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Objective To retrospectively evaluate the technical feasibility and midterm results of uncovered thoracoabdominal stent placement in complicated acute aortic dissection Stanford type B (cAADB). Patients and Methods Fourteen consecutive patients (3 females; range, 44-71 years) with cAADB who had symptomatic gastrointestinal malperfusion and claudication underwent immediate uncovered stent implantation (diameter, 7-28 mm; length, 40-100 mm) into the true lumen of the thoracoabdominal aorta (n = 23) and visceral arteries (n = 5). Results Stenting resulted in elimination of gastrointestinal ischemia and symptoms in 13 of 14 patients; persisting symptoms led to secondary surgical revascularization in only 1 patient. More than 1 stent (≤4) was placed in 7 patients (2 celiac, 1 mesenteric, 2 renal, 8 aorto-iliac). Follow-up computed tomographic angiography (CTA) revealed collapse of 4 aortic stents (diameter, 9-25 mm; length, 100 mm) at 1 week in the absence of symptoms. Balloon reexpansion was possible in all 4 stents, but recollapse occurred within 1 month. Despite stent collapse, the patients remained asymptomatic; ultrasonography and CTA documented sufficient perfusion of the visceral arteries in all patients. Follow-up ranged from 6 months to 5 years (average, 2.5 years). Except for the patient who underwent iliacomesenteric bypass for unspecific abdominal pain, no other patient required additional interventional or surgical therapy. Conclusions Acute aortic dissection with suspicion of visceral ischemia should prompt for immediate intervention. Thoracoabdominal uncovered stent implantation is a technically feasible and effective minimally invasive approach that provided successful relief of acute visceral ischemia and claudication in cAADB. Stent size should be less than the normal aortic diameter to avoid possible stent collapse.

Magnetic resonance imaging (MRI) performed at ultra-high field strengths beyond 3 Tesla (T) has become increasingly prevalent in research and preclinical applications. As such, the inevitable clinical implementation of such systems lies on the horizon. The major benefit of ultra-high field MRI is the markedly increased signal-to-noise ratios achievable, enabling acquisition of MR images with simultaneously greater spatial and temporal resolution. However, at field strengths higher than 3 T, the efficacy of Gd(III)-based contrast agents is diminished due to decreased r1 relaxivity, somewhat limiting imaging of the vasculature and contrast-enhanced imaging of tumors. There have been extensive efforts to design new contrast agents with high r1 relaxivities based on macromolecular compounds or nanoparticles; however, the efficacy of these agents at ultra-high field strengths has not yet been proven. The aim of this review article is to provide an overview of the basic principles of MR contrast enhancement processes and to highlight the main factors influencing relaxivity. In addition, challenges and opportunities for contrast-enhanced MRI at ultra-high field strengths will be explored. Various approaches for the development of effective contrast agent molecules that are suitable for a broad spectrum of applied field strengths will be discussed in the context of the current literature.

Background/Aims: Dry weight estimation in hemodialysis patients is still a substantial problem. Despite meticulous clinical assessment, fluid overload is common, leading to hypertension and left ventricular hypertrophy (LVH). Segmental calf bioimpedance spectroscopy (cBIS) is a novel tool for dry weight assessment. Here we tested the hypothesis, that its clinical routine use reduces arterial hypertension and left ventricular mass. Methods: Left ventricular mass (determined by magnetic resonance imaging), blood pressure and antihypertensive medication (defined daily doses, ddd) were assessed at baseline (BL). Thereafter post-dialytic target weight was reduced until cBIS-defined dry weight was reached (DW). During a 6-month follow up, DW was re-evaluated monthly by cBIS and end-dialytic weight was adjusted correspondingly. At the end, left ventricular mass, blood pressure and antihypertensive medication were determined a 3rd time (follow-up, FU). Results: Eleven out of 15 patients were available for analysis after 6 months. Left ventricular mass showed a declining trend during the study period (Mean±SD; BL 145±54g; DW 142±55g; FU 137±52g; p=0.61, linear mixed model). Comparable results were obtained for systolic blood pressure (BL 158±18mmHg; DW 144±19mmHg; FU 149±21mmHg; p=0.07), and antihypertensive medication (BL 3.28±2.82ddd; DW 2.86±2.81ddd; FU 3.36±3.05ddd; p=0.37). Conclusions: We conclude that attainment of dry weight assessed by cBIS tends to reduce left ventricular mass and blood pressure while antihypertensive medication remains unchanged. While the study was underpowered, its results provide an important hypothesis generating data basis for the design of larger studies.

