Clinical interest of integrating positron emission tomography imaging in the workup of 55 children with incidentally diagnosed brain lesions.

OBJECT: In this paper, the authors' goal was to evaluate the impact of PET data on the clinical management of incidental brain lesions in children. METHODS: Between 1995 and 2007, 442 children with a newly diagnosed brain lesion were referred to the authors' department. Of these, 55 presented with an incidental brain lesion and were selected for study because MR imaging sequences revealed limitations in assessing the tumor, its evolving nature, and/or the malignant potential of the lesion diagnosed. Thirteen children were studied using FDG-PET and 42 with L-(methyl-(11)C)-methionine (MET)-PET; 3 children underwent both FDG-PET and MET-PET but only the MET-PET results were used in the analysis. The PET and MR images were combined in image fusion navigation planning. Drawing on their experience with PET in adults, the authors proposed the following treatment plans: 1) surgery in children with imaging evidence of increased PET tracer uptake, which is highly specific of tumor and/or malignant tumor tissue; or 2) conservative treatment in children in whom there was little or no tracer uptake on PET. The authors compared the PET data with the MR imaging-based diagnosis and either 1) the results of histological examination in surgically treated cases, or 2) the long-term outcome in untreated cases. They studied PET and MR imaging sensitivity and specificity in detecting tumor and malignant tissues, and evaluated whether PET data altered their clinical management. RESULTS: Seventeen children had increased PET tracer uptake and underwent surgery. Tumor diagnosis was confirmed in all cases (that is, there were no false-positive findings). Cases in which there was little or no PET tracer uptake supported conservative treatment in 38 children. However, because PET was under evaluation, 16 of 38 lesions that were judged accessible for resection were surgically treated. Histological examination results demonstrated neither malignant nor evolving tumor tissue but yielded 9 indolent tumors (6 dysembryoplastic neuroectodermal tumors, 2 low-grade astrocytomas, and 1 low-grade astrocytoma and dysplasia) and 7 nontumoral lesions (3 cases of vasculitis, 3 of gliosis, and 1 of sarcoidosis). In 22 of the untreated 38 children, stable disease was noted during follow-up (range 18-136 months). Although an absence of PET tracer uptake might not exclude tumor tissue, PET did not reveal any false-negative findings in malignant or evolving tumor tissue detection in cases in which MR imaging showed false-positive and -negative cases in > 35 and 25% of the cases, respectively. CONCLUSIONS: These data confirmed the high sensitivity and specificity of PET to detect tumor as well as malignant tissue. Regarding the treatment of the incidental brain lesions, the PET findings enabled the authors to make more appropriate decisions regarding treatment than those made on MR imaging findings alone. Therefore, the risk of surgically treating a nontumoral lesion was reduced as well as that for conservatively managing a malignant tumor. Nowadays, it is estimated that these data justify conservative management in incidental lesions with low or absent PET tracer uptake.

Clinical impact of integrating positron emission tomography during surgery in 85 children with brain tumors.

OBJECT: In this paper, the authors' goal was to evaluate the impact of PET information on brain tumor surgery in children. METHODS: Between 1995 and 2007, 442 children were referred to the authors' institution for a newly diagnosed brain lesion. Of these, 85 were studied with FDG-PET and/or L-(methyl-(11)C)-methionine -PET in cases in which MR images were unable to assist in selecting accurate biopsy targets (35 patients) or to delineate tumors for maximal resection (50 patients). In surgical cases, PET and MR images were combined in image fusion planning for stereotactic biopsies or navigation-based resections. The preoperative planning images were compared postoperatively with MR imaging and PET findings and histological data for evaluating the clinical impact on the diagnostic yield and tumor resection. RESULTS: The PET data influenced surgical decisions or procedures in all cases. The use of PET helped to better differentiate indolent from active components in complex lesions (in 12 patients); improved target selection and diagnostic yield of stereotactic biopsies without increasing the sampling; provided additional prognostic information; reduced the amount of tissue needed for biopsy sampling in brainstem lesions (in 20 cases); better delineated lesions that were poorly delineated on MR imaging and that infiltrated functional cortex (in 50 cases); significantly increased the amount of tumor tissue removed in cases in which total resection influenced survival (in 20 cases); guided resection in hypermetabolic areas (in 15 cases); improved early postoperative detection of residual tumor (in 20 cases); avoided unnecessary reoperation (in 5 cases); and supported the decision to undertake early second-look resection (in 8 cases). CONCLUSIONS: The authors found that PET has a significant impact on the surgical decisions and procedures for managing pediatric brain tumors. Further studies may demonstrate whether PET improves outcomes in children.

