Intraoperative high-field-strength MR imaging: implementation and experience in 200 patients

Multifunctional surgical suite (MFSS) with 3.0 T iMRI: 17 months of experience

The 3T ioMRI in Prague is composed of two independent suites: the operating theatre and the 3T MR suite, both of which can and do work independently. They are connected by a double door and a special transportation system. The whole operating table is moved on rails to and from the MR gantry. Anaesthesiological equipment is built from paramagnetic material, which is also moved to and from the MR suite. The integral parts of the multifunctional surgical suite (MFSS) are the neuronavigation system, electrophysiological monitoring, surgical microscope with availability of indocyanin green angiography and fluorescence-guided glioma resection technique and endoscopy equipment. The operating theatre is equipped in a normal fashion with the exception of a head holder that is paramagnetic. MR radiologist and MR assistants are alerted approximately 30 min before the requested intraoperative and out-patient service is interrupted to clean the MR suite. The ioMRI takes 15-20 min and immediately after the door closes the out patient activity is resumed. Intraoperative MR was performed in 332 surgeries in the first 17 months of operation. The most frequent indications were pituitary adenomas, followed by gliomas. Other indications were less frequent and included meningiomas, cavernomas, aneurysms, epilepsy surgery, intramedullary lesions, non-pituitary sellar lesions, metastases and various other surgeries. In 332 cases no technical or medical complication connected with ioMRI was encountered.

One year experience with 3.0 T intraoperative MRI in pituitary surgery

A multifunctional surgical suite with intraoperative 3.0 T MRI (ioMRI) has been operating at the Central Military Hospital, Prague since April 2008. Our experiences over the past year and the effect of ioMRI on the extent of pituitary adenoma resection are evaluated. Eighty-six pituitary adenoma resections were performed in 85 patients with ioMRI in the first year of the ioMRI service. Pituitary adenoma suprasellar extension was present in 60 cases, invasion into cavernous sinus in 49 cases, and retrosellar growth in one case. The surgical goal was set before surgery: either a radical resection (49 cases) or a partial resection (37 cases). In the group of patients where a decision for a radical resection was taken the results are as follows: ioMRI confirmed radical resection in 69.4% of the cases; ioMRI disclosed unexpected adenoma residuum and further resection led to radical resection in 22.4%. In the group of patients where a decision for a partial resection was taken, the results are as follows: no further resection was perfomed after ioMRI in 51.3% of the cases and further resection was performed after ioMRI in 48.7% of the cases. ioMRI seems to be a valuable tool to increase the extent of pituitary adenoma resection.

Intraoperative imaging in neurosurgery: where will the future take us?

Intraoperative MRI (ioMRI) dates back to the 1990s and since then has been successfully applied in neurosurgery for three primary reasons with the last one becoming the most significant today: (1) brain shift-corrected navigation, (2) monitoring/controlling thermal ablations, and (3) identifying residual tumor for resection. IoMRI, which today is moving into other applications, including treatment of vasculature and the spine, requires advanced 3T MRI platforms for faster and more flexible image acquisitions, higher image quality, and better spatial and temporal resolution; functional capabilities including fMRI and DTI; non-rigid registration algorithms to register pre- and intraoperative images; non-MRI imaging improvements to continuously monitor brain shift to identify when a new 3D MRI data set is needed intraoperatively; more integration of imaging and MRI-compatible navigational and robot-assisted systems; and greater computational capabilities to handle the processing of data. The Brigham and Women's Hospital's "AMIGO" suite is described as a setting for progress to continue in ioMRI by incorporating other modalities including molecular imaging. A call to action is made to have other researchers and clinicians in the field of image guided therapy to work together to integrate imaging with therapy delivery systems (such as laser, MRgFUS, endoscopic, and robotic surgery devices).

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.

Influence of iMRI-Guidance on the Extent of Resection and Survival of Patients with Glioblastoma Multiforme

Intraoperative MRI (iMRI) is used in glioma surgery mainly to determine the extent of resection, allowing surgeons to immediately continue resection in case of residual tumor tissue. The aim of this study is to report on the influence of the use of iMRI on the extent of resection and survival of patients with glioblastoma multiforme (GBM).

We analyzed our prospectively collected database of patients with GBM operated upon during the initial period after installation of an iMRI; between July 2004 and December 2005, all patients with GBM undergoing intended complete tumor resection were included in this study, while patients undergoing mere tumor biopsy or intended incomplete resection were not.

In total, 43 Patients met the inclusion criteria. Of these, 10 patients (23.3%) were operated upon with the help of iMRI while 33 underwent conventional tumor resection. All patients underwent postoperative high-field MR imaging at 1.5 Tesla to determine the extent of resection. Subsequently, all patients received adjuvant treatment. Median patient age was 60.0 years; median overall survival was 70.7 weeks. Radiologically complete tumor resection (P < 0.001) and the administration of temozolomide chemotherapy (P < 0.01) were statistically significant prognostic factors in a multivariate analysis. The rate of complete tumor resections was significantly higher in the iMRI group than in the conventional surgery group (P < 0.05). Patient age was not a prognostic factor in our series of patients (P = 0.22). Intraoperative MRI is a helpful tool to increase the extent of resection in GBM surgery and thereby improve patient survival.

The role of outcomes data for assessing the expertise of a pituitary surgeon

PURPOSE OF REVIEW

Over the past four decades, advances in surgical technique, instrumentation, and anatomical knowledge have fueled the evolution and sophistication of transsphenoidal pituitary surgery. Paralleling these advances have been major improvements in endocrinological and overall clinical outcomes in patients with pituitary adenomas and other parasellar lesions such as Rathke's cleft cysts and craniopharyngiomas. In this review, we assess the impact of neurosurgeon expertise as a determinant of outcome in pituitary surgery.

RECENT FINDINGS

Published data since the 1980s indicate that remission rates, overall clinical outcomes and surgical complication rates in pituitary and parasellar surgery are related to neurosurgeon practice volume and cumulative clinical experience. More recently, pituitary surgery has been increasingly performed using an endonasal endoscopic approach. Reports over the last decade suggest when an experienced pituitary neurosurgeon performs a fully endoscopic or endoscope-assisted tumor removal; outcomes are similar if not better than when performed by a traditional microscopic transsphenoidal approach.