OBJECTIVE: A critical problem in cardiovascular MRI in small rodents is adjusting the sequence acquisition to the high heart and respiratory rates. The aim of this study was to compare a retrospectively self-gated fast low angle shot navigator (RSG-FLASH) sequence with a conventional prospectively triggered (PT-FLASH) sequence for cine imaging of the ascending aorta in mice at 9.4 T. MATERIAL AND METHODS: Ten C57/BL6 mice were examined with a horizontal bore 9.4 Tesla MRI animal scanner using a dedicated 2 × 2 phased-array surface coil. We acquired a RSG-FLASH sequence (RSG-FLASH sequences (repetition time (TR) / echo time (TE) = 6.5/2.5 ms, flip angle (FA) = 10 degrees, field of view (FOV) = 2 × 2 cm, matrix = 384 × 384, slice thickness = 1 mm, 25 movie frames) perpendicular to the ascending aorta using the IntraGate technique. At the same position, we performed a PT-FLASH sequence (TR/TE = 6.5/2.1 ms, FA = 10 degrees, FOV = 2 × 2 cm, matrix = 384 × 384, slice thickness = 1 mm) in which the maximum number of movie frames had to be adjusted to the interval between two R-peaks (RR interval) of the electrocardiogram (ECG) with: number of frames = RR interval / TR." Cross-sectional vessel areas at end-systole (AES) and end-diastole (AED) were measured to determine the aortic strain (ΔA = (AES-AED)/AED). Two blinded readers rated the sequences for presence of flow and trigger artifacts and their influence on the depiction of the blood/vessel-wall interface. Irregularities in displaying the cardiac cycle and the overall suitability of the sequence for aortic strain evaluation were assessed using a 5-level ordinal scale. Statistical differences were analyzed using Student t test and Wilcoxon signed rank test (P < 0.05). Intra- and interobserver variability was evaluated using Bland-Altman analyses. RESULTS: No significant differences were noted between techniques regarding the measured vessel areas (AED: P = 0.07, AES: P = 0.34), ΔA: P = 0.1). Similarly, there were no significant differences in heart (P = 0.06) and respiratory (P = 0.24) rates. The acquisition time for RSG-FLASH sequence was significantly shorter (P = 0.04). Significantly fewer flow and trigger artifacts were noted by both readers with the RSG-FLASH sequence. Likewise, both readers considered the RSG-FLASH sequence to be superior for depiction of the blood/vessel-wall interface. The RSG-FLASH sequence was also rated superior regarding irregularities in displaying the cardiac cycle and in terms of overall suitability for evaluation of AED, AES, and aortic strain (P < 0.05 each). CONCLUSION: RSG-FLASH is preferable for cine imaging of the aorta. It provides the same quantitative data as PT-FLASH cine imaging but is less prone to flow and trigger artifacts. RSG-FLASH permits more homogeneous depiction of the cardiac cycle and is faster than the PT-FLASH sequence. PT-FLASH is more prone to misregistration of the respiratory cycle or the ECG by the external monitoring device used for acquisition. This effect may be even more pronounced in animals with disease models that are less stable in terms of heart and respiration rate during anesthesia.

Interleukin-1 receptor-associated kinase 4 (IRAK-4) deficiency predisposes to severe invasive bacterial infections in infancy and early childhood, often with a fatal course caused by a defect in Toll-like receptor and interleukin-1 receptor signaling. Despite severe invasive infections, acute phase responses are often diminished. We report the successful treatment of a child with multiple liver abscesses, diaphragm perforation and pleural empyema, accompanied by strong acute phase responses as a unique presentation of IRAK-4 deficiency.

