Late-Onset Prosthetic Endocarditis with Paraaortic Abscess Caused by Cutibacterium acnes

Cutibacterium acnes, an integral component of the skin’s customary bacterial flora, represents a Gram-positive anaerobic bacterium characterized by its low virulence. Despite its low virulence, the pathogen can cause profound-seated infections as well as infections linked to medical devices. We report a case study of a prosthesis endocarditis accompanied by a paraaortic abscess caused by C. acnes, a development occurring five years prior to composite aortic root and valve replacement. At the point of admission, the patient presented with a combination of symptoms hinting at a subacute progression, such as weight loss, chest pain, and limitations of cardiopulmonary functionality. An anaerobic pathogen, namely C. acnes, was detected in a singular blood culture vial. Since first-line imaging modalities such as echocardiography did not reveal any signs of inflammation, and in the case of a suspected diagnosis for IE, did not show high pretest probability, further diagnostic imaging such as 18F-FDG PET CT was put to use. Here, a highly elevated glucose metabolism around the aortic valve ring was detected, pointing to an inflammatory process. The patient received adjusted intravenous antibiotic therapy over a course of six weeks; he then underwent surgical therapy via re-replacement of the aortic root and valve using a composite conduit. Advanced microbiological analyses, including the amplification of PCR and valve sequencing via 16S rDNA, mainly detected one pathogen: C. acnes. Delayed onset with mild symptoms and laboratory findings is characteristic of infective endocarditis by C. acnes. Due to its high rate of complications, mortality, and morbidity, an infection should not be disregarded as contamination. Recommendations from different studies underline a combination of a positive blood culture and microbiological evidence to differentiate between contamination and true infection in the case of an infection involving C. acnes. Serial blood cultures with prolonged incubation, advanced microbiological analyses, and modified Duke criteria including second-line imaging techniques should be utilized for further evaluation

Singlet NMR methodology in two-spin-1/2 systems

This paper discusses methodology developed over the past 12 years in order to access and manipulate singlet order in systems comprising two coupled spin-1/2 nuclei in liquid-state nuclear magnetic resonance. Pulse sequences that are valid for different regimes are discussed, and fully analytical proofs are given using different spin dynamics techniques that include product operator methods, the single transition operator formalism, and average Hamiltonian theory. Methods used to filter singlet order from byproducts of pulse sequences are also listed and discussed analytically. The theoretical maximum amplitudes of the transformations achieved by these techniques are reported, together with the results of numerical simulations performed using custom-built simulation code

Die rechtlichen Grundlagen der Ressourcenpolitik in der Bundesrepublik Deutschland. Ein Beitrag zur Rechtsgeographie

Available from the library of Bonn Univ. (DE) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Parahydrogen induced polarization on a clinical MRI system : polarization transfer of two spin order

Hyperpolarization techniques enhance the nuclear spin polarization and thus allow for new nuclear magnetic resonance applications like in vivo metabolic imaging. One of these techniques is Parahydrogen Induced Polarization (PHIP). It leads to a hyperpolarized 1H spin state which can be transferred to a heteronucleus like 13C by a radiofrequency (RF) pulse sequence. In this work, timing of such a sequence was analyzed and optimized for the molecule hydroxyethyl propionate. The pulse sequence was adapted for the work on a clinical magnetic resonance imaging (MRI) system which is usually equipped only with a single RF transmit channel. Optimal control theory optimizations were performed to achieve an optimized polarization transfer. A drawback of hyperpolarization is its limited lifetime due to relaxation processes. The lifetime can be increased by storing the hyperpolarization in a spin singlet state. The second part of this work therefore addresses the spin singlet state of the Cs-symmetric molecule dimethyl maleate which needs to be converted to the spin triplet state to be detectable. This conversion was realized on a clinical MRI system, both by field cycling and by two RF pulse sequences which were adapted and optimized for this purpose. Using multiple conversions enables the determination of the lifetime of the singlet state as well as the conversion efficiency of the RF pulse sequence. Both, the hyperpolarized 13C spin state and the converted singlet state were utilized for MR imaging. Careful choice of the echo time was shown to be crucial for both molecules.Hyperpolarisationsmethoden verstärken die Kernspinpolarisation und ermöglichen dadurch neue Anwendungen der Kernspinresonanz wie die Bildgebung von Stoffwechselprozessen. Eine dieser Methoden ist die Parawasserstoff Induzierte Polarisation (PHIP), welche einen hyperpolarisierten 1H-Zustand erzeugt. Diese Hyperpolarisation kann durch Sequenzen von Radiofrequenzpulsen auf einen Heterokern wie 13C übertragen werden. In dieser Arbeit wurde die Zeitabstimmung einer solchen Sequenz für das Molekül Hydroxyethylpropionat analysiert und optimiert. Die Pulssequenz wurde für einen klinischen Kernspintomographen angepasst, so dass sie mit einem einzigen Sendekanal verwendet werden kann. Optimierungssimulationen basierend auf der Theorie der optimalen Steuerung wurden durchgeführt, um den Polarisationstransfer zu verbessern. Ein Nachteil der Hyperpolarisation ist, dass sie aufgrund von Relaxationsprozessen nur eine eingeschränkte Lebensdauer hat. Diese kann erhöht werden, indem die Hyperpolarisation in einem Singulett-Zustand gespeichert wird. Der zweite Teil dieser Arbeit befasst sich daher mit dem Singulett-Zustand des Cs-symmetrischen Moleküls Dimethylmaleat, welcher für Messungen in einen Triplett-Zustand überführt werden muss. Diese Konversion wurde in einem klinischen Kernspintomographen zum einen durch eine Magnetfeldvariation zum anderen durch zwei Pulsssequenzen realisiert. Mehrfach aufeinanderfolgende Konversion wurden verwendet, um die Lebensdauer des Singulett-Zustands und die Konversionseffizienz der Pulssequenz zu bestimmen. Beide Möglichkeiten, der hyperpolarisierte 13C-Zustand und der konvertierte Singulett-Zustand, wurden zur Bildgebung verwendet. Die Notwendigkeit einer sorgfältigen Wahl der Echozeit wurde für beide Moleküle gezeigt

