Publications (5)12.52 Total impact
- [Show abstract] [Hide abstract]
ABSTRACT: To compare three patient stratification systems predicting survival: recursive partitioning analysis (RPA), score index for radiosurgery in brain metastases (SIR), and a proposed basic score for brain metastases (BS-BM). We analyzed the outcome of 110 patients treated with Leksell Gamma Knife radiosurgery between December 1999 and January 2003. The BS-BM was calculated by evaluating three main prognostic factors: Karnofsky performance status, primary tumor control, and presence of extracranial metastases. The median survival was 27.6 months for RPA Class I, 10.7 months for RPA Class II, and 2.8 months for RPA Class III (p <0.0001). Using the SIR, the median survival was 27.7, 10.8, 4.6, and 2.4 months for a score of 8-10, 5-7, 4, and 0-3, respectively (p <0.0001). The median survival was undefined in patients with a BS-BM of 3 (55% at 32 months) and was 13.1 months for a BS-BM of 2, 3.3 months for a BS-BM of 1, and 1.9 months for a BS-BM of 0 (p <0.0001). The backward elimination model in multivariate Cox analysis identified SIR and BS-BM as the only two variables significantly associated with survival (p = 0.031 and p = 0.043, respectively). SIR and BS-BM were the most accurate for estimating survival. They were specific enough to identify patients with short survival (SIR 0-3 and BS-BM 0). Because of it simplicity, BS-BM is easier to use.
- [Show abstract] [Hide abstract]
ABSTRACT: We developed a technique that allows the routine integration of PET in stereotactic neurosurgery, including radiosurgery. We report our clinical experience with the combined use of metabolic (i.e., PET) and anatomic (i.e., MRI and CT) images for the radiosurgical treatment of brain tumors. We propose a classification describing the relative role of the information provided by PET in this multimodality image-guided approach. Between December 1999 and March 2003, 57 patients had stereotactic PET as part of their image acquisition for the planning of gamma knife radiosurgery. Together with stereotactic MRI and CT, stereotactic PET images were acquired on the same day using either (18)F-FDG or (11)C-methionine. PET images were imported in the planning software for the radiosurgery dosimetry, and the target volume was defined using the combined information of PET and MRI or CT. To analyze the specific contribution of the PET findings, we propose a classification that reflects the strategy used to define the target volume. The patients were offered radiosurgery with PET guidance when their tumor was ill-defined and we anticipated some limitation of target definition on MRI alone. This represents 10% of the radiosurgery procedures performed in our center during the same period of time. There were 40 primary brain lesions, 7 metastases, and 10 pituitary adenomas. Abnormal PET uptake was found in 62 of 72 targets (86%), and this information altered significantly the MRI-defined tumor in 43 targets (69%). The integration of PET in radiosurgery provides additional information that opens new perspectives for the optimization of the treatment of brain tumors.
- [Show abstract] [Hide abstract]
ABSTRACT: Most of the patients treated with Leksell Gamma Knife(R) (LGK) present benign lesions, it is thus essential to evaluate extracranial doses. A Study of in vivo measurements on 228 unselected patients treated with LGK Model C is presented. Measurements were performed with TL dosimeters which were positioned on the lateral canthus, thyroid, breasts and gonads. Pathology, target maximum dose, reference isodose volume, integral dose, treatment time, distance and influences of plugs on extracranial doses are analyzed. The treatment of some benign pathologies like meningioma can give relatively important extracranial doses (mean dose of 13.3 cGy on thyroid). Surprisingly, no correlation could be shown between maximum dose, reference isodose volume, integral dose and extracranial doses. On the other hand, the total treatment time and the use of plugs have a significant influence on doses received on extracranial sites. Copyright (C) 2004 S. Karger AG, Basel.
