Intraoperative imaging techniques in the treatment of brain tumors

Cottonoid-guided intraoperative ultrasonography in neurosurgery: a proof-of-concept single surgeon case series

Ultrasonography was introduced into neurosurgery in the 1950s, but its successful utilization as an intraoperative tool dates from the early 1980s. However, it was not used widely because of limited technology, a lack of specific training, and, most importantly, the concurrent evolution of computerized tomography and magnetic resonance imaging. The intraoperative use of cottonoid patties as acoustical markers was first described in 1984, but the practice did not gain acceptance, and no articles have been published since. Herein, we reconsider the echogenic properties of the surgical cottonoid patty and demonstrate its usefulness with intraoperative ultrasonography (ioUS) in neurosurgical practice as a truly real-time neuronavigation tool. We also discuss its advantages and compare it with other intraoperative image guidance tools. The echogenic properties of the handmade cottonoid patties in various sizes used with ioUS are described. Details of our cottonoid-guided ioUS technique and its advantages with illustrated cases are also described. As an echogenic marker, cottonoid patties can be easily recognized with ioUS. Their usage with ultrasonography provides truly real-time anatomical orientation throughout the surgery, allowing easy access to intraparenchymal pathologies, and precise and safer resection. Cottonoid-guided ioUS helps not only to localize intraparenchymal pathologies but also to delineate the exact surgical trajectory for each type of lesion. Furthermore, it is not affected by brain shift and distortion. Thus, it is a truly real-time, dynamic, cost-effective, and easy-to-use image guidance tool. This technique can be used safely for every intraparenchymal pathology and increases the accuracy and safety of the surgeries.

Long-term surgical and seizure outcomes of frontal low-grade gliomas

INTRODUCTION

Low-grade gliomas are infrequent lesions requiring special emphasis because of their relatively long follow-up time, and therefore the need for patients' well-being. Surgery provides not only increased survival but also improved quality of life for these patients. The purpose of this study was to present surgical series of frontal low-grade gliomas that were operated in our clinic and to discuss their epileptic and functional outcomes.

METHODS

A series of 40 patients with low-grade glioma (WHO Grade II) were retrospectively analysed for patient characteristics, tumour location, epileptic history, surgery type (awake craniotomy, general anaesthesia), extent of resection and complications.

RESULTS

Tumour was localized to primary motor area in most of the cases (35%, n = 14), 25 patients were operated under general anaesthesia and 15 with awake craniotomy. New deficit rate in the early postoperative period was 32.5% (dysarthria in one patient and motor deficits in 12). Karnofsky scores were ≥90 in 92.5% of the patients at the late follow-up. 31 patients were Engel I (77.5%), 5 were Engel II (12.5%) and 4 were Engel IV (10%) postoperatively.

CONCLUSION

Frontal LGGs are eligible to resect vigorously without persistent functional deficits. Patients with immediate postoperative complications benefit from neuro-rehabilitation. However, pre-existing speech dysfunctions are hard to recover with surgery. Surgical resection ends with favourable epileptic outcomes whereas tumour location may influence the results.

Through the patient's eyes: an emphasis on patient-centered values in operative decision making in the management of malignant glioma

The Joint Section on Tumors of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons is now in its 30th year. In many ways its growth and development has paralleled neurosurgery and medicine as a whole. This is most evident in our endeavor towards more patient-centered care and focus on quantity and quality of life. As the push towards evidence-based care continues, it is important to ensure that individualized care remains a guiding principle. Conscientious surgeons continue to refine techniques and develop technologies that push the boundaries of surgical efficacy while better defining the risks of surgery and the impacts of surgical complications. This article provides a review of the factors involved in minimizing risk and obtaining maximal outcomes for patients through insightful patient selection and evidence-based surgical decision-making. Herein, we present the philosophy and practice of the Hermelin Brain Tumor Center at the Henry Ford Health System as one type of approach to caring for the patient with a malignant glioma.