To compare diffusion-weighted imaging (DWI) based on a fast spin echo (FSE) sequence using BLADE (PROPELLER) with conventional DWI-echoplanar imaging (EPI) techniques at 3 T and to demonstrate the influence of hardware developments on signal-to-noise ratio (SNR) with these techniques using 12- and 32-channel head coils.Fourteen patients with brain ischemia were evaluated with DWI using EPI and FSE BLADE sequences, with a 12-channel head coil, in the axial plane and 1 additional plane (either sagittal or coronal). SNR and CNR were calculated from region-of-interest measurements. Scans were evaluated in a blinded fashion by 2 experienced neuroradiologists. SNR of both DWI techniques was evaluated in 12 healthy volunteers using different parallel imaging (PI) factors (for the EPI sequence) and both the 12- and 32-channel coils.DWI-BLADE sequences acquired with the 12-channel coil revealed a significant reduction in SNR (mean +/- SD) of ischemic lesions (SNR(lesion) [5.0 +/- 2.5]), normal brain (SNR(brain) [3.0 +/- 1.9]), and subsequently in CNR (3.0 +/- 1.8) as compared with the DWI-EPI sequence (SNR(lesion) [9.3 +/- 5.2], SNR(brain) [7.7 +/- 3.5], CNR [6.1 +/- 2.8], P0.001). Despite this reduction in SNR and CNR, the blinded read revealed a marked preference for the DWI-BLADE sequence, or equality between the sequences, in the majority of patients because lesion detection was degraded by susceptibility artifacts on axial DWI-EPI scans in 14% to 43% of cases (but in no instance with the DWI-BLADE sequence). In particular, preference for the DWI-BLADE sequence or equality between the 2 techniques for lesion detection in the brainstem and cerebellum was observed. On some DWI-BLADE scans, in the additional plane, radial-like artifacts degraded lesion detection.In volunteers, SNR was significantly improved using the 32-channel coil, irrespective of scan technique. Comparing DWI-EPI acquired with the 12-channel coil (iPAT = 2) to DWI-BLADE acquired with the 32-channel coil, comparable SNR values were obtained. The 32-channel coil also makes feasible, with DWI-EPI, an increase in the PI factor to 4, which allows for a further reduction of bulk susceptibility artifacts. However, still DWI-BLADE sequences performed better because of absence of bulk susceptibility artifacts at comparable SNR values.Despite lower SNR at comparable PI factors, DWI-BLADE sequences acquired using the 12-channel coil are preferable in most instances, as compared with DWI-EPI sequences, because of the absence of susceptibility artifacts and subsequently improved depiction of ischemic lesions in the brainstem and cerebellum. With the 32-channel coil, recently FDA approved, DWI-BLADE acquired with an iPAT = 2 provides comparable SNR without bulk susceptibility artifacts as compared with the DWI-EPI sequences acquired for clinical routine to date and has the potential to replace the standard DWI technique for special indications like DWI of the cerebellum and the brainstem or in presence of metallic implants or hemorrhage.

Objective: In patients with hereditary hemorrhagic telangiectasia (HHT), pulmonary arteriovenous malformations (PAVMs) can cause serious neurological complications. Our aim was to evaluate the potential of contrast-enhanced Doppler ultrasound (CE-US) of the common carotid artery as a screening test for detection of PAVMs. Methods: A total of 124 consecutive patients with HHT or a positive family history underwent screening for PAVMs with CE-US and thoracic contrast-enhanced magnetic resonance angiography (CE-MRA). CE-US was performed after receiving (D)-galactose microparticulate, and CE-MRA with gadobenate dimeglumine. Twenty-five patients with confirmed PAVMs were referred to conventional pulmonary catheter angiography (PA). Findings on CE-US and CE-MRA were evaluated using contingency tables and McNemar’s test. Results: Using CE-MRA as the reference test, CE-US had a sensitivity of 100%, a specificity of 87%, and a negative predictive value of 100%. In 25 patients who underwent PA, PAVMs that had been diagnosed on CE-US and CE-MRA were confirmed. Of the PAVMs detected by CE-MRA, 24% were not identified on PA. Conclusion: CE-US is a simple, minimally invasive screening method that can easily be performed in different settings. CE-US can predict PAVMs with high probability of success. CE-US may be a simple alternative to transthoracic echocardiography in the assessment of PAVMs in certain HHT-patients.

