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The (68)Ge/(68)Ga generator is of increasing interest for clinical PET. For successful labelling, the eluate has to be purified. The aim of our approach is to improve the existing anionic methods which have a number of advantages compared to other methods but which use high concentrated HCl, and require an additional anionizing step. A new (68)Ga-eluate anionic purification method that enables rapid and high efficiency labelling of DOTA and NODAGA conjugated peptides in high radiochemical purity is described. The new method uses NaCl as an alternative Cl(-) source to the corrosive HCl and combines the three standard steps in a single step. The recovery yield was ≥90%, and the (68)Ge breakthrough was in conformity with the European Pharmacopeia limit. An automated labelling of DOTA and NODAGA-conjugated peptides was performed with the new method, using acetate sodium buffer, with a total duration of 13 min and a radiochemical yield >85%. The labelled peptides have a radiochemical purity exceeding 99% and can be used directly without any further purification step and without the quality control by gas chromatography. Furthermore, the new method has an economic advantage: it offers the possibility to use generator until 20 months after the calibration date., (Copyright © 2015 John Wiley & Sons, Ltd.)

We studied concomitantly the level of neuroinflammation and β-amyloid (Aβ) load in the APPswePS1dE9 transgenic mouse model of Alzheimer's disease using positron emission tomography. The translocator protein 18 kDa (TSPO) tracer [(18)F]DPA-714 was used to measure neuroinflammation and [(18)F]AV-45 for Aβ load in mice at 6, 9, 12, 15, and 19 months of age. At 19 months, we also analyzed the neuroinflammatory and neuroanatomic status of mice brains. The main affected brain areas were the cortex and hippocampus, with a concomitant progression of neuroinflammation with increased amyloid burden. At 19 months, no increase in TSPO binding was observed in the cerebellum; immunostaining revealed W0-2-positive plaques, indicating that the amyloid deposits seemed not stimulate inflammation. This finding was in agreement with the observed level of microglia and astrocytes staining. Our findings provide a better understanding of the relationships between neuroinflammation and plaque accumulation in the course of the disease in this mouse model. The monitoring of both processes should be of value to validate potential therapeutic approaches., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: The aim of this study is to compare regional cerebral metabolic rate of glucose metabolism and amyloid-β density in patients with Alzheimer disease (AD), mild cognitive impairment (MCI), and healthy elderly subjects., Methods: Eighteen patients (including 6 AD, 5 amnestic MCI, and 7 controls) were enrolled at the University Hospital of Tours, France, and submitted to clinical, neuropsychological, and MRI examinations. PET images using F-florbetapir (266 MBq) and F-FDG (185 MBq) were acquired. SUV ratios in specific regions were defined using PMOD3.2 software., Results: The mean values of F-FDG SUV ratio were significantly lower in frontal, anterior cingulate, and temporal regions in MCI patients than in normal elderly (-15%, -22%, and -11%, respectively). Alzheimer disease patients showed global cerebral metabolic rate of glucose metabolism decrease, especially in parietal and precuneus regions (-15% and -13% compared with healthy control subjects). Only precuneus cortex showed an increased F-florbetapir uptake in AD. There was no other significant regional difference in the amyloid-β density., Conclusions: In this study, we observed regional brain metabolic changes between MCI, AD, and controls, whereas only precuneus showed an increased amyloid-β density in AD. F-florbetapir PET analysis needs to be visual and global, whereas F-FDG analysis can be regional.

Objective: The objective of this study was to compare glucose metabolism and atrophy, in the precuneus and cingulate cortex, in patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI), using FreeSurfer., Methods: 47 individuals (17 patients with AD, 17 patients with amnestic MCI, and 13 healthy controls (HC)) were included. MRI and PET images using (18)F-FDG (mean injected dose of 185 MBq) were acquired and analyzed using FreeSurfer to define regions of interest in the hippocampus, amygdala, precuneus, and anterior and posterior cingulate cortex. Regional volumes were generated. PET images were registered to the T1-weighted MRI images and regional uptake normalized by cerebellum uptake (SUVr) was measured., Results: Mean posterior cingulate volume was reduced in MCI and AD. SUVr were different between the three groups: mean precuneus SUVr was 1.02 for AD, 1.09 for MCI, and 1.26 for controls (p < 0.05); mean posterior cingulate SUVr was 0.96, 1.06, and 1.22 for AD, MCI, and controls, respectively (p < 0.05)., Conclusion: We found graduated hypometabolism in the posterior cingulate cortex and the precuneus in prodromal AD (MCI) and AD, whereas atrophy was not significant. This suggests that the use of (18)F-FDG in these two regions could be a neurodegenerative biomarker.

Steroid hormone measurement, first developed with radioimmunoassay, is now becoming easier with the use of automated platforms of immunoassay. However, some hormones remain uneasily detectable because of their low blood concentration, their structural homology or the presence of interferences. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) can be considered as an alternative to immunoassays. This approach allows the simultaneous determination of several parameters thanks to its selectivity led by the detector mass spectrometer and the separate dimension of chromatography liquid. In addition, recourse to UHPLC (ultra high performance liquid chromatography) allows improving selectivity and sensitivity while limiting the samples volumes. The "ready-to-use" kits are now available and added to the "homemade" techniques developed by laboratories, thus giving opportunity for measurement of a wide steroid panel with only one sample. Finally, mass spectrometry methods, including a prior extraction step, allow the use of varied biological fluids (blood, urine, saliva…). Also, several clinical indications could gain from mass spectrometry, especially when hormone levels are low, when several steroids have to be identified, when the sample volume is low. However, this technology represents an important financial investment and in-depth staff training. In addition, some steroids are not easily quantifiable by mass spectrometry. It is likely by immunoassay and mass spectrometry, well-matched technologies, that we could answer the best to clinical questions about steroids.

Background: Posterior cortical atrophy (PCA) is characterized by progressive higher-order visuoperceptual dysfunction and praxis declines. This syndrome is related to a number of underlying diseases, including, in most cases, Alzheimer's disease (AD). The aim of this study was to compare the amyloid load with (18)F-AV45 positron emission tomography (PET) between PCA and AD subjects., Methods: We performed (18)F-AV45 PET, cerebrospinal fluid (CSF) biomarker analysis and a neuropsychological assessment in 11 PCA patients and 12 AD patients., Results: The global and regional (18)F-AV45 uptake was similar in the PCA and AD groups. No significant correlation was observed between global (18)F-AV45 uptake and CSF biomarkers or between regional (18)F-AV45 uptake and cognitive and affective symptoms., Conclusion: This (18)F-AV45 PET amyloid imaging study showed no specific regional pattern of cortical (18)F-AV45 binding in PCA patients. These results confirm that a distinct clinical phenotype in amnestic AD and PCA is not related to amyloid distribution.

In this paper, we extend the gradient vector flow field for robust variational segmentation of vector-valued images. Rather than using scalar edge information, we define a vectorial edge map derived from a weighted local structure tensor of the image that enables the diffusion of the gradient vectors in accurate directions through the 4D gradient vector flow equation. To reduce the contribution of noise in the structure tensor, image channels are weighted according to a blind estimator of contrast. The method is applied to biological volume delineation in dynamic PET imaging, and validated on realistic Monte Carlo simulations of numerical phantoms as well as on real images.

