European Institute for Molecular Imaging

Bad Münster am Stein-Ebernburg, Germany

European Institute for Molecular Imaging

Bad Münster am Stein-Ebernburg, Germany
Time filter
Source Type

Mannweiler D.,European Institute for Molecular Imaging | Mannweiler D.,University of Munster | Suhr S.,University of Munster | Modersitzki J.,University of Lübeck | Burger M.,University of Munster
2015 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2015 | Year: 2015

Motion-corrected image reconstruction approaches receive arising attention in nuclear medicine. With new hybrid scanners like PET/MRI the combination of multiple sources for motion information is possible. In current practice, separate gated data is reconstructed. Single gated reconstructions, in which the motion effect is negligible have inferior quality. The low quality is caused by bad signal-to-noise ratio in gated PET data. The motion in these gated images, in comparison to one reference gate, can be corrected successively and then obtained by overlaying. Disadvantages are artifacts caused by unclear convergence properties of the alternating iteration method of the reconstruction and the motion estimation. To solve this, we use a novel variational approach for motion estimation and image reconstruction of the PET data, based on a Bayesian model. With MRI information we receive more precise motion information, so that we can improve the PET motion estimation with MRI motion data. To verify this approach, the first experiments were done with the XCAT thorax phantom to evaluate results. We expand our experiments to real patient data to demonstrate its feasibility for clinical use. In conclusion, the results in our approach shows a more reasonable tracer distribution and a better reconstruction of the myocardium. The motion estimation is as good as the state-of-the-art motion correction with some benefits. The outlook deals with the problem of attenuation correction in motion-corrected PET reconstruction which has severe impact on the quality of reconstructed images, and with other options to improve our method. © 2015 IEEE.

Euskirchen P.,University of Bergen | Euskirchen P.,Max Planck Institute for Neurological Research | Skaftnesmo K.-O.,University of Bergen | Huszthy P.C.,University of Bergen | And 5 more authors.
Experimental Cell Research | Year: 2011

The cell fate determinant NUMB orchestrates asymmetric cell division in flies and mammals and has lately been suggested to have a tumor suppressor function in breast and lung cancer. Here, we studied NUMB in the context of malignant gliomas. We used ectopic expression of NUMB in order to inhibit proliferation and induce differentiation in glioma cells by alteration of Notch, Hedgehog and p53 signaling. We found that NUMB is consistently expressed in glioma biopsies with predominance of NUMB2/4 isoforms as determined by isoform-specific real-time PCR and Western blotting. Upon lentiviral overexpression, in vitro proliferation rate and the grade of differentiation as assessed by morphology and expression of neural and glial markers remained unchanged. Orthotopic xenografts of NUMB-transduced human U87 glioma cells could be established in nude rats without impairing engraftment or causing significant changes in morphology based on magnetic resonance imaging (MRI). The previously reported alteration of Hedgehog and p53 signaling by NUMB could not be recapitulated in glioma cells. We thus show that in experimental gliomas, NUMB overexpression most likely does not exert a tumor suppressor function such as seen in epithelial cancers. © 2011 Elsevier Inc.

Hoerr V.,University Hospital Muenster | Nagelmann N.,University Hospital Muenster | Nauerth A.,Bruker | Kuhlmann M.T.,European Institute for Molecular Imaging | And 2 more authors.
Journal of Cardiovascular Magnetic Resonance | Year: 2013

Background: To overcome flow and electrocardiogram-trigger artifacts in cardiovascular magnetic resonance (CMR), we have implemented a cardiac and respiratory self-gated cine ultra-short echo time (UTE) sequence. We have assessed its performance in healthy mice by comparing the results with those obtained with a self-gated cine fast low angle shot (FLASH) sequence and with echocardiography. Methods. 2D self-gated cine UTE (TE/TR = 314 μs/6.2 ms, resolution: 129 × 129 μm, scan time per slice: 5 min 5 sec) and self-gated cine FLASH (TE/TR = 3 ms/6.2 ms, resolution: 129 × 129 μm, scan time per slice: 4 min 49 sec) images were acquired at 9.4 T. Volume of the left and right ventricular (LV, RV) myocardium as well as the end-diastolic and -systolic volume was segmented manually in MR images and myocardial mass, stroke volume (SV), ejection fraction (EF) and cardiac output (CO) were determined. Statistical differences were analyzed by using Student t test and Bland-Altman analyses. Results: Self-gated cine UTE provided high quality images with high contrast-to-noise ratio (CNR) also for the RV myocardium (CNR§ssub§ blood-myocardium§esub§ = 25.5 ± 7.8). Compared to cine FLASH, susceptibility, motion, and flow artifacts were considerably reduced due to the short TE of 314 μs. The aortic valve was clearly discernible over the entire cardiac cycle. Myocardial mass, SV, EF and CO determined by self-gated UTE were identical to the values measured with self-gated FLASH and showed good agreement to the results obtained by echocardiography. Conclusions: Self-gated UTE allows for robust measurement of cardiac parameters of diagnostic interest. Image quality is superior to self-gated FLASH, rendering the method a powerful alternative for the assessment of cardiac function at high magnetic fields. © 2013 Hoerr et al.; licensee BioMed Central Ltd.

