Nephrogene systemische Fibrose (NSF): Wie hoch ist das Risiko und wie können wir es vermeiden?

Zusammenfassung: Das Krankheitsbild der nephrogenen systemischen Fibrose, das nach Durchführung einer Gadolinium unterstützen Magnetresonanztomographie/-angiographie bei Patienten mit schwerer Niereninsuffizienz auftreten kann, hat zu einer massiven Verunsicherung in der Anwendung dieser wertvollen Untersuchungstechnik geführt. Das Ziel der vorliegenden Arbeit ist es, neben der Diskussion des Krankheitskonzepts, der zugrundeliegenden Pathophysiologie, der Klinik und der therapeutischen Optionen, die Risikofaktoren zu beleuchten und Konzepte der Prävention aufzuzeige

Three-dimensional dynamic MR-hysterosalpingography; a new, low invasive, radiation-free and less painful radiological approach to female infertility

BACKGROUND: The purpose of this study was to propose a new method for imaging the uterine cavity and Fallopian tube patency by three-dimensional dynamic magnetic resonance hysterosalpingography (3D dMR-HSG) and to analyse if, by using a higher viscosity contrast solution, direct visualization of the Fallopian tubes may be achieved by this new technique. METHODS: 10 consecutive infertile women underwent 3D dMR-HSG and conventional HSG as gold standard. 3D dMR-HSG consisted of injection of 20 ml of a gadolinium-polyvidone solution into the uterine cavity while acquiring five consecutive three-dimensional (3D) T1-weighted MR-sequences. RESULTS: In three patients the catheter became dislodged during 3D dMR-HSG. However, in one of these patients the examination was still partially diagnostic. Imaging findings of 3D dMR-HSG showed good correlation with conventional hysterosalpingography and allowed 3D imaging of the uterine cavity and of Fallopian tube patency in 8/10 patients and direct visualization of the Fallopian tubes in 5/7 patients. CONCLUSION: 3D dMR-HSG represents a new and promising imaging approach to female infertility causing less pain and avoiding exposure of the ovaries to ionizing radiation. By using a higher viscosity MR-contrast agent it allows not only visualization of uterine cavity and Fallopian tube patency but also direct visualization of Fallopian tube

Total-body contrast-enhanced MRA on a short, wide-bore 1.5-T system: intra-individual comparison of Gd-BOPTA and Gd-DOTA

Total-body contrast-enhanced MRA (CE-MRA) provides information of the entire vascular system according to a one-stop-shop approach. Short, wide-bore scanners have not yet been used for total-body CE-MRA, probably due to their restricted field of view in the z-direction. The purpose of this feasibility study is to introduce an image protocol for total-body MRA on a short, wide-bore system. The protocol includes five to six table-moving steps and two injection runs. Two pharmacologically different contrast materials (CM) were applied in ten healthy volunteers in view of possible CM-dependent influences on the protocol outcome (Gd-Bopta, Gd-Dota). Differences consisted of significantly higher CNR with Gd-Bopta with a mean of 73.8 ± 38.7 versus 69.1 ± 34.3 (p = 0.008), significantly better arterial visualization values with Gd-Dota with a mean of 1.26 ± 0.44 versus 1.53 ± 0.73 (p = 0.003) and a tendency to less venous overlay with Gd-Dota, mean 1.19 ± 0.44 and 1.34 ± 0.72, respectively (p = 0.065) (two-tailed Wilcoxon matched-pairs test). Overall 94% of the steps were valued as qualitatively excellent or good. The good results with both CM suggest a transfer to further patient evaluatio

Low-dose intra-arterial contrast-enhanced MR aortography in patients based on a theoretically derived injection protocol