In this report, we describe the synthesis of a novel library of α7 nAChR ligands based on the modulation of the quinuclidine, quinazoline and tropane moieties. Spirane derivatives were newly synthesized under stereo specific 1,3 dipolar cylcoadditions. Only amide derivatives bonded efficiently to the receptor with Ki measured between 14 and 133 nM. The best fluorinated candidate was selected and radiolabeled. The potent [(18)F]4 PET tracer was evaluated in rats and its brain accumulation quantified., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Introduction: (11)C]MADAM is a radioligand suitable for PET studies of the serotonin transporter (SERT). Metabolite analysis in human and non-human plasma samples using HPLC separation has shown that [(11)C]MADAM was rapidly metabolized. A possible metabolic pathway is the S-oxidation which could lead to SOMADAM and SO2MADAM. In vitro evaluation of these two potential metabolites has shown that SOMADAM exhibited a good affinity for SERT and a good selectivity for SERT over NET and DAT., Methods: Comparative PET imaging studies in non-human primate brain with [(11)C]MADAM and [(11)C]SOMADAM were carried out, and plasma samples were analyzed using reverse phase HPLC. We have explored the metabolism of [(11)C]MADAM in rat brain with a view to understand its possible interference for brain imaging with PET., Results: PET imaging studies in non-human primate brain using [(11)C]SOMADAM indicated that this tracer does not bind with high amounts to brain regions known to be rich in SERT. The fraction of [(11)C]SOMADAM in non-human primate plasma was approximately 5% at 4min and 1% at 15min after [(11)C]MADAM injection. HPLC analysis of brain sample after [(11)C]MADAM injection to rats demonstrated that [(11)C]SOMADAM was not detected in the brain., Conclusions: (11)C]SOMADAM is not superior over [(11)C]MADAM as a SERT PET radioligand. Nevertheless, [(11)C]SOMADAM has been identified as a minor labeled metabolite of [(11)C]MADAM measured in monkey plasma. [(11)C]SOMADAM was not detected in rat brain., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Background: Cerebral stroke is a severe and frequent condition that requires rapid and reliable diagnosis. If administered shortly after the first symptoms manifest themselves, IV thrombolysis has been shown to increase the functional prognosis by restoring brain reperfusion. However, a better understanding of the pathophysiology of stroke should help to identify potential new therapeutic targets. Stroke is known to induce an inflammatory brain reaction that involves overexpression of the 18-kDa translocator protein (TSPO) in glial cells and infiltrated leukocytes, which can be visualised by positron emission tomography (PET). We aimed to evaluate post-stroke neuroinflammation using the PET TSPO radioligand (18) F-DPA-714., Methods: Nine patients underwent (18) F-DPA-714 PET and magnetic resonance imaging (MRI) between 8 and 18 days after the ictus. Co-registration of MRI and PET images was used to define three volumes of interest (VOIs): core infarction, contralateral region, and cerebellum ipsilateral to the stroke lesion. Time activity curves were obtained from each VOI, and ratios of mean and maximum activities between the VOIs were calculated., Results: We observed an increased uptake of (18) F-DPA-714 co-localised with the infarct tissue and extension beyond the region corresponding to the damage in the blood brain barrier. No correlation was identified between (18) F-DPA-714 uptake and infarct volume. (18) F-DPA-714 uptake in ischemic lesion (mainly associated with TSPO expression in the infarct area and in the surrounding neighbourhood) slowly decreased from 10 min pi to the end of the PET acquisition, remaining higher than that in both contralateral region and ipsilateral cerebellum., Conclusion: Our results show that (18) F-DPA-714 uptake after acute ischemia is mainly associated with TSPO expression in the infarct area and in the surrounding neighbourhood. We also demonstrated that the kinetics of (18) F-DPA-714 differs in injured tissue compared to normal tissue. Therefore, (18) F-DPA-714 may be useful in assessing the extent of neuroinflammation associated with acute stroke and could also help to predict clinical outcomes and functional recovery, as well as to assess therapeutic strategies, such as the use of neuroprotective/anti-inflammatory drugs.

Excitotoxicity leads to an inflammatory reaction involving an overexpression of: translocator protein 18 kDa (TSPO) in cerebral microglia and astrocytes. Therefore, we performed ex vivo explorations with [125]-CLINDE, a TSPO-specific radioligand, to follow the time course of TSPO expression, in parallel with lesion progression, over 90 days after induction of cerebral excitotoxicity in rats intrastriatally injected with quinolinic acid. Biodistribution data showed a significant increase in CLINDE uptake on the injured side from 1 days postlesion (dpl); the maximal striatal binding values evidenced a plateau between 7 and 30 dpl. [125I]-CLINDE binding was displaced from the lesion by PK11195, suggesting TSPO specificity. These results were confirmed by ex vivo autoradiography. Combined immunohistochemical studies showed a marked increase in microglial expression in the lesion, peaking at 14 dpl, and astrocytic reactivity enhanced at 7 and 14 dpl, whereas a prominent neuronal cell loss was observed. At 90 dpl, CLINDE binding and immunoreactivity targeting activated microglia, astrogliosis, and neuronal cell density returned to a basal level. These results show that both neuroinflammation and neuronal loss profiles occurred concomitantly and appeared to be transitory processes. These findings provide the possibility of a therapeutic temporal window to compare the differential effects of antiinflammatory treatments in slowing down neurodegeneration in this rodent model, with potential applications to humans.

Introduction: We examined whether [(18)F]LBT-999 ((E)-N-(4-fluorobut-2-enyl)2β-carbomethoxy-3β-(4'-tolyl)nortropane) is an efficient positron emission tomography (PET) tracer for the quantification of the dopamine transporter (DAT) in the healthy rat brain., Methods: PET studies were performed using several experimental designs, i.e. test-retest, co-injection with different doses of unlabelled LBT, displacement with GBR12909 and pre-injection of amphetamine., Results: The uptake of [(18)F]LBT-999 confirmed its specific binding to the DAT. The non-displaceable uptake (BP(ND)) in the striatum, between 5.37 and 4.39, was highly reproducible and reliable, and was decreased by 90% by acute injection of GBR12909. In the substantia nigra/ventral tegmental area (SN/VTA), the variability was higher and the reliability was lower. Pre-injection of amphetamine induced decrease of [(18)F]LBT-999 BP(ND) of 50% in the striatum., Conclusions: [(18)F]LBT-999 allows the quantification of the DAT in living rat brain with high reproducibility, sensitivity and specificity. It could be used to quantify the DAT in rodent models, thereby allowing to study neurodegenerative and neuropsychiatric diseases., (© 2013.)

Background/aims: Neuroinflammation plays a crucial role in the pathogenesis of Alzheimer's disease (AD). Its relationship with underlying β amyloid deposition remains unclear. In vivo visualization of microglial activation has become possible with the development of molecular imaging ligands when used with positron emission tomography (PET). The translocator protein (TSPO) is upregulated during neuroinflammation. Consequently, targeting TSPO with radiolabeled ligands for PET is an attractive biomarker for neuroinflammation., Methods: A review of the research literature on PET imaging which studied in vivo neuroinflammation in AD subjects and its relationship with amyloid load was performed, including papers published between 2001 and 2012., Results: Six studies were included using either [(11)C]PK-11195 or another non-TSPO radioligand that binds to the monoaminooxidase B. All the studies evaluated amyloid load with [(11)C]PIB. Microglial activation and astrocytosis are potentially early phenomena in AD. However, the individual levels of amyloid deposition and microglial activation were not correlated., Conclusion: Noninvasive in vivo molecular imaging to visualize neuroinflammation in AD may contribute to our understanding of the kinetics of neuroinflammation and its relationship to the hallmarks of the disease. Both are important for the development of future therapeutic modalities and for quantifying the efficacy of future disease-modifying treatments., (© 2013 S. Karger AG, Basel.)

In an effort toward the visualization of β-amyloid plaques by in vivo imaging techniques, we have conjugated an optimized derivative of the Pittsburgh compound B (PiB), a well-established marker of Aβ plaques, to DO3A-monoamide that is capable of forming stable, noncharged complexes with different trivalent metal ions including Gd(3+) for MRI and (111)In(3+) for SPECT applications. Proton relaxivity measurements evidenced binding of Gd(DO3A-PiB) to the amyloid peptide Aβ1-40 and to human serum albumin, resulting in a two- and four-fold relaxivity increase, respectively. Ex vivo immunohistochemical studies showed that the DO3A-PiB complexes selectively target Aβ plaques on Alzheimer's disease human brain tissue. Ex vivo biodistribution data obtained for the (111)In-analogue pointed to a moderate blood-brain barrier (BBB) penetration in adult male Swiss mice (without amyloid deposits) with 0.36% ID/g in the cortex at 2 min postinjection.