The aim of this study was to investigate hepatic macrophage activation and hepatocellular function after hemorrhagic shock in the rat using contrast-enhanced magnetic resonance imaging (MRI). In comparison to techniques requiring open surgery, such as intravital microscopy, MRI is a non-invasive tool; the experimental subject therefore remains intact, enabling the investigator to conduct additional follow-up procedures that may have important clinical implications. At 3 and 24 h following standardized hemorrhagic shock (40 mmHg for 90 min), MRI (2.4 T Magnet, Biospec, Bruker Karlsruhe, Germany) was performed. After application of a liver-specific contrast dye (Gd-EOB-DTPA; 50 μmol/kg BW), which is absorbed from hepatocytes and secreted into the gall fluid, the signal intensity (SI) was measured. For determination of hepatic macrophage activation, superparamagnetic ferrumoxid particles (ENDOREM® 10 μmol/kg BW) were injected and the SI was measured again. These data were compared with the findings of in vivo microscopy and bile flow performed in the animals after MRI. The sham groups received 2 ml/h Ringers Lactate for 24 h without initial hemorrhagic shock and reperfusion. In the shock group, a significantly smaller increase of SI enhancement after application of Gd-EOB-DTPA (shock group: 126.1%±10.4; sham group 159.3±3.5; p < 0.05) was found compared to the sham group 24 h after shock, which correlated with the bile flow measured. Application of ENDOREM® resulted in a decrease of SI in T2-weighted images after 3 h compared to 24 h after shock; however, no differences between the shock and sham animals could be observed (shock group -69.8%±2.8; sham group -75.8±1.6; p < 0.05). Intravital microscopy revealed a significant increase of latex beads in hepatic macrophages 3 h after shock compared to sham animals, thereby indicating enhanced macrophage activation. Intravital microscopy showed a significant increase of temporary and permanent adherent leukocytes 3 and 24 h after shock. Contrast-enhanced MRI is a useful, noninvasive method for long-term investigations of the liver after hemorrhagic shock, specifically with respect to monitoring alterations of hepatocellular function. However, a significant hepatic macrophage activation after shock was only observed by direct measurement of latex beads using intravital microscopy and not with contrast-enhanced MRI.

Since its introduction in the early 1990s, contrast-enhanced (CE) cardiac magnetic resonance imaging (MRI) has evolved rapidly for the assessment of cardiac pathologies, including in particular ischemic heart disease and inflammatory conditions. Likewise, CE-magnetic resonance angiography (MRA) is now used routinely to evaluate the thoracic vasculature. This article reviews the current use of extracellular gadolinium-based agents in CE cardiovascular imaging, focusing on ischemic heart disease, inflammatory myocardial conditions, and the use of CE-MRA in imaging of the pulmonary and aortic vasculature. Recent advances in fast and ultrafast MRI combined with the use of extracellular contrast media allow noninvasive measurements of multiple parameters of the cardiovascular system in less than 40 minutes. Beyond the assessment of left ventricular wall motion and morphology, CE cardiac MRI allows depiction of myocardial perfusion and thereby provides information regarding microvascular integrity and myocardial viability. The excellent spatial resolution of MRI, especially for the distinction of nontransmural versus transmural extent of pathology, has been shown to be superior to other modalities that are often nonlocalizing, nonspecific, or more invasive. Additional advantages of CE-MRA, particularly for the thoracic vasculature, include safety, its noninvasive character, large field of view, and the ability to demonstrate complicated three-dimensional relationships without the need for iodinated, nephrotoxic contrast media.

Bei einer 53-jahrigen, kardial bislang beschwerdefreien Patientin, die erfolgreich wegen Kammerflimmerns reanimiert worden war, zeigte sich trotz unauffalligem zweidimensionalem Echokardiogramm in einer unter Ruhebedingungen durchgefuhrten Gewebe-Doppler-Studie der longitudinalen Wandbewegung der pathologische Befund von postsystolischen Kontraktionen im Versorgungsgebiet der linken Kranzarterie. Der Verdacht auf eine Koronarischamie als mutmasliche Ursache der Arrhythmie bestatigte sich in der Koronarangiographie, die eine isolierte, hochgradige ostiale Hauptstammstenose ergab. Nach operativer Myokardrevaskularisation normalisierte sich auch der Gewebe-Doppler-Befund. Fazit: Gerade bei unauffalligem konventionellen Echokardiogramm kann die zusatzliche Analyse des longitudinalen Kontraktionsmusters mittels Gewebe-Doppler-Echokardiographie eine weitergehende Aussage erlauben.

