limitations in the intraoperative assessment of the radicalism of tumor resection by the neurosurgeon. Standard postoperative imaging is usually performed with a few months delay from the surgical intervention. The purpose of this report is to review briefly the facilities and kinds of intraoperative magnetic resonance imaging for all physician and surgeons involved in the management of pituitary adenomas on the basis of current literature. To date, there are several low- and high-field magnetic resonance imaging systems available for intraoperative use and depiction of the extent of tumor removal during surgery. Recovery of vision and the morphological result of surgery can be largely predicted from the intraoperative images. A variety of studies document that depiction of residual tumor allows targeted attack of the remnant and extent the resection. Intraoperative magnetic resonance imaging offers an immediate feedback to the surgeon and is a perfect quality control for pituitary surgery. It is also used as a basis of datasets for intraoperative navigation which is particularly useful in any kind of anatomical variations and repeat operations in which primary surgery has distorted the normal anatomy. However, setting up the technology is expensive and some systems even require extensive remodeling of the operation theatre. Intraoperative imaging prolongs the operation, but may also depict evolving problems, such as hematomas in the tumor cavity. There are several artifacts in intraoperative MR images possible that must be considered. The procedures are not associated with an increased complication rate.

[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.

Transsphenoidal resection of sellar tumors using high-field intraoperative magnetic resonance imaging

There has been increasing experience in the utilization of intraoperative magnetic resonance imaging (iMRI) for intracranial surgery. Despite this trend, only a few U.S centers have examined the use of this technology for transsphenoidal resection of tumors of the sella. We present the largest series in North America examining the role of iMRI for pituitary adenoma resection. We retrospectively reviewed our institutional experience of 59-patients who underwent transsphenoidal procedures for sellar and suprasellar tumors with iMRI guidance. Of these, 52 patients had a histological diagnosis of pituitary adenoma. The technical results of this subgroup were examined. A 1.5-T iMRI was integrated with the BrainLAB (Feldkirchen, Germany) neuronavigation system. The majority (94%) of tumors in our series were macroadenomas. Seventeen percent of tumors were confined to the sella, 49% had suprasellar extensions without involvement of the cavernous sinus, 34% had frank cavernous sinus invasion. All patients underwent at least one iMRI, and 19% required one or more additional sets of intraoperative imaging. In 58% of patients, iMRI led to the surgeon attempting more resection. A gross total resection was obtained in 67% of the patients with planned total resections. There was one case of permanent postoperative diabetes insipidus and no other instances of new hormone replacement. In summary, iMRI was most useful for tumors of the sella with and without suprasellar extension where the information from the iMRI extended the complete resection rate from 40 to 72% and 55 to 88%, respectively. As one would expect, it did not substantially increase the rate of resection of tumors with cavernous sinus invasion. Overall, iMRI was particularly useful in guiding resection safely, aiding in clinical decision making, and allowing identification and preservation of the pituitary stalk and normal pituitary gland. Limitations of the iMRI include a need for additional personnel and training as well as additional operative time, which diminishes over time as personnel learn to optimize workflow efficiency. Additional costs are mitigated in part by using the iMRI as an immediate postoperative scan. Other data emerging from our experience suggest that preservation of normal gland and thus avoidance of hypopituitarism may be improved by iMRI use, but longer follow-up periods are required to test this conclusion. iMRI can detect unsuspected complications sooner than routine postoperative imaging, potentially leading to improved outcomes. However, larger studies are needed.

Device setting modifications for 3D flatpanel imaging in skull base surgery

To evaluate the image quality and clinical implementation after setting modification of a three-dimensional isocentric C-arm fluoroscopic image intensifier system combined with a digital flatpanel detector as a new tool for sinus and petrous bone surgery. Image acquisition was performed using two cadaveric heads. Experimental design was oriented to the clinically sensible intraoperative setup. Different tube currents and orbital movements of the C-arm system were evaluated for image quality by three otolaryngological surgeons using predetermined landmarks. Modification of the X-ray intensity did not attain statistically significant values compared to the X-ray-intensity predetermined by producer (12.0-18.5 mA, p > 0.05) for either sinus or for petrous bone scans. Elliptical orbital movement resulted in significantly superior image quality than data sets acquired by circular orbital movement (3.194 vs. 2.809, p < 0.0001). New C-arm systems with 3D-capabiltity offer a promising tool for intraoperative near real-time image guidance. Image quality of the skull base can be improved significantly with optimized system settings.