Posterior cortical atrophy (PCA) is characterized by progressive higher-order visuo-perceptual dysfunction and praxis declines. This syndrome is related to several underlying diseases, including Alzheimer's disease (AD), sometimes involving an amyloidogenic process. The aims of the study were to 1) define cerebrospinal fluid (CSF) biomarker profiles in PCA patients compared to AD patients and 2) explore the amyloidogenic process through the Aβ(42)/Aβ(40) ratio in PCA patients to elucidate the underlying disease in vivo. CSF biomarker analysis (t-tau, p-tau, Aβ(42), and Aβ(42)/Aβ(40) ratio) and neuropsychological examination were performed in 22 PCA patients and compared with those of age-matched AD patients. Associated clinical neurological signs were investigated (e.g., extrapyramidal motor signs, myoclonus). CSF biomarker profiles did not differ significantly between the PCA and AD groups; 82% of patients with PCA fulfilled the biological criteria for typical AD with abnormal levels of the three markers and 18% of PCA patients presented atypical CSF profiles. All PCA patients with associated clinical neurological signs presented typical AD CSF profiles. The clinical presentations of these patients were similar to other PCA subjects. The Aβ(42)/Aβ(40) ratio for all PCA patients, including those with atypical CSF profiles, was decreased. Most PCA syndromes were associated with CSF biomarkers suggestive of AD, even in cases with associated clinical neurological signs. The amyloidogenic process was confirmed by the decreased Aβ(42)/Aβ(40) ratio for all patients. This analysis avoids misdiagnosis in the presence of physiologically high or low amyloid peptide production rates and provides information in vivo to improve understanding of the underlying disease in PCA.

Background: Positron emission tomography (PET) imaging of brain amyloid (Aβ) and neurofibrillary tangle (NFT) load is a candidate biomarker of Alzheimer's disease (AD)., Objectives: To compare brain Aβ and NFT load and glucose metabolism in advanced elderly (70 years and older) patients with AD and healthy controls (HCs) by PET with [18F]FDDNP and [18F]FDG., Methods: Seven AD patients (mean ± SD age 79.3 ± 3.6 y, Mini-Mental State Examination (MMSE) score 22.1 ± 2.5) and eight HCs (mean age ± SD, 75.7 ± 3.9 y; MMSE score 29.0 ± 1.2) underwent PET with [18F]FDDNP and [18F]FDG., Results: Global [18F]FDDNP uptake was significantly higher (p < 0.05) in AD patients (1.15 ± 0.04) than in HCs (1.10 ± 0.06), while global brain metabolism was lower in AD patients than in HCs (AD patients 0.96 ± 0.09; HCs 1.13 ± 0.11; p < 0.05). In HCs, brain glucose metabolism was correlated with age for both the global [18F]FDG SUVr and in the parietal and posterior cingulate regions, while no correlation was found between age and [18F]FDDNP uptake. In AD patients, global [18F]FDDNP uptake and uptake in the frontal and anterior cingulate regions of interest were correlated with MMSE score, while no correlation was observed with brain glucose metabolism., Conclusion: Imaging Aβ load and NFT with [18F]FDDNP can distinguish AD patients from HCs in an advanced elderly population. It seems to be less sensitive than [18F]FDG to the brain changes observed with normal aging, but more sensitive to cognitive decline in advanced elderly AD patients.

Gray matter atrophy, glucose hypometabolism, and β-amyloid Aβ deposition are well-described hallmarks of Alzheimer's disease, but their relationships are poorly understood. The present study aims to compare the local levels of these three alterations in humans with Alzheimer's disease. Structural magnetic resonance imaging, (18)F-fluorodeoxyglucose positron emission tomography (PET), and (18)F-florbetapir PET data from 34 amyloid-negative healthy controls and 20 demented patients with a high probability of Alzheimer's disease etiology (attested using neuroimaging biomarkers as recently recommended) were analyzed. For each patient and imaging modality, age-adjusted Z-score maps were computed, and direct between-modality voxelwise comparison and correlation analyses were performed. Significant differences in the levels of atrophy, hypometabolism, and Aβ deposition were found in most brain areas, but the hierarchy differed across regions. A cluster analysis revealed distinct subsets of regions: (1) in the hippocampus, atrophy exceeded hypometabolism, whereas Aβ load was minimal; (2) in posterior association areas, Aβ deposition was predominant, together with high hypometabolism and lower but still significant atrophy; and (3) in frontal regions, Aβ deposition was maximal, whereas structural and metabolic alterations were low. Atrophy and hypometabolism significantly correlated in the hippocampus and temporo-parietal cortex, whereas Aβ load was not significantly related to either atrophy or hypometabolism. These findings provide direct evidence for regional variations in the hierarchy and relationships between Aβ load, hypometabolism, and atrophy. Altogether, these variations probably reflect the differential involvement of region-specific pathological or protective mechanisms, such as the presence of neurofibrillary tangles, disconnection, as well as compensation processes.

Alzheimer's disease (AD), the most common age-related neurodegenerative disorder, is characterized by the accumulation of β-amyloid peptide. In man, [18F]AV-45 with positron emission tomography (PET) is currently studied and used to track in vivo amyloid accumulation. Here, [18F]-AV45-PET was used to visualize amyloid deposition in a transgenic murine model of amyloidosis (APP/PS1-21). Studies were performed ex vivo by autoradiography and in vivo by microPET. Autoradiograms of the brain sections highlighted an increased uptake of [18F]AV-45 in APP/PS1-21 mice compared with age-matched control mice. From 8 months, an intense labeling was observed in cortex, hippocampus, and striatum. The marked accumulation of radiotracer was found in close association with thioflavin S-positive amyloid plaques. The longitudinal microPET assessment, performed from 3 to 12 months of age, demonstrated an increased [18F]AV-45 uptake in APP/PS1-21 compared with control mice. The elevated tracer uptake was increased in association with age. This study opens the possibility of [18F]AV-45, coupled with microPET, to visualize and quantitatively measure amyloid deposits in the brains of living APP/PS1 mice., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Purpose: To evaluate the integrity of brain cholinergic pathways in vivo in patients with progressive supranuclear palsy (PSP) by measuring the vesicular acetylcholine transporter expression at single photon emission computed tomography (SPECT) with [123I]-iodobenzovesamicol., Materials and Methods: All participants provided informed written consent according to institutional human ethics committee guidelines. Ten patients with PSP and 12 healthy volunteers underwent dynamic [123I]-iodobenzovesamicol SPECT and magnetic resonance (MR) imaging. CT and MR images were used to register the dynamic SPECT image to the Montreal Neurologic Institute brain template, which includes the regions of interest of the striatum and the septo-hippocampal, innominato-cortical, and ponto-thalamic cholinergic pathways. For each region of interest, pharmacokinetic modeling of regional time activity curves was used to calculate [123I]-iodobenzovesamicol to vesicular acetylcholine transporter binding potential value, proportional to vesicular acetylcholine transporter expression., Results: When compared with control participants, patients with PSP had binding potential values that were unchanged in the striatum and septohippocampal pathway, significantly lower in the anterior cingulate cortex (P=.017) in the innominatocortical pathway, and significantly decreased in the thalamus (P=.014) in the pontothalamic cholinergic pathway. In addition, binding potential values in the thalamus were positively correlated with those in the pedunculopontine nucleus (ρ=0.81, P<.004) and binding potential values in both the thalamus (ρ=-0.88, P<.001) and pedunculopontine nucleus (ρ=-0.80, P<.010) were inversely correlated with disease duration., Conclusion: Cholinergic pathways were differentially affected in the PSP group, with a significant alteration of pontothalamic pathways that increased with disease progression at both cell body and terminal levels, while the innominatocortical pathway was only mildly affected, and the septohippocampal pathway and the striatum were both preserved., (© RSNA, 2012)

As neuroinflammatory processes are involved in the pathogenesis of Parkinson's disease (PD), we achieved the longitudinal evaluation of them in parallel with the modifications of dopaminergic function at several time-points after 6-hydroxydopamine (6-OHDA) lesion in the rat mimicking an early stage of PD. After unilateral intrastriatal 6-OHDA administration, we quantified the temporal evolution of the 18 kDa translocator protein (TSPO), TH-immunoreactivity and dopamine transporters in the striatum and substantia nigra pars compacta (SNc) from 3- to 56-days postlesion (dpl). Increased binding of TSPO ligands used, i.e., [(3)H]PK11195 and [(125)I]CLINDE, was observed in the lesioned striatum at 3, 7, and 14 dpl, followed by a progressive return to the basal level at 56 dpl. The binding profile in the SNc showed progressive binding beginning at 3 dpl, peaking at 14 dpl, and progressively decreasing until 56 dpl. In this model, the neuroinflammatory and neurodegenerative processes occurred concomitantly. The transitory occurrence of microglial activation could be involved in the lasting installation of dopaminergic neuron loss., (Copyright © 2012 Wiley Periodicals, Inc.)