Die echokardiographische Bestimmung linksventrikularer Muskelmassen (LVM) und Volumina ist zur Beurteilung kardialer Adaptationsmechanismen und Risikostratifizierung von wesentlicher Bedeutung. Allerdings neigen die ublicherweise angewandten ein- und zweidimensionalen Verfahren bei krankhaft hypertrophierten Herzen zur Uberschatzung der LVM. Fur physiologisch hypertrophierte Herzen liegt bisher noch keine vergleichende Untersuchung der unterschiedlichen echokardiographischen Bestimmungsmethoden mit der Referenzmethode Magnetresonanztomographie (MRT) vor. An 23 gesunden mannlichen Ausdauerathleten mit Sportherz (A; 28±4 Jahre) sowie 26 gesunden mannlichen Untrainierten (U; 26±4 Jahre) wurde die LVM mittels MRT und folgenden echokardiographischen Methoden bestimmt: ASE-Cube (ASE), Devereux (DEV), Troy (TRO) Teichholz (TEI), Reichek (REI) und Dickhuth (DIC). Die auf die Korperoberflache bezogenen LVM betrugen: MRT: 107±6g/m2 (A), 79±7g/m2 (U); ASE: 170±20g/m2 (A), 119±14g/m2 (U); DEV: 134±16g/m2 (A), 95±11g/m2 (U); TRO: 134±16g/m2 (A), 92±12g/m2 (U); TEI: 115±10 g/m2 (A), 91±8g/m2 (U); REI: 114±14g/m2 (A), 89±11g/m2 (U); DIC: 110±14g/m2 (A); 80±9g/m2 (U). Bei A und U wird die kernspintomographische LVM durch ASE, DEV, TRO, TEI und REI im Gegensatz zu DIC signifikant uberschatzt (p

The Brugada syndrome is characterized by a distinct ECG pattern consisting of ST segment elevation in the right precordial leads and right bundle branch block, a propensity for life-threatening arrhythmias, and an apparently structurally normal heart. The authors describe the case of a patient with an aborted sudden cardiac death and the typical ECG signs of Brugada syndrome. Nevertheless, magnetic resonance imaging displayed signal enhancement in the left ventricular myocardium. Additionally, histologic examination, in-situ hybridization, and PCR revealed evidence of a locally restricted inflammation due to parvovirus B19. Brugada syndrome is regarded as a primary electrical disease due to dysfunction of distinctive ion channels, but focal myocarditis may serve as a trigger for ventricular arrhythmias in this patient. Further morphologic studies will be helpful to establish the possible role of structural changes in the pathophysiology of this syndrome.

Magnetic resonance imaging (MRI) performed at ultra-high field strengths beyond 3 Tesla (T) has become increasingly prevalent in research and preclinical applications. As such, the inevitable clinical implementation of such systems lies on the horizon. The major benefit of ultra-high field MRI is the markedly increased signal-to-noise ratios achievable, enabling acquisition of MR images with simultaneously greater spatial and temporal resolution. However, at field strengths higher than 3 T, the efficacy of Gd(III)-based contrast agents is diminished due to decreased r1 relaxivity, somewhat limiting imaging of the vasculature and contrast-enhanced imaging of tumors. There have been extensive efforts to design new contrast agents with high r1 relaxivities based on macromolecular compounds or nanoparticles; however, the efficacy of these agents at ultra-high field strengths has not yet been proven. The aim of this review article is to provide an overview of the basic principles of MR contrast enhancement processes and to highlight the main factors influencing relaxivity. In addition, challenges and opportunities for contrast-enhanced MRI at ultra-high field strengths will be explored. Various approaches for the development of effective contrast agent molecules that are suitable for a broad spectrum of applied field strengths will be discussed in the context of the current literature.

RATIONALE AND OBJECTIVES To investigate whether nonionic, iodinated, radiographic contrast media (RCM) could modulate calcium release from or calcium entry into smooth muscle cells of the swine renal artery. METHODS Intracellular calcium concentrations of isolated myocytes loaded with the calcium-sensitive dye fluo-3 were analyzed using a fluorescence imaging system. Calcium signals were compared with isometric contractions of vascular segments in an organ bath. The effects of the triiodinated monomer iomeprol were compared with those of a mannitol solution. RESULTS Stimulation of alpha-receptors by phenylephrine caused a biphasic calcium signal. Transient liberation of calcium from intracellular stores triggered the sustained entry of extracellular calcium (capacitative entry). Iomeprol and mannitol slightly inhibited the initial transient spike to the same extent. The calcium influx was reversibly inhibited by RCM by about 50%. Up to a concentration of 40 mmol/L, the inhibition induced by iomeprol was significantly higher than that induced by mannitol (P < 0.05-0.01). In isolated arterial segments, relaxation of the contraction phase depending on the calcium influx was significantly higher with the RCM than with mannitol (P < 0.01). CONCLUSIONS Vasodilatation by CM is associated with a reduction in the capacitative entry of calcium. The mechanism of this effect is not clear, but it can be ruled out that it is mainly due to the high osmolarity of these compounds.