The aryl hydrocarbon receptor contributes to the proliferation of human medulloblastoma cells

The aryl hydrocarbon receptor (AhR), a ligand-activated member of the basic helix-loop-helix (bHLH)/PER-ARNT-SIM (PAS) transcription superfamily, is known to regulate the toxicity of polyaromatic halogenated hydrocarbon environmental chemicals, most notably dioxin. However, the AhR has also been implicated in multiple stages of tumorigenesis. Medulloblastoma (MB), a primary cerebellar brain tumor arising in infants and children, is thought to originate from abnormally proliferating cerebellar granule neuron precursors (GNPs). GNPs express high levels of the AhR in the external germinal layer of the developing cerebellum. Moreover, our laboratory has previously reported that either abnormal activation or deletion of the AhR leads to dysregulation of GNP cell cycle activity and maturation. These observations led to the hypothesis that the AhR promotes the growth of MB. Therefore, this study evaluated whether the AhR serves a pro-proliferative role in an immortalized MB tumor cell line (DAOY). We produced a stable AhR knockdown DAOY cell line [AhR short hairpin RNA (shRNA)], which exhibited a 70% reduction in AhR protein levels. Compared with wild-type DAOY cells, AhR shRNA DAOY cells displayed an impaired G(1)-to-S cell cycle transition, decreased DNA synthesis, and reduced proliferation. Furthermore, these cell cycle perturbations were correlated with decreased levels of the pro-proliferative gene Hes1 and increased levels of the cell cycle inhibitor p27(kip1). Supplementation experiments with human AhR restored the proliferative activity in AhR shRNA DAOY cells. Taken together, our data show that the AhR promotes proliferation of MB cells, suggesting that this pathway should be considered as a potential therapeutic target for MB treatment.

Preoperative and intraoperative brain mapping for the resection of eloquent-area tumors. A prospective analysis of methodology, correlation, and usefulness based on clinical outcomes

BACKGROUND

Localization of brain function is a fundamental requisite for the resection of eloquent-area brain tumors. Preoperative functional neuroimaging and diffusion tensor imaging can display cortical functional organization and subcortical anatomy of major white matter bundles. Direct cortical and subcortical stimulation is widely used in routine practice, however, because of its ability to reveal tissue function in eloquent regions. The role and integration of these techniques is still a matter of debate. The objective of this study was to assess surgical and functional neurological outputs of awake surgery and intraoperative cortical and subcortical electrical stimulation (CSES) and to use CSES to examine the reliability of preoperative functional magnetic resonance (fMRI) and diffusion tensor imaging fiber tracking (DTI-FT) for surgical planning.

PATIENTS AND METHODS

We prospectively studied 27 patients with eloquent-area tumors who were selected to undergo awake surgery and direct brain mapping. All subjects underwent preoperative sensorimotor and language fMRI and DTI tractography of major white matter bundles. Intra- and postoperative complications, stimulation effects, extent of resection, and neurological outcome were determined. We topographically correlated intraoperatively identified sites (cortical and subcortical) with areas of fMRI activation and DTI tractography.

RESULTS

Total plus subtotal resection reached 88.8%. Twenty-one patients (77.7%) suffered transient postoperative worsening, but at 6 months follow-up only three (11.1%) patients had persistent neurological impairment. Sensorimotor cortex direct mapping correlated 92.3% with fMRI activation, while direct mapping of language cortex correlated 42.8%. DTI fiber tracking underestimated the presence of functional fibers surrounding or inside the tumor.

CONCLUSION

Preoperative brain mapping is useful when planning awake surgery to estimate the relationship between the tumor and functional brain regions. However, these techniques cannot directly lead the surgeon during resection. Intraoperative brain mapping is necessary for safe and maximal resection and to guarantee a satisfying neurological outcome. This multimodal approach is more aggressive, leads to better outcomes, and should be used routinely for resection of lesions in eloquent brain regions.

Awake craniotomy for brain tumors near eloquent cortex: correlation of intraoperative cortical mapping with neurological outcomes in 309 consecutive patients

OBJECTIVE

Intraoperative localization of cortical areas for motor and language function has been advocated to minimize postoperative neurological deficits. We report herein the results of a retrospective study of cortical mapping and subsequent clinical outcomes in a large series of patients.

METHODS

Patients with intracerebral tumors near and/or within eloquent cortices (n = 309) were clinically evaluated before surgery, immediately after, and 1 month and 3 months after surgery. Craniotomy was tailored to encompass tumor plus adjacent areas presumed to contain eloquent cortex. Intraoperative cortical stimulation for language, motor, and/or sensory function was performed in all patients to safely maximize surgical resection.