Introduction: The translocator protein 18 kDa (TSPO), although minimally expressed in healthy brain, is up-regulated in pathological conditions, coinciding with microglial activation. It is thereby a suitable in vivo biomarker of neuroinflammation for detection, evaluation and therapeutic monitoring of brain diseases. We aimed to estimate the radiation dosimetry of the positron emission tomography (PET) TSPO radioligand [(18)F]DPA-714, and we evaluated in healthy volunteers its whole-body uptake and cerebral kinetics., Methods: Biodistribution data from mice were used for the prediction of radiation dosimetry. In human studies, a 90-min dynamic PET scan was performed in seven healthy volunteers after injection of [(18)F]DPA-714 (245±45 MBq). Arterial and venous samples were collected from two subjects, and two additional subjects were submitted to whole-body acquisition. Regions of interest were defined over cerebral structures to obtain mean time-activity curves and to estimate the distribution volume ratios by Logan graphical analysis, and over peripheral organs to obtain standard uptake values., Results: The effective dose estimated from biodistribution in mice was 17.2 μSv/MBq. Modeling of regional brain and plasma data showed good in vivo stability of [(18)F]DPA-714 in humans, with only 20% of blood metabolites 20 min postinjection (p.i.). Maximum cerebral uptake was observed 5 min p.i., followed by two decreasing phases: a rapid washout (5-30 min) followed by a slower phase for the remainder of PET acquisition. Whole-body images demonstrate high activity in the gallbladder, heart, spleen and kidneys., Conclusions: This initial study in humans shows that [(18)F]DPA-714 is a promising PET radioligand with excellent in vivo stability and biodistribution, and acceptable effective dose estimation. Therefore, [(18)F]DPA-714 could provide a sensitive measure of neuroinflammatory changes in subsequent clinical investigations., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Purpose: Positron emission tomography (PET) imaging of brain amyloid load has been suggested as a core biomarker for Alzheimer's disease (AD). The aim of this study was to test the feasibility of using PET imaging with (18)F-AV-45 (florbetapir) in a routine clinical environment to differentiate between patients with mild to moderate AD and mild cognitive impairment (MCI) from normal healthy controls (HC)., Methods: In this study, 46 subjects (20 men and 26 women, mean age of 69.0 ± 7.6 years), including 13 with AD, 12 with MCI and 21 HC subjects, were enrolled from three academic memory clinics. PET images were acquired over a 10-min period 50 min after injection of florbetapir (mean ± SD of radioactivity injected, 259 ± 57 MBq). PET images were assessed visually by two individuals blinded to any clinical information and quantitatively via the standard uptake value ratio (SUVr) in the specific regions of interest, which were defined in relation to the cerebellum as the reference region., Results: The mean values of SUVr were higher in AD patients (median 1.20, Q1-Q3 1.16-1.30) than in HC subjects (median 1.05, Q1-Q3 1.04-1.08; p = 0.0001) in the overall cortex and all cortical regions (precuneus, anterior and posterior cingulate, and frontal median, temporal, parietal and occipital cortex). The MCI subjects also showed a higher uptake of florbetapir in the posterior cingulate cortex (median 1.06, Q1-Q3 0.97-1.28) compared with HC subjects (median 0.95, Q1-Q3 0.82-1.02; p = 0.03). Qualitative visual assessment of the PET scans showed a sensitivity of 84.6% (95% CI 0.55-0.98) and a specificity of 38.1% (95% CI 0.18-0.62) for discriminating AD patients from HC subjects; however, the quantitative assessment of the global cortex SUVr showed a sensitivity of 92.3% and specificity of 90.5% with a cut-off value of 1.122 (area under the curve 0.894)., Conclusion: These preliminary results suggest that PET with florbetapir is a safe and suitable biomarker for AD that can be used routinely in a clinical environment. However, the low specificity of the visual PET scan assessment could be improved by the use of specific training and automatic or semiautomatic quantification tools.

There is evidence that excitotoxicity and prolonged microglial activation are involved in neuronal death in neurodegenerative disorders. Activated microglia express various molecules, including the translocator protein 18 kDa (TSPO; formerly known as the peripheral benzodiazepine receptor) on the outer mitochondrial membrane. The TSPO is a novel target for neuroprotective treatments which aim to reduce microglial activation. The effect of PK 11195 and three other TSPO ligands on the level of microglial activation and neuronal survival was evaluated in a quinolinic acid (QUIN) rat model of excitotoxic neurodegeneration. All three ligands were neuroprotective at a level comparable to PK 11195. All of the ligands decreased microglial activation following the injection of QUIN but had no effect on astrogliosis. Interestingly, we also observed neuroprotective effects from the vehicle, dimethyl sulfoxide (DMSO).

The dopamine transporter (DAT) plays a pivotal role in the regulation of dopamine neurotransmission, and is involved in a number of physiological functions and brain disorders. Furthermore the DAT analysis by molecular imaging techniques is a useful tool for the diagnosis and follow up treatment of diseases involving the DAT. In order to predict the affinity of new derivatives for the DAT, different QSAR molecular modeling models based on cocaine were compared. We have evaluated in these models tropane derivatives synthesized with original synthons which coupled properties of both fluorine and iodine atoms. One compound showed a high in vitro affinity and selectivity for the DAT (K(i)=0.87±0.04 nM). This compound should be radiolabeled with radioiodine for further investigations by SPECT., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

There is growing evidence of activated microglia and inflammatory processes in the cerebral cortex in amyotrophic lateral sclerosis (ALS). Activated microglia is characterized by increased expression of the 18 kDa translocator protein (TSPO) in the brain and may be a useful biomarker of inflammation. In this study, we evaluated neuroinflammation in ALS patients using a radioligand of TSPO, (18)F-DPA-714. Ten patients with probable or definite ALS (all right-handed, without dementia, and untreated by riluzole or other medication that might bias the binding on the TSPO), were enrolled prospectively and eight healthy controls matched for age underwent a PET study. Comparison of the distribution volume ratios between both groups were performed using a Mann-Whitney's test. Significant increase of distribution of volume ratios values corresponding to microglial activation was found in the ALS sample in primary motor, supplementary motor and temporal cortex (p = 0.009, p = 0.001 and p = 0.004, respectively). These results suggested that the cortical uptake of (18)F-DPA-714 was increased in ALS patients during the "time of diagnosis" phase of the disease. This finding might improve our understanding of the pathophysiology of ALS and might be a surrogate marker of efficacy of treatment on microglial activation.