Intraoperative MRI and endocrinological outcome of transsphenoidal surgery for non-functioning pituitary adenoma

BACKGROUND

Transsphenoidal surgery guided by intraoperative MRI (iMRI) is related to higher rates of tumour resection. The influence of iMRI on endocrinological outcome is still unclear. This study evaluates the endocrinological outcome of iMRI-guided transsphenoidal surgery.

METHODS

A series of 60 patients operated by iMRI-guidance for inactive adenomas were matched to a previous series of 32 controls. The following factors were used for matching: gender; age; tumour volume; Hardy's grade; pituitary function; pituitary stalk configuration; stalk effect hyperprolactinemia; arterial hypertension; diabetes mellitus; smoking.

RESULTS

Total resection rates were higher in the iMRI group (85%) than in the control group (69%). Follow-up times were 3.2 ± 1.0 years in the iMRI group and 6.8 ± 4.1 years for controls. No patient in the iMRI group needed additional tumour treatment, as opposed to 13% of the controls. The rate of postoperative hypopituitarism was 29% in the iMRI and 45% in the control group. Predictors for new hypopituitarism in the iMRI group were age >65 years, Hardy's grade >2 tumours and hypertension. Recovery rates were 59% in the iMRI and 45% for controls. Predictors of better recovery rates were female gender and age <65 years. The following predictors lead to an endocrinological benefit of iMRI-guidance: Hardy's grade <3 tumours; age <65 years; no hypertension; non-smokers; dysfunction of two or three axes pre-operatively.

CONCLUSION

The use of iMRI in transsphenoidal surgery for non-functioning pituitary adenoma might lead to higher total resection rates. In our series, resection of remnants detected by iMRI was neither associated with higher incidences of postoperative hypopituitarism nor with lower recovery rates of pituitary axes.

Advances in pituitary imaging technology and future prospects

There have been substantial advances in pituitary imaging in the last half-century. In particular, magnetic resonance imaging is now established as the imaging modality of choice, providing high quality images of the hypothalamic-pituitary axis and adjacent structures. More recent technological advances, such as the emergence of 3 Tesla MRI, are already being widely incorporated into imaging practice. However, other advanced techniques, including a variety of potential imaging biomarkers, still require further research to evaluate their potential and define their precise role. The recent development of intraoperative MRI appears promising and may have the potential to improve the outcome of pituitary surgery. Modern high quality imaging inevitably leads to the discovery of incidental lesions, including those within the pituitary gland, although it also plays a central role in their subsequent evaluation and management.

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.

Combined intraoperative magnetic resonance imaging and navigated neuroendoscopy in children with multicompartmental hydrocephalus and complex cysts: a feasibility study

OBJECT

The rationale for using endoscopy to treat complex cysts and multiloculated hydrocephalus is to combine several CSF compartments into a minimum number, establish a connection to functioning CSF compartments (that is, ventricles), and decrease shunt dependency. The aim is to decrease the number of proximal shunt catheters, the number of shunt revisions, and in selected cases even to avoid a shunt. In cases of distorted anatomy and multiloculated cysts, endoscopy may be problematic because of orientation issues. Standard navigation becomes useless soon after CSF loss due to brain shift. Therefore, the concept of "real-time" navigation and intraoperative imaging in combination with endoscopic surgery has been previously suggested. The goal of the present study was to assess the feasibility and efficacy of combining intraoperative MR (iMR) imaging and navigated neuroendoscopy in infants.

METHODS

The authors report their experience in treating 5 infants (aged 6-14 months), who underwent surgery for multicystic hydrocephalus presenting with shunt malfunction (4 patients) and a quadrigeminal fetal arachnoid cyst (1 patient). In all infants, a low-field portable iMR imaging system (0.12-T PoleStar N-10/0.15-Tesla PoleStar N-20) was used in conjunction with navigated endoscopy. The authors used e-steady, T1-weighted, and T2-weighted sequences (acquisition time 24 seconds to 3.5 minutes).

RESULTS

The iMR imaging system provided clear images that correlated with the endoscopic appearance of the cystic membranes in all patients, and the images were helpful in determining trajectories and redefining targets. The iMR images documented brain shift and changes in CSF spaces during surgery. There were no intraoperative complications or technical difficulties of visualization. No infection or any other immediate postoperative complication occurred. Patients were followed up for 9 months to 7 years. The infant presenting with the quadrigeminal cyst remains shunt free since surgery, and the patients with multicystic hydrocephalus have 1-2 shunts each. Following endoscopic, iMR imaging-guided surgery, shunt catheter positioning was found to be optimal and as planned according to the postoperative imaging.

