282 research outputs found
Supplemental material for Validation and reproducibility of cardiovascular 4D-flow MRI from two vendors using 2 <b>×</b> 2 parallel imaging acceleration in pulsatile flow phantom and in vivo with and without respiratory gating
No full textSupplemental Material for Validation and reproducibility of cardiovascular 4D-flow MRI from two vendors using 2 × 2 parallel imaging acceleration in pulsatile flow phantom and in vivo with and without respiratory gating by Jelena Bock, Johannes Töger, Sebastian Bidhult, Karin Markenroth Bloch, Per Arvidsson, Mikael Kanski, Håkan Arheden, Frederik Testud, Andreas Greiser, Einar Heiberg and Marcus Carlsson in Acta Radiologica</p
Retraction notice to Gadolinium-free cardiac MR stress T1-mapping to distinguish epicardial from microvascular coronary disease: J Am Coll Cardiol 71 (2018) 957-968
No full textThis article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawl).
The JACC Journals Ethics Board has voted to retract this paper, relying on the findings of misconduct after an investigation by the University of Oxford (outlined below).The decision to retract the paper follows the conclusion of an investigation under the University of Oxford’s (“the University’s”) Code of Practice and Procedure on Academic Integrity in Research (“the Code”). The Registrar of the University convened a Panel under the Code. The Panel considered a number of issues, including in relation to this paper. The Panel concluded that the first author, Dr Alexander Liu, was responsible for misconduct in research. The Panel’s findings with regards to misconduct were limited to the actions of the first author. No other co-author was found to be involved in the misconduct. It is understood that the first author disagrees with the Panel’s findings. The first author has raised a complaint with the Office of the Independent Adjudicator for Higher Education (OIA) (The OIA reviews complaints from students about their higher education provider).
In relation to this paper, the Panel’s findings included that:
— certain data had been fabricated by the first author amending the actual study data so that the paper and the central illustration would show a compelling case that T1 mapping could distinguish between epicardial obstructive coronary artery disease and coronary microvascular dysfunction;
— the number of control subjects, their age, and the statistical test to calculate the significance of a difference between the patients in this paper were incorrect; and
— Figure 2 had been fabricated.
The Panel’s view was that this paper would likely need to be retracted from the literature as it had major irregularities and its conclusions were unsafe.
The following co-authors agree that a retraction is appropriate: Vanessa Ferreira, Rajesh Kharbanda, Stefan Neubauer, Stefan Piechnik, Keith Channon, John C. Forfar, Michael Jerosch-Herold, Andreas Greiser, Joanna Liu and Rohan Wijesurendra
The Public Trial and Execution of Arthur Greiser in Poznań: Visual Rhetoric of Documentary Photography and Local Memory
No full textOn the example of the ethically controversial photographs made by Zbigniew Zielonacki from the public trial and execution of Arthur Greiser, the Nazi deputy in the Wartheland, the author demonstrates the visuality of local memory at the intersection of the narrative and non-narrative, private and public, individual and collective sphere. The photographs have become an inherent element of Poznań inhabitants’ memory of World War II and its outcomes, although they did not fit any of the emerging main war narratives.Publiczny proces i egzekucja Arthura Greisera w Poznaniu. Retoryka wizualna fotografii dokumentalnej i pamięć lokalnaNa przykładzie etycznie kontrowersyjnych fotografii Zbigniewa Zielonackiego z publicznego procesu i egzekucji Arthura Greisera, nazistowskiego namiestnika w Kraju Warty, autorka pokazuje, jak wizualność pamięci lokalnej funkcjonuje na przecięciu sfery narracyjnej i nienarracyjnej, prywatnej i publicznej, indywidualnej i zbiorowej. Omawiane w artykule fotografie stały się elementem pamięci mieszkańców Poznania o drugiej wojnie światowej i jej zakończeniu, mimo że nie wpasowywały się w żadną z wyłaniających się głównych narracji wojennych
Ciało zbrodniarza. Wizualne reprezentacje procesu i egzekucji Arthura Greisera