Positron emission tomography (PET) images are corrupted by noise. This is especially true in dynamic PET imaging where short frames are required to capture the peak of activity concentration after the radiotracer injection. High noise results in a possible bias in quantification, as the compartmental models used to estimate the kinetic parameters are sensitive to noise. This paper describes a new post-reconstruction filter to increase the signal-to-noise ratio in dynamic PET imaging. It consists in a spatio-temporal robust diffusion of the 4D image based on the time activity curve (TAC) in each voxel. It reduces the noise in homogeneous areas while preserving the distinct kinetics in regions of interest corresponding to different underlying physiological processes. Neither anatomical priors nor the kinetic model are required. We propose an automatic selection of the scale parameter involved in the diffusion process based on a robust statistical analysis of the distances between TACs. The method is evaluated using Monte Carlo simulations of brain activity distributions. We demonstrate the usefulness of the method and its superior performance over two other post-reconstruction spatial and temporal filters. Our simulations suggest that the proposed method can be used to significantly increase the signal-to-noise ratio in dynamic PET imaging.

Purpose: Partial volume effects (PVEs) are consequences of the limited spatial resolution in emission tomography leading to underestimation of uptake in tissues of size similar to the point spread function (PSF) of the scanner as well as activity spillover between adjacent structures. Among PVE correction methodologies, a voxel-wise mutual multiresolution analysis (MMA) was recently introduced. MMA is based on the extraction and transformation of high resolution details from an anatomical image (MR/CT) and their subsequent incorporation into a low-resolution PET image using wavelet decompositions. Although this method allows creating PVE corrected images, it is based on a 2D global correlation model, which may introduce artifacts in regions where no significant correlation exists between anatomical and functional details., Methods: A new model was designed to overcome these two issues (2D only and global correlation) using a 3D wavelet decomposition process combined with a local analysis. The algorithm was evaluated on synthetic, simulated and patient images, and its performance was compared to the original approach as well as the geometric transfer matrix (GTM) method., Results: Quantitative performance was similar to the 2D global model and GTM in correlated cases. In cases where mismatches between anatomical and functional information were present, the new model outperformed the 2D global approach, avoiding artifacts and significantly improving quality of the corrected images and their quantitative accuracy., Conclusions: A new 3D local model was proposed for a voxel-wise PVE correction based on the original mutual multiresolution analysis approach. Its evaluation demonstrated an improved and more robust qualitative and quantitative accuracy compared to the original MMA methodology, particularly in the absence of full correlation between anatomical and functional information.

Unlabelled: The aim of this study was to evaluate the quantification, biodistribution, and radiation dosimetry of the novel dopamine transporter (DAT) radioligand (18)F-(2S,3S)-methyl 8-((E)-4-fluorobut-2-en-1-yl)-3-(p-tolyl)-8-azabicyclo[3.2.1]octane-2-carboxylate ((18)F-LBT-999) in nonhuman primates., Methods: The brain study was conducted in 4 female rhesus monkeys. PET measurements were conducted for 243 min using the high-resolution research tomograph (HRRT) with the measurement of the metabolite-corrected arterial input function and protein binding. Quantification was performed with kinetic analysis using 2-tissue- and 1-tissue-compartment models, with Logan graphical analysis and with different reference tissue models. The outcome measures were total distribution volume (V(T)), nondisplaceable distribution volume (V(ND)), binding potential relative to the free concentration of radioligand in plasma (BP(F)), and binding potential relative to the concentration of nondisplaceable radioligand in tissue (BP(ND)) = V(T) - V(ND)/V(ND) using the cerebellum as a reference region. For the biodistribution and radiation dosimetry, 2 female cynomolgus monkeys were studied. Whole-body PET scans were obtained using a PET/CT system for approximately 250 min. Estimates of the absorbed radiation dose in humans were calculated using OLINDA/EXM software., Results: (18)F-LBT-999 showed good brain uptake (300% standardized uptake value) and regional distribution according to known DAT density. The 2-tissue-compartment model was the preferred model for the quantification. Late peak equilibrium (120-140 min) and slow washout were observed in the striatum, with high variability of V(T), BP(F), and BP(ND). When the different models were compared with the 2-tissue-compartment model, the underestimation of V(T) or BP(ND) was larger in the caudate and putamen than in the midbrain and thalamus. The reference tissue models were suitable for the quantification. The whole-body distribution study showed that the main routes of excretion of (18)F-LBT-999 were the urinary and gastrointestinal systems, with the bladder being the critical organ. Accumulation of (18)F-LBT-999 was found in the bone and skull, with a relatively high dose estimated for the osteogenic cells. The range of calculated effective dose was 0.021-0.022 mSv/MBq., Conclusion: (18)F-LBT-999 seemed to be a suitable PET radioligand for the DAT quantification, particularly for extrastriatal regions. The skull uptake did not seem to be a limitation for brain imaging. The calculated dosimetry estimates based on data in nonhuman primates seemed comparable with those of other clinically used (18)F-labeled radioligands, for example, (18)F-FDG (0.024-0.027 mSv/MBq).

Environmental challenges during the prenatal period can result in behavioral abnormalities and cognitive deficits that appear later in life such as autism. Prenatal exposure to valproic acid, ethanol, thalidomide and misoprostol has been shown to be associated with an increased incidence of autism. In addition, rodents exposed in utero to some of these drugs show autism-like abnormalities, including brain changes and lifelong behavior dysfunction. Our aim is to summarize current understanding of the relationship between in utero exposure to these drugs and autism in humans and in autism-like animal model phenotypes. It also highlights the importance of these models to understanding the neurobiology of autism, particularly in the identification of susceptibility genes. These drugs are able to modulate the expression of many genes involved in processes such as proliferation, apoptosis, neuronal differentiation and migration, synaptogenesis and synaptic activity. It seems essential to focus research on genes expressed during early neurodevelopment which may be the target of mutations or affected by drugs such as those included in this review., (Copyright © 2011. Published by Elsevier Ltd.)

Unlabelled: 18F-(E)-N-(3-iodoprop-2-enyl)-2β-carbofluoroethoxy-3β- (4'-methyl-phenyl)nortropane (18F-FE-PE2I) is a novel radioligand for dopamine transporter (DAT) PET. As compared with 11C-N-(3-iodoprop-2E-enyl)-2β-carbomethoxy-3β-(4-methylphenyl)nortropane (11C-PE2I), 18F-FE-PE2I shows faster kinetics and more favorable metabolism, with less production of a radiometabolite with intermediate lipophilicity (M1), which-in the case of 11C-PE2I-has been shown to enter the rat brain. In this study, we compared DAT quantification with 11C-PE2I and 18F-FE-PE2I in nonhuman primates, using kinetic and graphical analysis with the input function of both the parent and the radiometabolite, to assess the potential contribution of the radiometabolite., Methods: Three rhesus monkeys were examined with 11C-PE2I and 18F-FE-PE2I using the HRRT system. Arterial input functions of the parent and radiometabolite M1 were measured. Kinetic and graphical analyses were applied using either the parent input (methods 1 and 3) or the parent plus radiometabolite input (methods 2 and 4). Outcome measures were distribution volumes (VT and VND), specific-to-nondisplaceable tissue radioactivity ratio at equilibrium (BPND; parent input), and specific-to-nondisplaceable tissue radioactivity ratio at equilibrium in the presence of metabolites (RT; parent plus radiometabolite input)., Results: 11C-PE2I showed higher distribution volumes than 18F-FE-PE2I calculated with methods 1 and 3 (striatal VT, ∼300%; VND in cerebellum, ∼30%). With methods 2 and 4, VT in the striatum was approximately 60% higher in the case of 11C-PE2I, whereas no difference in VND was found in the cerebellum. For each radioligand, BPND estimated with methods 1 and 3 tended to be higher than RT estimated with methods 2 and 4. However, the bias of BPND, compared with RT, was much larger for 11C-PE2I (40%-60% in the caudate and putamen) than for 18F-FE-PE2I (<10% in the caudate and putamen)., Conclusion: The direct comparison between the radioligands confirmed that 18F-FE-PE2I shows faster kinetics and more favorable metabolism than 11C-PE2I. The kinetic and graphical analyses with the input function of the parent and radiometabolite showed that the bias in BPND was much lower for 18F-FE-PE2I than for 11C-PE2I and suggested that the lower production of the radiometabolite M1 would make 18F-FE-PE2I more suitable for the DAT quantification. Further studies in humans are necessary to confirm these findings.