Computer-assisted needle positioning for liver tumour radiofrequency ablation (RFA).

BACKGROUND: The RFA procedures rely on a precise positioning of the radiofrequency electrode and the complete destruction of the tumour. This article presents new optimization techniques to improve such surgical procedures. METHODS: A method to optimize the coverage of the tumour by successive RFA destructions and an in vitro procedure with simulated tumours have been developed. RESULTS: The guidance system and optimization coverage have been tested on 3D simulation and by the surgeon in vitro on a heifer liver. In this context, the RFA electrode is optically tracked and guided. CONCLUSIONS: The optimization method provides needle placements that ensure a complete theoretical ablation of the tumour, and the guidance system helps the surgeon to reach each position of destruction.

Positron emission tomography-guided volumetric resection of supratentorial high-grade gliomas: a survival analysis in 66 consecutive patients.

OBJECTIVE: Integrating positron emission tomographic (PET) images into the image-guided resection of high-grade gliomas (HGG) has shown that metabolic information on tumor heterogeneity and distribution are useful for planning surgery, improve tumor delineation, and provide a final target contour different from that obtained with magnetic resonance imaging (MRI) alone in about 80% of the procedures. Moreover, PET guidance helps to increase the amount of tumor removed and to target image-guided resection to anaplastic tissue areas. The present study aims to evaluate whether PET-guided volumetric resection (VR) in supratentorial HGG might add benefit to the patient's outcome. METHODS: PET images using [18F]fluorodeoxyglucose (n=23) and [11C]methionine (n=43) were combined with MRI scans in the planning of VR procedures performed at the initial stage in 66 consecutive patients (43 M/23 F) with supratentorial HGG according to the technique previously described. In all cases (35 anaplastic gliomas [20 astrocytomas, 10 oligoastrocytomas, 5 oligodendrogliomas] and 31 glioblastomas [GBM]), level and distribution of PET tracer uptake were analyzed to define a PET contour projected on MRI scans to define a final target contour for VR. Maximal tumor resection was accomplished in each case, with the intention to remove the entire abnormal metabolic area comprised in the surgical planning. Early postoperative MRI and PET assessed tumor resection. Survival analysis was performed separately in anaplastic gliomas and glioblastoma multiforme according to the presence or absence of residual tracer uptake on postoperative PET and according to the presence or absence of residual contrast enhancement on postoperative MRI. RESULTS: Preoperatively, metabolic information helped the surgical planning. In all procedures, PET contributed to define a final target contour different from that obtained with MRI alone. Postoperatively, 46 of 66 patients had no residual PET tracer uptake (total PET resection), 23 of 66 had no residual MRI contrast enhancement. No additional neurological morbidity due to the technique was reported. A total PET tracer uptake resection was associated with a significantly longer survival in anaplastic gliomas (P = 0.0071) and in glioblastoma multiforme (P = 0.0001), respectively. A total MRI contrast enhancement resection was not correlated with a significantly better survival, neither in anaplastic gliomas (P = 0.6089) nor in glioblastoma multiforme (P = 0.6806). CONCLUSIONS: Complete resection of the increased PET tracer uptake prolongs the survival of HGG patients. Because PET information represents a more specific marker than MRI enhancement for detecting anaplastic tumor tissue, PET-guidance increases the amount of anaplastic tissue removed in HGG.

Radiosurgery: operative technique, pitfalls and tips.

