Neuroimaging clinics of North America
-
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.
-
The grave outlook for malignant glioma patients in spite of improvements to current modalities has ushered in new approaches to therapy. Viruses have emerged on the scene and gained attention for their ability to play essentially two roles: first, as vectors for therapeutic gene delivery and second, as engineered infectious agents capable of selectively lysing tumor cells. ⋯ Clinical oncolytic studies, on the other hand, have evaluated a conditionally replicating HSV as an antineoplastic agent. Despite some promise afforded by these trials, further studies are warranted; the investigation of additional viruses to play these roles is inevitable and is now precedented.
-
Assessment of the oxygenation status of brain tumors has been studied increasingly with imaging techniques in light of recent advances in oncology. Tumor oxygen tension is a critical factor influencing the effectiveness of radiation and chemotherapy and malignant progression. Hypoxic tumors are resistant to treatment, and prognostic value of tumor oxygen status is shown in head and neck tumors. ⋯ Quantification of cerebral blood oxygen saturation using MR imaging has promising clinical applications; however, technical difficulties have to be resolved. Blood oxygen level dependent MR imaging is an emerging technique to evaluate the cerebral blood oxygen saturation, and it has the potential and versatility to assess oxygenation status of brain tumors. Upon improvement and validation of current MR techniques, better diagnostic, prognostic, and treatment monitoring capabilities can be provided for patients with brain tumors.
-
Dynamic susceptibility contrast imaging has proven to be useful in brain tumor studies, and it provides additional information on tumor characteristics based on the microvascular structure of gliomas. The cerebral blood volume maps can be used to noninvasively grade gliomas, to determine optimal biopsy sites, to separate radiation necrosis from tumor regrowth, and to plan and follow irradiation, chemo- and antiangiogenic therapy. Besides of cerebral blood volume mapping, dynamic susceptibility contrast imaging sets also contain information about the flow and permeability properties of the tumor microvascular system. When combined with the conventional MRI, dynamic susceptibility contrast techniques offer important functional information about the biology of gliomas in a cost-effective way.
-
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.