Purpose: Neuroinflammation is involved in stroke pathophysiology and might be imaged using radioligands targeting the 18 kDa translocator protein (TSPO)., Methods: We studied microglial reaction in brain areas remote from the primary lesion site in two rodent models of focal cerebral ischaemia (permanent or transient) using [125I]-CLINDE, a promising TSPO single photon emission computed tomography radioligand., Results: In a mouse model of permanent middle cerebral artery occlusion (MCAO), ex vivo autoradiographic studies demonstrated, besides in the ischaemic territory, accumulation of [125I]-CLINDE in the ipsilateral thalamus with a binding that progressed up to 3 weeks after MCAO. [125I]-CLINDE binding markedly decreased in animals pre-injected with either unlabelled CLINDE or PK11195, while no change was observed with flumazenil pre-treatment, demonstrating TSPO specificity. In rats subjected to transient MCAO, [125I]-CLINDE binding in the ipsilateral thalamus and substantia nigra pars reticulata (SNr) was significantly higher than that in contralateral tissue. Moreover, [125I]-CLINDE binding in the thalamus and SNr was quantitatively correlated to the ischaemic volume assessed by MRI in the cortex and striatum, respectively., Conclusion: Clinical consequences of secondary neuronal degeneration in stroke might be better treated thanks to the discrimination of neuronal processes using in vivo molecular imaging and potent TSPO radioligands like CLINDE to guide therapeutic interventions.

Purpose: A characteristic of prion diseases which affect both animals and humans is the aggregation of PrP amyloid fibrils in the brain, associated with a chronic inflammatory response dominated by microglial activation. In this study, we hypothesised that specific ligands of the 18-kDa translocator protein (TSPO) would be effective in the evaluation of microglial activation related to PrP(sc) deposits in prion disease., Procedures: Chronological studies using in vitro autoradiography were carried out with [(3)H]-PK11195 and [(125)I]-IMPY on frozen cerebral sections from scrapie-infected mice and controls. Accumulation of prion deposits was confirmed by histoblot staining with prion protein-specific monoclonal antibody. Ex vivo autoradiographic studies were carried out with [(125)I]-CLINDE and [(125)I]-IMPY at the terminal stage of infection., Results: Chronological studies using in vitro autoradiography showed that PrP(sc) deposits were co-localised with activated microglia as early as 60 days post-inoculation. Progressive levels of PrP(sc) and TSPO staining were successively observed in the hippocampus, cortex and left thalamus of infected mouse brain sections in the course of the disease and were correlated with the signals obtained by histoblot staining. Significant TSPO labelling was also observed ex vivo in the cortex, hippocampus and thalamus of scrapie-infected mice. In parallel, [(125)I]-IMPY showed labelling in the same cerebral regions but with high background staining., Conclusions: These findings indicate the ability of [(125)I]-IMPY and [(125)I]-CLINDE to evaluate prion deposits and microglial activation in vitro and ex vivo in scrapie-infected mice at different stages of the disease.

Located in presynaptic cholinergic nerve terminals, the vesicular acetylcholine transporter (VAChT) represents a potential target for quantitative visualization of early degeneration of cholinergic neurons in Alzheimer's disease using PET. Benzovesamicol derivatives are proposed as radioligands for this purpose. We report QSAR studies of vesamicol and benzovesamicol derivatives taking into account the stereoselectivity of the VAChT binding site. Use of different data sets and different models in this study revealed that both enantiomers of 5-fluoro-3-(4-phenyl-piperidin-1-yl)-1,2,3,4-tetrahydro-naphthalen-2-ol (5-FBVM) are promising candidates, with predicted VAChT affinities between 6.1 and 0.05 nM. The synthesis of enantiopure (R,R)- and (S,S)-5-FBVM and their corresponding triazene precursors for future radiofluorination is reported. Both enantiomers exhibited high in vitro affinity for VAChT [(+)-5-FBVM: K(i)=6.95 nM and (-)-5-FBVM: K(i)=3.68 nM] and were selective for σ(2) receptors (∼70-fold), only (+)-5-FBVM is selective for σ(1) receptors (∼fivefold). These initial results suggest that (+)-(S,S)-5-FBVM warrants further investigation as a potential radioligand for in vivo PET imaging of cholinergic nerve terminals., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

In order to explore whether some aspects of the autistic phenotype could be related to impairment of the serotonergic system, we chose an animal model which mimics a potential cause of autism, i.e. rats exposed to valproate (VPA) on the 9th embryonic day (E9). Previous studies have suggested that VPA exposure in rats at E9 caused a dramatic shift in the distribution of serotonergic neurons on postnatal day 50 (PND50). Behavioral studies have also been performed but on rats that were exposed to VPA later (E12.5). Our aim was to test whether VPA exposure at E9 induces comparable behavioral impairments than at E12.5 and causes serotonergic impairments which could be related to behavioral modifications. The results showed significant behavioral impairments such as a lower tendency to initiate social interactions and hyperlocomotor activity in juvenile male rats. The serotonin levels of these animals at PND50 were decreased (-46%) in the hippocampus, a structure involved in social behavior. This study suggests that VPA could have a direct or indirect action on the serotonergic system as early as the progenitor cell stage. Early embryonic exposure to VPA in rats provides a good model for several specific aspects of autism and should help to continue to explore pathophysiological hypotheses., ((c) 2009 Elsevier Ireland Ltd. All rights reserved.)

As the serotonin transporter (SERT) is involved in several neurodegenerative and psychiatric disorders; radiopharmaceuticals to image the SERT by PET would be valuable in studying these diseases. To this end we synthesized diphenyloxide derivatives and sulfide analogs, as new tracers, incorporating a fluorine or oxyalkyl fluorinated group on 4' or 5'-position on phenyl ring B. Three of these exhibited good to high in vitro affinity (7

The vesicular acetylcholine transporter (VAChT) is a glycoprotein responsible for the accumulation of acetylcholine into pre-synaptic vesicules of cholinergic neurons. Cholinergic innervation has been shown to be decreased at the earlier stages of Alzheimer's disease (AD). Thus, the expression of VAChT has been correlated with the severity of the dementia and has been considered as a significant diagnostic target for AD. To this end numerous radioligands based on the vesamicol scaffold have been developed for imaging the VAChT using positron emission tomography (PET). Among the various radioligands only a small number have been evaluated in vivo in non-human primate and human. Despite promising in vitro, ex vivo and first in vivo studies, most of them are unsuitable for clinical use in humans due to poor selectivity over σ receptors, low extraction from the blood, slow brain kinetics or fast metabolism. To date (-)-[(11)C]OMV (1), (-)-[(11)C]MABV (2), (-)-[(18)F]-FEOBV (6), (-)-trans-2-hydroxy-3-(4-(4-[(18)F]fluorobenzoyl)piperidine)tetralin (8) and [(18)F]FBMV (12) are promising radioligands for the VAChT, though further validation is required to confirm their clinical usefulness.

This study evaluated the in vitro and in vivo characteristics of a new dopamine transporter (DAT) radioligand, [(18)F]fluoroethyl(FE)PE2I, by autoradiography from postmortem human brain and by positron emission tomography (PET) in three cynomolgus monkeys. In the autoradiography experiments, high [18F]FE-PE2I accumulation was observed in caudate and putamen that was selectively abolished by GBR12909 or beta-CIT but not by maprotiline. High doses of citalopram (>5 microM) also inhibited [18F]FE-PE2I binding in the striatum. In vitro Ki of the radioligand was 12 nM at rodent dopamine transporter. [18F]FE-PE2I brain uptake measured by PET was approximately 4-5% of the injected dose, with highest uptake in striatum followed by midbrain and thalamus, lower uptake in neocortex, and lowest in cerebellum. Peak specific binding in striatum was reached approximately 40 min and in midbrain 20-30 min postinjection. The ratio-to-cerebellum was 7-10 in striatum and 1.5-2.3 in midbrain. BP(ND) measured with simplified reference tissue method using the cerebellum as reference region was 4.5 in striatum and 0.6 in midbrain. No displacement was shown after citalopram or maprotiline administration, while GBR12909 decreased the binding in striatum and midbrain to the level of cerebellum. [18F]FE-PE2I showed relatively fast elimination and metabolism with the presence of two metabolite peaks with similar retention time as the labeled metabolites of [11C]PE2I. [18F]FE-PE2I showed in vivo selectivity for the DAT and compared with [11C]PE2I, it showed faster kinetics and earlier peak equilibrium. The potential influence of the two radiometabolites on PET quantification requires further evaluation., (Copyright 2009 Wiley-Liss, Inc.)