SUMMARY

A focused clinical practice and large transsphenoidal surgical volume appear to be important outcome determinants for patients with pituitary and parasellar tumors. Strategies that may further improve patient outcomes include establishing guidelines for pituitary tumor centers of excellence and more focused residency and fellowship training in endonasal endoscopic transsphenoidal surgery. Encouraging regionalization of care to higher volume pituitary tumor centers of excellence and promoting patient education on the importance of surgical expertise may further enhance pituitary patient outcomes.

The combination of semi-sitting position and intraoperative MRI--first report on feasibility

INTRODUCTION

Intraoperative MRI (iMRI) has been established as a routine imaging modality with a remarkable impact on specific neurosurgical procedures. The technological advancement continuously extends the spectrum of iMRI, leading to an increasing number of installations. Yet, procedures in which a semi-sitting position would be advantageous were beyond the reach of iMRI.

MATERIALS AND METHODS

We performed an iMRI-guided surgical procedure in a patient with a cystic lesion of the inferior parieto-occipital lobe while the patient was placed in a semi-sitting position, employing a mobile 0.15-T intraoperative MRI system. For that purpose, we adapted a standard OR table according to the needs of iMRI.

FINDINGS

Patient positioning could be accomplished easily. For intraoperative scanning, the OR table was tilted backwards so as to position the patient's head in the magnet's aperture. Obtained images were used for neuronavigated cyst evacuation via burr hole trephination after repositioning the OR table. Subsequent intraoperative imaging documented collapse of the cyst at the end of the procedure. There were no adverse effects resulting from the combination of semi-sitting position and iMRI guidance.

CONCLUSION

This report demonstrates for the first time that the combination of iMRI and the semi-sitting position is feasible and that this procedure bears specific benefits. Issues such as brain shift due to table tilting warrant further investigations in order to expand this technique to posterior fossa craniotomies.

Clinical indications for high-field 1.5 T intraoperative magnetic resonance imaging and neuro-navigation for neurosurgical procedures. Review of initial 100 cases

Initial experiences are reviewed in an integrated operation theater equipped with an intraoperative high-field (1.5 T) magnetic resonance (MR) imager and neuro-navigation (BrainSUITE), to evaluate the indications and limitations. One hundred consecutive cases were treated, consisting of 38 gliomas, 49 other tumors, 11 cerebrovascular diseases, and 2 functional diseases. The feasibility and usefulness of the integrated theater were evaluated for individual diseases, focusing on whether intraoperative images (including diffusion tensor imaging) affected the surgical strategy. The extent of resection and outcomes in each histological category of brain tumors were examined. Intraoperative high-field MR imaging frequently affected or modified the surgical strategy in the glioma group (27/38 cases, 71.1%), but less in the other tumor group (13/49 cases, 26.5%). The surgical strategy was not modified in cerebrovascular or functional diseases, but the success of procedures and the absence of complications could be confirmed. In glioma surgery, subtotal or greater resection was achieved in 22 of the 31 patients (71%) excluding biopsies, and intraoperative images revealed tumor remnants resulting in the extension of resection in 21 of the 22 patients (95.4%), the highest rate of extension among all types of pathologies. The integrated neuro-navigation improved workflow. The best indication for intraoperative high-field MR imaging and integrated neuro-navigation is brain tumors, especially gliomas, and is supplementary in assuring quality in surgery for cerebrovascular or functional diseases. Immediate quality assurance is provided in several types of neurosurgical procedures.

Application of intraoperative high-field magnetic resonance imaging in pediatric neurosurgery

OBJECT

Over the past decade, the use of intraoperative MR (iMR) imaging in the pediatric neurosurgical population has become increasingly accepted as an innovative and important neurosurgical tool. The authors summarize their experience using a mobile 1.5-T iMR imaging unit with integrated neuronavigation with the goal of identifying procedures and/or pathologies in which the application of this technology changed the course of surgery or modified the operative strategy.

METHODS

A database has been prospectively maintained for this patient population. The authors reviewed the hospital charts and imaging results for all patients in the database. This review revealed 105 neurosurgical procedures performed in 98 children (49 male and 49 female) between March 1998 and April 2008. Intradissection (ID) and/or quality assurance images were obtained at the discretion of the surgeon.

RESULTS

The median age at surgery was 12 years (4 months-18 years). One hundred intracranial and 5 spinal procedures were performed; 22 of these procedures were performed for recurrent pathology. Surgical planning scans were obtained for 102 procedures, and neuronavigation was used in 93 patients. The greatest impact of iMR imaging was apparent in the 55 procedures to resect neoplastic lesions; ID scans were obtained in 49 of these procedures. Further surgery was performed in 49% of the procedures during which ID scans had been obtained. A smaller proportion of ID scans in the different cranial pathology groups (5 of 21 epilepsy cases, 4 of 9 vascular cases) resulted in further resections to meet the surgical goal of the surgeon. Two ID scans obtained during 5 procedures for the treatment of spinal disease did not lead to any change in surgery. Postoperative scans did not reveal any acute adverse events. There was 1 intraoperative adverse event in which a Greenberg retractor was inadvertently left on during ID scanning but was removed after the scout scans.

CONCLUSIONS

The application of iMR imaging in the pediatric neurosurgical population allows, at minimum, the opportunity to perform less invasive surgical exposures. Its potential is greatest when its high-quality imaging ability is coupled with its superior neuronavigation capabilities, which permits tracking of the extent of resection of intracranial tumors and, to a lesser extent, other lesions during the surgical procedure.

Intraoperative MRI: safety

Intraoperative and interventional MR have opened a new chapter in neurosurgery bringing both new therapeutic opportunities and creating unique safety challenges for the MR operating room. The presence of a large magnetic field in the otherwise familiar environment of the operating room necessitates site-specific comprehensive policies for safety, staff training, infection control, and MR compatibility. Intraoperative MRI also creates unique MR image interpretation challenges that are of paramount significance for patient safety. These safety concerns are reviewed with particular reference to the nine years experience of the authors.

Impact of intraoperative high-field magnetic resonance imaging guidance on glioma surgery: a prospective volumetric analysis

OBJECTIVE

To determine the impact of intraoperative magnetic resonance imaging (iMRI) on the decision to proceed with additional glioma resection during surgery and to maximize extent of resection (EOR).

