Search results for "Positron-Emission Tomography"
showing 10 items of 228 documents
Cognitive reserve impacts on inter-individual variability in resting-state cerebral metabolism in normal aging
2012
There is a great deal of heterogeneity in the impact of aging on cognition and cerebral functioning. One potential factor contributing to individual differences among the elderly is the cognitive reserve, which designates the partial protection from the deleterious effects of aging that lifetime experience provides. Neuroimaging studies examining task-related activation in elderly people suggested that cognitive reserve takes the form of more efficient use of brain networks and/or greater ability to recruit alternative networks to compensate for age-related cerebral changes. In this exploratory multi-center study, we examined the relationships between cognitive reserve, as measured by educa…
Diaschisis-Like Association of Hippocampal Atrophy and Posterior Cingulate Cortex Hypometabolism in Cognitively Normal Elderly Depends on Impaired In…
2017
Hippocampal atrophy and hypometabolism of the posterior cingulate cortex (PCC), early markers of Alzheimer's disease (AD), have been shown to be associated in late mild cognitive impairment and early AD via atrophy of connecting cingulum fibers. Recently, a direct association of hippocampal atrophy and PCC hypometabolism has been shown in cognitively normal elderly. We aimed to investigate if this association might be modulated by partly non-hippocampogenic alterations of parahippocampal cingulum (PHC) integrity. 45 cognitively healthy elderly aged 59 to 89 years were included from the Alzheimer's Disease Neuroimaging Initiative. Hippocampal volumes and PCC glucose metabolism were measured …
Resting state glucose utilization and the CERAD cognitive battery in patients with Alzheimer's disease
2004
The present study examined the cortical functional representation of neuropsychological domains in Alzheimer's disease (AD) using positron emission tomography (PET) and the neuropsychological assessment battery of the Consortium to Establish a Registry of Alzheimer's Disease (CERAD). Thirty patients with clinical probable AD and 10 elderly healthy controls underwent (18)FDG brain PET imaging during a resting state. Correlations between metabolic values and cognitive measures were determined using a region of interest analysis with NEUROSTAT (University of Michigan, USA) and a voxel-based analysis with SPM96 (Wellcome Department, London, UK). Specific correlations were seen between measures …
[11C]-DASB microPET imaging in the aged rat: Frontal and meso-thalamic increases in serotonin transporter binding
2011
Whereas molecular imaging studies in the aging human brain have predominantly demonstrated reductions in serotonin transporter (5-HTT) availability, the majority of the rodent studies, using autoradiographic methods, report increases in neural 5-HTT levels with age. To our knowledge, however, no previous rodent studies have assessed this topic in vivo, and therefore it remains unclear whether this discrepancy arises from methodological or inter-species differences. We performed an [(11)C]-DASB microPET study to evaluate the effects of aging on 5-HTT availability in the rat brain. To generate binding potential estimates, quantitative tracer kinetic modeling was applied using the simplified r…
Synthesis and evaluation in rats of the dopamine D2/3 receptor agonist 18F-AMC20 as a potential radioligand for PET
2015
Dopamine D2/3 receptor (D2/3R) agonist PET tracers are better suited for the imaging of synaptic dopaminergic neurotransmission than D2/3R antagonists and may also offer the opportunity to study in vivo the high-affinity state of D2/3R (D2/3RHigh). With the aim to develop 18F-labeled D2/3R agonists suitable for widespread clinical application, we report here on the synthesis and in vitro and in vivo evaluation of a D2/3R agonist ligand from the aminomethyl chromane (AMC) class-(R)-2-[(4- 18Fluorobenzylamino)methyl]chroman-7-ol (18F-AMC20). Methods: In vitro affinities of AMC20 toward dopaminergic receptor subtypes were measured in membrane homogenates prepared from HEK293 cells expressing h…
PEGylation of HPMA-based block copolymers enhances tumor accumulation in vivo: a quantitative study using radiolabeling and positron emission tomogra…
2013
Abstract This paper reports the body distribution of block copolymers (made by controlled radical polymerization) with N-(2-hydroxypropyl)methacrylamide (HPMA) as hydrophilic block and lauryl methacrylate (LMA) as hydrophobic block. They form micellar aggregates in aqueous solution. For this study the hydrophilic/hydrophobic balance was varied by incorporation of differing amounts of poly(ethylene glycol) (PEG) side chains into the hydrophilic block, while keeping the degree of polymerization of both blocks constant. PEGylation reduced the size of the micellar aggregates (Rh = 113 to 38 nm) and led to a minimum size of 7% PEG side chains. Polymers were labeled with the positron emitter 18F,…
[(11)C]PR04.MZ, a promising DAT ligand for low concentration imaging: Synthesis, efficient (11)C-O-methylation and initial small animal PET studies.