A new dopamine transporter (DAT) ligand, (E)-N-(3-iodoprop-2-enyl)-2beta-carbofluoroethoxy-3beta-(4'-methyl-phenyl) nortropane (FE-PE2I, 6), derived from PE2I (1), was prepared and found to be a potent inhibitor of rodent DAT in vitro. Compound 6 was radiolabelled with fluorine-18 (t(1/2)=109.8 min) for PET studies in monkeys. In vivo PET measurements showed a regional distribution in brain that corresponds to the known distribution of DAT. This binding was specific, reversible and the kinetics of [(18)F]6 binding in brain were faster than for its lead compound, [(11)C]1. The possible presence of a hydroxymethyl-radiometabolite formed by oxidation in the 3beta-benzylic position of [(18)F]6 warrants further detailed evaluation of the metabolism of [(18)F]6. [(18)F]6 is a potential radioligand for imaging DATs in the human brain with PET.

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Background: The translocator protein (TSPO; 18 kDa), the new name of the peripheral-type benzodiazepine receptor, is localised in mitochondria of glial cells and expressed in very low concentrations in normal brain. Their expression rises after microglial activation following brain injury. Accordingly, TSPO are potential targets to evaluate neuroinflammatory changes in a variety of CNS disorders., Purpose: To date, only a few effective tools are available to explore TSPO by SPECT. We characterised here 6-chloro-2-(4'iodophenyl)-3-(N,N-diethyl)-imidazo[1,2-a]pyridine-3-acetamide or CLINDE in a rat model with different stages of excitotoxic lesion., Methods: Excitotoxicity was induced in male Wistar rats by unilateral intrastriatal injection of different amounts of quinolinic acid (75, 150 or 300 nmol). Six days later, two groups of rats (n = 5-6/group) were i.v. injected with [(125)I]-CLINDE (0.4 MBq); one group being pre-injected with PK11195 (5 mg/kg). Brains were removed 30 min after tracer injection and the radioactivity of cerebral areas measured. Complementary ex vivo autoradiography, in vitro autoradiography ([(3)H]-PK11195) and immunohistochemical studies (OX-42) were performed on brain sections., Results: In the control group, [(125)I]-CLINDE binding was significantly higher (p < 0.001) in lesioned than that in intact side. This binding disappeared in rats pre-treated with PK11195 (p < 0.001), showing specific binding of CLINDE to TSPO. Ex vivo and in vitro autoradiographic studies and immunohistochemistry were consistent with this, revealing a spatial correspondence between radioactivity signal and activated microglia. Regression analysis yielded a positive relation between the ligand binding and the degree of neuroinflammation., Conclusion: These results demonstrate that CLINDE is suitable for TSPO in vivo SPECT imaging to explore their involvement in neurodegenerative disorders associated with microglial activation.

The purpose of this guideline is to help investigators by giving an overview of relevant current EU requirements concerning the quality of starting materials and final drug products (the radiopharmaceuticals), the non-clinical safety studies and dosimetry considerations whilst designing a human clinical trial which includes the use of radiopharmaceutical compounds.

In order to predict affinity of new diphenylsulfides for the serotonin transporter (SERT), a molecular modeling model was used to compare potential binding affinity of new compounds with known potent ligands. The aim of this study is to identify a suitable PET radioligand for imaging the SERT, new derivatives, and their precursors for a C-11 or F-18 radiolabeling, were synthesized. Two fluorinated derivatives displayed good in vitro affinity for the SERT (K(i)=14.3+/-1 and 10.1+/-2.7 nM) and good selectivity toward the other monoamine transporters as predicted by the docking study.

Objective: The present study examined the kinetic of plasma triacylglycerol (TAG) and gut emptying after sequential ingestion of breakfast and lunch, and the contribution of dietary fat ingested at breakfast to subsequent TAG after lunch., Methods: Nine subjects ingested a breakfast (0730 h) and a lunch (1200 h) containing 25 and 44 g of fat, respectively. [1-(13)C] palmitate was added in breakfast only. Plasma TAG and chylomicron-TAG (CM-TAG) concentrations and [1-(13)C] palmitate enrichment were sequentially measured. On a consecutive day, an identical breakfast labeled with (123)I-Lipiodol was ingested, followed by a lunch for three controls. (123)I-Lipiodol dynamics was followed in vivo by scintigraphic imaging focused on the stomach, small bowel, and thoracic duct arch., Results: An early rise in plasma and CM-TAG was observed after lunch ingestion. After breakfast, [1-(13)C] palmitate enrichment was maximal 150 and 210 min in plasma TAG and CM-TAG, respectively, decreased thereafter, and increased rapidly (50 min for plasma TAG and 30 min for CM-TAG) after lunch ingestion. Scintigraphic imaging appeared to show that fat ingested at breakfast was retained in part within the gut at lunch time. For the three subjects who ingested a lunch, a decrease of activity in the stomach and small bowel and a tendency for increased activity in the thoracic arch were observed., Conclusion: Contribution of fat ingested at breakfast to lipemia after lunch is confirmed. Fat ingested at breakfast was partly retained within the gut and was mobilized after lunch ingestion, as assessed by acceleration of gut emptying and thoracic duct flow after lunch.

Cellular therapy with adult stem cells appears as an opportunity for treatment of Parkinson's disease. To validate this approach, we studied the effects of transplantation of rat adult bone-marrow mesenchymal stem cells in a rat model of Parkinson's disease. Animals were unilaterally lesioned in the striatum with 6-hydroxydopamine. Two weeks later, group I did not undergo grafting, group II underwent sham grafting, group III was intra-striatal grafted with cells cultured in an enriched medium and group IV was intra-striatal grafted with cells cultured in a standard medium. Rotational amphetamine-induced behavior was measured weekly until animals were killed 6 weeks later. One week after graft, the number of rotations/min was stably decreased by 50% in groups III and IV as compared with groups I and II. At 8 weeks post-lesion, the density of dopaminergic markers in the nerve terminals and cell bodies, i.e. immunoreactive tyrosine hydroxylase, membrane dopamine transporter and vesicular monoamine transporter-2 was significantly higher in group III as compared with group I. Moreover, using microdialysis studies, we observed that while the rate of pharmacologically induced release of dopamine was significantly reduced in lesioned versus intact striatum in no grafted rats, it was similar in both sides in animals transplanted with mesemchymal stem cells. These data demonstrate that graft of adult mesemchymal stem cells reduces behavioral effects induced by 6-hydroxydopamine lesion and partially restores the dopaminergic markers and vesicular striatal pool of dopamine. This cellular approach might be a restorative therapy in Parkinson's disease.