METHODS

Patients who underwent craniotomy for glioma resection with high-field iMRI guidance were prospectively evaluated between September 2006 and August 2007. Volumetric analysis and EOR were assessed with iMRI, using postcontrast T1-weighted images for tumors showing contrast enhancement and T2-weighted images for nonenhancing tumors.

RESULTS

Forty-six patients underwent resection using iMRI guidance, with iMRI being used to evaluate the EOR in 44 patients and for reregistration in 2 patients. Surgery was terminated after iMRI in 23 patients (52%) because gross total resection was achieved or because of residual tumor infiltration in an eloquent brain region. Twenty-one patients (47%) underwent additional resection of residual tumor after iMRI. For enhancing gliomas, the median EOR increased significantly from 84% (range, 59%-97%) to 99% (range, 85%-100%) with additional tumor removal after iMRI (P < 0.001). For nonenhancing gliomas, the median EOR increased (from 63% to 80%) with additional tumor removal after iMRI, but not significantly, owing to the small sample size (7 patients). Overall, the EOR increased from 76% (range, 35%-97%) to 96% (range, 48%-100%) (P < 0.001). Gross total resection was achieved after additional tumor removal after iMRI in 15 of 21 patients (71%). Overall, 29 patients (65%) experienced gross total resection, and in 15 (52%), this was achieved with the contribution of iMRI.

CONCLUSION

High-field iMRI is a safe and reliable technique, and its use optimizes the extent of glioma resection.

The predictive value of low–field strength magnetic resonance imaging for intraoperative residual tumor detection

Object

Neurosurgeons have been utilizing intraoperative MR (iMR) imaging to evaluate the extent of tumor resection since the 1990s. A low–field strength (0.12 T) MR imaging unit (PoleStar N20, Medtronic) is a practical and relatively inexpensive iMR imaging system that has found increased use in neurosurgery. The gold standard for postoperative detection of residual tumor has been high-strength MR imaging performed within 48 hours of resection. The object of this study was to determine the predictive concordance of low-strength iMR imaging with standard high-strength MR imaging for detection of residual tumor.

Methods

The authors retrospectively evaluated the MR images from 74 intracranial tumor resections, comparing the intraoperative images obtained using a 0.12-T iMR imaging unit to the immediate postoperative images obtained using a standard 1.5-T MR imaging unit within 48 hours after surgery.

Results

The sensitivity of low-field MR imaging for detection of residual tumor was 0.74 (95% CI 0.58–0.86), and its specificity was 0.97 (95% CI 0.83–1). When only glial tumors (42 of the 74 lesions) were analyzed, the sensitivity was 0.82 (95% CI 0.59–0.94) and the specificity was 0.95 (95% CI 0.73–1).

Conclusions

These data could assist the neurosurgeon who has to decide intraoperatively whether the observed iMR images show residual tumor or not.

Use of real‐time magnetic resonance image guidance in endoscopic sinus surgery

We evaluated the effectiveness of magnetic resonance image (MRI) guidance using an optical tracking system (MRI-guided therapy: MRT) in performing endoscopic sinus surgery (ESS). The profiles of the fourteen patients in the present study were as follows: eleven with mucocele in the paranasal sinus, one with recurrent chronic sinusitis, one with maxillary cancer, and one with Graves' ophthalmopathy. Preparation of the MRT system required an additional 54 min in cases involving general anesthesia, and an additional 17 min in cases involving local anesthesia, in comparison with corresponding control groups undergoing ESS in a traditional operating room. We developed nonmetal probes that were visualized in a real-time mode and assistive devices for the optical tracking system that were equipped to avoid obstruction caused by surgical instruments as well as by the hands of surgeons. Using these unique devices, anatomic landmarks were visualized using the present MRT system. The prognosis of patients was favorable, and in particular, no patients with sinus mucocele showed a recurrence of their lesions. We concluded that the MRT system used here for performing ESS was beneficial, especially in terms of the intranasal marsupialization of sinus mucoceles and for the verification of orbital contents.

TRANSSPHENOIDAL PITUITARY MACROADENOMAS RESECTION GUIDED BY POLESTAR N20 LOW-FIELD INTRAOPERATIVE MAGNETIC RESONANCE IMAGING

OBJECTIVE

To evaluate the applicability of low-field intraoperative magnetic resonance imaging (iMRI) during transsphenoidal surgery of pituitary macroadenomas.

METHODS

Fifty-five transsphenoidal surgeries were performed for macroadenomas (modified Hardy's Grade II–IV) resections. All of the surgical processes were guided by real-time updated contrast T1-weighted coronal and sagittal images, which were acquired with 0.15 Tesla PoleStar N20 iMRI (Medtronic Navigation, Louisville, CO). The definitive benefits as well as major drawbacks of low-field iMRI in transsphenoidal surgery were assessed with respect to intraoperative imaging, tumor resection control, comparison with early postoperative high-field magnetic resonance imaging, and follow-up outcomes.

RESULTS

Intraoperative imaging revealed residual tumor and guided extended tumor resection in 17 of 55 cases. As a result, the percentage of gross total removal of macroadenomas increased from 58.2% to 83.6%. The accuracy of imaging evaluation of low-field iMRI was 81.8%, compared with early postoperative high-field MRI (Correlation coefficient, 0.677; P &lt;0.001). A significantly lower accuracy was identified with low-field iMRI in 6 cases with cavernous sinus invasion (33.3%) in contrast to the 87.8% found with other sites (Fisher's exact test, P &lt;0.001).

CONCLUSION

The PoleStar N20 low-field iMRI navigation system is a promising tool for safe, minimally invasive, endonasal, transsphenoidal pituitary macroadenomas resection. It enables neurosurgeons to control the extent of tumor resection, particularly for suprasellar tumors, ensuring surgical accuracy and safety, and leading to a decreased likelihood of repeat surgeries. However, this technology is still not satisfying in estimating the amount of the parasellar residual tumor invading into cavernous sinus, given the false or uncertain images generated by low-field iMRI in this region, which are difficult to discriminate between tumor remnant and blood within the venous sinus.