No full text THE BODY OF A WAR CRIMINAL: VISUAL REPRESENTATIONS OF ARTHUR GREISER’S TRIAL AND EXECUTIONThe essay depicts the representations of the public image of Arthur Greiser, the Governor of Reichsgau Wartheland and a war criminal, tried and sentenced to death in post-war Poland in 1946. The author analyzes visual sources, such as photographs and films. The post-war images of Arthur Greiser suggest a different figure of the Nazi leader who tried to create his own, well-considered public image as a beginner member of the Nazi party, and later — as the leader of an occupied territory. The Polish discourse, as the anti-war and anti-Nazi one, broke the majestic and proud figure of Greiser, presented him as a ruthless war criminal responsible for persecutions and genocide, an unhuman being without compassion and a monster with specific physiological features. Simulta-neously, the official mass media rhetoric and visual narratives strived to take over the body of Greiser, deprived him the right to dispose of it. The author describes and interprets the pictures of the trial and execution where Greiser is considered as the accused and a dead body/corpse. The visual representations uncover the practice of subjugating the perpetrator’s body in public discourse, as well as the social behaviour and attitudes in the liberated communist country. THE BODY OF A WAR CRIMINAL: VISUAL REPRESENTATIONS OF ARTHUR GREISER’S TRIAL AND EXECUTIONThe essay depicts the representations of the public image of Arthur Greiser, the Governor of Reichsgau Wartheland and a war criminal, tried and sentenced to death in post-war Poland in 1946. The author analyzes visual sources, such as photographs and films. The post-war images of Arthur Greiser suggest a different figure of the Nazi leader who tried to create his own, well-considered public image as a beginner member of the Nazi party, and later — as the leader of an occupied territory. The Polish discourse, as the anti-war and anti-Nazi one, broke the majestic and proud figure of Greiser, presented him as a ruthless war criminal responsible for persecutions and genocide, an unhuman being without compassion and a monster with specific physiological features. Simulta-neously, the official mass media rhetoric and visual narratives strived to take over the body of Greiser, deprived him the right to dispose of it. The author describes and interprets the pictures of the trial and execution where Greiser is considered as the accused and a dead body/corpse. The visual representations uncover the practice of subjugating the perpetrator’s body in public discourse, as well as the social behaviour and attitudes in the liberated communist country
Individuelle Kompetenzen fördern – Erfahrungen und neue Modelle mit Kompetenzfeststellung und Förderplanung
No full textThiessen B, Aigle G, Greiser P, et al. Individuelle Kompetenzen fördern – Erfahrungen und neue Modelle mit Kompetenzfeststellung und Förderplanung. In: Bundesministerium für Bildung und Forschung, ed. Kompendium des Programms „Kompetenzen fördern“. Schriftenreihe zum Programm "Kompetenzen fördern - Berufliche Qualifizierung für Zielgruppen mit besonderem Förderbedarf (BQF-Programm)". Vol II a. 2006: 68-84
Right and left ventricle native T1 mapping in systolic phase in patients with congenital heart disease
No full textBackground
T1 mapping is emerging as a powerful tool in cardiac magnetic resonance (CMR) to evaluate diffuse fibrosis. However, right ventricular (RV) T1 mapping proves difficult due to the limited wall thickness in diastolic phase. Several studies focused on systolic T1 mapping, albeit only on the left ventricle (LV).
Purpose
To estimate intra- and inter-observer variability of native T1 (nT1) mapping of the RV, and its correlations with biventricular and pulmonary function in patients with congenital heart disease (CHD).
Material and Methods
In this retrospective, observational, cross-sectional study we evaluated 36 patients with CHD, having undergone CMR on a 1.5-T scanner. LV and RV functional evaluations were performed. A native modified look-locker inversion recovery short-axis sequence was acquired in the systolic phase. Intra- and inter-reader reproducibility were reported as complement to 100% of the ratio between coefficient of reproducibility and mean. Spearman rho and Mann-Whitney U-test were used to compare distributions.
Results
Intra- and inter-reader reproducibility was 84% and 82%, respectively. Median nT1 was 1022 ms (interquartile range [IQR] 1108-972) for the RV and 947 ms (IQR 986-914) for the LV. Median RV-nT1 was 1016 ms (IQR 1090-1016) in patients with EDVI <= 100 mL/m(2) and 1100 ms (IQR 1113-1100) in patients with EDVI >100 mL/m(2) (P = 0.049). A significant negative correlation was found between RV ejection fraction and RV-nT1 (rho = -0.284, P = 0.046).