Galstyan A.,University of Munster | Block D.,Universitatsklinikum Munster | Niemann S.,Universitatsklinikum Munster | Gruner M.C.,University of Munster | And 10 more authors.
Chemistry (Weinheim an der Bergstrasse, Germany) | Year: 2016

Carbohydrate-conjugated silicon(IV) phthalocyanines with bimodal photoactivity were developed as probes with both fluorescent labeling and photosensitizing capabilities, and the concomitant fluorescent labeling and photoinduced inactivation of Gram-positive and Gram-negative models was explored. The maltohexaose-conjugated photoprobe provides a dual readout to distinguish between both groups of pathogens, as only the Gram-positive species was inactivated, even though both appeared labeled with near-infrared luminescence. Antibiotic resistance did not hinder the phototoxic effect, as even the methicillin-resistant pathogen Staphylococcus aureus (MRSA) was completely photoinactivated. Time-resolved confocal fluorescence microscopy analysis suggests that the photoprobe sticks onto the outer rim of the microorganisms, explaining the resistance of Gram-negative species on the basis of their membrane constitution. The mannose-conjugated photoprobe yields a different readout because it is able to label and to inactivate only the Gram-positive strain. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ropinski T.,University of Munster | Doring C.,European Institute for Molecular Imaging | Rezk-Salama C.,Mediadesign University of Applied Social Sciences
IEEE Computer Graphics and Applications | Year: 2010

Advanced illumination models can support depth perception. However, for volume rendering, gradient-based shading models are still the standard. This is because the computation of more advanced lighting effects is expensive and thus strongly affects rendering performance. Nevertheless, interactive frame rates are important for both the interactive design of visual representations and the exploration process. An interactive volumetric lighting model simulates scattering and shadowing to generate high-quality images. Compared to gradient-based shading, this model achieves superior image quality and higher frame rates. To evaluate this model, a user study had participants perform depth perception tasks. The study's results indicate that this model can significantly improve depth perception, compared to conventional gradient-based volume shading. Additionally, because this model isn't based on a gradient computation, it's less sensitive to noise and therefore applicable to imaging modalities suffering from a low signal-to-noise ratio, such as magnetic resonance imaging or 3D ultrasound. © 2006 IEEE.

Claesener M.,University of Munster | Breyholz H.-J.,University of Munster | Hermann S.,European Institute for Molecular Imaging | Faust A.,European Institute for Molecular Imaging | And 4 more authors.
Nuclear Medicine and Biology | Year: 2012

Introduction: The natural occurring vitamin biotin, also known as vitamin H or vitamin B7, plays a major role in various metabolic reactions. Caused by its high binding affinity to the protein avidin with a dissociation constant of about 10-15M the biotin-avidin system was extensively examined for multiple applications. We have synthesized a fluorine-18 labeled biotin derivative [18F]4 for a potential application in positron emission tomography (PET). Methods: Mesylate precursor 3 was obtained by an efficient two-step reaction via a copper catalyzed azide-alkyne cycloaddition (CuAAC) from easily accessible starting materials. [18F]4 was successfully synthesized by a nucleophilic radiofluorination of precursor 3. A biodistribution study by means of small-animal PET imaging in wt-mice was performed and serum stability was examined. Results: Compound [18F]4 was obtained from precursor compound 3 with an average specific activity of 16GBq/μmol within 45min and a radiochemical yield of 45±5% (decay corrected). [18F]4 demonstrated only negligible decomposition in human serum. A qualitative binding study revealed the high affinity of the synthesized biotin derivative to avidin. Blocking experiments with native biotin showed that binding was site-specific. Biodistribution studies showed that [18F]4 was cleared quickly and efficiently from the body by hepatobiliary and renal elimination. Conclusion: An efficient synthesis for [18F]4 was established. In vivo characteristics were determined and demonstrated the pharmacokinetic behaviour of [18F]4. © 2012 Elsevier Inc..

Bunk E.C.,Stem Cell Biology and Regeneration Group | Stelzer S.,Stem Cell Biology and Regeneration Group | Hermann S.,European Institute for Molecular Imaging | Schafers M.,European Institute for Molecular Imaging | And 2 more authors.
Aging Cell | Year: 2011

Adult neurogenesis within the subgranular zone (SGZ) of the hippocampal dentate gyrus and the subventricular zone (SVZ) of the lateral ventricle (LV) has been most intensely studied within the brains of rodents such as mice and rats. However, little is known about the cell types and processes involved in adult neurogenesis within primates such as the common marmoset (Callithrix jacchus). Moreover, substantial differences seem to exist between the neurogenic niche of the LV between rodents and humans. Here, we set out to use immunohistochemical and autogradiographic analysis to characterize the anatomy of the neurogenic niches and the expression of cell type-specific markers in those niches in the adult common marmoset brain. Moreover, we demonstrate significant differences in the activity of neurogenesis in the adult marmoset brain compared to the adult mouse brain. Finally, we provide evidence for ongoing proliferation of neuroblasts within both the SGZ and SVZ of the adult brain and further show that the age-dependent decline of neurogenesis in the hippocampus is associated with a decrease in neuroblast cells. © 2010 The Authors. Aging Cell © 2010 Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland.