Intraoperative cone-beam computed tomography in oral and maxillofacial surgery using a C-arm prototype: first clinical experiences after treatment of zygomaticomaxillary complex fractures

PURPOSE

To describe the first clinical applications of intraoperative cone-beam computed tomography with an integrated flat-panel detector in oral and maxillofacial surgery after surgical treatment of zygomaticomaxillary complex fractures

PATIENTS AND METHODS

Nine cone-beam computed tomography datasets of patients with zygomaticomaxillary complex fractures were intraoperatively acquired using a mobile isocentric C-arm (PowerMobil; Siemens Medical Solutions, Erlangen, Germany), including a flat-panel detector. Datasets based on 400, 200, and 100 fluoroscopic images were performed with different tube currents (4.6 mA, 3.3 mA, 2.3 mA, 1.2 mA, and 0.5 mA) and a current tube voltage of 100 kV. Postprocessing resulted in 15 different datasets available for comparison with corresponding preoperative computed tomography datasets. Four oral and maxillofacial surgeons and 2 experienced radiologists evaluated each dataset regarding noise, transition, and the delimitation of landmarks.

RESULTS

All examinations were successfully performed. Reconstructed datasets showed high-resolution images of all midfacial osseous structures in near-computed tomography quality. Regarding high-contrast structures, detailed analyses of datasets acquired in this study suggest that the parameters 400 projections, 1.2 mA, and 100 kV are sufficient. In terms of soft-tissue visualization, a higher level of mA seems preferable.

CONCLUSIONS

The tested prototype predicts a new era in cone-beam computed tomography imaging. The integration of a flat-panel detector will overcome the limitations of current available systems. The size of the field of view is increased allowing regularly the visualization of the whole facial skeleton. Particularly in cases of open reduction of unilateral fractures, the assessment of symmetry is of clinical value.

Updating navigation with intraoperative image data

OBJECTIVES

To localize overlooked tumor remnants by updating navigation with intraoperative magnetic resonance imaging compensating for the effects of brain shift.

METHODS

In 112 patients among 805 patients that were investigated by combined use of intraoperative high-field (1.5 T) magnetic resonance imaging and navigation, mostly glioma cases (n = 85), an update of the navigation was performed. Intraoperative image data were rigidly registered with the preoperative image data, the tumor remnant was segmented, and then the initial patient registration was restored so that the registration coordinate system of the preoperative image data was applied on the intraoperative images, allowing navigation updating without intraoperative patient re-registration.

RESULTS

Navigation could be updated reliably in all cases. Potential positional shifting impairing the initial update strategy was observed only in 2 cases so that a patient re-registration was necessary. The target registration error of the initial patient registration was 1.33 +/- 0.63 mm, and registration of preoperative and intraoperative images could be performed with high accuracy, as proven by landmark checks. Updating of navigation resulted in increased resections or correction of a catheter position or biopsy sampling site in 94%. In the remaining 7 patients, the intraoperative images were used for correlation with the surgical site but without changing the surgical strategy.

CONCLUSIONS

Navigation can be reliably updated with intraoperative image data without repeated patient registration, facilitating the update procedure. Updated navigation allows achieving enlarged resections and compensates for the effects of brain shift.

Intraoperative 3T MR imaging for spinal cord tumor resection: feasibility, timing, and image quality using a "twin" MR-operating room suite

We assessed feasibility, safety, and timing of an original intraoperative MR procedure in 3 cases of resection of spinal cord glioma by using a clinical 3T MR system connected to an adjacent operating room in a design being coined "twin" or "dual" MR-operating room suite.

Comparison of navigated 3D ultrasound findings with histopathology in subsequent phases of glioblastoma resection

OBJECTIVE

The purpose of the study was to compare the ability of navigated 3D ultrasound to distinguish tumour and normal brain tissue at the tumour border zone in subsequent phases of resection.

MATERIALS AND METHODS

Biopsies were sampled in the tumour border zone as seen in the US images before and during surgery. After resection, biopsies were sampled in the resection cavity wall. Histopathology was compared with the surgeon's image findings.

RESULTS

Before resection, the tumour border was delineated by ultrasound with high specificity and sensitivity (both 95%). During resection, ultrasound had acceptable sensitivity (87%), but poor specificity (42%), due to biopsies falsely classified as tumour by the surgeon. After resection, sensitivity was poor (26%), due to tumour or infiltrated tissue in several biopsies deemed normal by ultrasound, but the specificity was acceptable (88%).

CONCLUSIONS

Our study shows that although glioblastomas are well delineated prior to resection, there seem to be overestimation of tumour tissue during resection. After resection tumour remnants and infiltrated brain tissue in the resection cavity wall may be undetected. We believe that the benefits of intraoperative ultrasound outweigh the shortcomings, but users of intraoperative ultrasound should keep the limitations shown in our study in mind.

Usefulness of Intraoperative Ultra Low-field Magnetic Resonance Imaging in Glioma Surgery

Objective:

The aim of this study was to demonstrate the usefulness of a mobile, intraoperative 0.15-T magnetic resonance imaging (MRI) scanner in glioma surgery.

Methods:

We analyzed our prospectively collected database of patients with glial tumors who underwent tumor resection with the use of an intraoperative ultra low-field MRI scanner (PoleStar N-20; Odin Medical Technologies, Yokneam, Israel/Medtronic, Louisville, CO). Sixty-three patients with World Health Organization Grade II to IV tumors were included in the study. All patients were subjected to postoperative 1.5-T imaging to confirm the extent of resection.

Results:

Intraoperative image quality was sufficient for navigation and resection control in both high-and low-grade tumors. Primarily enhancing tumors were best detected on T1-weighted imaging, whereas fluid-attenuated inversion recovery sequences proved best for nonenhancing tumors. Intraoperative resection control led to further tumor resection in 12 (28.6%) of 42 patients with contrast-enhancing tumors and in 10(47.6%) of 21 patients with noncontrast-enhancing tumors. In contrast-enhancing tumors, further resection led to an increased rate of complete tumor resection (71.2 versus 52.4%), and the surgical goal of gross total removal or subtotal resection was achieved in all cases (100.0%). In patients with noncontrast-enhancing tumors, the surgical goal was achieved in 19 (90.5%) of 21 cases, as intraoperative MRI findings were inconsistent with postoperative high-field imaging in 2 cases.