RESULTS

A gross total resection (> or =95%) was obtained in 64%, and a resection of 85% or more was obtained in 77% of the procedures. Eloquent areas were identified in 65% of cases, and in that group, worsened neurological deficits were observed in 21% of patients, whereas only 9% with negative mapping sustained such deficits (P < 0.01). Intraoperative neurological deficits occurred in 64 patients (21%); of these, 25 (39%) experienced worsened neurological outcome at 1 month, whereas only 27 of 245 patients (11%) without intraoperative changes had such outcomes (P < 0.001). At 1 month, 83% overall showed improved or stable neurological status, whereas 17% had new or worse deficits; however, at 3 months, 7% of patients had a persistent neurological deficit. Extent of resection less than 95% also predicted worsening of neurological status (P < 0.025).

CONCLUSION

Negative mapping of eloquent areas provides a safe margin for surgical resection with a low incidence of neurological deficits. However, identification of eloquent areas not only failed to eliminate but rather increased the risk of postoperative deficits, likely indicating close proximity of functional cortex to tumor.

A Ratiometric Fluorescence Imaging System for Surgical Guidance

A 3-chip CCD imaging system has been developed for quantitative in vivo fluorescence imaging. This incorporates a ratiometric algorithm to correct for the effects of tissue optical absorption and scattering, imaging “geometry” and tissue autofluorescence background. The performance was characterized, and the algorithm was validated in tissue-simulating optical phantoms for quantitative measurement of the fluorescent molecule protoporphyrin IX (PpIX). The technical feasibility to use this system for fluorescence-guided surgical resection of malignant brain tumor tissue was assessed in an animal model in which PpIX was induced exogenously in the tumor cells by systemic administration of aminolevulinic acid (ALA).

A probability-based spectroscopic diagnostic algorithm for simultaneous discrimination of brain tumor and tumor margins from normal brain tissue

This paper reports the development of a probability-based spectroscopic diagnostic algorithm capable of simultaneously discriminating tumor core and tumor margins from normal human brain tissues. The algorithm uses a nonlinear method for feature extraction based on maximum representation and discrimination feature (MRDF) and a Bayesian method for classification based on sparse multinomial logistic regression (SMLR). Both the autofluorescence and the diffuse-reflectance spectra acquired in vivo from patients undergoing craniotomy or temporal lobectomy at the Vanderbilt University Medical Center were used to train and validate the algorithm. The classification accuracy was observed to be approximately 96%, 80%, and 97% for the tumor, tumor margin, and normal brain tissues, respectively, for the training data set and approximately 96%, 94%, and 100%, respectively, for the corresponding tissue types in an independent validation data set. The inherently multi-class nature of the algorithm facilitates a rapid and simultaneous classification of tissue spectra into various tissue categories without the need for a hierarchical multi-step binary classification scheme. Further, the probabilistic nature of the algorithm makes it possible to quantitatively assess the certainty of the classification and recheck the samples that are classified with higher relative uncertainty.

Intraoperative MR imaging: preliminary results with 3 tesla MR system

Aim of this study is to present the initial clinical experience with 3 tesla intraoperative MR (ioMR).

MATERIAL AND METHODS

The 3T MRI suite is built adjacent to the neurosurgical operation theatre. The magnet room and the operation theatre are interconnected by a door and both RF-shielded. Before the operation, the magnet (3T Trio, Siemens) and the console rooms are disinfected. Whenever imaging is needed during the operation, the door is opened and the patient is transferred from the operation table to the magnet cradle. Axial, sagittal and/or coronal TSE T2, SE T1 and 3D Flash T1 weighted images (4-6 mm section thickness, 1 mm interslice gap) are obtained according to the lesion. Total examination time is approximately 10 minutes.

RESULTS

Twenty-six patients were examined with ioMR. There were ten female and seven male patients. Lesions were pituitary adenoma in 10, low grade glial tumor in 9, meningioma and high grade glial tumor in 2 each and metastasis, haemangioblastoma and chordoma in one each. Follow-up time was 1 to 9 months. In 16 patients the first intraoperative examination revealed gross total tumor excision. However, in 10 patients due to tumor remnants surgical intervention was continued and a second examination revealed gross total tumor excision in all. Postoperative routine MR examinations confirmed total tumor excision in all patients. No complication occurred in this series.

CONCLUSION

This small group of patients examined with ioMR demonstrated that the procedure is simple, helpful in achieving gross total tumor excision without complications.

Intraoperative sonography for neurosurgery

OBJECTIVE

The purpose of this study was to review the technical aspects and the clinical applications of intraoperative sonography of the central nervous system (CNS) as well as the characteristic appearances of brain and spine diseases.