Article: Modern multimodal neuroimaging for radiosurgery: the example of PET scan integrationUse of stereotactic PET images in dosimetry planning of radiosurgery for brain tumors: clinical experience and proposed classification[Dosimetric planning for radiosurgical treatment of vestibular schwannomas][Imaging for stereotaxic treatment of vestibular schwannomas. Error factors and corrections][Stereotactic mapping for radiosurgical treatment of vestibular schwannomas]The integration of metabolic imaging in[Show abstract] [Hide abstract]
ABSTRACT: Radiosurgery relies critically on medical imaging modalities. 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 new imaging modalities opens 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 80 patients treated with the combination of MR/CT and PET guidance. In order to analyze the specific contribution of PET findings, we developed a classification reflecting the strategy used to define the target volume. When combining PET and MR information, 102 target volumes were defined, because some patients presented with multiple lesions or multifocal tumor areas. Abnormal PET uptake was found in 86% of the lesions, and this information altered significantly the MR-defined tumor in 73%. In conclusion, integration of PET in radiosurgery provides additional 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. We developed a technique that allows the routine integration of PET in stereotactic neurosurgery, including radiosurgery. We report our clinical experience with the combined use of metabolic (i.e., PET) and anatomic (i.e., MRI and CT) images for the radiosurgical treatment of brain tumors. We propose a classification describing the relative role of the information provided by PET in this multimodality image-guided approach. METHODS: Between December 1999 and March 2003, 57 patients had stereotactic PET as part of their image acquisition for the planning of gamma knife radiosurgery. Together with stereotactic MRI and CT, stereotactic PET images were acquired on the same day using either (18)F-FDG or (11)C-methionine. PET images were imported in the planning software for the radiosurgery dosimetry, and the target volume was defined using the combined information of PET and MRI or CT. To analyze the specific contribution of the PET findings, we propose a classification that reflects the strategy used to define the target volume. RESULTS: The patients were offered radiosurgery with PET guidance when their tumor was ill-defined and we anticipated some limitation of target definition on MRI alone. This represents 10% of the radiosurgery procedures performed in our center during the same period of time. There were 40 primary brain lesions, 7 metastases, and 10 pituitary adenomas. Abnormal PET uptake was found in 62 of 72 targets (86%), and this information altered significantly the MRI-defined tumor in 43 targets (69%). CONCLUSION: The integration of PET in radiosurgery provides additional information that opens new perspectives for the optimization of the treatment of brain tumors. Dosimetry planning is certainly the most typical neurosurgical instant in the radiosurgical procedure for the treatment of vestibular schwannomas (VS). Indeed, it is a key-moment in which the therapeutical choices will have a major influence on the clinical results, in terms of efficacy and safety. The therapist has to inform the patient about the rationale of the treatment, its limitations, the expected results, and the specific risks. Deep knowledge of the radiosurgical technique, of the principles of dosimetry, and of the therapist's personal experience, allows an a posteriori analytical study of the influence of the dosimetry therapeutic choices on the patient's outcome. Correlation between the preoperative therapeutic choices and the postoperative clinico-radiological information is mandatory to optimize therapeutic strategies. These therapeutic choices should be the result of a reflection integrating the clinical status of the patient, an understanding of the specific pathology of VS, awareness of the other therapeutic choices, and knowledge of radiological and surgical anatomy. The way a certain number of parameters will be defined during the dosimetry planning will have a major influence on the clinical results. This explains wide variability of clinical results from one operator to another, for the same radiological and radiosurgical tools. This emphasizes the need for specific and long-term training, associated with continuous education and a good knowledge of the very active literature. BACKGROUND AND PURPOSE: Gamma Knife radiosurgery treatment of vestibular schwannomas requires high accuracy for the prescribed dose definition and delivery. The main factors contributing to the error are the anatomical distortions of imaging modalities used for treatment planning. Imaging limitations and error factors are reviewed and detailed. Multimodality rationale for the delineation of vestibular schwannomas and surrounding structures are assessed. Quality control strategies are discussed and a distortion correction technique using a radiological phantom is presented. METHODS: Computed tomography is considered as the reference for spatial accuracy after appropriate scanner quality control using the stereotaxic fiducials system. Magnetic resonance imaging pulse sequence distortions are measured with a phantom designed for 3D non-linear local distortion evidence. A distortion correction transformation is computed from the phantom images and applied to the patient images. Results are verified using the stereotaxic fiducials system. RESULTS: Fiducials registration errors show spatial accuracy improvement, approaching computed tomography quality, after distortion correction of magnetic resonance images. CONCLUSIONS: The multimodal imaging approach for the dose planning of vestibular schwannomas radiosurgery treatment is relevant. Quality