Conclusion
Systolic RV-nT1 showed a high reproducibility and a negative correlation with RV ejection fraction, potentially reflecting an adaptation of the RV myocardium to pulmonary valve/conduit (dys)-function
Towards the exhaustive analysis of left ventricle dysfunctions in ischemic cardiomyopathy: integrating MR-derived wall kinetics, scar transmurality and fluid dynamics
No full textSegment-by-segment assessment of left ventricular myocardial affection in Anderson-Fabry disease by non-enhanced T1-mapping
No full textBackground: Anderson-Fabry disease (AFD) is an X-linked lysosomal enzyme disorder associated with an intracellular accumulation of sphingolipids, which shorten myocardial T1 relaxation times. Myocardial affection, however, varies between different segments. Purpose: To evaluate the specific segmental distribution and degree of segmental affection in AFD patients. Material and Methods: Twenty-five patients with AFD, 14 patients with hypertrophic cardiomyopathy (HCM), and 21 controls were included. A Modified Look-Locker Inversion Recovery sequence (MOLLI) was used for non-enhanced T1 mapping at 1.5 T in addition to standard cardiac imaging in 10-12 short axis views. T1 values were evaluated with a mixed model ANOVA and regression analysis to determine the best diagnostic cutoff values for T1 for each myocardial segment. Results: Regression analysis showed the best diagnostic cutoff compared to controls in cardiac segments 1-4, 8-9, and 14. Mean differences between T1 for AFD versus HCM were greatest in segment 3, 4, and 9 (99ms, 103ms, 86ms, respectively). Overall T1 times were 88870ms and 903 +/- 14ms (AFD with and without LVH); 1014 +/- 17ms and 1001 +/- 22ms (HCM and controls, P<0.05). Conclusion: Myocardial segments are affected by a varying degree of T1 shortening in AFD patients. Segment-specific cutoff values allow the most specific detection and quantification of the extent of myocardial affection
Density-weighted phase-encoding for efficient k-space sampling in NMR Imaging
No full textDie spektroskopische NMR-Bildgebung (Chemical Shift Imaging, CSI) kombiniert die Lokalisationstechniken der NMR-Tomographie mit der NMR-Spektroskopie und bietet so eine ortsaufgelöste metabolische Information über das untersuchte Gewebe. Mit dieser Technik können Stoffwechselvorgänge direkt und quantitativ untersucht werden. Deshalb finden die Verfahren der spektroskopischen NMR-Bildgebung in der medizinischen Forschung eine immer breitere Anwendung. Zwei Aspekte erschweren hierbei die klinische Etablierung dieser Methoden: die aufgrund der geringen Empfindlichkeit langen notwendigen Messzeiten bei dennoch geringer räumlicher Auflösung und die im Vergleich zur herkömmlichen NMR-Tomographie aufwendigere Datenauswertung. In der vorliegenden Arbeit wurden in beiden Punkten substantielle methodische Fortschritte erzielt. In einer Fallstudie mit Herzpatienten konnten erstmals die Veränderungen der Metabolitensignale auf 31P-Karten visualisiert werden. Die dabei erreichte Empfindlichkeit erlaubt auch die Untersuchung der Herzhinterwand, wobei hier die Sensitivität an der Grenze des für eine Individualdiagnostik minimal akzeptablen Signal-Rausch-Verhältnisses (SNR) liegt. Der Einsatz höherer Grundfeldstärken in der 31P-NMR-Spektroskopie läßt einen deutlichen Empfindlichkeitsgewinn erwarten. Im Rahmen dieser Arbeit wurde eine umfassende Vergleichsstudie zwischen einem klinischen 1,5 T NMR-Bildgebungssystem und einem 2,0 T Tomographen durchgeführt. Der beobachtete Empfindlichkeitsgewinn von 45% steht im Rahmen der Messgenauigkeit in Einklang mit einem theoretisch zu erwartenden, linearen Anstieg des SNR. Die Lokalisationseigenschaften eines ortsaufgelösten NMR-Experiments werden dadurch bestimmt, wie die der k-Raum, der Raum der räumlichen Frequenzen, abgetastet wird. Insbesondere in räumlich niedrig aufgelösten Experimenten führen die Seitenbanden der räumlichen Antwortfunktion zu Signalkontamination. Bei der Phasenkodierung kann diese Kontamination durch eine auf unterschiedlichen Mittelungszahlen beruhende Wichtung der k-Raumabtastung unterdrückt werden. Bei vorgegebener Experimentdauer und räumlicher Auflösung verringert diese Akkumulations-gewichtetete Phasenkodierung jedoch im Vergleich zum ungewichteten Experiment den abdeckbaren Bildbereich. Der Schwerpunkt der vorliegenden Arbeit lag deshalb auf der Entwicklung eines neuen k-Raum-Abtastschemas. Dieses Abtastschema basiert auf einer Modulation der Abtastdichte im k-Raum und wird deshalb als Dichte-Wichtung („DW“) bezeichnet. Zur Diskretisierung einer gewünschten kontinuierlichen