RATIONALE: From frame placement to dose administration, each step of the procedure must be optimized in every detail for better preservation of global precision, accuracy, safety and efficacy. METHODS: Quality control for resolution, accuracy and acquisition parameter optimization of both computed tomography (CT) scanners and magnetic resonance imaging (MRI) must be performed. Inaccuracies should then be quantified through systematic combination of MRI and CT in the radiosurgery planning system. Topography of petrous structures such as cochlea, vestibulum and facial nerve canal should be visible on the CT scan. T1-weighted volumetric MRI pulse sequences (3DT1) show a contrast-enhanced signal that is useful for both the pons interface delineation in Koos III cases, and the canal ending. High-resolution CISS T2-weighted volumetric pulse sequences (3DT2) allow direct nerve visualization and give superior stereotactic definition attributable to their better resolution minimizing partial volume effects and to their lower magnetic susceptibility minimizing distortions. The 3DT2 pulse sequences with contrast injection, show improved distinction between the pons and the nerves due to signal differences within the schwannomas. Fat saturation pulse sequences are of interest in postmicrosurgery conditions. The previous technical requirements and the dose planning elaboration will be balanced depending on the lesion volume staging (Koos), treatment history (microsurgery), clinical condition (hearing quality), pathological context (NF2) or age of the patient. The recommended marginal dose is 11-12 Gy. Tumor volume delineation allows the calculation of conformity, selectivity and gradient indexes. These global indexes must be weighted according to the relationship to critical structures and functional status of the patient. CONCLUSIONS: As an exclusively image-guided surgical method, radiosurgery requires special attention in the choice of imaging modalities and their acquisition parameters need extreme care. Technical nuances during the elaboration of the dose planning itself will directly influence both the toxicity risk and the chance of cure.

Development of a computer assisted system aimed at RFA liver surgery.

Radio frequency ablation (RFA) is a minimally invasive treatment for either hepatocellular carcinoma or metastasis liver carcinoma. In order to resect large lesions, the surgeon has to perform multiple time-consuming destruction cycles and reposition the RFA needle for each of them. The critical step in handling a successful ablation and preventing local recurrence is the correct positioning of the needle. For small tumors, the surgeon places the middle of the active needle tip in the center of the tumor under intra-operative ultrasound guidance. When one application is not enough to cover the entire tumor, the surgeon needs to repeat the treatment after repositioning of the needle, but US guidance is obstructed by the opacity stemming from the first RFA application. In this case the surgeon can only rely on anatomical knowledge and the repositioning of the RFA needle becomes a subjective task limiting the treatment accuracy. We have developed a computer assisted surgery guidance application for this repositioning procedure. Our software application handles the complete process from preoperative image analysis to tool tracking in the operating room. Our framework is mostly used for this RFA procedure, but is also suitable for any other medical or surgery application.

Combination of functional magnetic resonance imaging-guided neuronavigation and intraoperative cortical brain mapping improves targeting of motor cortex stimulation in neuropathic pain.

OBJECTIVE: To evaluate, regardless of the clinical results, the contribution of combining functional magnetic resonance imaging (fMRI) with intraoperative cortical brain mapping (iCM) as functional targeting methods for epidural chronic motor cortex stimulation (MCS) in refractory neuropathic pain. METHODS: Eighteen neuropathic pain patients (central stroke in six; trigeminal neuropathy in six; syrinx or amputation in six) who underwent operations for epidural MCS were studied with preoperative fMRI and iCM. fMRI investigated motor tasks of hands (as well as foot and tongue, when painful). fMRI data were analyzed with Statistical Parametric Mapping99 software (University College London, London, England; initial analysis threshold corresponding to P < 0.001), registered in a neuronavigation system, and correlated during surgery with iCM. The primary aim of this study was to improve the topographical precision of MCS. Matching of fMRI and iCM specifically was examined. RESULTS: Correspondence between the contour of the fMRI activation area and iCM in precentral gyrus (mean distance, 3.8 mm) was found in 17 (94%) of 18 patients. Eleven of them showed correspondence for more restrictive values of the analysis threshold (P < 0.0001); in six patients, the quality of the iCM was reduced by somatosensory wave attenuation and general anesthesia. In this group of six patients, a combination of both techniques was used for the final targeting. Correspondence was not found in one patient as the result of image distortion and residual motion artifact. At follow-up (4-60 mo), MCS induced significant pain relief in a total of 11 patients (61%). CONCLUSION: This study confirms the functional accuracy of fMRI guidance in neuropathic pain and illustrates the usefulness of combining fMRI guidance with iCM to improve the functional targeting in MCS. Because appropriate targeting is crucial to obtaining pain relief, this combination may increase the analgesic efficacy of MCS.

