Browsing by Author "Dupont P."

Now showing 1 - 7 of 7
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    A comparison of the effects of citalopram and moclobemide on resting brain perfusion in social anxiety disorder.
    (2006) Warwick, James M.; Carey P.; Van der Linden G.; Prinsloo C.; Niehaus D.; Seedat S.; Dupont P.; Stein D.J.
    INTRODUCTION: The serotonin specific reuptake inhibitor (SSRI) citalopram and the reversible mono-amine oxidase-A inhibitor (RIMA) moclobemide have both been used successfully for the treatment of social anxiety disorder (SAD). In this study we investigate the effects of these compounds on resting brain function using single photon emission computed tomography (SPECT). METHODS: Subjects meeting DSM-IV criteria for SAD underwent regional cerebral blood flow (rCBF) SPECT using Tc-HMPAO at baseline and after 8 weeks of treatment with either citalopram or moclobemide. Using statistical parametric mapping brain SPECT studies were analysed to determine the effects of treatment on rCBF, to compare the effects of citalopram and moclobemide, and to detect correlations between changes in rCBF and clinical response. RESULTS: Subjects received citalopram (n=17) or moclobemide (n=14) as therapy. Subjects in both treatment groups demonstrated a significant improvement of SAD symptoms as measured by the Liebowitz Social Anxiety Scale total score. All subjects demonstrated a decrease in rCBF in the insulae post therapy. Subjects receiving citalopram had decreased superior cingulate rCBF after therapy compared to those receiving moclobemide. CONCLUSION: Both SSRI's and RIMA's decreased rCBF in the insulae during treatment of SAD; an effect that may be consistent with the role of these regions in processing internal somatic cues evoked by emotional stimuli. Citalopram had a greater effect on superior cingulate perfusion, an effect that is consistent with evidence of high levels of 5-HT transporters in this region.
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    Changes in regional brain volumes in social anxiety disorder following 12 weeks of treatment with escitalopram
    (2010) Cassimjee N.; Fouche J.-P.; Burnett M.; Lochner C.; Warwick, James M.; Dupont P.; Stein D.J.; Cloete K.J.; Carey P.D.
    It has been suggested that antidepressants, including the selective serotonin reuptake inhibitors have neurotrophic effects. Nevertheless, the impact of treatment with a selective serotonin re-uptake inhibitor on regional brain volumes in social anxiety disorder has not been studied. 11 subjects with social anxiety disorder completed magnetic resonance imaging both before and after 12-weeks of treatment with 20 mg/day escitalopram. No increases in structural grey matter were found, but there were decreases in bilateral superior temporal cortex, vermis and the left cerebellum volumes following 12 weeks of treatment with escitalopram. These preliminary findings require replication to determine their reliability, and extension to determine whether or not they are disorder specific. © 2010 Springer Science+Business Media, LLC..
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    Dopamine transporter binding in social anxiety disorder: The effect of treatment with escitalopram
    (2012) Warwick, James M.; Carey P.D.; Cassimjee N.; Lochner C.; Hemmings, Sian M. J.; Moolman-Smook H.; Beetge E.; Dupont P.; Stein D.J.
    Social anxiety disorder (SAD) is characterised by fear of social or performance situations where the individual is exposed to unfamiliar people or to possible scrutiny by others. The literature on dopamine ligands and dopamine genotypes in SAD is however inconsistent. In this study we measured the effects of SSRI pharmacotherapy on dopamine transporter (DAT) binding in patients with SAD, also addressing variability in DAT genotype. Adult subjects meeting DSM-IV criteria for generalised SAD were studied before and after 12 weeks of pharmacotherapy with the selective serotonin reuptake inhibitor (SSRI) escitalopram. DAT single photon emission computed tomography (SPECT) using 123I-FP-CIT was performed at baseline, and repeated at 12 weeks. Striatal DAT binding was analysed for changes following therapy, and for correlations with clinical efficacy, in the whole group as well as for a subgroup with the A10/A10 DAT genotype. The study included 14 subjects (9 male, 5 female) with a mean (SD) age of 41 (±13) years. The subjects' Liebowitz Social Anxiety Scale (LSAS) score was significantly decreased following pharmacotherapy. In the combined group the left caudate and left putamen showed clusters of increased DAT binding after therapy. The left caudate changes were also observed in the subgroup of 9 A10/A10 homozygotes. However no correlation was found between improved symptoms and DAT binding. The changes found in DAT binding in the caudate and putamen may be due to serotonergic activation of dopamine function by SSRI therapy. This is consistent with previous work indicating decreased DAT binding in SAD, and increased DAT binding after SSRI administration. © Springer Science+Business Media, LLC 2012.
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    Kinetic modelling in small animal imaging with PET
    (2009) Dupont P.; Warwick J.