1. Gesetzgebung In das Kassenarztrecht ist Bewegung gekommen. Diese Feststellung erstreckt sich gleich auf mehrere Ebenen: der Gesetzgeber hat sich des Kassenarztrechts seit einigen Jahren wiederholt und zunehmend angenommen, und zwar im Rahmen verschiedener „Stufen“ der sog. Gesundheitsreform, zuletzt mit dem „Zweiten Gesetz zur Neuordnung von Selbstverwaltung und Eigenverantwortung in der gesetzlichen Krankenversicherung (2. GKV-Neuordnungsgesetz – 2. GKV-NOG)“ vom 23. 6. 19971, und, blickt man auf die Entwicklung der Gesetzgebung, in immer kurzeren Halbwertszeiten. Seit Neuestem wird – schlagwortartig ausgedruckt – die Losung offenbar nicht mehr in einer „globalgesteuerten“ Budgetierung gesucht; die Losung soll vielmehr im Wege der Neubestimmung von Solidaritat und Eigenverantwortung und zugleich der Starkung der Selbstverwaltungen gefunden werden.

This paper reports results from a Swiss National Science Research Council project which aimed to develop a scale of language proficiency in the form of a ‘descriptor bank’. Up until now, most scales of language proficiency have been produced by appeal to intuition and to those scales which already exist rather than to theories of linguistic description or of measurement. The intention in this project was to use an item-banking methodology to develop a flexible scale of stand-alone criterion statements with known difficulty values. The project took place in two rounds: the first for English (1994), the second for French, German and English (1995). In each year pools of descriptors were produced by analysing available proficiency scales. Through workshops with representative teachers, the descriptors were then refined into stand-alone criterion statements considered to be clear, useful and relevant to the sectors concerned. Selected descriptors presented on questionnaires were then used by participating teachers to assess the proficiency of learners in their classes. This data was used to scale the descriptors using the Rasch rating scale model. The difficulty estimates for the descriptors produced in relation to English in 1994 proved remarkably stable in relation to French, German and English in 1995.

The aim of this study was to evaluate lesion enhancement (LE) and contrast-to-noise ratio (CNR) properties of P846, a new intermediate sized, high relaxivity Gd-based contrast agent at 3 Tesla in a rat brain glioma model, and to compare this contrast agent with a high relaxivity, macromolecular compound (P792), and a standard extracellular Gd-chelate (Gd-DOTA).Seven rats with experimental induced brain glioma were evaluated using 3 different contrast agents, with each MR examination separated by at least 24 hours. The time between injections assured sufficient clearance of the agent from the tumor, before the next examination. P792 (Gadomelitol, Guerbet, France) and P846 (a new compound from Guerbet Research) are macromolecular and high relaxivity contrast agents with no protein binding, and were compared with the extracellular agent Gd-DOTA (Dotarem, Guerbet, France). T1w gradient echo sequences (TR/TE 200 milliseconds/7.38 milliseconds, flip angle = 90 degrees , acquisition time: 1:42 minutes:sec, voxel size: 0.2 x 0.2 x 2.0 mm, FOV = 40 mm, acquisition matrix: 256 x 256) were acquired before and at 5 consecutive time points after each intravenous contrast injection in the identical slice orientation, using a dedicated 4-channel head array animal coil. The order of contrast media injection was randomized, with however Gd-DOTA used either as the first or second contrast agent. Contrast agent dose was adjusted to compensate for the different T1 relaxivities of the 3 agents. Signal-to-noise ratio, CNR, and LE were evaluated using region-of-interest analysis. A veterinary histopathologist confirmed the presence of a glioma in each subject, after completion of the imaging study.P792 showed significantly less LE as compared with Gd-DOTA within the first 7 minutes after contrast agent injection (P0.05) with, however, reaching comparable LE values at 9 minutes after injection (P = 0.07). However, P792 provided significantly less CNR as compared with Gd-DOTA (P0.05) for all examination time points. P846 provided comparable but persistent LE as compared with Gd-DOTA (P0.05) and demonstrated significantly greater LE and CNR when compared with P792 (P0.05). No statistically significant differences between CNR values for Gd-DOTA and P846 were noted for all examination time points (P0.05), with P846 administered at one-fourth the dose as compared with Gd-DOTA.The intravascular contrast medium P792 showed significantly less LE and CNR in comparison to Gd-DOTA and P846, suggesting that it does not show marked extravasation from tumor neocapillaries and does not significantly cross the disrupted blood brain-barrier in this rat glioma model. In distinction, P846 provides comparable enhancement properties at a field strength of 3 Tesla to the extracellular contrast agent Gd-DOTA, using the adjusted dose, suggesting that it crosses the disrupted blood-brain-barrier and tumor capillaries, most likely based on the decreased molecular weight as compared with P792. At the same time, the high relaxivity of this compound allows for decreasing the injected gadolinium dose by a factor of 4 whereas providing comparable enhancement properties when compared with a standard extracellular Gd-chelate (Gd-DOTA) at a dose of 0.1 mmol/kg body weight.