Selective image-guided venous sinus exposure for direct embolization of dural arteriovenous fistula: technical case report.

BACKGROUND: Transcranial approaches for transsinusal endovascular therapy of DAVF have been sporadically reported by large craniectomies. Large craniectomies carry nevertheless a risk of postembolization extradural hematoma, reduced by delaying the endovascular procedure. We report a 1-session technique of SIGC for percutaneous transvenous DAVF embolization. CASE DESCRIPTION: This 58-year-old woman developed a right-sided cerebellar hematoma in relation with a high-grade left transverse and sigmoid sinus DAVF. The DAVF was fed by branches from the left vertebral artery, left internal, and left external carotid arteries, draining into the transverse sinus with retrograde flow in cortical veins. Transvenous retrograde embolization was not feasible either through the left internal jugular vein because of thrombosis, or through the right one because of torcular septa. During the same anaesthetic session, a 5-cm-length selective craniectomy was shaped under magnetic resonance image guidance navigation according to the left transverse sinus with high-speed drill. Thereafter, back in the angiography room, the transverse sinus was taped and coiled resulting in a complete exclusion of the DAVF. CONCLUSION: Selective image-guided craniectomy is efficient and safe for direct percutaneous transvenous embolization of DAVF in a single anesthetic session. Leaving bone beside the sinus prevents a parenchymal traumatic puncture. This bone has nevertheless to be drilled to allow an adequate sharp puncture angle. Doing so, postoperative hematoma is prevented by the small bone opening, the natural adherence of the dura matter and the possibility of direct compression.

Irradiation of cochlear structures during vestibular schwannoma radiosurgery and associated hearing outcome.

OBJECT: The purpose of this study was to measure the dose of radiation delivered to the cochlea during a Gamma knife surgery (GKS) procedure for treatment of patients with vestibular schwannomas (VSs), and to analyze the relationship between cochlear irradiation and the hearing outcome of these patients. METHODS: Eighty-two patients with VSs were treated with GKS using a marginal dose of 12 Gy. No patient had neurofibromatosis Type 2 disease, and all had a Gardner-Robertson hearing class of I to IV before treatment, and a radiological and audiological follow-up of at least 1-year after GKS. The dosimetric data of the volume of the cochlea were retrospectively analyzed and were correlated with the auditory outcome of patients. RESULTS: The mean radiation dose delivered to the cochlear volume ranged from 1.30 to 10.00 Gy (median 4.15 Gy). The cochlea received significantly higher radiation doses in patients with worsening of hearing after GKS. A highly significant association between the cochlear and the intracanalicular dose of radiation delivered during GKS was found. CONCLUSIONS: During GKS for VSs, relatively high doses of radiation can be delivered to the cochlea. Worsening of hearing after GKS can be the consequence of either radiation injury to the cochlea or the irradiation dose delivered into the auditory canal, or both.

Integration of functional imaging in radiosurgery: the example of PET scan.

Radiosurgery relies critically on the imaging modalities that are used for targeting. Leksell Gamma Knife (LGK) radiosurgery presents the highest requirements in terms of imaging accuracy as the treatment is applied in a single high-dose session with no other spatial control than medical imaging. The advent of functional imaging modalities opens new challenges for LGK planning strategies. The integration of stereotactic PET in LGK represents an example of such application of modern multimodality imaging in radiosurgery. Our experience consists of 130 patients treated with the combination of MR/CT and PET guidance. In order to analyze the specific contribution of PET, we developed a classification reflecting the strategy used to define the target volume. When combining PET and MR information, 149 target volumes were defined, because some patients presented with multiple lesions or multifocal tumor areas. Abnormal PET uptake was found in 88% of the lesions; using the classification, we found that the information provided by PET altered significantly the MR-based definition of the tumor in 73%. In conclusion, integration of PET in radiosurgery provides additional functional information opening new perspectives for the treatment of brain tumors. The use of a standardized classification allows to assess the relative role of PET. A similar approach could be useful and may serve as a template for the evaluation of the integration of other new imaging modalities in radiosurgery.

The role of computer technology in radiosurgery.