Multiple intra-arterial contrast agent injections are necessary during MR-guided endovascular interventions. In respect to the approved limits of maximum daily gadolinium dose, a low-dose injection protocol is mandatory. The objective of this study was to derive and apply a low-dose injection protocol for intra-arterial 3D contrast-enhanced MR aortography in patients. Injection rate (Qinj), concentration of injected gadolinium [Gd]inj and aortal blood flow rate (Qblood) were included for the theoretical evaluation of signal intensity (SI) of the arterial lumen. SI simulations were carried out at Qinj=2 versus 4ml/s in the [Gd]inj range between 0-500mM. Qinj and [Gd]inj with SI above the 75% threshold of the maximal SI were regarded as optimal injection parameters. [Gd]inj=50mM and Qinj=4ml/s were considered as optimal and were administered in five patients for 3D MR aortography. All images revealed clear delineation of the abdominal aorta and its major branches. Mean±SD of contrast-to-noise ratios of the abdominal aorta, common iliac and renal artery were 70.2±15.2, 58.6±12.3 and 67.4±12.3. Approximately seven intra-aortal injections would be permissible in patients during MR-guided interventions without exceeding the maximal dose of gadoliniu

Vestibular disease in dogs: association between neurological examination, MRI lesion localisation and outcome.

OBJECTIVES To determine whether the neurological examination correctly distinguishes between central and peripheral vestibular lesions in dogs. MATERIALS AND METHODS Retrospective study on dogs with vestibular disease presenting to two referral clinics in Germany. RESULTS Ninety-three dogs were included; neurological examination suggested central vestibular disease in 62 and a peripheral lesion in 31. MRI diagnosis was central vestibular disease in 68 dogs and peripheral in 25. Of the 62 dogs with a lesion localisation diagnosed as central vestibular by neurological exam, 61 were correctly identified (98.4%). Twenty-four of the 31 dogs diagnosed with a peripheral lesion by neurological exam had a consistent lesion on MRI (77.4%). CLINICAL SIGNIFICANCE The neurological examination is efficient at identifying lesions in the central vestibular system but less so for peripheral lesions. Therefore it is prudent to recommend imaging in dogs that show signs of peripheral vestibular syndrome but do not rapidly respond to treatment

Cycle-finite module categories

We describe the structure of module categories of finite dimensional algebras over an algebraically closed field for which the cycles of nonzero nonisomorphisms between indecomposable finite dimensional modules are finite (do not belong to the infinite Jacobson radical of the module category). Moreover, geometric and homological properties of these module categories are exhibited

Global Optimization of Gaussian processes

Gaussian processes~(Kriging) are interpolating data-driven models that are frequently applied in various disciplines. Often, Gaussian processes are trained on datasets and are subsequently embedded as surrogate models in optimization problems. These optimization problems are nonconvex and global optimization is desired. However, previous literature observed computational burdens limiting deterministic global optimization to Gaussian processes trained on few data points. We propose a reduced-space formulation for deterministic global optimization with trained Gaussian processes embedded. For optimization, the branch-and-bound solver branches only on the degrees of freedom and McCormick relaxations are propagated through explicit Gaussian process models. The approach also leads to significantly smaller and computationally cheaper subproblems for lower and upper bounding. To further accelerate convergence, we derive envelopes of common covariance functions for GPs and tight relaxations of acquisition functions used in Bayesian optimization including expected improvement, probability of improvement, and lower confidence bound. In total, we reduce computational time by orders of magnitude compared to state-of-the-art methods, thus overcoming previous computational burdens. We demonstrate the performance and scaling of the proposed method and apply it to Bayesian optimization with global optimization of the acquisition function and chance-constrained programming. The Gaussian process models, acquisition functions, and training scripts are available open-source within the "MeLOn - Machine Learning Models for Optimization" toolbox~(https://git.rwth-aachen.de/avt.svt/public/MeLOn)

Torsion pairs and rigid objects in tubes

We classify the torsion pairs in a tube category and show that they are in bijection with maximal rigid objects in the extension of the tube category containing the Pruefer and adic modules. We show that the annulus geometric model for the tube category can be extended to the larger category and interpret torsion pairs, maximal rigid objects and the bijection between them geometrically. We also give a similar geometric description in the case of the linear orientation of a Dynkin quiver of type A.Comment: 25 pages, 13 figures. Paper shortened. Minor errors correcte