CONCLUSIONS

Navigated neuroendoscopy and iMR imaging may complement each other, offering an advantage over other modalities in complicated cases of hydrocephalus. Whenever targets and trajectories need to be redefined, the iMR images provided an updated navigation data set, allowing accurate navigation of the endoscope and minimizing the number of CSF compartments. Direct vision through the endoscope provides microanatomical details for the optimization of fenestration and catheter positioning. The combined usage of the two modalities may transform a conventional procedure into a visually controlled real-time navigated process.

Intraoperative magnetic resonance imaging and early prognosis for vision after transsphenoidal surgery for sellar lesions

Object

Sellar lesions with suprasellar extension may cause loss of visual acuity and visual field damage due to compression of the optic chiasm. Using intraoperative MR (iMR) imaging to detect symptomatic lesion remnants adjacent to the optic chiasm (that may be resected in the same procedure) may positively affect the functional outcome of patients with these lesions. The aim of this study was to evaluate the correlation between visual improvement and optic nerve decompression detected by iMR imaging in patients undergoing transsphenoidal resection of pituitary lesions.

Methods

A total of 32 patients (23 men and 9 women) who underwent transsphenoidal resection of sellar lesions causing visual impairment were included in this study. Tumor volume ranged from 0.9 cm3 to 55.7 cm3 (mean 9.8 ± 11.7 cm3). Preoperative assessment showed visual field damage in 31 patients (97%) and loss of visual acuity in 28 patients (88%). The latency period between the appearance of symptoms and transsphenoidal decompression was 14.9 ± 19.5 weeks.

Results

Intraoperative MR imaging was performed after the resection was believed to be complete, or if further tumor removal was not safely possible due to changed conditions in the surgical field. Complete resection was detected on these initial scans in 17 patients (53%). Partial resection was achieved in 9 patients (28%) and tumor debulking in 6 (19%). Additional resection was possible in 8 (53%) of these 15 patients. Four (50%) of these 8 cases had suprasellar remnants and the optic chiasm was subsequently decompressed. In 5 cases optimal decompression of the optic chiasm was not possible. On early follow-up within 1 month after surgery, overall improvement of visual field damage was observed in 27 patients (87%). In 23 patients (74%), the Goldmann perimetry demonstrated complete recovery. Improvement of visual acuity was noted in 24 patients (86%). Eighteen patients (64%) regained full visual acuity. Identification of a decompressed optic chiasm on iMR imaging was significantly correlated with visual field improvement (p = 0.0007; positive predictive value 0.96, 95% CI 0.81–0.99) and relief of visual acuity deficits (p = 0.0002; positive predictive value 0.96, 95% CI 0.79–0.99). Two patients needed transcranial procedures for symptomatic tumor remnants detected on iMR imaging.

Conclusions

Intraoperative MR imaging findings correlate with prognosis of visual deficits after transsphenoidal decompression of the anterior optic pathways. The use of iMR imaging may prevent revision surgery for unexpected symptomatic remnants.

Clinical and economic outcomes of low-field intraoperative MRI-guided tumor resection neurosurgery

PURPOSE

To compare low-field (0.15 T) intraoperative magnetic resonance imaging (iMRI)-guided tumor resection with both conventional magnetic resonance imaging (cMRI)-guided tumor resection and high-field (1.5 T) iMRI-guided resection from the clinical and economic point of view.

MATERIALS AND METHODS

We retrospectively compared 65 iMRI patients with 65 cMRI patients in terms of hospital length of stay, repeat resection rate, repeat resection interval, complication rate, cost to the patient, cost to the hospital, and cost effectiveness. In addition, we compared our low-field results with previously published high-field results.

RESULTS

The complication rate was lower for iMRI vs. cMRI in patients presenting for their initial tumor resection (45 vs. 57 complications, P = 0.048). The iMRI repeat resection interval was longer for this cohort (20.1 vs. 6.7 months, P = 0.020). iMRI was more cost-effective than cMRI for patients who had repeat resections ($10,690/RFY vs. $76,874/RFY, P < 0.001). We found no other clinical or economic differences between iMRI- and cMRI-guided tumor resection surgeries. Overall, we did not find the advantages to low-field iMRI that have been reported for high-field iMRI.

CONCLUSION

There is no adequate justification for the widespread installation of low-field iMRI in its current development state.

Intra-operative MRI facilitates tumour resection during trans-sphenoidal surgery for pituitary adenomas

Background

During trans-sphenoidal microsurgical resection of pituitary adenomas, the extent of resection may be difficult to assess, especially when extensive suprasellar and parasellar growth has occurred. In this prospective study, we investigated whether intra-operative magnetic resonance imaging (iMRI) can facilitate tumour resection.