Stereotactic radiosurgery treatment principles and irradiation techniques have shown little evolution since its introduction in 1968. Conversely, technology progress linked to computers has produced a major impact on the methods used for treatment planning and dose delivery. In order to fully comprehend modern radiosurgery approaches, one has to acquire good insight of the underlying technology, specifically computer software. In this chapter, we describe the evolution from X-ray films to high-resolution digital imaging, the shift from simple trigonometric calculation to highly complex algorithms and new perspectives in patient follow-up. If these changes open new prospects, they also add complexity, which leads to new pitfalls and limits of the stereotactic radiosurgery method.

Results of positron emission tomography guidance and reassessment of the utility of and indications for stereotactic biopsy in children with infiltrative brainstem tumors.

OBJECT: Most intrinsic infiltrative brainstem lesions diagnosed in children are gliomas, and these carry a very bad prognosis. Although the utility and risk of stereotactically guided biopsy procedures in intrinsic infiltrative brainstem lesions have been widely questioned, the neuroimaging diagnosis may be inaccurate in approximately 25% of cases, and the consequences of empirical therapy should not be underestimated. Stereotactic biopsy sampling is still performed in many centers, but the reported diagnostic yield ranges from 83 to 96%. The authors integrated positron emission tomography (PET) images into the planning for stereotactic biopsy procedures to direct the biopsy needle's trajectory to hypermetabolic foci of intrinsic infiltrative brainstem lesions. Their aim was to assess the benefit of the technique in terms of target selection and diagnostic yield. METHODS: Twenty children with newly diagnosed intrinsic infiltrative brainstem lesions underwent a PET-guided stereotactic biopsy procedure. The PET tracer was(18)F-2-fluoro-2-deoxy-D-glucose (FDG) in six cases, (11)C-methionine in eight, and both agents were used in six. A single biopsy target was selected in the area of highest PET tracer uptake in all cases. The PET data were compared with diagnoses and outcome. RESULTS: Use of PET guidance improved target selection and provided tumor diagnosis in all trajectories and in all children (high-grade glioma was diagnosed in 10, low-grade glioma in five, and nonglial tumor in five). The PET-guided trajectories provided a higher diagnostic yield than those guided by magnetic resonance imaging alone, which allowed the sampling to be reduced to a single trajectory. The PET data might also carry a prognostic value that could be useful for oncological management. CONCLUSIONS: These data support the suggestion that PET guidance improves the diagnostic yield of stereotactic biopsy sampling, allows the practitioner to reduce the number of sampling procedures, and might lead to a reassessment of the utility of and indications for stereotactic biopsy in children with intrinsic infiltrative brainstem lesions.

Correlation between dynamic susceptibility contrast perfusion MRI and methionine metabolism in brain gliomas: preliminary results.

PURPOSE: To evaluate in brain gliomas the relationship between tumor vascularity measured by MR-based maximum regional cerebral blood volume (rCBV) and tumor amino-acid metabolism based on maximum carbon-11 methionine (MET) uptake on positron emission tomography (PET). MATERIALS AND METHODS: Eighteen patients with histologically proven primary brain gliomas were included in the study. In addition to conventional MR sequences, dynamic MR images, including a first-pass gadopentetate dimeglumine T2*-weighted echo-planar perfusion sequence and a PET study using MET, were acquired. Eleven patients had low-grade gliomas, and seven had high-grade gliomas. rCBV ratios and MET uptake ratios normalized to the contralateral white matter (WM) corresponding values were measured in each tumor. Both maximum rCBV ratios and maximum MET uptake ratios were correlated to histopathology. The maximum rCBV ratios were correlated to the maximum MET uptake ratios. RESULTS: Both the maximum rCBV ratios and maximum MET uptake ratios of high-grade gliomas were significantly higher than those of low-grade gliomas (P<0.05). There was a significant positive correlation between maximum rCBV ratios and maximum MET uptake ratios (Spearman: r=0.89, P<0.00001). CONCLUSION: The maximum rCBV ratio and maximum MET uptake ratio are significantly correlated in gliomas, reflecting a close link between amino acid uptake and vascularity in these tumors.

Integrated positron emission tomography and magnetic resonance imaging-guided resection of brain tumors: a report of 103 consecutive procedures.