To prospectively determine diagnostic performance and safety of contrast material-enhanced (CE) magnetic resonance (MR) angiography with 0.1 mmol per kilogram of body weight gadobenate dimeglumine for depiction of significant steno-occlusive disease (or =51% stenosis) of renal arteries, with digital subtraction angiography (DSA) as reference standard.This multicenter study was approved by local institutional review boards; all patients provided written informed consent. Patient enrollment and examination at centers in the United States complied with HIPAA. Two hundred ninety-three patients (154 men, 139 women; mean age, 61.0 years) with severe hypertension (82.2%), progressive renal failure (11.3%), and suspected renal artery stenosis (6.5%) underwent CE MR angiography with three-dimensional spoiled gradient-echo sequences after administration of 0.1 mmol/kg gadobenate dimeglumine at 2 mL/sec. Anteroposterior and oblique DSA was performed in 268 (91.5%) patients. Three independent blinded reviewers evaluated CE MR angiographic images. Sensitivity, specificity, and accuracy of CE MR angiography for detection of significant steno-occlusive disease (or =51% vessel lumen narrowing) were determined at segment (main renal artery) and patient levels. Positive and negative predictive values and positive and negative likelihood ratios were determined. Interobserver agreement was analyzed with generalized kappa statistics. A safety evaluation (clinical examination, electrocardiogram, blood and urine analysis, monitoring for adverse events) was performed.Of 268 patients, 178 who were evaluated with MR angiography and DSA had significant steno-occlusive disease of renal arteries at DSA. Sensitivity, specificity, and accuracy of CE MR angiography for detection of 51% or greater stenosis or occlusion were 60.1%-84.1%, 89.4%-94.7%, and 80.4%-86.9%, respectively, at segment level. Similar values were obtained for predictive values and for patient-level analyses. Few CE MR angiographic examinations (1.9%-2.8%) were technically inadequate. Interobserver agreement for detection of significant steno-occlusive disease was good (79.9% agreement; kappa = 0.69). No safety concerns were noted.CE MR angiography performed with 0.1 mmol/kg gadobenate dimeglumine, compared with DSA, is safe and provides good sensitivity, specificity, and accuracy for detection of significant renal artery steno-occlusive disease.