Conclusion:

The use of the PoleStar N-20 intraoperative ultra low-field MRI scanner helps to evaluate the extent of resection in glioma surgery. Further tumor resection after intraoperative scanning leads to an increased rate of complete tumor resection, especially in patients with contrast-enhancing tumors. However, in noncontrast-enhancing tumors, the intraoperative visualization of a complete resection seems less specific, when compared with postoperative 1.5-T MRI.

How to overcome the limitations to determine the resection margin of pituitary tumours with low-field intra-operative MRI during trans-sphenoidal surgery: usefulness of Gadolinium-soaked cotton pledgets

OBJECTIVE

Intra-operative MRI (iMRI) is used as an immediate intra-operative quality control, allowing surgeons to extend resections in situations involving residual tumour remnants. Despite these advantages, low-field iMRI has some limitations with regards to image quality and artefacts. The aim of this study is to report our experience with bone wax and Gadolinium-soaked cotton pledgets in obtaining precise tumour resection margins using low-field iMRI.

PATIENTS AND METHODS

The study group included 63 consecutive patients who underwent endonasal trans-sphenoidal surgery with use of intra-operative low-field iMRI (0.15 T, PoleStar N20, Medtronic Navigation, Louisville, CO, U.S.A.). The indications for intra-operative MRI use included a suprasellar or retrosellar extension (n = 23), cavernous sinus invasion (n = 21), a tumour located in the vicinity of critical anatomic structures (such as the internal carotid artery, n = 10), recurrent or revision procedures (n = 5), and pre-operative imaging revealing unusual anatomy (n = 4).

RESULTS

Overall, among the 51 patients with intended complete tumour removal, iMRI revealed definite tumour remnants or suspicious findings in 13 patients (25.5%), leading to an extended resection and allowing completion of the resection in 10 patients. There was an increased rate of complete tumour removal from 74.5% (38 out of 51) to 94.1% (48 out of 51). The iMRI scan for complete tumour removal was more efficient in the group receiving Gadolinium-soaked cotton pledgets (85.2-100%) than in the group receiving bone wax or the conventional method (62.5-87.5%). The results of iMRI and the estimation by the surgeon concerning the extent of resection revealed a discrepancy in five patients (15.6%) in the Gadolinium-soaked cotton pledgets application group, and in 14 (45.2%) of the bone wax application group.

CONCLUSIONS

More valuable information for determining the resection margin can be obtained with the use of contrast-soaked cottonoid packing in the tumour resection cavity during iMRI scanning. We believe that the use of this simple method reduces the false-positive results and also overcomes the disadvantages of low-field iMRI.

MR systems for MRI-guided interventions

The field of MR imaging has grown from diagnosis via morphologic imaging to more sophisticated diagnosis via both physiologic and morphologic imaging and finally to the guidance and control of interventions. A wide variety of interventional procedures from open brain surgeries to noninvasive focused ultrasound ablations have been guided with MR and the differences between diagnostic and interventional MR imaging systems have motivated the creation of a new field within MR. This review discusses the various systems that research groups and vendors have designed to meet the requirements of interventional MR and suggest possible solutions to those requirements that have not yet been met. The common requirements created by MR imaging guidance of interventional procedures are reviewed and different imaging system designs will be independently considered. The motivation and history of the different designs are discussed and the ability of the designs to satisfy the requirements is analyzed.

Dynamic chemical shift imaging for image-guided thermal therapy: analysis of feasibility and potential

A fast chemical shift imaging (CSI) technique based on a multiple gradient-recalled acquisition using a small number of echoes with intentional aliasing of the reference lipid peak is studied to determine its feasibility for temperature monitoring. Simulations were implemented to find parameters where the lipid and water peaks can be measured using a Fourier-based peak fitting approach as well as using an innovative autoregressive moving average technique. A phantom consisting of 50% mayonnaise/50% lemon juice was calibrated to temperature and compared to literature values. A porcine kidney was treated ex vivo with an external laser and imaged with the CSI technique with comparisons to temperature readings from a fluoroptic monitoring system and complex phase difference (CPD) calculations. To demonstrate the technique in vivo, a Balb/c mouse with a CT26 xenograft in the subcutaneous lower back was treated using gold-coated, silica-core nanoshells heated with an 808 nm interstitial laser. Compared to standard CPD techniques using a two-dimensional fast spoiled gradient recalled echo, this technique maintains spatiotemporal resolution, has high signal-to-noise ratio and accuracy over a wide range of T2* tissue values, can separate water and lipid signals, and additionally can use the lipid peak, when present, as an internal reference.

Reliability of neuronavigation-assisted trans-sphenoidal tumor resections

OBJECTIVE

To analyse the surgical reliability of neuronavigation-assisted trans-sphenoidal tumor resections.

METHOD

In the past 7 years, all patients, who underwent neuronavigation-assisted trans-sphenoidal tumor resection in our department, were additionally intraoperatively controlled with a radioscopic device. Tumor removal was repeatedly checked up with the navigator and the tip of the pointer was correlated with the lateral intraoperative skull radiologic examination to confirm the real pointer deepness, spatial location and trajectory. The reliability of these assessments was analysed by simple images comparison and searching for tumor-related differences, and controlled with post-operative magnetic resonance studies.

RESULTS

During the analysed period, a total of 36 patients were treated in our department. Diagnosis included 14 non-secreting adenomas, 18 secreting adenomas and four non-pituitary tumors. Tumors diameter ranged from 1.4 to 4.5 cm. A mean accuracy of 0.8 mm could be achieved for all patients. In all cases, the real deepness, position and trajectory of the navigator were identical to those observed with X-ray examinations. At least nine from ten pointer determinations were identical in all cases. Particularly, all pituitary tumors with suprasellar extension could be safely controlled, even during advanced stages of resection and before the tumor capsule detached from suprasellar neighbor structures. Intrasellar, clival and suprasellar tumors were adequately removed as confirmed with MRI.

CONCLUSIONS

Radioscopic controlled neuronavigation shows high reliability and allows surgeons to be more confident during the trans-sphenoidal resection of skull base tumors. This offers the advantage to reduce the patient's X-ray exposure and the possibility of simultaneous multiplanar images evaluation.

