Journal of nuclear medicine : official publication, Society of Nuclear Medicine
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The concept of the ischemic penumbra was formulated on the basis of animal experiments showing functional impairment and electrophysiologic disturbances with decreasing flow to the brain below defined values (the threshold for function) and irreversible tissue damage with blood supply further decreased (the threshold for infarction). The perfusion range between these thresholds was termed the "penumbra," and restitution of flow above the functional threshold was able to reverse the deficits without permanent damage. In further experiments, the dependency of the development of irreversible lesions on the interaction of the severity and the duration of critically reduced blood flow was established, proving that the lower the flow, the shorter the time for efficient reperfusion. ⋯ Some of these discrepancies can be explained by the nonselective application of relative perfusion thresholds, which might be improved by more complex analytic procedures. The heterogeneity of the MRI signatures used for the definition of the mismatch are also responsible for disappointing results in the application of perfusion-weighted or diffusion-weighted MRI to the selection of patients for clinical trials. As long as validation of the mismatch selection paradigm is lacking, the use of this paradigm as a surrogate marker of outcome is limited.
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Early diagnosis of infective endocarditis (IE) is based on the yielding of blood cultures and echocardiographic findings. However, they have limitations and sometimes the diagnosis is inconclusive, particularly in patients with prosthetic valves (PVs) and implantable cardiac electronic devices (ICEDs). The primary aim of this study was to evaluate the diagnostic accuracy of 18F-FDG PET/CT in patients with suspected IE and ICED infection.
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Biomarkers can be used to characterize disease status or predict disease behavior. Cancer biomarkers have typically relied on assays of blood or tissue; however, molecular imaging has a promising and complementary role as a cancer biomarker. This "Focus on Molecular Imaging" article reviews the current role of biomarkers to direct cancer clinical trials and clinical practice, along with current and future cancer biomarker applications of molecular imaging.
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Noninvasive reporter gene imaging is a component of molecular imaging. Reporter imaging can provide noninvasive assessments of endogenous biologic processes in living subjects and can be performed using different imaging modalities. ⋯ Selected applications are discussed, including adoptive cell therapies, gene and oncoviral therapies, oncogenesis, signal pathway monitoring, and imaging drug treatment. Molecular imaging, and noninvasive reporter gene imaging in particular, are making important contributions to our understanding of disease development, progression, and treatment in our current era of molecular medicine and individualized patient care.
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(18)F-FDG PET is an established functional imaging modality for the evaluation of human disease. Diffusion-weighted MRI (DWI) is another rapidly evolving functional imaging modality that can be used to evaluate oncologic and nononcologic lesions throughout the body. ⋯ This article will describe the basic principles, clinical applications, and limitations of DWI. In addition, the available evidence that correlates and compares (18)F-FDG PET and DWI will be reviewed.