Marc Levivier

Quantitative imaging study of extent of surgical resection and prognosis of malignant astrocytomas.

OBJECTIVE: This study used quantitative radiological imaging to determine the effect of surgical resection on postoperative survival of patients with malignant astrocytomas. Previous studies relied on the surgeons impressions of the amount of tumor removed, which is a less reliable measure of the extent of resection. METHODS: Information concerning possible prognostic factors was collected for 75 patients undergoing magnetic resonance imaging or computed tomography preoperatively and within 10 days postoperatively. Image analysis of the neuroradiological studies was conducted to quantify pre- and postoperative total tumor volumes and enhancing volumes. Univariate and multivariate proportional hazards models were used to analyze the regression of survival regarding 22 covariates that might affect survival. The covariates that were entered included age, gender, tumor grade, cumulative radiation dose, chemotherapy, seizures as a first symptom, Karnofsky performance status at presentation, pre- and postoperative total and enhancing tumor volumes, ratio of pre- to postoperative total and enhancing tumor volumes, tumor location, surgeons impression of the degree of resection, and subsequent surgery. RESULTS: There were 23 patients with anaplastic astrocytomas and 52 with glioblastomas multiforme. The estimated mean survival time was 27 months for patients undergoing gross total resection, 33 months for subtotal resection, and 13 months for open or stereotactic biopsy. Five factors that were significant predictors of survival in multivariate analysis were tumor grade, age, Karnofsky performance status, radiation dose, and postoperative complications (P < 0.05). In univariate analysis, tumor grade, radiation dose, age, Karnofsky status, complications, presence of enhancing tumor in postoperative imaging, and postoperative volume of enhancing tumor were significantly associated with survival (P < 0.05). CONCLUSION: We conclude that the most important prognostic factors affecting survival of patients with anaplastic astrocytomas and glioblastomas multiforme are tumor grade, age, preoperative performance status, and radiation therapy. Postoperative complications adversely affect survival. Aggressive surgical resection did not impart a significant increase in survival time. Surgical resection may improve survival, but its importance is less than that of other factors and may be demonstrable only by larger studies.

Prognostic value positron emission tomography with [18F]fluoro-2-deoxy-D-glucose in the low-grade glioma.

OBJECTIVEnThe natural history of the supratentorial low-grade glioma (LGG) of the adult is variable, and its malignant transformation is hardly predictable. Because positron emission tomography with [18F]fluoro-2-deoxy-D-glucose (FDG) has prognostic value in high-grade gliomas, this study was designed to search for a possible relationship between glucose metabolism and risk of malignant evolution in LGGs.nnnMETHODSnPositron emission tomography with FDG was performed in 28 patients with LGGs (22 at the time of diagnosis and 6 after the diagnosis). A metabolic grading system based on the visual inspection of the positron emission tomographic images was used.nnnRESULTSnIn 19 patients, no area of FDG uptake higher than in the white matter was detected (metabolic Grade 1). All of those patients were alive at the end of the follow-up period. Only one of the patients presented a histological modification 7 months after the diagnosis. Nine patients presented areas of increased FDG uptake (metabolic Grade 2 or 3). Those areas were found in the tumor area in eight patients and in an area of radionecrosis in one. Of the nine patients with FDG hot spots, six died, two had recurrence but were alive at the end of the follow-up period, and the patient with radionecrosis had no signs of recurrence.nnnCONCLUSIONSnThe presence of areas of increased FDG uptake in a histologically proven LGG predicts, in most cases, a deleterious evolution. This metabolic feature, detectable with a noninvasive procedure, may provide a clue to cellular changes, announcing malignant transformation in a tumor that retains the histological features of an LGG. Protocols with aggressive therapeutic strategies in this situation should be considered for evaluation.