OBJECT: The aim of this study was to evaluate the integration of positron emission tomography (PET) scanning data into the image-guided resection of brain tumors. METHODS: Positron emission tomography scans obtained using fluorine-18 fluorodeoxyglucose (FDG) and L-[methyl-11C]methionine (MET) were combined with magnetic resonance (MR) images in the navigational planning of 103 resections of brain tumors (63 low-grade gliomas [LGGs] and 40 high-grade gliomas [HGGs]). These procedures were performed in 91 patients (57 males and 34 females) in whom tumor boundaries could not be accurately identified on MR images for navigation-based resection. The level and distribution of PET tracer uptake in the tumor were analyzed to define the lesion contours, which in turn yielded a PET volume. The PET scanning-demonstrated lesion volume was subsequently projected onto MR images and compared with MR imaging data (MR volume) to define a final target volume for navigation-based resection-the tumor contours were displayed in the microscope's eyepiece. Maximal tumor resection was accomplished in each case, with the intention of removing the entire area of abnormal metabolic activity visualized during surgical planning. Early postoperative MR imaging and PET scanning studies were performed to assess the quality of tumor resection. Both pre- and postoperative analyses of MR and PET images revealed whether integrating PET data into the navigational planning contributed to improved tumor volume definition and tumor resection. Metabolic information on tumor heterogeneity or extent was useful in planning the surgery. In 83 (80%) of 103 procedures, PET studies contributed to defining a final target volume different from that obtained with MR imaging alone. Furthermore, FDG-PET scanning, which was performed in a majority of HGG cases, showed that PET volume was less extended than the MR volume in 16 of 21 cases and contributed to targeting the resection to the hypermetabolic (anaplastic) area in 11 (69%) of 16 cases. Performed in 59 LGG cases and 23 HGG cases, MET-PET demonstrated that the PET volume did not match the MR volume and improved the tumor volume definition in 52 (88%) of 59 and 18 (78%) of 23, respectively. Total resection of the area of increased PET tracer uptake was achieved in 54 (52%) of 103 procedures. CONCLUSIONS: Imaging guidance with PET scanning provided independent and complementary information that helped to assess tumor extent and plan tumor resection better than with MR imaging guidance alone. The PET scanning guidance could help increase the amount of tumor removed and target image-guided resection to tumor portions that represent the highest evolving potential.

Role of intracanalicular volumetric and dosimetric parameters on hearing preservation after vestibular schwannoma radiosurgery.

PURPOSE: To analyze the relationship between hearing preservation after gamma knife radiosurgery (GKR) for vestibular schwannoma (VS) and some volumetric and dosimetric parameters of the intracanalicular components of VS. METHODS AND MATERIALS: This study included 82 patients with a VS treated by GKR; all patients had no NF2 disease, a Gardner-Robertson hearing class 1-4 before treatment, a marginal dose of 12 Gy, and a radiologic and audiologic follow-up > or =1 year post-GKR. The volume of both the entire tumor and the intracanalicular part of the tumor and the mean and integrated dose of these two volumes were correlated to the auditory outcomes of patients. RESULTS: At last hearing follow-up, 52 patients had no hearing worsening, and 30 patients had an increase of > or =1 class on Gardner-Robertson classification. We found that hearing preservation after GKR is significantly correlated with the intracanalicular tumor volume, as well as with the integrated dose delivered to the intracanalicular tumor volume. CONCLUSIONS: Some volumetric and dosimetric parameters of the intracanalicular part of the tumor influence hearing preservation after GKR of VS. Consequently, we advise the direct treatment of patients with preserved functional hearing and a VS including a small intracanalicular volume.

Comparison of functional MR imaging guidance to electrical cortical mapping for targeting selective motor cortex areas in neuropathic pain: a study based on intraoperative stereotactic navigation.