2009
PR04.MZ was designed as a highly selective dopamine transporter inhibitor, derived from natural cocaine. Its binding profile indicates that [{sup 11}C]PR04.MZ may be suited as a PET radioligand for the non-invasive exploration of striatal and extrastriatal DAT populations. As a key feature, its structural design facilitates both, labelling with fluorine-18 at its terminally fluorinated butynyl moiety and carbon-11 at its methyl ester function. The present report concerns the efficient [{sup 11}C]MeI mediated synthesis of [{sup 11}C]PR04.MZ from an O-desmethyl precursor trifluoroacetic acid salt with Rb{sub 2}CO{sub 3} in DMF in up to 95 {+-} 5% labelling yield. A preliminary {mu}PET-experim…
HPMA-LMA copolymer drug carriers in oncology: an in vivo PET study to assess the tumor line-specific polymer uptake and body distribution.
2013
Polymeric drug carriers aim to selectively target tumors in combination with protecting normal tissue. In this regard polymer structure and molecular weight are key factors considering organ distribution and tumor accumulation of the polymeric drug delivery system. Four different HPMA based copolymer structures (random as well as block copolymers with lauryl methacrylate as hydrophobic block) varying in molecular weight, size and resulting architecture were analyzed in two different tumor models (AT1 prostate carcinoma and Walker-256 mammary carcinoma) in vivo. Polymers were labeled with (18)F and organ/tumor uptake was followed by μPET imaging and ex vivo biodistribution. Vascular permeabi…
44Sc-DOTA-BN[2-14]NH2 in comparison to 68Ga-DOTA-BN[2-14]NH2 in pre-clinical investigation. Is 44Sc a potential radionuclide for PET?
2011
In the present study we demonstrate the in vitro and in vivo comparison of the (44)Sc and (68)Ga labeled DOTA-BN[2-14]NH(2). (44)Sc is a positron emitter with a half life of 3.92 h. Hence it could be used for PET imaging with ligands requiring longer observation time than in the case of (68)Ga.The binding affinity of (nat)Sc-DOTA-BN[2-14]NH(2) and (nat)Ga-DOTA-BN[2-14]NH(2) to GRP receptors was studied in competition to [(125)I-Tyr(4)]-Bombesin in the human prostate cancer cell line PC-3. A preliminary biodistribution in normal rats was performed, while first microPET images were assessed in male Copenhagen rats bearing the androgen-independent Dunning R-3327-AT-1 prostate cancer tumor.The …
Ileal Melanoma, A Rare Cause of Small Bowel Obstruction: Report of a Case, and Short Literature Review.
2020
Background: Malignant melanoma frequently spreads to the gastrointestinal tract, with 60% of patients with advanced metastatic disease showing digestive involvement; however, primary MM of the small intestine is a controversial diagnosis. In fact, whether these lesions arise as true small bowel primary neoplasms or represent metastases from unidentified cutaneous melanomas remains debatable. The most common complications are intestinal obstruction, massive gastrointestinal bleeding, and perforation. Objective & Methods: We report a case of a 64-year-old patient, with an unremarkable medical history, in which a late diagnosis of primary ileal malignant melanoma in the setting of an emer…