FDG-PET as a prognostic factor in high-grade astrocytoma

AbstractBackground: The prognostic value of the metabolic status of cerebral gliomas determined by positron emission tomography with [18F]-fluoro-deoxy-D-glucose (FDG-PET) has been established in populations with a mixture of grades 2, 3 and 4 gliomas, but remains uncertain when only malignant gliomas are considered (grade 3 and 4).nMethods: FDG-PET performed in 30 patients with anaplastic astrocytoma (grade III) and 61 patients with glioblastoma (grade 4) were classified according to a metabolic grading. The uptake of FDG was lower in the tumor compared to white matter (WM) in grade 1 (4 glioblastoma, 4 anaplastic astrocytoma), it was intermediate between WM and cortex in grade 2 (20 glioblastoma, 22 anaplastic astrocytoma), and it was superior to cortex in grade 3 (38 glioblastoma, 4 anaplastic astrocytoma).nResults: Kaplan–Meier survival curves were similar in patient with grades 1 and 2, but were significantly worse (p = 0.007) in grade 3. In multivariate analysis considering age, pathological grade (anaplastic astrocytoma versus glioblastoma), and metabolic grades, the metabolic grade did not appear to be an independent prognostic factor. When anaplastic astrocytomas and glioblastomas were considered separately, metabolic grade is of predictive value only in the group of glioblastomas.nConclusion: In malignant gliomas, metabolic grading determined by FDG-PET was not superior to the pathological grading for survival prediction. Still, it remains of predictive value when applied to malignant gliomas histologically classified as glioblastoma.

Three-quarter prone approach to the pineal-tentorial region. Report of seven cases.

We report our preliminary results (seven cases) with a three-quarter prone approach to the pineal-tentorial region using an opening beneath the midline. The technique we have used eliminates the risk of air embolism because the head is just over the right atrium, the table remaining in an horizontal plane. Using the natural effect of gravity, it is no more necessary to use retraction on the occipital lobe. So, hemianopsia is eliminated. We confirm the results of other teams who have used this approach which seems to us to be the best way to treat any lesion in the pineal-tentorial area.

Invading Meningiomas of Sphenoid Wing. What Must we Know Before Surgery

Sphenoid wing meningiomas are very invasive tumours. The only permanent treatment is total eradication. But quality of life should also be taken into account. Several surgical approaches have been proposed with more and more aggressivity. We have raised a list of 9 questions which is not exhaustive. We recommend solving them before surgery and to be sure to have an answer before a surgical decision is made. This would be of great benefit for more efficacious results with less sequelae.

Update of diagnostic preoperative images using low-field interventional MRI for navigation in neurosurgery: rigid-body registration

This study looks into the rigid-body registration of pre-operative anatomical high field and interventional low field magnetic resonance images (MRI). The accurate 3D registration of these modalities is required to enhance the content of interventional images with anatomical (CT, high field MRI, DTI), functional (DWI, fMRI, PWI), metabolic (PET) or angiography (CTA, MRA) pre-operative images. The specific design of the interventional MRI scanner used in the present study, a PoleStar N20, induces image artifacts, such as ellipsoidal masking and intensity inhomogeneities, which affect registration performance. On MRI data from eleven patients, who underwent resection of a brain tumor, we quantitatively evaluated the effects of artifacts in the image registration process based on a normalized mutual information (NMI) metric criterion. The results show that the quality of alignment of pre-operative anatomical and interventional images strongly depends on pre-processing carried out prior to registration. The registration results scored the highest in visual evaluation only if intensity variations and masking were considered in image registration. We conclude that the alignment of anatomical high field MRI and PoleStar interventional images is the most accurate when the PoleStars induced image artifacts are corrected for before registration.

Problems and challenges of image-guided neurosurgical navigation and intervention

Interventional MRI scanners now allow neurosurgeons to make images throughout the course of surgery. While these machines are still relatively rare today, they are bound to become a key instrument in the operating theatres of major medical centers. The successful use of such machines requires close collaboration between surgeons and engineers. This presentation describes the problem of neurosurgical navigation and discusses some of its algorithmic challenges, such as the joint use of multiple imaging modalities (CT, MRI, PET, etc), image registration, field-artifact removal, multi-modality image segmentation, biomechanical models of the brain, finite-element models (FEM) for tracking tissue deformation, and a generalization of FEM, known as XFEM, to handle the cuts, retractions, and resections occuring during surgery.