Tumor-biology and current treatment of skull-base chordomas

Chordomas are rare, slow growing tumors of the axial skeleton, which derive from the remnants of the fetal notochord. They can be encountered anywhere along the axial skeleton, most commonly in the sacral area, skull base and less commonly in the spine. Chordomas have a benign histopathology but exhibit malignant clinical behavior with invasive, destructive and metastatic potential. Genetic and molecular pathology studies on oncogenesis of chordomas are very limited and there is little known on mechanisms governing the disease. Chordomas most commonly present with headaches and diplopia and can be readily diagnosed by current neuroradiological methods. There are 3 pathological subtypes of chordomas: classic, chondroid and dedifferentiated chordomas. Differential diagnosis from chondrosarcomas by radiology or pathology may at times be difficult. Skull base chordomas are very challenging to treat. Clinically there are at least two subsets of chordoma patients with distinct behaviors: some with a benign course and another group with an aggressive and rapidly progressive disease. There is no standard treatment for chordomas. Surgical resection and high dose radiation treatment are the mainstays of current treatment. Nevertheless, a significant percentage of skull base chordomas recur despite treatment. The outcome is dictated primarily by the intrinsic biology of the tumor and treatment seems only to have a secondary impact. To date we only have a limited understanding this biology; however better understanding is likely to improve treatment outcome. Hereby we present a review of the current knowledge and experience on the tumor biology, diagnosis and treatment of chordomas.

Improving lesion detection and visualization: implications for neurosurgical planning and follow-up

Contrast-enhanced magnetic resonance (MR) imaging is considered the most sensitive method for detecting tumors in the central nervous system (CNS). The primary objective is to improve lesion detection, delineation, and characterization (benign or malignant) in order to more accurately define the location, extent, and type of disease and the appropriate treatment option for improved patient outcome (surgical intervention, radiation therapy or cytotoxic chemotherapy). This article reviews the various types of tumor occurring in the brain and the specific role of contrast-enhanced MR imaging for the evaluation of these tumors. Emphasis is placed on the value of contrast-enhanced MR imaging in the evaluation of primary intra-axial brain lesions and how high relaxivity contrast agents such as MultiHance (Bracco Imaging, Milan, Italy) might improve detection, treatment planning, and follow-up.

Usefulness of intraoperative magnetic resonance imaging for glioma surgery

BACKGROUND

Radical resection of gliomas can increase patient's survival. There is known concern, however, that aggressive tumour removal can result in neurological morbidity. The objective of the present study was to evaluate the usefulness of low magnetic field strength (0.3 Tesla) open intraoperative magnetic resonance imaging (iMRI) for complete resection of glioma with emphasis on functional outcome.

METHODS

From 2000 to 2004, 96 patients with intracranial gliomas underwent tumour resection with the use of iMRI in Tokyo Women's Medical University. There were 50 men and 46 women; mean age was 39 years. Tumour volume varied from 1.2 ml to 198 ml (median: 36.5 mL). Resection rate and postoperative neurological status were compared between control group (46 cases, operated on during the initial period after installation of iMRI), and study group (50 most recent cases, in whom surgery was done using established treatment algorithm and improved image quality).

FINDINGS

Overall, mean resection rate was 93%, and medial residual tumour volume was 0.17 ml. Total tumour removal was achieved in 44 cases (46%). Compared to control group, resection rate in the study group was significantly higher (91%, vs. 95%; P < 0.05), whereas residual tumour volume was significantly smaller (1.7 mL vs. 0.025 mL; P < 0.001). Nine patients in the control group (20%) and 24 in the study group (48%) experienced temporary postoperative neurological deterioration (P < 0.01), however, the rate of permanent morbidity evaluated 3 months after surgery did not differ significantly between the groups investigated (13% vs. 14%).

CONCLUSIONS

Use of iMRI during surgery for intracranial gliomas permits to attain aggressive tumour resection with good functional outcome. Nevertheless, surgical experience with the iMRI system, establishment of treatment algorithm, and improvement of image quality are of paramount importance for optimal results.

Clinical validation of vessel-based registration for correction of brain-shift

In this paper, we have tested and validated a vessel-based registration technique for correction of brain-shift using retrospective clinical data from five patients: three patients with brain tumors, one patient with an aneurysm and one patient with an arteriovenous malformation. The algorithm uses vessel centerlines extracted from segmented pre-operative MRA data and intra-operative power Doppler ultrasound images to compute first a linear fit and then a thin-plate spline transform in order to achieve non-linear registration. The method was validated using (i) homologous landmarks identified in the original data, (ii) selected vessels, excluded from the fitting procedure and (iii) manually segmented, non-vascular structures. The tracking of homologous landmarks show that we are able to correct the deformation to within 1.25 mm, and the validation using excluded vessels and anatomical structures show an accuracy of 1mm. Pre-processing of the data can be completed in 30 s per dataset, and registrations can be performed in less than 30s. This makes the technique well suited for intra-operative use.

CLINICAL EVALUATION AND FOLLOW-UP OUTCOME OF DIFFUSION TENSOR IMAGING-BASED FUNCTIONAL NEURONAVIGATION

OBJECTIVE

To evaluate diffusion tensor imaging (DTI)-based functional neuronavigation in surgery of cerebral gliomas with pyramidal tract (PT) involvement with respect to both perioperative assessment and follow-up outcome.

METHODS

A prospective, randomized controlled study was conducted between 2001 and 2005. A consecutive series of 238 eligible patients with initial imaging diagnosis of cerebral gliomas involving PTs were randomized into study (n = 118) and control (n = 120) groups. The study cases underwent DTI and three-dimensional magnetic resonance imaging scans. The maps of fractional anisotropy were calculated for PT mapping. Both three-dimensional magnetic resonance imaging data sets and fractional anisotropy maps were integrated by rigid registration, after which the tumor and adjacent PT were segmented and reconstructed for presurgical planning and intraoperative guidance. The control cases were operated on using routine neuronavigation.