Computational Fluid Dynamics Simulations of Contrast Agent Bolus Dispersion in a Coronary Bifurcation: Impact on MRI-Based Quantification of Myocardial Perfusion

Contrast-enhanced first-pass magnetic resonance imaging (MRI) in combination with a tracer kinetic model, for example, MMID4, can be used to determine myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). Typically, the arterial input function (AIF) required for this methodology is estimated from the left ventricle (LV). Dispersion of the contrast agent bolus might occur between the LV and the myocardial tissue. Negligence of bolus dispersion could cause an error in MBF determination. The aim of this study was to investigate the influence of bolus dispersion in a simplified coronary bifurcation geometry including one healthy and one stenotic branch on the quantification of MBF and MPR. Computational fluid dynamics (CFD) simulations were combined with MMID4. Different inlet boundary conditions describing pulsatile and constant flows for rest and hyperemia and differing outflow conditions have been investigated. In the bifurcation region, the increase of the dispersion was smaller than inside the straight vessels. A systematic underestimation of MBF values up to −16.1% for pulsatile flow and an overestimation of MPR up to 7.5% were found. It was shown that, under the conditions considered in this study, bolus dispersion can significantly influence the results of quantitative myocardial MR-perfusion measurements

Magnetic resonance imaging of 1H long lived states derived from parahydrogen induced polarization in a clinical system

Hyperpolarization is a powerful tool to overcome the low sensitivity of nuclear magnetic resonance (NMR). However, applications are limited due to the short lifetime of this non equilibrium spin state caused by relaxation processes. This issue can be addressed by storing hyperpolarization in slowly decaying singlet spin states which was so far mostly demonstrated for non-proton spin pairs, e.g. 13C-13C. Protons hyperpolarized by parahydrogen induced polarization (PHIP) in symmetrical molecules, are very well suited for this strategy because they naturally exhibit a long-lived singlet state. The conversion of the NMR silent singlet spin state to observable magnetization can be achieved by making use of singlet-triplet level anticrossings. In this study, a low-power radiofrequency pulse sequence is used for this purpose, which allows multiple successive singlet-triplet conversions. The generated magnetization is used to record proton images in a clinical magnetic resonance imaging (MRI) system, after 3 min waiting time. Our results may open unprecedented opportunities to use the standard MRI nucleus 1H for e.g. metabolic imaging in the future.Fil: Graafen, Dirk. Max Planck Institute for Polymer Research; Alemania. Johannes Gutenberg University Medical Center; AlemaniaFil: Franzoni, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Max Planck Institute for Polymer Research; AlemaniaFil: Schreiber, Laura M.. Johannes Gutenberg University Medical Center; AlemaniaFil: Spiess, Hans W.. Max Planck Institute for Polymer Research; AlemaniaFil: Münnemann, Kerstin. Max Planck Institute for Polymer Research; Alemani