PURPOSE: To assess the concordance between data from functional MR imaging (fMRI) guidance and the intraoperative electrical cortical mapping (iCM) in targeting selective motor cortex areas in refractory neuropathic pain. METHODS: Twenty-one patients (11 women and 10 men; mean age, 55.6 years) with refractory central (ischemic, 8 cases) and neuropathic pain (trigeminal neuropathy, 6 cases; syrinx/amputation/plexus trauma, 7 cases) underwent surgery for the implantation of an epidural electrode for chronic motor cortex stimulation (MCS) with general anesthesia and a frameless neuronavigation system used for the image-guided targeting procedure. All patients were studied by preoperative fMRI and epidural iCM with somatosensory evoked potentials and motor cortex stimulodetection. fMRI investigated systematically motor tasks of both hands and that related to the somatic area (foot or tongue) affected by pain. fMRI data were analyzed with the Statistical Parametric Mapping99 software (initial analysis threshold [AT] corresponding to P < .001), registered in the neuronavigation system and correlated intraoperatively with iCM. Matching of fMRI and iCM was specifically examined, focusing the study on hand mapping. RESULTS: Concordance between contours of fMRI activation area and iCM in precentral gyrus (mean distance, 3.8 mm) was found in 20/21 patients (95%). Because precision of iCM was suboptimal in 7 patients, concordance for more restrictive values of the AT (P < .0001) was found in only 13 of these 20 patients. Concordance was not found in one patient, as result of image distortion and residual motion artifact. CONCLUSIONS: In this study, fMRI guidance provides information that matches those of an independent functional method. These data illustrate the functional accuracy of fMRI guidance for the operative targeting of selective motor cortex areas in neuropathic pain.

Integration of [11C]methionine-positron emission tomographic and magnetic resonance imaging for image-guided surgical resection of infiltrative low-grade brain tumors in children.

OBJECTIVE: To evaluate the interest of integrating positron emission tomography (PET) images with the radiolabeled tracer [(11)C]methionine (Met) into the image-guided navigation planning of infiltrative low-grade brain tumors (LGBTs) in children. METHODS: Twenty-two children underwent combined Met-PET with magnetic resonance imaging (MRI) scans in the planning of a navigation procedure. These children presented an LGBT (astrocytomas, 10; oligodendrogliomas, 4; ependymomas, 4; gangliogliomas, 4) located close to functional areas. Tumor boundaries were ill-defined on MRI (including T2-weighted and fluid-attenuated inversion-recovery scans) and could not be clearly identified for allowing a complete, or at least a large, image-guided resection. The PET tracer Met was chosen because of its higher sensitivity and specificity than MRI to detect tumor tissue. The level and extension of MET uptake were analyzed to define the PET contour, subsequently projected onto MRI scans to define a final target contour for volumetric resection. The quality of tumor resection was assessed by an early postoperative MRI and Met-PET workup. RESULTS: In 20 of the 22 children with ill-defined LGBTs, PET improved tumor delineation and contributed to define a final target contour different from that obtained with MRI alone. Met-PET guidance allowed a total resection of Met uptake in 17 cases that were considered total tumor resections because the operative margin left in place contained nontumor tissue. CONCLUSION: These data suggested that Met-PET guidance could help to improve the number of total resections and the amount of tumor removed in infiltrative LGBTs in children.

Combination of functional magnetic resonance imaging-guided neuronavigation and intraoperative cortical brain mapping improves targeting of motor cortex stimulation in neuropathic pain.

OBJECTIVE: To evaluate, regardless of the clinical results, the contribution of combining functional magnetic resonance imaging (fMRI) with intraoperative cortical brain mapping (iCM) as functional targeting methods for epidural chronic motor cortex stimulation (MCS) in refractory neuropathic pain. METHODS: Eighteen neuropathic pain patients (central stroke in six; trigeminal neuropathy in six; syrinx or amputation in six) who underwent operations for epidural MCS were studied with preoperative fMRI and iCM. fMRI investigated motor tasks of hands (as well as foot and tongue, when painful). fMRI data were analyzed with Statistical Parametric Mapping99 software (University College London, London, England; initial analysis threshold corresponding to P < 0.001), registered in a neuronavigation system, and correlated during surgery with iCM. The primary aim of this study was to improve the topographical precision of MCS. Matching of fMRI and iCM specifically was examined. RESULTS: Correspondence between the contour of the fMRI activation area and iCM in precentral gyrus (mean distance, 3.8 mm) was found in 17 (94%) of 18 patients. Eleven of them showed correspondence for more restrictive values of the analysis threshold (P < 0.0001); in six patients, the quality of the iCM was reduced by somatosensory wave attenuation and general anesthesia. In this group of six patients, a combination of both techniques was used for the final targeting. Correspondence was not found in one patient as the result of image distortion and residual motion artifact. At follow-up (4-60 mo), MCS induced significant pain relief in a total of 11 patients (61%). CONCLUSION: This study confirms the functional accuracy of fMRI guidance in neuropathic pain and illustrates the usefulness of combining fMRI guidance with iCM to improve the functional targeting in MCS. Because appropriate targeting is crucial to obtaining pain relief, this combination may increase the analgesic efficacy of MCS.