control of spatial accuracy for imaging modalities is mandatory and realistic in clinical routine. RATIONALE: As an exclusively image-guided surgery method, radiosurgery requires special attention in the choice of imaging modalities and acquisition parameters must be set with extreme care. METHODS: Quality control for resolution and accuracy of computed tomography (CT) scanners must be performed. Magnetic resonance imaging (MRI) distortions should be limited through magnetic field homogeneity adjustment (shimming) and acquisition parameters optimization. These inaccuracies should then be quantified through systematic combination of MRI and CT in the radiosurgery planning system. MRI pulse sequences selection criteria are defined by their ability to delineate tumor contrast enhancement and to image cranial nerves and vessels relative arrangement in the cistern and canal. Topography of the petrous structures, such as cochlea, vestibulum and facial nerve canal should be visible. Exact definition of real extension of the lesion at the end of the canal may require specific technical solutions. These technical requirements must be balanced depending on the lesion Volume staging (Koos), the treatment history (microsurgery), the clinical condition (hearing quality), the pathological context (NF2) or the age of the patient. RESULTS: T1-weighted Volumetric MRI pulse sequences (3D-T1) show a contrast enhanced signal that is useful for both the pons interface delineation in Koos III cases, and the canal ending in Ohata A and B. On the other hand, 3D-T1 introduce inaccuracies from magnetic susceptibility distortions and partial Volume effects. High resolution CISS T2-weighted Volumetric pulse sequences (3D-T2) give superior stereotaxic definition attributable to their better resolution (half a millimeter) minimizing partial Volume effects and to their lower magnetic susceptibility minimizing distortions. 3D-T2 allows direct nerve visualization. Moreover, this pulse sequence 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 post-microsurgery conditions. CONCLUSIONS: Radiology phase quality is critical and its complexity requires a high commitment to obtain satisfactory clinical results. Solelt the 3D-T1 MRI modality seems to us not to comply to minimum security criteria. OBJECT: The authors review their experience with the clinical development and routine use of positron emission tomography (PET) during stereotactic procedures, including the use of PET-guided gamma knife radiosurgery (GKS). METHODS: Techniques have been developed for the routine use of stereotactic PET, and accumulated experience using PET-guided stereotactic procedures over the past 10 years includes more than 150 stereotactic biopsies, 43 neuronavigation procedures, and 34 cases treated with GKS. Positron emission tomography-guided GKS was performed in 24 patients with primary brain tumors (four pilocytic astrocytomas, five low-grade astrocytomas or oligodendrogliomas, seven anaplastic astrocytomas or ependymomas, five glioblastomas, and three neurocytomas), five patients with metastases (single or multiple lesions), and five patients with pituitary adenomas. CONCLUSIONS: Data obtained with PET scanning can be integrated with GKS treatment planning, enabling access to metabolic information with high spatial accuracy. Positron emission tomography data can be successfully combined with magnetic resonance imaging data to provide specific information for defining the target volume for the radiosurgical treatment in patients with recurrent brain tumors, such as glioma, metastasis, and pituitary adenoma. This approach is particularly useful for optimizing target selection for infiltrating or ill-defined brain lesions. The use of PET scanning contributed data in 31 cases (93%) and information that was specifically utilized to adapt the target volume in 25 cases (74%). It would seem that the integration of PET data into GKS treatment planning may represent an important step toward further developments in radiosurgery: this approach provides additional information that may open new perspectives for the optimization of the treatment of brain tumors.
- [Show abstract] [Hide abstract]
ABSTRACT: The authors report their experience using the Leksell gamma knife C (GK-C) for the treatment of meningioma and vestibular schwannoma (VS). In December 1999, the first commercially available clinical GK-C was installed at the Université Libre de Bruxelles (Erasme Hospital, Brussels, Belgium). In January 2000, the system was upgraded and equipped with the automatic positioning system (APS). Between February 2000 and February 2003, the APS-equipped GK-C was used to perform 532 radiosurgical treatments, including those in 97 meningiomas and 101 VSs. Meningioma and VS represent 18 and 19%, respectively, of lesions in patients treated with GK-C at the authors' center. The mean number of isocenters per lesion was 9.5 (range 1-36): 18.1 (range 1-36) for meningioma and 12.8 (range 1-27) for VS. In 77.6% of the cases, the authors used a single helmet of collimators (55.5% in meningioma and 74.3% in VS). The most frequently used collimator size was 4 mm (46.7%). Whereas it was 4 mm in cases of VS (64.3%), it was 8 mm in cases of meningioma (41.6%). The APS could be used in 86% of the cases, either alone (79%) or in combination with trunnions (7%). There was a difference in the APS-based treatment success rate in meningiomas (85%) and VSs (94%). A significant difference was also noted in the conformity of the radiosurgical treatments between the two lesions. The APS-equipped GK-C represents an evolutionary step in radiosurgery. It requires adjustments by the treating team for its specific limitations, which vary among indications, as exemplified by the differences inherent between meningioma and VS in this series.
Université Libre de Bruxelles
Bruxelles, Brussels Capital Region, Belgium
- Gamma Knife Centre