Unlabelled: The translocator protein (18 kDa) (TSPO), formerly known as the peripheral benzodiazepine receptor, is dramatically upregulated under pathologic conditions. Activated microglia are the main cell type expressing the TSPO at sites of central nervous system pathology. Radioligands for the TSPO can therefore measure active disease in the brain. This article details the synthesis, radiofluorination, and pharmacologic evaluation of a new TSPO-specific pyrazolopyrimidine, DPA-714., Methods: The affinity of DPA-714 for the TSPO was measured in rat kidney membranes with (3)H-PK11195. The in vitro functional activity of DPA-714 was measured in a steroidogenic assay in which the ability of DPA-714 to increase pregnenolone synthesis was measured with rat C6 glioma cells. The radiofluorination of DPA-714 was achieved by nucleophilic (18)F-fluoride displacement of the tosylate precursor. (18)F-DPA-714 was assessed in rats harboring unilateral quinolinic acid (QA) lesions. In addition, pretreatment experiments were performed with PK11195 (5 mg/kg), DPA-714 (1 mg/kg), and DPA-713 (1 mg/kg). The in vivo binding and biodistribution of (18)F-DPA-714 were determined in a baboon with PET. Experiments involving presaturation with PK11195 (1.5 mg/kg) and displacement with DPA-714 (1 mg/kg) were conducted to evaluate the specificity of radioligand binding., Results: In vitro binding studies revealed that DPA-714 displayed a high affinity for the TSPO (dissociation constant, 7.0 nM). DPA-714 stimulated pregnenolone synthesis at levels 80% above the baseline. (18)F-DPA-714 was prepared at a 16% radiochemical yield and a specific activity of 270 GBq/mumol. In rats harboring unilateral QA lesions, an 8-fold-higher level of uptake of (18)F-DPA-714 was observed in the ipsilateral striatum than in the contralateral striatum. Uptake in the ipsilateral striatum was shown to be selective because it was inhibited to the level in the contralateral striatum in the presence of PK11195, nonlabeled DPA-714, or DPA-713. PET studies demonstrated rapid penetration and good retention of (18)F-DPA-714 in the baboon brain. Pretreatment with PK11195 effectively inhibited the uptake of (18)F-DPA-714 in the whole brain, indicating its selective binding to the TSPO. The injection of nonlabeled DPA-714 20 min after the injection of (18)F-DPA-714 resulted in radioligand washout, demonstrating the reversibility of (18)F-DPA-714 binding., Conclusion: (18)F-DPA-714 is a specific radioligand for the TSPO, displaying promising in vivo properties and thus warranting further investigation.

The membrane dopamine transporter (DAT) has a pivotal role in the regulation of dopamine (DA) neurotransmission involved in a number of physiological functions and brain disorders. Molecular imaging techniques, such as positron emission tomography (PET) and single photon emission computerized tomography (SPECT), are relevant tools to explore the DAT, and we developed the cocaine derivative N-(3-iodopro-2E-enyl)-2beta-carbomethoxy-3beta-(4'-methylphenyl) nortropane (PE2I) that has proved to be a very potent radiopharmaceutical to image the DAT by these techniques. Several methods are available to obtain PE2I labeled with iodine-123 or -125, carbon-11 and tritium. The pharmacological properties of PE2I have demonstrated that it has good affinity for the DAT (4 nM) and is one of the most selective DAT ligands. [(125)I]PE2I characterized postmortem in human brains has revealed very intense and selective binding in the basal ganglia. Ex vivo autoradiography in rats has shown that high level of [(125)I]PE2I accumulates in the striatum and also in the substantia nigra and ventral tegmental area. [(125)I]PE2I accumulation in the rat striatum is rapid, high, and selective, providing a maximum striatum/cerebellum ratio of 10 during the first 30 min post injection. Using SPECT or PET, rapid, high, and selective accumulation of PE2I was found in the caudate nucleus and putamen in monkeys, whereas rapid wash out from the cerebellum was observed. In vivo investigations in healthy humans have demonstrated that PE2I has high striatal uptake, low nonspecific binding, low radiation exposure, and a fairly short scanning time. A number of findings in various animal models of Parkinson's disease in rats and monkeys have demonstrated the high efficacy of PE2I for detection of reduction in the density of DAT, thus showing the potential value of PE2I for early diagnosis and evaluation of treatment of this disease. The excellent properties of PE2I are basis for the development of new DAT tracers for use in future PET explorations using fluor-18.

Introduction: Little is known about cholinergic activity in the early stage of Alzheimer's disease. We investigated differences in the distribution of vesicular acetylcholine transporter, using [(123)I]-iodobenzovesamicol ([(123)I]-IBVM) and Single Photon Computed Tomography (SPECT), in early AD and age-matched controls., Materials and Methods: Sixteen subjects (8 controls, 8 AD) underwent [(123)I]-IBVM SPECT scanning, T1-weighted anatomic scan by Magnetic Resonance (MR) imaging and Mini-Mental State Evaluation (MMSE). Image analysis, using Statistical Parametric Mapping (SPM 02), involved coregistration of each SPECT image to the MR scan, followed by a spatial normalisation to the Montreal Neurological Institute standard brain and a smoothing of each SPECT image. Group effects and correlation were assessed using two sample t-tests and linear regression respectively. Atrophy difference between the two groups was assessed by voxel-based morphometry of each MR scan using two sample t-tests., Results: MMSE values were significantly different between AD and controls. Relative to controls, a significant decrease in [(123)I]-IBVM binding (47-62%) was apparent in AD subjects in cingulate cortex and parahippocampal-amygdaloïd complex. These patterns appeared to be independent of atrophied areas., Conclusion: These results strongly suggest that a cholinergic degeneration occurs in the early stage of AD and could be involved in the impairment of the cognitive functions. Imaging of cholinergic neurons used here could be effective in identifying potential cholinergic treatment responders.

Introduction: A potential single-photon emission computed tomography imaging agent for labeling of A beta plaques of Alzheimer's disease, IMPY (2-(4'-dimethylaminophenyl)-6-iodo-imidazo[1,2-a]pyridine), would be effective in detection of prion amyloid deposits in transmissible spongiform encephalopathies (TSEs)., Methods: In vitro autoradiographic studies were carried out with [125 I]IMPY on brain sections from scrapie-infected mice and age-matched controls. Competition study was performed to evaluate the prion deposit binding specificity with nonradioactive IMPY., Results: Binding of [125 I]IMPY was observed in infected brain sections, while on age-matched control brain sections, there was no or very low labeling. Prion deposit binding was confirmed by histoblots with prion protein-specific monoclonal antibody 2D6. In the presence of nonradioactive IMPY, the binding of [125 I]IMPY was significantly inhibited in all regions studied., Conclusions: These findings indicate that IMPY can detect the prion deposits in vitro in scrapie-infected mice. Labeled with 123 I, this ligand may be useful to quantitate prion deposit burdens in TSEs by in vivo imaging.

Introduction: [2'-[(18)F]Fluoroethyl (lR-2-exo-3-exe)-8-methyl-3-(4-chlorophenyl)-8-azabicyclo[3.2.1]-octane-2-carboxylate] ([(18)F]FECT) is a positron emission tomography (PET) tracer for imaging the dopamine transporter (DAT) in vivo. We report an improved radiosynthesis procedure and affinity data and have analyzed both brain tissue and plasma samples for the presence of radiometabolites as a function of time post intravenous injection of [(18)F]FECT to rats., Methods: The radiosynthesis of [(18)F]FECT was carried out using [(18)F]fluoroethyltriflate ([(18)F]FEtOTf) as a labeling agent. The affinity of FECT for DAT was determined in vitro by binding experiments on rat striatal membranes. Three rats were injected with [(18)F]FECT and blood samples were collected at 1 or 3 h post injection (p.i.). Plasma was separated and analyzed using reversed-phase high-performance liquid chromatography (RP-HPLC). Similarly, cerebrum and cerebellum were isolated after sacrifice of the animals at 3 h p.i. of the tracer and homogenized. HPLC analysis was performed on extracts of both samples to examine the presence of metabolites., Results: The radiochemical yield for [(18)F]FECT was 85% relative to the starting activity of [(18)F]FEtOTf. The inhibitory constant (K(i)) of FECT for DAT was found to be 6 nM. The fraction of radioactivity corresponding to intact [(18)F]FECT was 93% in plasma at both 1 and 3 h p.i. and 96% in cerebrum as well as cerebellum samples at 3 h p.i., Conclusions: FECT has a high affinity for the dopamine transporter. [(18)F]FECT was found to be stable in vivo and the amount of radiolabeled metabolites in plasma and brain at 3 h p.i. is negligible. Hence, [(18)F]FECT can be used for the in vivo quantification of DAT using PET.