Neuroimaging clinics of North America
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Neuroimaging Clin. N. Am. · Nov 2009
Presurgical mapping of verbal language in brain tumors with functional MR imaging and MR tractography.
Functional magnetic resonance (fMR) imaging and diffusion MR tractography have emerged as valuable tools in the evaluation of verbal language in brain tumor patients, and have changed the way neurosurgeons look at patients with a mass in the dominant hemisphere. The techniques have obtained recognition as valuable presurgical clinical tools in the determination of hemispheric dominance and in the selection of candidates who may benefit from awake craniotomy. In the near future fMRI and diffusion MR Tractography may contribute to elucidate mechanisms of brain plasticity and may provide predictors of favorable postoperative clinical outcome. The functional anatomy of the language network and the role of fMR imaging and diffusion MR tractography in the evaluation of patients with a brain tumor are the focus of this article.
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Despite the recognized limitations of (18)Fluorodeoxyglucose positron emission tomography (FDG-PET) in brain tumor imaging due to the high background of normal gray matter, this imaging modality provides critical information for the management of patients with cerebral neoplasms with regard to the following aspects: (1) providing a global picture of the tumor and thus guiding the appropriate site for stereotactic biopsy, and thereby enhancing its accuracy and reducing the number of biopsy samples; and (2) prediction of biologic behavior and aggressiveness of the tumor, thereby aiding in prognosis. Another area, which has been investigated extensively, includes differentiating recurrent tumor from treatment-related changes (eg, radiation necrosis and postsurgical changes). Furthermore, FDG-PET has demonstrated its usefulness in differentiating lymphoma from toxoplasmosis in patients with acquired immune deficiency syndrome with great accuracy, and is used as the investigation of choice in this setting. ⋯ The value of hypoxia imaging tracers (such as fluoromisonidazole or more recently EF5) is substantial in radiotherapy planning and predicting treatment response. In addition, they may play an important role in the future in directing and monitoring targeted hypoxic therapy for tumors with hypoxia. Development of optimal image segmentation strategy with novel PET tracers and multimodality imaging is an approach that deserves mention in the era of intensity modulated radiotherapy, and which is likely to have important clinical and research applications in radiotherapy planning in patients with brain tumor.
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Neuroimaging Clin. N. Am. · Nov 2009
Brain irradiation: effects on normal brain parenchyma and radiation injury.
Radiation therapy is a major treatment modality for malignant and benign brain tumors. Concerns of radiation effects on the brain tissue and neurocognitive function and quality of life increase as survival of patients treated for brain tumors improves. In this article, the clinical and neurobehavioral symptoms and signs of radiation-induced brain injury, possible histopathology, and the potential of functional, metabolic, and molecular imaging as a biomarker for assessment and prediction of neurotoxicity after brain irradiation and imaging findings in radiation necrosis are discussed.
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This article briefly discusses the imaging approach to lesions of the anterior skull base. A brief review of normal anatomy and imaging techniques is followed by a discussion about common neoplastic and non-neoplastic pathologies involving this region.
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The central skull base (CSB) constitutes a frontier between the extracranial head and neck and the middle cranial fossa. The anatomy of this region is complex, containing most of the bony foramina and canals of the skull base traversed by several neurovascular structures that can act as routes of spread for pathologic processes. ⋯ Crosssectional imaging is indispensable in the diagnosis, treatment planning, and follow-up of patients with CSB lesions. This review focuses on a systematic approach to this region based on an anatomic division that takes into account the major tissue constituents of the CSB.