METHODS

A pictorial review of cases is presented on the basis of the performance and interpretation of intraoperative sonography of the CNS from January 1998 to December 2004 at a single academic institution.

RESULTS

This technique is most commonly used for the localization and characterization of intracranial and spinal masses. Indications for intraoperative sonography of the CNS are biopsy guidance, tumor resection, and drainage or removal of inflammatory masses. It provides important additional information to the surgeon at the time of the operation and contributes to intraoperative decision making and surgical planning. This article reviews the advantages and limitations of intraoperative sonography of the CNS and highlights the typical appearance of CNS diseases.

CONCLUSIONS

Intraoperative sonography of the CNS is an interactive technique and helps the neurosurgeon in decision making and surgical planning.

Vibrography during tumor neurosurgery

OBJECTIVE

The aim of this study was to determine whether elastography, a sonographically based real-time strain imaging method for registering the elastic properties of tissue, can be used in brain tumor surgery.

METHODS

A modification of classic elastography called vibrography was applied in these measurements with static compression replaced by low-frequency axial vibration. Twenty patients were examined with this technique during brain tumor surgery. A conventional sonographic system with a custom-designed radio frequency (RF) interface was used. The RF data were digitized with a 50-MHz, 12-bit peripheral component interconnect analog/digital converter for real-time or offline processing. Sonographic RF data were acquired with a 6.5-MHz endocavity curved array. A special applicator equipped with a stepping motor moved the ultrasonic probe and produced a low-frequency mechanical vibration of approximately 5 to 10 Hz with a vibration amplitude of 0.3 mm.

RESULTS

Detection of tumors was possible in 18 of 20 cases. Brain tissue was normally color coded orange or red. Three major groups of tumors with different elastic properties relative to brain tissue could be differentiated. In 3 cases, the stiffness of the tumor was identical to that of brain tissue, but the tumors were surrounded by a thin yellow border. Six tumors displayed higher strain than brain, whereas 7 tumors exhibited lower strain than the surrounding cerebrum. Two patients could not be assigned clearly to either of these groups.

CONCLUSIONS

These findings indicate that vibrography is a feasible imaging method for brain tumor surgery and may have numerous potential applications in neurosurgery if further improvements are made.

Advances in neurosurgical technique in the current management of brain tumors

Despite significant advances in anatomical and functional neuroimaging modalities (eg, magnetic resonance [MR] imaging [MRI], MR spectroscopy [MRS], diffusion and perfusion MR, functional MRI [fMRI], magnetic-source imaging [MSI], diffusion tensor imaging [DTI]) and neuronavigation techniques, intraoperatively obtained functional information remains of crucial importance to the neurosurgeon, especially when operating on tumors that are located in or adjacent to functional cortical sites and subcortical pathways. This article focuses on recent advances in the surgical management of of intracerebral tumors with special emphasis on intraoperative cortical and subcortical stimulation mapping methods, and the prognostic significance of surgery on patient outcome.

A multispectral fluorescence imaging system: design and initial clinical tests in intra-operative Photofrin-photodynamic therapy of brain tumors

BACKGROUND AND OBJECTIVES

Intra-operative identification of tumor by fluorescence may improve surgical resection or photodynamic therapy (PDT). A novel instrument was designed, constructed, and tested for this purpose.

STUDY DESIGN/MATERIALS AND METHODS

The instrument was designed to provide high-resolution, multi-spectral (five band) fluorescence imaging, and non-contact point spectroscopy, with long working distance ( approximately 50 cm), large field-of-view ( approximately 3 cm diameter), large depth of view ( approximately 2 cm), and 'point-and-shoot' operation. Its performance was determined in tissue-simulating phantoms and in pilot studies in brain tumor resection patients, with or without intra-operative Photofrin-PDT.

RESULTS

In phantoms the imaging resolution was approximately 150 microm, while Photofrin concentrations as low as 0.05 or 0.1 microg/g could be detected at the tissue surface or at 0.5 mm depth, respectively. Red Photofrin fluorescence could be clearly visualized post radical resection in all PDT patients, with biopsy confirmation of residual tumor tissue in regions that were not seen as tumor under white light. Photobleaching of Photofrin during PDT was also demonstrated.

CONCLUSIONS

The system performed to specification under realistic operating conditions and could reveal unresected residual tumor tissue. It may be used for either PDT dosimetry/monitoring and/or for surgical guidance.