Semi-quantification of methionine uptake and flair signal for the evaluation of chemotherapy in low-grade oligodendroglioma.

UNLABELLED: 11C-Methionine (MET) is a useful positron emission tomography (PET) tracer for the evaluation of low-grade gliomas. Among these tumors, a high percentage of low-grade oligodendrogliomas (ODG) are sensitive to chemotherapy with procarbazine, CCNU, and vincristine (PCV). We aimed at: (1) objectively assessing ODG response to PCV by a metabolic index (the Activity Volume Index or AVI) generated from an automated semi-quantification of PET with MET (PET-MET); (2) comparing AVI and quantitative magnetic resonance imaging (MRI) measurements of response to PCV. METHODS: seven patients with ODG were followed for a period of 19.9+/-6.6 months after the completion of PCV chemotherapy. Regions of interest (ROI) were generated by covering all voxels with count values above a threshold level set at 120% of the mean cerebellar activity. On each slice, ROI volume and mean count values were calculated. AVI was calculated as the sum over all ROI of tumor volumex(tumor mean count/cerebellum count). Tumor volume measurements on MRI, were based on signal abnormalities visually detected on fluid-attenuated inversion recovery (FLAIR) sequences. RESULTS: PCV therapy was associated with a drastic decrease in AVI (mean+/-SD, cm3): AVI post-PCV=0.80+/-1.45 vs. AVI prior PCV=12.94+/-11.46 (P=0.03). Likewise, we observed a decrease in tumor volume estimated from the FLAIR signal (31.37+/-11.99 post-PCV vs. 67.95+/-39.96 prior PCV, P=0.03) although AVI decrease after PCV was significantly more pronounced (P=0.015). CONCLUSION: This study, based on limited number of patients and follow-up period indicates that AVI may be a sensitive and observer-independent method applicable to the assessment of ODG responsiveness to PCV treatment and may offer a major added value to both clinical assessment and MRI evaluation of chemotherapeutic outcomes.

Combined use of 18F-fluorodeoxyglucose and 11C-methionine in 45 positron emission tomography-guided stereotactic brain biopsies.

OBJECT: The aim of this study was to compare the contribution of the tracers 11C-methionine (Met) and 18F-fluorodeoxy-glucose (FDG) in positron emission tomography (PET)-guided stereotactic brain biopsy. METHODS: Forty-five patients underwent combined Met-PET and FDG-PET studies associated with computerized tomography (CT)- or magnetic resonance (MR)-guided stereotactic biopsy. Each patient presented with a lesion that was in proximity to the cortical or subcortical gray matter. The Met-PET and FDG-PET scans were analyzed to determine which tracer offers the best information to guide at least one stereotactic biopsy trajectory. Histologically based diagnoses were rendered in all patients (39 tumors, six nontumorous lesions) and biopsies were performed in all tumors with the aid of PET guidance. When tumor FDG uptake was higher than that in the gray matter (18 tumors), FDG was used for target definition. When FDG uptake was absent or equivalent to that in the gray matter (21 tumors), Met was used for target definition. Parallel review of all histological and imaging data showed that all tumors had an area of abnormal Met uptake and 33 had abnormal FDG uptake. All six nontumorous lesions had no Met uptake and biopsies were performed using CT or MR guidance only. All tumor trajectories had an area of abnormal Met uptake; all nondiagnostic trajectories in tumors had no abnormal Met uptake. CONCLUSIONS: When FDG shows limitations in target selection, Met is a good alternative because of its high specificity in tumors. Moreover, in the context of a single-tracer procedure and regardless of FDG uptake, Met is a better choice for PET guidance in neurosurgical procedures.