Methods

Twenty patients with macroadenomas, (16 non-functioning, three growth-hormone secreting and one pharmaco-resistant prolactinoma) were selected for surgery in the iMRI. The mean tumour diameter was 27 mm (range 11–41). The mean parasellar grade, according to the Knosp classification, was 2.3. Pre-operative coronal and sagittal T1-weighted and T2-weighted images were obtained. The trans-sphenoidal tumour resection was performed at the edge of the tunnel of a Signa SP 0.5-Tesla MRI. The surgeon aimed at a radical tumour resection that was followed by a peri-operative MRI scan. When a residual tumour was visualised and deemed resectable, an extended resection was performed, followed by another MRI scan. This procedure was repeated until the imaging results were satisfactory. In all patients, we were able to obtain images to assess the extent of resection and to classify the resection as either total or subtotal.

Results

After primary resection, eight out of 20 cases were classified as total resections. A second resection was performed in 11 of 12 cases classified as subtotal resections, and in four of these, total resection was achieved. A third resection was performed in three of the remaining seven cases with subtotal resections, but we did not achieve total resection in any of these cases. Therefore, the use of iMRI increased the number of patients with total resection from 8/20 (40%) to 12/20 (60%). The only observed complication was a transient spinal fluid leakage.

Conclusion

Intra-operative MRI during trans-sphenoidal microsurgery is useful in selected patients for a safe and more complete resection.

Implementation of the ultra low field intraoperative MRI PoleStar N20 during resection control of pituitary adenomas

OBJECTIVE

To describe our experience with the application of an intraoperative ultra low field magnetic resonance imaging system (ioMRI) PoleStar N20, Medtronic Surgical Navigation Technologies, Louisville, USA during resection control of pituitary adenomas.

METHODS

Forty-four patients were operated on a pituitary adenoma (1 microadenoma, 43 macroadenomas; mean size 26.0 ± 9.7 mm). The ioMRI system was used for navigation and resection control after transseptal, transsphenoidal microsurgical tumour removal using standard instruments and standard microscope. If any accessible tumour remnant was suspected surgery was continued for navigation guided re-exploration and if necessary continued resection.

RESULTS

The applications of the scanner integrated navigation system, with a 3-planar reconstruction of the coronal scan, enabled the surgeon to safely approach and remove the tumour. The quality of preoperative tumour visualization with the ultra low field ioMRI in patients with macroadenomas is very good and has a good congruency with the preoperative 1.5 T MRI. For microadenomas the preoperative visualization is poor and very difficult to interpret. In seven patients ioMRI resection control showed residual tumours leading to further resection. After final tumour resection the ioMRI scan documented adequate decompression of the optic pathway in all patients. However, the intraoperative image interpretation was equivocal in four patients in whom it was difficult to distinguish between small intrasellar tumour remnants and perioperative changes.

CONCLUSIONS

The PoleStar N20 is a safe, helpful and feasible tool for navigation guided pituitary tumour approach. Image interpretation is requires some experience, but decompression of the optic system can be reliable shown in cases with pituitary macroadenomas. This system is of limited value for resection control of pituitary microadenomas.

Intraoperative computed tomography registration and electromagnetic neuronavigation for transsphenoidal pituitary surgery: accuracy and time effectiveness

Object

The authors assessed the feasibility, anatomical accuracy, and cost effectiveness of frameless electromagnetic (EM) neuronavigation in conjunction with portable intraoperative CT (iCT) registration for transsphenoidal adenomectomy (TSA).

Methods

A prospective database was established for data obtained in 208 consecutive patients who underwent TSA in which the iCT/EM navigation technique was used. Data were compared with those acquired in a retrospective cohort of 65 consecutive patients in whom fluoroscope-assisted TSA had been performed by the same surgeon. All patients in both groups underwent transnasal removal of pituitary adenomas or neuroepithelial cysts, using identical surgical techniques with an operating microscope. In the iCT/EM technique–treated cases, a portable iCT scan was obtained immediately prior to surgery for registration to the EM navigation system, which did not require rigid head fixation. Preexisting (nonnavigation protocol) MR imaging studies were fused with the iCT scans to enable 3D navigation based on MR imaging data. The accuracy of the navigation system was determined in the first 50 iCT/EM cases by visual concordance of the navigation probe location to 5 preselected bony landmarks. For all patients in both cohorts, total operating room time, incision-to-closure time, and relative costs of imaging and surgical procedures were determined from hospital records.