    Small animal imaging with positron emission tomography has undergone a major evolution. This has been driven by technical improvements and the development of dedicated PET camera's for small animals. The focus has shifted from detection of tracer uptake and visualization of the tracer distribution towards the quantification of the physiological parameters necessary to use this technique for kinetic modelling of tracers. At the moment there are still several issues which need further research and evaluation before we can fully employ the possibilities of PET as an in-vivo measurement of underlying molecular biology. These issues relate to improved quantification of measurements, improved image reconstruction and processing, and the use of blood plasma data in combination with kinetic models. Besides the more technical issues, there are two more issues which need further clarification: the effect of the anaesthesia, and the effect of radiation on the experiment itself. In this review, we will give an overview of how the technique can be used but we will also discuss the issues mentioned above. The focus will be on the three major parts of the imaging procedure: acquisition, reconstruction of images, and kinetic modelling of the data. © 2009 Elsevier Inc. All rights reserved.
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    Self-injection ictal SPECT during partial seizures
    (2000) Van Paesschen W.; Dupont P.; Van Heerden B.; Vanbilloen H.; Mesotten L.; Maes A.; Van Driel G.; Mortelmans L.
    The authors compared ictal SPECT injection performed by medical personnel with self-injection ictal SPECT in six patients with refractory temporal lobe epilepsy. Self-injection was safe and started faster Self- injection subtraction ictal SPECT coregistered to MRI (SISCOM) was localizing in three patients who had a complex partial seizure, but only one or three patients who had a simple partial seizure, which may limit its usefulness in clinical practice. The localizing information of self-injection was better in three patients, and obviated the need for depth-EEG studies in one patient.
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    The influence of attenuation correction and reconstruction techniques on the detection of hypo-perfused lesions in brain SPECT images
    (2006) Ghoorun S.; Baete K.; Nuyts J.; Groenewald W.; Dupont P.
    BACKGROUND: We evaluated the effects of attenuation correction and reconstruction techniques on the detection of hypoperfused lesions in brain SPECT imaging. METHODS: A software phantom was constructed using the data available on the BrainWeb database by assigning activity values to grey and white matter. The true attenuation map was generated by assigning attenuation coefficients to six different tissue classes to create a non-uniform attenuation map. The uniform attenuation map was calculated using an attenuation coefficient of 0.15 cm. Hypoperfused lesions of varying intensities and sizes were added. The phantom was then projected as typical SPECT projection data, taking into account attenuation and collimator blurring with the addition of Poisson noise. The projection data were reconstructed using four different methods: filtered back-projection in combination with Chang's first-order attenuation correction using the uniform or the true attenuation map and maximum likelihood iterative reconstruction using the uniform or the true attenuation map. Different Gaussian post-smoothing kernels were applied onto the reconstructed images and the performance of each procedure was analysed using figures of merit such as signal-to-noise ratio, bias and variance. RESULTS: Uniform attenuation correction offered only slight deterioration of the signal-to-noise ratio compared to the true attenuation map. Maximum likelihood produced superior signal-to-noise ratios and lower bias at the same variance in comparison to the filtered back-projection. CONCLUSION: Uniform attenuation correction is adequate for lesion detection while maximum likelihood provides enhanced lesion detection when compared to filtered back-projection. © 2006 Lippincott Williams & Wilkins.
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    Use of excess height and cluster extent in subtraction SPECT
    (2002) Baete K.; Nuyts J.; Van Paesschen W.; Maes A.; Ghoorun S.; Suetens P.; Dupont P.
    Subtraction of ictal and interictal single photon emission computed tomography (SPECT) perfusion images of the brain has the potential of locating the epileptogenic region. This region generally shows large differences between both images. However, differences can also be induced by noise in the projection data. We hypothesized that the extent, besides the intensity, of observed clusters of voxels in thresholded subtraction images, is an important parameter in the classification of clusters into real perfusion differences and noise-induced differences. To test this hypothesis, we performed a number of simulation experiments. Using a Monte Carlo approach, we constructed cumulative distribution functions (CDFs) of the excess height (i.e., the largest difference in a cluster) and the cluster extent under the condition of no perfusion change (i.e., only noise-induced clusters). The reproducibility of the CDF curves was shown using measured patient data. Furthermore, a three-dimensional (3-D) brain software phantom experiment was used to examine the detection and classification of an induced region of hyperperfusion. In a first experiment, we compared two detection criteria: detection of the induced hyperperfusion based on the observed cluster with the largest excess height and based on the observed cluster with the largest extent. Detection based on the largest extent showed a better sensitivity. In a second experiment, we assigned to every observed cluster a probability, derived from the CDF curves, for excess height and extent. For different probability thresholds, sensitivity and specificity of the detection of the induced hyper-perfusion based on its probability for excess height and cluster extent were measured. These measurements were combined in receiver operating characteristic (ROC) curves. These ROC curves showed a better performance when using classification based on cluster extent. We conclude that the cluster extent is an important parameter in the characterization of clusters in thresholded subtraction of perfusion SPECT images of the brain.