AlSi type eutectics (AlSi, AgSi, AgGe, ZnGe) form 〈100〉 — textured eutectic dendrites of the semiconductor phase when a certain growth rate R and liquid temperature gradient G are held. The spacings of these eutectic dendrites λ follow the relationship: λ = (rλ ≈ 0.2; g ≈ 0.5). The exponents of this relationship can be explained by the model of phase lead determined growth. This model is based on the consideration of the analogy to dendrite growth. The AlSi type eutectics have geometrically similar morphologies for determined Gx/R-relations (x = 1.25 in the case of AgGe) and the relation λ2R = const. is valid. In this paper the AgGe eutectic will be discussed in close detail. Die AlSi ahnlichen Eutektika (AlSi, AgSi, AgGe, ZnGe) bilden bei bestimmten Wachstumsraten R und Temperaturgradienten an der Grenzflache fest-flussig G 〈100〉-texturierte eutektische Dendriten der Halbleiterphase aus. Der Abstand der eutektischen Dendriten λ folgt der Beziehung: λ = (rλ ≈ 0.2; gλ ≈ 0.5). Die Exponenten dieser Beziehungen konnen mit dem Modell des phasenfuhrungsbestimmten Wachstums erklart werden, das auf Analogiebetrachtungen zum Dendritenwachstum basiert. Fur bestimmte Gx/R-Verhaltnisse (x = 1.25 fur AgGe) haben die AlSi-ahnlichen Eutektika geometrisch ahnliche Morphologien, und die Beziehung λ2R = const. ist gultig. In dieser Arbeit wird das AgGe-Eutektikum detailliert diskutiert.

Metallurgically grown M(metal)–S(semiconductor) phase boundaries in directionally solidified AgSi alloys were investigated relative to their behaviour as Schottky junctions. By the aid of point contacts I/V characteristics have been measured which correspond to these ones of Schottky diodes. The Si crystallites were proved to be n-doped. Reverse breakdown voltages of 8 … 24 V are not incompatible with the purity of the used materials. In forward direction the value of diode factor n = 1.1 … 5 shows the existence of several current flow mechanisms. In order to be able to interpret the characteristics it is necessary to have exact information on the specific resistivity of the Si crystallites and on the content of grain boundaries and dislocations in silicon. Beyond that the complicated shape of Si crystallites prevents the necessary determination of the interface size. Es wurden die metallurgisch gewachsenen Phasengrenzen in AgSi-Legierungen hinsichtlich ihrer Eigenschaften als Schottky-Ubergange untersucht. Dazu sind mit Hilfe von Spitzenkontakten I/U-Kennlinien gemessen worden, die denen von Schottkydioden entsprechen. Die Si-Kristallite erwiesen sich als n-dotiert. Gemessene Durchbruchspannungen von 8 … 24 V in Sperrichtung stehen nicht im Widerspruch zur Reinheit der eingesetzten Materialien. In Flusrichtung deutet der Wert des Diodenfaktors n = 1,1 … 5 auf das Wirken mehrerer Stromflusmechanismen hin. Die Interpretation der Kennlinien erfordert genauere Kenntnisse uber den spezifischen Widerstand und uber den Gehalt an Korngrenzen und Versetzungen in der Si-Phase. Daruber hinaus verhindert die komplizierte Form der Si-Kristallite die notwendige Bestimmung der Grose der Grenzflache.

Different geometry parameters for the cross-like germanium crystallites (eutectic dendrites) of the Zn-Ge eutectic alloys unidirectionally solidified have been related to the growth rate R and liquid temperature gradient G using linear regression analysis. It has been found that for eutectic dendrite spacing λ, balk length d and balk thickness b follow the relationship of the type w = CwR−rwG−gw; Cw is a constant. The spacing relationship of eutectic dendrites (rλ = 0.21; gλ = 0.48) shows a similarity with published experimental and theoretical results on primary dendrite arm spacing (rλ = 0.25; gλ = 0.5). It has been shown in terms of a profile ration λ/d that for geometrical similar morphologies the relationship λ2R = const. is valid. Fur verschiedene Geometrieparameter der kreuzformigen Germaniumkristallite (eutektische Dendriten) der gerichtet erstarrten eutektischen Zn—Ge-Legierung wurden die funktionellen Abhangigkeiten von der Wachstumsrate R und dem Temperaturgradienten in der Schmelze G mittels linearer Regression ermittelt. Es wurde gefunden, das der Abstand der eutektischen Dendriten λ, die Balkenlange d und die Balkendicke b durch die Beziehung w = CwR−rwG−gw beschrieben werden konnen; Cw ist eine Konstante. Die Exponenten der Beziehung fur den Abstand der eutektischen Dendriten (rλ = 0,21; gλ = 0,48) sind veroffentlichten experimentellen und theoretischen Exponenten der Beziehungen fur den Abstand der Primarstamme von Dendriten ahnlich (rλ = 0,25; gλ = 0,5). Mittels des Ahnlichkeitsparameters λ/d konnte gezeigt werden, das fur geometrisch ahnliche Morphologien die Beziehung λ2R = const. gultig ist.