Galstyan A.,University of Munster | Galstyan A.,European Institute for Molecular Imaging | Kauscher U.,University of Munster | Block D.,University of Munster | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2016

The host-guest complexation of a tailored Si(IV) phthalocyanine with supramolecular β-cyclodextrin vesicles (CDV) was studied, revealing a reduced aggregation of the photoactive center upon binding to the CDV, even in aqueous environments. For this purpose, a photosensitizing unit axially decorated with one adamantyl group and one pyridinium moiety on the other side was obtained by two successive click reactions on a bis-azido-functionalized derivative of Si(IV) phthalocyanine. To evaluate its potential as a photosensitizer against antibiotic-resistant bacteria, comparative studies of the photophysical properties including absorption and emission spectroscopy, lifetimes as well as fluorescence and singlet oxygen quantum yields were determined for the Si(IV) phthalocyanine alone and upon self-assembly on the CDV surface. In vitro phototoxicity against the methicillin-resistant Staphylococcus aureus (MRSA) USA300 was evaluated, showing an almost complete inactivation. © 2016 American Chemical Society.

Galstyan A.,European Institute for Molecular Imaging | Galstyan A.,University of Munster | Riehemann K.,University of Munster | Schafers M.,European Institute for Molecular Imaging | And 3 more authors.
Journal of Materials Chemistry B | Year: 2016

Zinc(ii)phthalocyanines (Zn(ii)Pc) have shown promising applications in photodynamic therapy due to their high quantum yield of singlet oxygen generation; however, optimization of their overall properties are required before their clinical application as photosensitizers (PSs). The photosensitization efficiency of photoprobes is strongly influenced by the nature of the conjugated moieties and often it can be efficiently tuned by variation in the substitution pattern. Through this study we examined how the structural design of amphiphilic carbohydrate-based Zn(ii)Pcs affects their photophysical properties, binding affinity to human serum albumin (HSA) and photodynamic activity against human cancer melanoma cells. The replacement of oxygen with sulfur at non-peripheral positions of low-symmetry Zn(ii)Pcs contributes to the bathochromic shift of maximum absorption, which is relevant for the activation of the PS in deeper tissues. Moreover, this modification also influences the overall flexibility of the macrocyclic core and results in different behaviour towards HSA. Density functional theory calculations have been carried out to substantiate the effect of the peripheral environment on the photophysical characteristics and geometry of the molecules. © The Royal Society of Chemistry 2016.

Hesselmann V.,University of Munster | Niederstadt T.,University of Munster | Dziewas R.,University of Munster | Ritter M.,University of Munster | And 7 more authors.
American Journal of Neuroradiology | Year: 2012

BACKGROUND AND PURPOSE: Our research focuses on interventional neuroradiology (stroke treatment including imaging methods) and general neuroimaging with an emphasis on functional MR imaging. Our aim was to determine the efficacy of revascularization (TIMI) of middle cerebral and/or carotid artery occlusion by means of mechanical recanalization techniques and to evaluate the impact of collateralization, mismatch in perfusion CT, time to revascularization, grade of revascularization on tissue, and clinical outcome in patients with acute ischemic stroke. MATERIALS AND METHODS: Thirty-one patients with MCA and/or ICA occlusion were included. Ischemic stroke was diagnosed by NECT, CTA, and volume PCT for grading collateralization and mismatch. Time to recanalization was measured from the onset of stroke to the time point of DSA-proved mechanical recanalization. Tissue outcome was calculated by segmentation of infarct size between pre- and postinterventional CT and percentage mismatch lost. Clinical outcome was determined by the mRS. RESULTS: Twenty-one of 31 patients (61.8%) presented with MCA and 10/31 patients (38.2%), with distal ICA occlusions. Sufficient recanalization (TIMI 2 and 3) was achieved in 23/31 (75%). Clinical evaluation revealed an mRS score of ≤2 in 25.5%. Age (r = 0.439, P = .038) and TIMI (r = 0.544, P = .002) showed the strongest correlation with clinical outcome. Time to recanalization, TIMI score, and mismatch were associated with a good tissue outcome in ANOVA. CONCLUSIONS: Favorable outcome after mechanical recanalization of acute MCA and ICA occlusion depends on time to and grade of recanalization, mismatch, and collateralization. These results indicate that multimodal stroke imaging is helpful to guide therapy decisions and to indicate patients amenable for mechanical recanalization.

Loading European Institute for Molecular Imaging collaborators
Loading European Institute for Molecular Imaging collaborators