RESULTS

There was a trend for high-grade gliomas (HGGs) in the study group to be more likely to achieve gross total resection (74.4 versus 33.3%, P &lt; 0.001). There was no significant difference of low-grade gliomas resection between the two groups. Postoperative motor deterioration occurred in 32.8% of control cases, whereas it occurred in only 15.3% of the study cases (P &lt; 0.001). The 6-month Karnofsky Performance Scale score of study cases was significantly higher than that of control cases (86 ± 20 versus 74 ± 28 overall, P &lt; 0.001; 93 ± 10 versus 86 ± 17 for low-grade gliomas, P = 0.013; and 77 ± 27 versus 53 ± 32 for HGGs, P = 0.001). For 81 HGGs, the median survival of study cases was 21.2 months (95% confidence interval, 14.1–28.3 mo) compared with 14.0 months (95% confidence interval, 10.2–17.8 mo) of control cases (P = 0.048). The estimated hazard ratio for the effect of DTI-based functional neuronavigation was 0.570, representing a 43.0% reduction in the risk of death.

CONCLUSION

DTI-based functional neuronavigation contributes to maximal safe resection of cerebral gliomas with PT involvement, thereby decreasing postoperative motor deficits for both HGGs and low-grade gliomas while increasing high-quality survival for HGGs.

Intraoperative magnetic resonance imaging in pituitary macroadenoma surgery: an assessment of visual outcome

✓Pituitary macroadenomas most frequently present with visual loss. Although transsphenoidal surgery remains the treatment of choice for patients with neurological manifestations, there have been several advances in its implementation over the last 5 years. Intraoperative magnetic resonance (MR) imaging has emerged as a novel quality control measure, with the potential to guide the surgeon to tumor remnants concealed from the operating microscope. Investigators have reported enhanced resections when using intraoperative MR imaging, leading to complete tumor removal in a larger proportion of cases. Further debulking of unresectable lesions may also prove beneficial in delaying symptom recurrence and facilitating radiotherapy, where distance between the tumor and optic chiasm is an important predictor of visual outcome. However, confirmation of such advantages is complicated by the fact that most macroadenomas are both indolent and hormonally silent, necessitating years of follow-up. Experienced pituitary surgeons will operate as safely with intraoperative MR imaging as without it, perhaps due to a balance between more elaborate resections and better visualization. Intraoperative MR imaging represents a new technique applied to an old problem in tumor surgery: complete, safe resection.

Cervical soft tissue imaging using a mobile CBCT scanner with a flat panel detector in comparison with corresponding CT and MRI data sets

OBJECTIVE

The aim of this study was to evaluate soft tissue image quality of a mobile cone-beam computed tomography (CBCT) scanner with an integrated flat-panel detector.

STUDY DESIGN

Eight fresh human cadavers were used in this study. For evaluation of soft tissue visualization, CBCT data sets and corresponding computed tomography (CT) and magnetic resonance imaging (MRI) data sets were acquired. Evaluation was performed with the help of 10 defined cervical anatomical structures.

RESULTS

The statistical analysis of the scoring results of 3 examiners revealed the CBCT images to be of inferior quality regarding the visualization of most of the predefined structures. Visualization without a significant difference was found regarding the demarcation of the vertebral bodies and the pyramidal cartilages, the arteriosclerosis of the carotids (compared with CT), and the laryngeal skeleton (compared with MRI). Regarding arteriosclerosis of the carotids compared with MRI, CBCT proved to be superior.

CONCLUSIONS

The integration of a flat-panel detector improves soft tissue visualization using a mobile CBCT scanner.

Role of magnetic resonance tractography in the preoperative planning and intraoperative assessment of patients with intra-axial brain tumours

PURPOSE

This study was conducted to assess the possibility of identifying precise white matter tracts situated in proximity to intracranial tumours, to define the anatomical and topographical relations between the same white matter tracts and the tumour, to verify the possibility of integrating tractographic images in the context of a package of three-dimensional anatomical images to send to the neuronavigation system, to assess the impact of this information on surgical planning, and to analyse, both pre-and postoperatively, the patient's clinical conditions as an index of the functional integrity of the fibres themselves.

MATERIALS AND METHODS

Twenty-five patients underwent diffusion tensor study prior to neurosurgery. With the use of dedicated software, relative colour maps were obtained and the trajectories of the white matter tracts adjacent to the tumour were reconstructed in three dimensions. These were then processed for preoperative planning. Planning, which was performed with the neuronavigator, was based on analysis of the location of the course of the main white matter tracts adjacent to the lesion (pyramidal tract, optic radiation and arcuate fasciculus). Two neurosurgeons were asked whether the tractography images had modified the access and/or intraoperative approach to the tumour. All patients were clinically assessed both pre-and postoperatively 1 month after the procedure to define the presence of symptoms related to the involvement of the white matter tracts studied and therefore to assess the integrity of the fibres after the operation.

RESULTS

In one patient, the tumour was situated away from all the tracts studied and did not compress them in any way. Overall, 40/75 tracts studied had no anatomical relation with the tumour, were not displaced by the tumour or could not be visualised in their entire course. Analysis of the remaining 35 white matter tracts led to an a priori change in the surgical approach for corticotomy in four patients (16%), with no disagreement between the two neurosurgeons and an impact on the extent of resection during surgery in 17 (68%), thus an overall impact on the surgical procedure in 80% of cases. Eight patients showed no symptoms related to the involvement of the white matter tracts studied. In the remaining 17 patients, the symptoms were related to involvement of the pyramidal tract, arcuate fasciculus or optic radiation. At 1-month follow-up, one previously asymptomatic patient reported a speech disorder (transcortical sensory dysphasia); in the remaining 24, symptoms remained unchanged, with a tendency to improvement in 14/17 with symptoms related to involvement of white matter tracts studied.

CONCLUSIONS

Magnetic resonance (MR) tractography offers the neurosurgeon an anatomical panoramic view that can improve surgical planning for the resection of intracranial tumours. Despite the high incidence of cases in which the lesion is responsible for changes that hinder the reconstruction of white matter tracts, the technique can change the surgical approach for corticotomy, defines the extent of resection and leads to some change in the procedure in 80% of cases. The improvement of pre-existing symptoms and the absence of new symptoms in the postoperative phase, in our opinion, confirms the value of the technique.