Intraoperative imaging in glioblastoma resection

The use of intraoperative imaging (IOI) in neurosurgical practice is proving to be yet another important advance in the evolution of brain tumor resection, particularly for the most common adult primary brain tumor--glioblastoma (GBM). The number of surgeons using IOI continues to increase, and the experience to date affords an opportunity to assess the value of the various techniques used for IOI.

Iterative neuronavigation using 3D ultrasound. A feasibility study

Intra-operative ultrasound (iUS) can generate 2D images in real-time as well as near real-time 3D datasets of the current situation during an intervention. Tracked ultrasound can locate the images in 3D space and relate them to patient, devices, andpre-operative planning data. Therefore, tracked US is an efficient means for controlling the validity of pre-operative planning, recognition of changes (brain shift) during the intervention, replanning of the operational path due to situational changes (iterative navigation), and finally, controlling the results (residual tumor). This paper describes a neuronavigation system exploiting this potential of interventional tracked US for permanent control of intervention progress and iterative adaptation of the planned procedure to the current situation.

Intracarotid RMP-7 enhanced indocyanine green staining of tumors in a rat glioma model

OBJECTIVE

The extent of resection in patients with primary brain tumors may affect the quality of life, time to tumor progression, and survival. Currently, the extent of resection during surgery is guided by the visual appearance and consistency of tumor, frozen sections of the margins, intraoperative ultrasound, and frameless navigational systems and intraoperative imaging modalities. A new method that enhances the visualization of an infiltrating tumor and its margins may further aid in obtaining a more complete resection. A study was thus undertaken to assess the staining of brain tumors using Indocyanine green (ICG), a water-soluble emerald green tricarbocynanine dye concomitantly with RMP-7, a bradykinin analog, that selectively increases vascular permeability in brain tumors.

METHODS

A syngeneic ethyl-nitrosourea-induced F-344 rat cell line (36B-10) was stereotactically implanted into 25 rats, and allowed to mature for 15-18 days. Intracarotid administration of 0.75 ml of RMP-7 at a standard dose of 0.4 microg/ml over 15 min was then infused. Varying doses of ICG (range, 0-60 mg/kg) were then injected 15 min after the RMP-7 infusion ended. The animals were sacrificed 15 min after the ICG infusion was completed, and the brains examined macroscopically and microscopically for evidence of tumor staining.

RESULTS

This study demonstrated consistent staining of the tumor at only slightly lower ICG doses than previously described, however uptake at the tumor margins was evident at much lower doses. Thus the combination of ICG and RMP-7 administered preoperatively may provide visual enhancement of an infiltrating tumor and its margins to help facilitate a radical tumor removal.

Intraoperative electrophysiological monitoring of oculomotor nuclei and their intramedullary tracts during midbrain tumor surgery

OBJECTIVE

During surgery for intrinsic midbrain lesions, we intraoperatively recorded evoked compound muscle action potentials (ECMAPs) from the extraocular muscles and evaluated how this type of intraoperative electrophysiological monitoring could minimize postoperative oculomotor nerve palsy (ptosis and/or diplopia).

METHODS

The ECMAPs were recorded through a spring electrode applied to the extraocular muscle (Method 1, seven cases) or a needle electrode inserted into the superior intraorbital space (Method 2, five cases). The surgeon repeated electrical stimulations whenever tissue of unknown origin was encountered intraoperatively, and this information was used to safely guide surgical resection of the tumors.

RESULTS

Using these monitoring techniques, the response-free areas were resected and the areas from which ECMAP responses were recorded were avoided. For all 12 patients, ECMAPs were successfully recorded from the extraocular muscles. Ten patients did not exhibit any postoperative deterioration of oculomotor nerve function. Two patients exhibited deterioration of oculomotor nerve function immediately after surgery, which resolved within 1 month. Equally robust ECMAPs could be recorded with Method 2, compared with Method 1.

CONCLUSION

Intraoperative ECMAP recordings from the extraocular muscles precisely indicated the locations of the oculomotor nuclei and/or intramedullary oculomotor tracts. Although Method 2 is a more indirect method for recording ECMAPs than is Method 1, Method 2 was equally useful in recording ECMAPs, which seemed to be the summed potentials from the superior rectus muscle and the levator palpebrae superioris muscle. These monitoring techniques are valuable in guiding surgeons to avoid causing inadvertent harm to the oculomotor nuclei and tracts during midbrain surgery, particularly when the neuroanatomic features are distorted by the presence of tumor.