Results

In every case, iCT registration was successful and preoperative MR images were fused to iCT scans without affecting navigation accuracy. There was 100% concordance between probe tip location and predetermined bony loci in the first 50 cases involving the iCT/EM technique. Total operating room time was significantly less in the iCT/EM cases (mean 108.9 ± 24.3 minutes [208 patients]) compared with the fluoroscopy group (mean 121.1 ± 30.7 minutes [65 patients]; p < 0.001). Similarly, incision-to-closure time was significantly less for the iCT/EM cases (mean 61.3 ± 18.2 minutes) than for the fluoroscopy cases (mean 71.75 ± 19.0 minutes; p < 0.001). Relative overall costs for iCT/EM technique and intraoperative C-arm fluoroscopy were comparable; increased costs for navigation equipment were offset by savings in operating room costs for shorter procedures.

Conclusions

The use of iCT/MR imaging–guided neuronavigation for transsphenoidal surgery is a time-effective, cost-efficient, safe, and technically beneficial technique.

A sparse intraoperative data-driven biomechanical model to compensate for brain shift during neuronavigation

BACKGROUND AND PURPOSE

Intraoperative brain deformation is an important factor compromising the accuracy of image-guided neurosurgery. The purpose of this study was to elucidate the role of a model-updated image in the compensation of intraoperative brain shift.

MATERIALS AND METHODS

An FE linear elastic model was built and evaluated in 11 patients with craniotomies. To build this model, we provided a novel model-guided segmentation algorithm. After craniotomy, the sparse intraoperative data (the deformed cortical surface) were tracked by a 3D LRS. The surface deformation, calculated by an extended RPM algorithm, was applied on the FE model as a boundary condition to estimate the entire brain shift. The compensation accuracy of this model was validated by the real-time image data of brain deformation acquired by intraoperative MR imaging.

RESULTS

The prediction error of this model ranged from 1.29 to 1.91 mm (mean, 1.62 ± 0.22 mm), and the compensation accuracy ranged from 62.8% to 81.4% (mean, 69.2 ± 5.3%). The compensation accuracy on the displacement of subcortical structures was higher than that of deep structures (71.3 ± 6.1%:66.8 ± 5.0%, P < .01). In addition, the compensation accuracy in the group with a horizontal bone window was higher than that in the group with a nonhorizontal bone window (72.0 ± 5.3%:65.7 ± 2.9%, P < .05).

CONCLUSIONS

Combined with our novel model-guided segmentation and extended RPM algorithms, this sparse data-driven biomechanical model is expected to be a reliable, efficient, and convenient approach for compensation of intraoperative brain shift in image-guided surgery.

Long term outcome following repeat transsphenoidal surgery for recurrent endocrine-inactive pituitary adenomas

It is widely accepted that the standard first-line treatment for most endocrine inactive pituitary macroadenomas (EIA) is surgery, usually via a transsphenoidal approach. What is less clear is what approach to take when these tumors recur, especially when this recurrence involves areas which are difficult to surgically remove tumor from, such as the suprasellar region or cavernous sinuses. We present long term follow-up for a series of 81 patients who underwent repeat surgery for recurrent non-secreting pituitary adenomas. We analyzed data collected from all adult patients undergoing their second microsurgical transsphenoidal resection of a histologically proven endocrine-inactive pituitary adenoma at the University of California at San Francisco between January 1970 and March 2001. Data for these patients were collected by review of medical records, mail, and/or telephone interviews. Visual function, anterior pituitary function, and tumor control rates were analyzed for the series. Records were available for a total of 81 recurrent EIA patients. The median time between their initial and repeat operations was 4.1 years. The mean tumor size was 2.2 +/- 0.2 cm. A total of 35/81 patients had greater than 5 years of follow-up. A total of 24/81 patients had greater than 10 years of follow-up. Over one half of these patients presented with visual disturbance, and we found that 39% of these patients experienced improved vision with a second surgery. More importantly, no one with normal vision suffered any appreciable decline in vision. Approximately, 35% of patients with pre-operative anterior pituitary dysfunction recovered function after surgery in our series; and no patient's function worsened. A total of 4/52 (8%) patients with greater than 2 years of post-op follow-up experienced a clinically meaningful tumor recurrence requiring additional treatment. Our data suggest that when performed by experienced transsphenoidal surgeons, durable tumor control can be obtained in these frequently locally aggressive tumors with acceptable rates of post-operative morbidity.