Validation of vessel-based registration for correction of brain shift

The displacement and deformation of brain tissue is a major source of error in image-guided neurosurgery systems. We have designed and implemented a method to detect and correct brain shift using pre-operative MR images and intraoperative Doppler ultrasound data and present its validation with both real and simulated data. The algorithm uses segmented vessels from both modalities, and estimates the deformation using a modified version of the iterative closest point (ICP) algorithm. We use the least trimmed squares (LTS) to reduce the number of outliers in the point matching procedure. These points are used to drive a thin-plate spline transform to achieve non-linear registration. Validation was completed in two parts. First, the technique was tested and validated using realistic simulations where the results were compared to the known deformation. The registration technique recovered 75% of the deformation in the region of interest accounting for deformations as large as 20 mm. Second, we performed a PVA-cryogel phantom study where both MR and ultrasound images of the phantom were obtained for three different deformations. The registration results based on MR data were used as a gold standard to evaluate the performance of the ultrasound based registration. On average, deformations of 7.5 mm magnitude were corrected to within 1.6 mm for the ultrasound based registration and 1.07 mm for the MR based registration.

COMBINED X-RAY AND MAGNETIC RESONANCE IMAGING FACILITY

OBJECTIVE

To assess the feasibility of a hybrid imaging setup combining x-ray and magnetic resonance imaging (MRI) in the setting of both stereotactic and functional neurosurgery.

METHODS

A combined x-ray and MRI scanning facility with a trolley system for a fast patient transfer between both modalities was installed in a neurosurgical setting. A registration algorithm for fusion of MRI scans and x-ray images was derived for augmentation of fluoroscopic x-ray projection images with MRI scan data, such as anatomic structures and planned probe trajectories. Phantom measurements were obtained between both modalities for estimation of registration accuracy. Practical application of our system in stereotactic and functional neurosurgery was tested in brachytherapy, deep brain stimulation, and motor cortex stimulation.

RESULTS

Phantom measurements yielded a mean spatial deviation of 0.7 +/- 0.3 mm with a maximum deviation of 1.1 mm for MRI scans versus x-rays. Augmentation of x-ray images with MRI scan data allowed intraoperative verification of the planned trajectory and target in three types of neurosurgical procedures: positioning iodine seeds in brachytherapy in one case with cerebellar metastasis, placement of electrodes for deep brain stimulation in two cases of advanced Parkinson's disease, and placement of an epidural grid for motor cortex stimulation in two cases of intractable pain.

CONCLUSION

Combined x-ray and MRI-guided stereotactic and functional neurosurgery is feasible. Augmentation of x-ray projection images with MRI scan data, such as planned probe trajectories and MRI scan segmented anatomic structures may be beneficial for probe guidance in stereotactic and functional neurosurgery.

Evaluation of intraaxial enhancing brain tumors on magnetic resonance imaging: intraindividual crossover comparison of gadobenate dimeglumine and gadopentetate dimeglumine for visualization and assessment, and implications for surgical intervention

Object

The goal in this article was to compare 0.1 mmol/kg doses of gadobenate dimeglumine (Gd-BOPTA) and gadopentetate dimeglumine, also known as gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), for enhanced magnetic resonance (MR) imaging of intraaxial brain tumors.

Methods

Eighty-four patients with either intraaxial glioma (47 patients) or metastasis (37 patients) underwent two MR imaging examinations at 1.5 tesla, one with Gd-BOPTA as the contrast agent and the other with Gd-DTPA. The interval between fully randomized contrast medium administrations was 2 to 7 days. The T1-weighted spin echo and T2-weighted fast spin echo images were acquired before administration of contrast agents and T1-weighted spin echo images were obtained after the agents were administered. Acquisition parameters and postinjection acquisition times were identical for the two examinations in each patient. Three experienced readers working in a fully blinded fashion independently evaluated all images for degree and quality of available information (lesion contrast enhancement, lesion border delineation, definition of disease extent, visualization of the lesion's internal structures, global diagnostic preference) and quantitative enhancement (that is, the extent of lesion enhancement after contrast agent administration compared with that seen before its administration [hereafter referred to as percent enhancement], lesion/brain ratio, and contrast/noise ratio). Differences were tested with the Wilcoxon signed-rank test. Reader agreement was assessed using kappa statistics.

Significantly better diagnostic information/imaging performance (p < 0.0001, all readers) was obtained with Gd-BOPTA for all visualization end points. Global preference for images obtained with Gd-BOPTA was expressed for 42 (50%), 52 (61.9%), and 56 (66.7%) of 84 patients (readers 1, 2, and 3, respectively) compared with images obtained with Gd-DTPA contrast in four (4.8%), six (7.1%), and three (3.6%) of 84 patients. Similar differences were noted for all other visualization end points. Significantly greater quantitative contrast enhancement (p < 0.04) was noted after administration of Gd-BOPTA. Reader agreement was good (κ > 0.4).

Conclusions

Lesion visualization, delineation, definition, and contrast enhancement are significantly better after administration of 0.1 mmol/kg Gd-BOPTA, potentially allowing better surgical planning and follow up and improved disease management.

Glioma therapy in adults

BACKGROUND

Gliomas are the most common type of primary brain tumor. Nearly two-thirds of gliomas are highly malignant lesions that account for a disproportionate share of brain tumor-related morbidity and mortality. Despite recent advances, two-year survival for glioblastoma with optimal therapy is less than 30%. Even among patients with low-grade gliomas that confer a relatively good prognosis, treatment is almost never curative.

REVIEW SUMMARY

Surgery and radiation have been the mainstays of therapy for most glioma patients, but temozolomide chemotherapy has recently been proven to prolong overall survival in patients with glioblastoma. Intriguing data suggests that activity of O6-methylguanine-DNA methyltransferase (MGMT), in tumor cells may predict responsiveness to temozolomide and other alkylating agents. Novel treatment approaches, especially targeted molecular therapies against critical components of glioma signaling pathways, appear promising in preliminary studies. Optimal treatment for patients with low-grade gliomas has yet to be determined. Advances in oligodendroglioma biology have identified loss of chromosomes 1p and 19q as powerful indicators of a favorable prognosis. These same changes may predict response to chemotherapy.

CONCLUSIONS

Though the prognosis for many patients with gliomas is poor, the last decade produced a number of important advances, some of which have translated directly into survival benefits. Rapid progress in the field of glioma molecular biology continues to identify therapeutic targets and provide hope for the future of this challenging disease.