Neuroimaging clinics of North America
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Neuroimaging Clin. N. Am. · Nov 2002
ReviewMolecular abnormalities and correlations with tumor response and outcome in glioma patients.
Molecular analysis approaches hold promise to refine the management of patients with malignant gliomas. An important step in the application of these techniques to guide clinical decision-making involves transitioning these approaches from the research setting into the clinical diagnostic arena, using methods that can be performed rapidly and reliably on surgically obtained tumor specimens. ⋯ An associated challenge involves demonstrating that biological stratification can support therapeutic stratification that will influence, rather than merely predict, the outcome of patients with brain tumors. The realization of this long-range goal will require the identification of novel therapeutic strategies that hold promise for improving the outcome of molecularly defined subsets of high-grade gliomas, which as a group remain largely resistant to conventional therapies.
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A wide variety of metabolic features of brain tumors can be imaged using PET, including glucose metabolism, blood flow, oxygen consumption, amino acid metabolism, and lipid synthesis. Currently, FDG is the most widely available PET tracer for body imaging and brain imaging. Malignant brain tumors, like many other soft tissue tumors, show increased glucose metabolism, which is reflected on FDG-PET imaging. ⋯ Other tracers, such as 11C-methionine and FCH, also avidly accumulate in brain tumors and have the advantage of low background cortical activity. The relationship between degree of uptake of these agents and tumor grade is not established. These tracers may be useful in specific clinical situations, however, such as tumor localization for treatment planning or evaluation of low-grade tumors.
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Neuroimaging Clin. N. Am. · Nov 2002
ReviewViral imaging in gene therapy noninvasive demonstration of gene delivery and expression.
Gene therapy is a rapidly developing modality of treatment, with applications in acquired and inherited disorders. Gene delivery vehicles ("vectors") are the main impediment in the evolution of gene therapy into a clinically acceptable mainstream therapy. Vectors based on viral particles are the most commonly used vehicles to carry genes to the organs and tissues of interest. ⋯ Recent progress in viral vector production and better understanding of molecular aspects of vector delivery and targeting issues has created the need for imaging techniques that would be useful in addressing the problems and opportunities inherent in viral gene therapy development. Two integral components of gene therapy monitoring, the imaging of gene delivery and the imaging of resultant exogenous gene expression, are recognized. These molecular imaging components provide a realistic means for assessment of safety and efficacy of preclinical and clinical development of gene therapy.
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As an immunization platform for brain tumors, dendritic cells supply an impressive host of advantages. On the simplest level, they provide the safety and tumor-specificity so wanted by current therapeutic options. ⋯ Directions to take now include the identification of new tumor-specific and tumor-associated antigens; the determination of the optimal dendritic cell subtype, generation, loading method, maturation state, dose, and route of delivery for immunizations; the further characterization of dendritic cells and their activities; and, potentially, the discovery of ways to pulse dendritic cells efficiently in vivo. Preclinical studies continue to play an important role in refining this form of active immunotherapy.
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Neuroimaging Clin. N. Am. · Nov 2002
ReviewIntraoperative magnetic resonance imaging and magnetic resonance imaging-guided therapy for brain tumors.
Since their introduction into surgical practice in the mid 1990s, intraoperative MRI systems have evolved into essential, routinely used tools for the surgical treatment of brain tumors in many centers. Clear delineation of the lesion, "under-the-surface" vision, and the possibility of obtaining real-time feedback on the extent of resection and the position of residual tumor tissue (which may change during surgery due to "brain-shift") are the main strengths of this method. High-performance computing has further extended the capabilities of intraoperative MRI systems, opening the way for using multimodal information and 3D anatomical reconstructions, which can be updated in "near real time." MRI sensitivity to thermal changes has also opened the way for innovative, minimally invasive (LASER ablations) as well as noninvasive therapeutic approaches for brain tumors (focused ultrasound). Although we have not used intraoperative MRI in clinical applications sufficiently long to assess long-term outcomes, this method clearly enhances the ability of the neurosurgeon to navigate the surgical field with greater accuracy, to avoid critical anatomic structures with greater efficacy, and to reduce the overall invasiveness of the surgery itself.