Molecular imaging and biology : MIB : the official publication of the Academy of Molecular Imaging
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Comparative Study
[11C]-DPA-713 and [18F]-DPA-714 as new PET tracers for TSPO: a comparison with [11C]-(R)-PK11195 in a rat model of herpes encephalitis.
Activation of microglia cells plays an important role in neurological diseases. Positron emission tomography (PET) with [(11)C]-(R)-PK11195 has already been used to visualize activated microglia cells in neurological diseases. However, [(11)C]-(R)-PK11195 may not possess the required sensitivity to visualize mild neuroinflammation. In this study, we evaluated the PET tracers [(11)C]-DPA-713 and [(18)F]-DPA-714 as agents for imaging of activated microglia in a rat model of herpes encephalitis. ⋯ [(11)C]-DPA-713 may be more suitable for visualizing mild inflammation than [(11)C]-(R)-PK11195. In addition, the fact that [(18)F]-DPA-714 is an agonist PET tracer opens new possibilities to evaluate different aspects of neuroinflammation. Therefore, both tracers warrant further investigation in animal models and in a clinical setting.
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Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease for which no single diagnostic modality is able to evaluate the activity of the disease process. Cis-4-(18)F-fluoro-L: -proline ((18)F-proline) was shown in animal studies to be a reliable marker for fibrosis formation. We tested this candidate radioligand for imaging of fibrogenesis in patients with IPF. ⋯ Due to the low pulmonary uptake of (18)F-proline in patients with IPF, (18)F-proline does not seem to be a suitable radioligand to evaluate the activity of fibrosis formation in patients with IPF. The low uptake in the lungs of patients with interstitial fibrosis may be explained by the slow nature of fibrogenesis or to the relatively low dose of proline that can be used.
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The role of 2-deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography (FDG-PET) imaging in the clinical management of paraneoplastic neurological syndrome (PNS) is in evolution. The initial results are promising, and the potential of this modality in this setting has been demonstrated in the literature. In the setting of PNS, FDG-PET imaging can be of value from the following standpoints: (1) detection of the occult malignant focus and (2) objective assessment of the presence and extent of the functional abnormality in the brain and correlation of the imaging findings with the clinical features and disease activity. ⋯ The functional-anatomic discordance between PET and MRI in PLE needs to be examined further, which might open up new insights into the disease process and might generate further subgroups within this entity. Both modalities complement each other in PLE, and frequently, abnormalities noted on FDG-PET images can provide additional clinical information which is of great value in further patient management. In the setting of paraneoplastic cerebellar degeneration, FDG-PET generally reveals cerebellar hypometabolism similar to the cerebellar atrophy demonstrated by MRI, and FDG-PET tends to show the abnormality more often than MRI.
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Neuroimaging studies have provided a major contribution to our understanding of the mechanisms of the placebo effect in neurological and psychiatric disorders. Expectation of symptom improvement has long been believed to play a critical role in the placebo effect, and is associated with increased endogenous striatal dopamine release in Parkinson's disease and increased endogenous opioid transmission in placebo analgesia. ⋯ The ventral striatum is involved in the expectation of rewarding stimuli and, together with the prefrontal cortex, has also been shown to play an important role in the placebo-induced expectation of therapeutic benefit. Understanding the mechanisms of the placebo effect has important implications for treatment of several medical conditions, including depression, pain, and Parkinson's disease.
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2-deoxy-2-[F-18]fluoro-D-glucose (FDG)-positron emission tomography (PET) has an established role in restaging of various cancers, including papillary and undifferentiated thyroid carcinoma. However, controversies exist regarding its ability to reliably assess recurrent medullary thyroid cancer (MTC). We were therefore prompted to review our experience with FDG-PET for detection of occult MTC. ⋯ Our findings suggest a significant role for FDG-PET in patients with suspected MTC recurrence, with sensitivity of 85.7% and specificity of 83.3% for disease detection. FDG-PET provides additional information in a significant fraction of cases (54%) and could be used for restaging of patients with MTC and elevated levels of biomarkers (calcitonin). Additional studies are necessary to further evaluate the role of FDG-PET in MTC.