Wichtungsfunktion dient ein neuer, nicht-iterativer Algorithmus, der aus den Eingangsparametern räumliche Auflösung und Gesamt-Akkumulationszahl ein geeignetes Abtastschema generiert. Die Lokalisations-Eigenschaften der Dichte-Wichtung wurden ausführlich analysiert und mit den etablierten Phasenkodierschemata verglichen. Die Dichte-gewichtete k-Raumabtastung kombiniert die Vorteile der Akquisitions-gewichteten Phasenkodierung mit einem maximierten Bildbereich. So kann bei kürzeren Experimentdauern ein deutlicher Gewinn an Lokalisationsqualität erzielt werden, ohne dabei die Vorteile einer reinen Phasenkodierung aufzugeben. Für die Dichte-gewichtete Phasenkodierung gibt es ein weites Anwendungsfeld. Sie wurde im Rahmen dieser Arbeit in mehreren vorklinischen Studien erfolgreich eingesetzt. Die theoretisch zu erwartenden Vorteile bezüglich der Lokalisationseigenschaften bestätigten sich experimentell. Im Bereich der spektroskopischen 31P-NMR-Bildgebung in vivo erwies sich die Dichte-Wichtung als deutlich bessere Alternative zur Akkumulations-Wichtung. Die Einfaltungen des starken Brustmuskelsignals, welche im bisher verwendeten 31P CSI Protokoll den Informationsgehalt der Metabolitenkarten beeinträchtigt hatten, konnten unterdrückt werden. In der 23Na-NMR-Bildgebung am Herzen wurde das DW Abtastschema eingesetzt, um die Verbesserung der Lokalisationsqualität durch Akquisitions-Wichtung erstmals auch in der 23Na-NMR-Bildgebung am menschlichen Herzen zu nutzen. Es konnte gezeigt werden, daß die DW Methode deutliche Vorteile im Vergleich zu den herkömmlichen Abtastungen liefert. Mit der DW Methode gelang es, 23Na-Bilder des menschlichen Herzens von bisher unerreichter Qualität zu erzeugen. Insgesamt wurde mit der Dichte-gewichteten k-Raumabtastung in der vorliegenden Arbeit eine flexible und effiziente Art der Akquisitionswichtung entwickelt. Zusätzlich zu einer deutlichen Verbesserung der Lokalisationsqualität bei optimaler Empfindlichkeit wird mit DW auch die Optimierung des abdeckbaren Bildbereichs erreicht. Somit bietet DW im Vergleich zum Akkumulations-gewichteten Experiment eine größere Flexibilität bei der Wahl der experimentellen Parameter Auflösung und Experimentdauer. Darüber hinaus ist das DW Abtastschema potentiell für jedes NMR-Bildgebungsexperiment mit niedriger räumlicher Auflösung von Nutzen.Magnetic Resonance Spectroscopic imaging (Chemical Shift Imaging, CSI) combines the localization techniques of MRI with MR spectroscopy and therefore povides spatially resolved metabolic information of the investigated tissue. Two aspects hamper the clinical acceptance of this method: the long measurement durations and the more elaborate data evaluation. In the presented work in both aspects significant improvements were achieved. In a case study with patients after myocardial infarction the changes in the 31P metabolite levels could be visualized. In combination with an automated data evaluation the acceptance of spectroscopic 31P MRI will be improved. Higher field strengths can improve the sensitivity in MRI. In an extended volunteer study a gain of 45% in sensitivity could be achieved at a field strength of 2.0 T compared to the clinically established 1.5 T. The localization properties in a spatially resolved NMR experiment are determined by the way how the k-space, representing the spatial frequencies that are acquired, is sampled. In particular in experiments with low spatial resolution, the sidebands of the spatial response function result in severe signal contamination. In phase-encoded expeiments this contamination can be suppressed by variable accumulation numbers at different positions in k-space. However, this results in a reduced spatial coverage in image space. The main goal of this work was the implementation of a new k-pace sampling scheme, that is based on the variation of the sampling density and is therefore referred to as "Density-weighting". To generate the discrete sampling matrix a new, non-iterative algorithm was developed, that calculates the sampling scheme from the input parameters spatial resolution and total number of accumulations. The new ampling scheme was extensively analyzed and compard to the established schemes. Density-weighting combines the advantages of Accumulation-weighting with a maximized field of view. At shorter experiment durations and maintained optimal sensitivity a significant improvement in image quality could be achieved. In several applications of cardiac spectroscopic MR imaging the advantages could be demonstrated
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